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LEAN : TETRAHYDROFURFURAN-2 : 5-DICARBOXYLIC ACID. 103 XI.-Ethyl Dibromobutanetetracarboxylate and the Synthesis of Tetrahydrofurfuran-2 : 5-diccwboxylic Acid. By BEVAN LEAN, D,Sc., B.A. IN a paper communicated t o the Society a few years ago (Trans., 1894, 65, 995), the author described a number of homologues of butanetetracarboxylic acid and of adipic acid. It was shown that ethyl butanetetracarboxylate, when treated with sodium ethoxide and alkyl haloids, yields disubstitution derivatives of the general formula ( C02C2H,),RC*CH,* CH2* CR( C02C2H5)2. From these, symmetrical dialkyl butanetetracarboxylic acids and dialkyl ndipic acids were obtained, and it was shown that the latter always existed in two modifications, usually differing from one another markedly in melting point, solubility, and other physical properties.A t the time that this communication was made, it had also been found that bromine could readily replace the hydrogen atoms of the two CH groups in ethyl butanetetracarboxylate, and that the two bromine atoms of the resulting compound could, in turn, be replaced by hydroxyl groups on digestion with barium hydroxide. The in- vestigation of dihydroxybutanetetracarboxylic acid and of its deriva- tives proved, however, to be a matter of much greater di5culty and interest than was anticipated, and it now appears desirable to no longer postpone the communication of the results of this part of the inquiry. Ethyl butanetetrncarboxylate, like ethyl pentanetetracarboxylate (Perkin, Trans., 1891, 59, 827)) readily reacts, in chloroform solution, with bromine with the formation of ethyl as-dibroruobutanetetra- carboxylate and evolution of hydrogen bromide, thus : $!H,*CH(CO C H 5 2 ) + 2Br2 = CH2* I CBr(C02C2H6)2 + 2HBr, CH2* CH(C02C2H6)2 CH2* CBr(C0,C2H5)2 1 2104 LEAN : ETHYL DIBROMOBUTANETETRACARBOXYLATE ANb The beautiful, crystalline dibromo-compound thus obtained, when digested for some hours with a strong solution of barium hydroxide, yields an insoluble barium salt of dihydroxybutanetetrncarboxylic acid, crystallising apparently with one molecular proportion of water.When this salt is decomposed by sulphuric acid, dihydroxybutane- te t racarbox ylic acid, (CO,H),C(OH)*CH,* CH,* C(OH)(CO,H),, is obtained in solution, as is shown by the preparation and analysis of its silver salt, which has the composition C,H6010Ag,.On slowly concentrating the aqueous solution of dihgdroxybutane- tetracarboxylic acid over strong sulphuric acid, beautiful, long, prismatic needles are obtained of the corresponding 8-monolactone, (CO,H),F*CH,* CH,* ?(OH)*CO,H 0 co The silver salt prepared from this substance is silver dihydroxy- butanetetracarboxylate, C,H,O,,Ag,, thus confirming this view of its constitution. On heating an aqueous solution of this 8-lactone in a sealed tube at 150°, decomposition ensues with the elimination of carbon dioxide. I f the aqueous solution of the product is evaporated to a, small bulk on a water-bath and placed over sulphuric acid in a vacuum, small, star-shaped clusters of crystals appear after one or two days; if left longer over sulphuric acid, the whole eventually becomes solid, but the last traces of moisture disappear very slowly.The product had the composition C,H,O,, which is that of dihydroxyadipic acid, less 1 molecular proportion of water, C8Hlo0,0 = C6H805 + 2C0, + H,O. In this case, again, the simplest explanation would be that the substance is the Glactone of dihydroxyadipic acid, namely, CO,H*$!H*CH,*CH,* YH*OH 0 co Careful investigation, however, has shown tbat the silver salt prepared from i t has the composition C,H6O5Ag,, rendering it very improbable that the substance C,H,O, is a &lactone : for this t o be the case, it would be necessary to suppose the lactonic ring to be quite exception- ally stable, remaining intact when the substance is dissolved in water, and also to assume that the hydrogen atom of the hydroxyl group has an acidic character-a very unusual occurrence in an aliphatic compound.Further consideration shows, however, that the elimination of waterTETRAHYDHOFURFURAN-2 : 5-DICABBOXYLIC ACID. 105 actually take9 place between the two hydroxyl groups, and that the substance is tetrahydrofurfuran-2 : 5-dicarboxylic acid, formed in the following way : C02H*C y 3 2 - p 2 y*C02H = C0,H.C y"s'yH2 C*CO,H + H20. \/ 0 AH OH It was found that the tetrahydrofurfurandicarboxylic acid (C,H,05) obtained by heating an aqueous solution of dihydroxybutanetetra- oarboxylic acid begins t o melt about 65", but on raising the tempera- ture the fusion proceeds only gradually, and is not complete until about 120'.The absence of a definite melting point suggested the possi- bility of the substance being a mixture of stereoisomeric acids, and experiments were instituted to separate them if possible by fractional crystallisation from water. Using 32 grams of material, there was little difficulty in separating 6 grams of a tetrahydrofurfurandicarboxylic acid which melted at 123-125'. This was shown to be dibasic by the preparation and analysis of its silver salt, which was found to have the composition C,H,O,Ag,. It is to be noted that it crystallised fairly readily from a little water in star-shaped clusters, and that it was not necessary to dry the crystals over strong sulphuric acid for analysis, exposure in the air being sufficient. It appeared to have no tendency to combine with a molecular proportion of water, as would be the case with a &lactone, for an aqueous solution, after being boiled, gave again the silver salt mentioned above, and not a salt of the formula c6H,06Ag2.The mother liquor from which this acid had been separated was care- fully examined, as is described later (p. 11 3), and from it were isolated 8 grams of small, white crystals, which when dried in the air melted at 56.5-62'. It was at first expected that this substance was a second tetrahydrof urf urandicarboxylic acid ; analysis, however, proved i 1; to have the composition C,H,O,+H,O or C6H1006. The silver salt prepared from it had the composition C6H,Ag20,, a result which led to the conclusion that the substance C,H,,06 was not dihydroxyadipic acid, but the isomeric monohydrate of tetrahydrofurfurandicarboxylic acid.The only solvent from which it was found at all feasible to crystallise this substance was strong hydrochloric acid ; it then melted at 63-64', and analysis proved it to be unchanged in composition. When placed a Few hours over strong sulphuric acid,it was found that the monohydrate, C6H1006, could no longer be fused below 70°, and after 8 days the product melted a t 93-95' and had the composition C,H,O,. Its silver salt was found to have the composition C,H,o,Ag,, ooufirming the conclusion that the substawe was a tetrahydrofurf urm-106 LEAN : ETHYL DIBROMOBUTANETETRACARBOXYLATE AND dicarboxylic acid, and not the isomeric &monolactone of dihydroxy- adipic acid. When this acid (m. p.93-94O) was exposed in the air or dissolved in a little water and the solution evaporated over solid potassium hydroxide, the product melted a t 57-62’, the monohydrate having been reformed. I n the previous paragraphs it has been shown that if an aqueous solution of dihydroxybutanetetracarboxylic acid is heated in a sealed tube at 150°, the product must be regarded as a mixture of isomeric tetrahydrofurfurandicarboxylic acids, the one melting at 123--125O, the other at about 93-94’. The isomerism of these must be geo- metric ; they are, in fact, cis- and trans-forms, recalling the isomeric hexahydroterephthalic acids, and may be represented thus : So far as is known, this is the first case of geometrical isomerism which has been established in the furfuran series.Few instances are recorded of the formation of a furfuran derivative by the removal of the elements of water from an open chain hydroxylic compound. Fischer (Bey., 1891, 24, 2140) has shown that water can be split off from the tetrahydroxyadipic acids, with the formation of 8 furfurandicarboxylic acid (dehydromucic acid), thus : QH(OH)-YH*OH FH-QH YH*OH QH’OH - 3H20 = CO2H*C C*CO,H. C0,H C0,H \/ 0 This action, however, is not strictly analogous t o the case discussed in the present paper, because water was eliminated only when the hydroxyadipic acids were heated with strong acids. Another instance which is more nearly parallel seems t o exist in the case of Tiemann’s ‘isosaccharic acid’ (Bey., 1884, 17, 247 ; 1886, 19, 1257). This was at first regarded as a tetrahydroxyadipic acid, C,H,,OS, but more recently (Ber., 1894, 27, 11 8) was shown t o have the composition C,H&.Tiemann gave the name ‘ nor-isosaccharic acid’ to the tetrahydroxyadipic acid fromwhich ‘ isosaccharic acid ’ might be considered to be derived, and pointed out that on the analogy of saccharic and mucic acids, the substance C,H,07 might be regarded as the lactone of this acid but for the facts that it proved to be dibasic, andTETRAHYDROFURFURAN-2 : b-DICARBOXYLIC ACID. 107 that when heated alone, or in a stream of dry hydrogen chloride, it was changed, without charring, into pyromucic acid, He therefore con- cluded that ‘ isosaccharic acid ’ was really 3 : 4-dihydroxytetrahydro- f urf wan-2 : 5-dicarboxylic acid, OH*HC---CH* OH Of the various compounds prepared from this substance, Tiemann found that several were derivatives of what he continued to term isosaccharic acid,’ but that others contained, in addition, the elements of one molecular proportion of water.The latter, he pointed out, might be regarded as f urfuran derivatives crystallised with lH20, but, as other dihydroxyfurfurans were not known, and as a tetrahydroxy- adipic acid, which lost water when its aqueous solution was evaporated, might be expected to undergo hydration under the influence of chemical agents, he continued to speak of them as formed from ‘ nor-isosaccharic acid.’ In confirmation of this view, he described a tetracetyl derivative of ‘nor-isosaccharic acid’ (Bey., 1894,27, 128)’ but it is not stated how this was isolated, nor are any analyses quoted.It may be noted that some of the derivatives of ‘ nor-isosaccharic acid ’ were found to lose readily one molecular proportion of water, giving rise to corresponding derivatives of ‘ isosaccharic acid,’ and that the latter readily recombined with water in molecular proportion. A number of salts of ‘ nor-isosaccharic acid ’ were described, but almost all of these contained water of crystallisation, and it is not clear how Tiemann satisfied himself that they were not derived from ‘ isosaccharic acid.’ From a review of these facts, it appears t o the author of the present paper that the compounds described by Tiemann as derivatives of 6 isosaccharic acid,’ or of ‘ nor-isosacuharic acid,’ are in reality de- rivatives of 3 : 4-dihydroxytetrahydrofurfuran-2 : 5-dicarboxglic acid, and that the names ‘ isosaccharic acid ’ and ‘ nor-isosaccbaric acid ’ should be abandoned.EXPERIMENTAL. QH2* CBr(CO,C,H,), Eth,yl Dib.r.omobutultetetracarbox~lccte, CH,* CBr(CO 2 2 5 2 80 grams of ethyl butsnetetracarboxylate, free from ethyl butane- tricarhoxylate (compare Lean and Lees, Trans., 1897, ’73, 1062), were dissolved in 230 grams of chloroform in a flask connected with a reflux condenser, and 73 grams of dry bromine run in drop by drop, the flask108 LEAN : EI'HYL DIBROMOBUTANETETRACARBOXYLATE AND being kept cool during the operation. The liquid remained colourless until nearly the whole of the bromine had been added; the flask was then warmed a t 60' for 5 hours on the water-bath, and finally for 1 hour at 70'.The product, which mas still coloured by bromine, was shaken with a small quantity of a solution of sodium hydrogen sulphite, and the residual heavy, yellowish oil washed with water and dehydrated by cal- cium chloride. After the chloroform had been removed as far as possible by evaporation on the water-bath, the residue, on standing, solidified almost completely, forming a beautiful, crystalline mass (about 108 grams). This was broken up and separated as completely as possible from oil by washing with a little ethyl alcohol with the aid of a pump. The white, crystalline product (87 grams) was further freed from traces of oil by dissolving i t in the least possible quantity of hot ethyl alcohol, when the solution deposited, on standing, about 76 grams of colourless, monoclinic prisms.If crystallised again from alcohol, almost exactly the same weight (75 grams) was recovered. On analysis : 0,1517 gave 0,2127 CO, and 0.0680 H,O. 0,1639 ,, 0.1283 AgBr. Br= 32.01. 0,2385 ,, 0.1775 AgBr. Br = 31-67. C!= 38.33 ; H=4*98. C,6H,,08Br, requires C = 38.09 ; H = 4.76 ; Br = 31-74 per cent. E thy1 di bromobutanetetracarboxylate crystallises i n well-formed, mono- clinic crystals from a warm solution in light petroleum, or in methyl or ethyl alcohol, melts at 83O, and is readily soluble in ether, benzene, toluene, or glacial acetic acid. VH2* C(OH)(CO,H), Dih?/drox~bzltanetetracurbox?llic Acid, cH,. C(OH-(CO,H), - When ethyl dibromobutanetetracarboxylnte is hydrolysed in a glass flask, a considerable quantity of si1ic.t and alkali is introduced into solution, from which it is very difficult to free the product, no solvent besides water having been found from which dihydroxybutanetetra- carboxylic acid can be crystallised ; the hydrolysis therefore was carried oiit in a silver flask of 750 O.C.capacity. 80 grams of ethyl dibromobutanetetrncnrboxylate (1 mol.) along with 157 grams of barium hydroxide (2 mols.) freshly crystnllised in a platinum basin,and about 300c.c. of water were introduced into thesilver flask, to the neck of which a small reflux condenser was attached. The mixture was then boiled on a sand-bath for 6 hours. A further quantity of barium hydroxide (157 grams) was then added, and the heating continued for another 6 hours. The product, whiIe still hot, was filtered with the aid of a pump, and the insoluble, white, crystallineTETRAHYDROFURFURAN-2 : 5-DICARBOXYLIC ACID.109 barium dihydroxybutanetetracarboxylate was washed many times with hot water, then suspended in water, and decomposed with the necessary amount of sulphuric acid. After filtration from barium sulphate, the solution was always found to contain a small quantity of bromine ; t o remove this, silver hydroxide was added, and, lastly, the excess of silver was removed by sulphuretted hydrogen. The filtered solution was then evaporated t o about 150 C.C. on the water bath. Silver Salt.-A portion of the solution was neutxalised with ammonium hydroxide solution, poiired into a large excess of silver nitrate solution, and the mixture well shaken ; the white, amorphous precipitahe was collected on a filter, well washed with water and dried on a porous plate, and finilly over sulphuric acid.0.2910 gave 0.1820 AgBr. Ag= 62.54. C,H,0,,Ag4 requires Ag = 62-23 per cent. Bcwium SaZt.--Some of the barium salt formed in preparing the acid was washed many times with boiling water, and afterwards dried on n porous tile and by exposure on a watch glass in the air for some days. 0.6248 gave 0.5218 Bn80,. Ba = 49.1 2. C8H,0,,,Ba, + H,O requires Ba = 49.50 per cent. This salt apparently ~rystitllise~ with lH,O, but the water cannot be estimated by desiccation a t 1 loo, as further decomposition ensues. A strong solution of dihydroxgbutanetetracarboxylic acid has an extremely acrid taste, whilst a dilute solution has a taste very similar t o that of alum.The acid readily liberates carbon dioxide from a carbonate. When the aqueous solution of the acid was concentrated over sulphuric acid in a vacuum, a deposit of barium sulphate formed before crystallisation began. On further evaporation, a little more barium sulphate separated out, and shortly afterwards beautiful, long, prismatic needles of the monolactone of dihydroxybutanetetracarb- oxylic acid began to separ:tte from the slightly yellow, gelatinous mass. &Monolactone OJ Di~~ydroxl/butanetet~acnrbox?/lic Acid3 (CO,H),Q*C H,* CH,. Y(OI-I)CO,H. 0-- co The gelatinous product, in which crystals had begun t o form, was stirred up and after exposure for some days in a vacuum over sulphuric acid became solid and dry. The hard, white, porcelain-like mass was powdered and again exposed over sulphuric acid.The yield from 80 grams of ethyl dibromobutanetetrrtcarboxylate was usually 30-35 grams. The substance began to soften at 145O, and at 1 5 6 O it was110 LEAN : ETHYL DIBROMOBUTAXETETHACARBOXYLATE AND completely fused and frothed up the capillary tube. A t a higher temperature, it charred rapidly, On igniting 1.0966 grams of the substance, 0.0056 gram or 0.5 per cent, of ash was left, which proved to be mainly barium sulphate. In the following analyses, a correction of 0.5 per cent. was made upon the weight of substance taken. No solvent, besides water, was found from which the acid could be crystallised. 0.1548 gave 0.2168 CO, and 0-0505 H,O. C = 38.24 ; H = 3.65, 0.1616 ,, 0.2304 00, ,, 0.0523 H,O.(2-38.86 ; H=3.61. C,H,,Olo requires C = 36-06 ; H = 3-78 per cent. C,H, 0, ,, C=38.68; H-3.25 ,, These analyses showed that the substance consisted probably of the &monolactone of dihydroxybutanetetracarboxylic acid : i t was proved to be a lactone, and not a furfuran derivative, by analysis of the silver salt. The silver salt was prepared, and proved t o be tetrabasic. 0.3410 gave 0.3697 AgBr. Ag = 62.27. 0.245 ,, 0.2662 AgBr. Ag= 62.41. The lactone of dihydroxybutanetetracarboxylic acid crystallises in long needles on slow evaporation of its aqueous solution. It is readily soluble in water, ether, methyl, or ethyl alcohol, but in- soluble in benzene, toluene, or light petroleum. On exposure in the air, it absorbs moisture, but only very slowly. C,HGOloAg, requires Ag = 62.23 per cent.Tetrahydrofurfuran-2 : 5-dicarboxylic Acid. On heating an aqueous solution of the lactone of dihydroxybutane- tetracarboxylic acid in a sealed glass tube, the acid decomposed with the elimination of carbon dioxide. About 2 grams of the lactone of dihydroxybutanetetracarboxylic acid, dissolved in 20 C.C. of water, were heated at 150' in a sealed tube for 6 hours. A very considerable pressure was developed within the tube, so much so that until a special quality of Jena glass tubing was obtained, almost every tube was shattered, and much valuable material lost. On opening the t4ube, a violent escape of carbon dioxide took place, and the decomposition was found to be complete. Fifty-six grams of the lactone were successfully decomposed, and the contents of the tubes were mixed and filtered from a little sediment. A portion was examined as follows : 120 C.C.were evaporated to a small bulk on a water-bath and placed over sulphuric acid in a vacuum; in the course of the next night, a small sediment separated out, which proved to be barium sulphate (compare p. 109) ; th' IS wasTETRAHYDROFURFURAN-2 : 5-DICAHBOXYLIC ACID. 111 removed by filtration and the slow evaporation continued. 'In the course of another day, small, star-shaped forms resembling snow- crystals began to appear, and after four more days almost the whole became solid. The cake was then broken up and placed for a fort- night over sulphuric acid in a vacuum ; the last traces of moisture seemed to disappear very slowly. On ignition, a small amount of mineral matter was left ; 0.5327 gram gave 0.0068 gram or 1-3 per cent, of ash, This was mainly barium sulphate and silica, introduced unavoidably in previous operations ; as no way was found of removing this inorganic material, the necessary correction was made in the following analyses, which proved that the product is not dihydroxyadipic acid.0.1253 gave 0.2056 CO, and 0.0598 H,O. C = 44.73 ; H=5*33. 0.1758 ,, 0.2902 CO, ,, 0,0823 H20. C=44.99 ; H=5*23. CGHl006 requires C = 40.42 ; H = 5.66 per cent. C,H,O, ,, C=44*95 ; H=5*03 5, The siZuei* scdt was prepared in the usual way from a neutral solu- tion of the ammonium salt; it was dried over sulphuric acid and anal y sed. 0.1871 silver salt gave, on ignition, 0.1078 Ag. Ag = 57.63. 0.1692 ,, 9 , ,, 0.0976 Ag.Ag = 57.68. C,H,0,Ag2 requires Ag = 55-09 per cent. cGH,05Ag, ,, Ag=57.73 ,, These analyses, showing the silver salt to be dibasic but with the composition C,H60,Ag,, make it very improbable that the acid C,H,05 is the &lactone of dihydroxyadipic acid ; it must, in fact, be regarded as a tetrahydrofurf urandicarboxyiic acid. This conclusion is supported by the fact that the same silver salt was obtained, without the previous isolation of the acid C,H805, directly from an aqueous solution of dihydroxybutanetetracarboxylic acid, heated at 170' in a sealed tube for 6 hours, and then evaporated on a water- bath with addition of water t o ensure the removal of carbon dioxide. 0.1779 gave 0.1214 CO,, 0,0286 H20, and 0.1019 Ag. C= 18.60 ; H = 1-80 ; Ag = 57.28. C,H,O,Ag, requires C = 19.24 ; H = 1.62 ; Ag = 57.73 per cent.As stated in the introduction, the acid C,H& began to melt a t about 65', but on raising the temperature the fusion proceeded only graduallyand was not complete until about 120'. This absence of a definite melting point could not be attributed to impurity, or to the material being a mixture of entirely different substances in view of the analytical results adduced above, and pointed rather to the112 LEAN : ETHYL DIBROMOBUTANETETRACARBOXYLATE AND possibility of the substance consisting of a mixture of stereoisomeric acids. After preliminary experiments had shown that fracbional crystal- lisation from water, although tedious, promised to effect a separation, the method was carefully applied to 32 grams of the tetrahydro- furfurandicarboxylic acid, Tetrahydrofurfuran-2 : 5dicccrboxyZic Acid, m.p. 123-1 25'. Thirty-two grams of the acid C,H,O, were dissolved in water, and the aqueous solution evaporated slowly to a small bulk on the water-bath, filtered from a little sediment of barium sulphate, and placed over sulphuric acid in a vacuum, when star-shaped clusters of crystals soon began to appear. As soon as at least half of the product had crystal- lised, the crystals were separated as completely as possible from the brown, syrup-like mother liquor by the aid of a pump and dried over sulphuric acid. They melted between 90' and 122'. On repeating the fractional crystallisation, 6 grams of beautiful, white crystals were ultimately obtained which melted at 123-125' ; after solidification, they melted again at the same temperature.The crystals had the same melting point, whether dried a t 100' in a steam oven or by exposure in the air. On analysis, the substance proved to have a composition corre- sponding to that of tetrahydrof urf urandicarboxylic acid. 0.1372 gave 0,2264 CO, and 0.0638 H,O. C = 44.98 ; H = 5.12. C,H,O, requires C = 44.95 ; H = 5.03 per cent. The acid has a very acrid taste. It is extremely soluble in cold water, methyl or ethyl alcohol, acetone, or glacial acetic acid, but is not readily dissolved by ether, and is practically insoluble in chloroform, benzene, or light petroleum. It dissolves in boiling toluene, and is rapidly precipitated, on cooling, in arborescent masses of minute crys- tals.It can be crystallised from a concentrated aqueous solution and from a verystrong solution of hydrochloric acid. The acid is charred extremely readily if cautiously heated in a dry test-tube. A neutral solution of the ammonium salt does not readily yield a precipitate on the addition of solutions ol metallic salts, except in the case of silver and mercurous salts. The silver salt of the acid was prepared and analysed both by igni- tion and by combustion. It was found impossible to estimate the carbon accurately, on account of the great tendency of the salt t o explode, even at a very moderate temperature,TETRAHYDROFUBFURAN-2 : 5bDICARBOXYLIC ACID 113 0,2984 gave 0.1704 Ag. 0.2248 ,, 0.1374 CO,, 0.0382 H,O, and 0.1291 Ag. C = 16.66; C6H60,Ag, requires c = 19.24 ; H = 1 *62 ; Ag =L: 57.73 per cent.The basicity of the acid was determined by titration with a solution of pure barium hydroxide, of which 1 C.C. contained 0.007607 gram Ba(OH),. 0.5160 gram acid required 58-9 C.C. or 0.4480 gram Ba(OH), for neutralisation, whether phenolphthalein or litmus was used as an indicator. Calculated for C6H805, 0.4452 gram, and for G,H,,O,, 0.4002 gram of Ba(OH), would be required to form a dibasic salt with this amount of acid, a difference equivalent t o 6 C.C. of solution. An attempt was made t o open the ring by boiling half a gram of the acid, dissolved in a little water for 6 hours, in a small Geissler flask. The silver salt was then prepared and analysed, proving that no change had occurred; a result which made it still less probable that the substance could be a &lactone.Ag= 57.41. C,H60,Ag2 requires Ag = 57.73 per cent. Ag = 57.10. H = 1.90 ; Ag = 57.40. 0.2292 gave 0.1316 Ag. C6H80&g2 ,, Ag=55.09 ,, ~eti~ahydrofurfurcn-2 : 5-dicarboxylic Acid, m. p . 93-95', and its Hydrate. The brown, syrup-like mother liquor obtained in the course of the isolation of the acid of higher melting point was placed over sulphuric acid in a vacuum, but, even after standing some days, crystallisation did not begin until a fragment of the acid melting at 123-125' was added, and the solution vigorously stirred with a glass rod, when a pasty, crys- talline mass resulted. This was at once filtered by means of a pump, and gave about 6 C.C. of a reddish-brown mother liquor and 11 grams of small, nearly white, sand-like crystals, which, after being spread on a porous plate, were found to melt gradually between 50° and 65'.The crystals were dissolved in a little cold water, and the solution, after filtration from a slight sediment, allowed to evaporate slowly over sulphuric acid in a vacuum until it became syrupy, without, however, any separation of crystals occurring, but on adding a small fragment and stirring the syrup suddenly became almost solid with sensible evolution of heat. The product was dried in the air on a porous tile, giving 8 grams of small, white crystals, which were found to melt at 56.5-62"aiid when dried over solid caustic potmh in a vacuum,114 LEAN : ETHYL DISROMOBUTANETETRACARkOXYLA'l'E A N D showed no change in the melting point.A small portion was more completely dried in a steam oven at 100'; after melting, it did not solidify on cooling until scratched with a glass rod, when it at once became solid and brittle; it then melted at 59-62O. A portion mas also placed in a vacuum over sulphuric acid, and the next day was found to be caked together, crisp, and nodular ; it then began to melt a t 63O, but was not completely fused even at 70". This raising of the melting point was subsequently found t o be due t o the partial dehydration of the hydrate of tetrahydrofurfuran- dicarboxylic acid (m. p. 59-62O), the anhydrous acid having a higher melting point (see p. 115). I n the account of the isolation of these substances, mention is made of 5 C.C. of a reddish-brown mother liquor which might conceivably con- tain a compound of still lower melting point, although contaminated by impurities accumulated in the numerous processes of the prepara- tion.Careful examination, however, failed to reveal the presence of any other substance, Hydrate of Tetrahydrq%rfuraficrficrccn-2 ; 5-dicarboxylic Acid, C6H80, -+ H,O. -The small, wbite crystals (8 grams), which when dried in the air melted at 56-5-62', proved t o be a hydrate of tetrahydrofurfuran- dicarboxylic acid. Prior to analysis, the crystals were dried over solid caustic potash in a vacuum f o r 3 days; they gave a slight amount of ash after ignition (0.3 per cent.), and the necessary cor- rection WAS applied t o the analytical results : 0.1593 gave 0.2360 CO, and 0.0812 H20.C = 40.37 ; H= 5.70. 0.1188 ,, 0*1777 GO, ,, 0.0633 H,O. C =r 40.76 ; H = 5.95. C6HI0O6 requires C = 40.42 ; H = 5-66 per cent. C6H,0, ,, C144.95; H = ~ 5 * 0 3 ,, This conclusion was confirmed by determining the bccsicity of the acid with a solution of barium hydroxide containing 0.007607 gram Ba(OH), per C.C. 0.4340 gmm acid required 55.2 c.c., or 0.4801 gram Brt(OK), for neutralisation whether phenolphthalein or litmus was used as an indicator, Calculated for CGHZO06, 0-4176 gram, and for C6H805, 0.4645 gram of (BaOH), would be required to form a dibasic salt with this amount of acid. The formula C,HlOO6 represents both dihydroxyadipic acid and also monohydrated tetrahydrofurfurandicarboxylic acid. The for- mation and analysis of the silver salt showed, however, that the substance was the latter.The silver salt was prepared and dried a t looo 1TETRAHYDROFURFURAN-2 : 5-DICARBOXYLIC ACID. 115 0'1735 gave 0*1288 CO,, 0.0292 H,O, and U*OO91 Ag. C = 19.30 ; H = 1 *87 ; Ag = 57.14. C,H,O,Ag, requires C = 19624 ; H = 1.62 ; Ag = 57.73 per cent, From another preparation, made 3 years previously, a silver salt was prepared which gave Ag = 57.53 per cent. The hydrate of t etrahydrofurfurandicarboxylic acid is extremely soluble in cold water, methyl or ethyl alcohol, acetone, or glacial acetic acid, but is not at all readily soluble in boiling ether, and dissolves only sparingly in boiling benzene, toluene, or light petrol- eum. It is soluble in concentrated hydrochloric acid, but if the solution is stirred and left over solid caustic potash the hydrate can be induced to crystallisc in beautiful, white plates.Concentrated hydrochloric acid is therefore the only solvent from which the hydrate can be crystallised without very great loss. The crystallisation was carried out as follows : 3 grams of the hydrate were dissolved in a little water, the solution filtered from a very small amount of sediment, and hydrogen chloride passed into it until the solution was saturated. After concentration in a vacuum, a white, crystalline precipitate was induced to form by adding a crystal and stirring vigorously. The product was collected, washed with a little strong hydrochloric acid, spread on a porous tile, and dried over solid caustic potash in a vacuum. I n this way, 1.3 grams were obtained, which on analysis proved t o be the substance C,H,,O, un- changed in composition.I t melted at 63-64', and this may probably be taken as the correct melting point rather than 56-5-62', the melting point before crystallisation from hydrochloric acid. An aqueous solution of the hydrate is intensely acrid. A neutral solution of its ammonium salt gives a white precipitate with silver or mercurous nitrate,' but no precipitate with barium nitrate, calcium chloride, lead acetate, or mercuric chloride. Tetrahyd~ofurfu~an-2 ; 5-dicarboxylic acid, m. p . 93-95°.--It has already been stated that, after the hydrate of tetrahydrofurfurandi- carboxylic acid had been placed for 1 day over sulphuric acid in a vacuum, the crystals were found to be caked together and could no longer be melted below 70'.A portion of the hydrate, which had been recrystallised from hydrochloric acid and melted at 63--64O, was exposed for 8 days over strong sulphuric acid in a vacuum. It then melted at 93-95'. On analysis : 0.1513 gave 0.2486 CO, and 0*0700 H,O. C = 44.79 ; H = 5-17. C,H,O, requires C = 44-95 ; H = 5.03 per cent. This result showed that the riiising OF the melting point mas due to the loss of a mcleculw proportion of water, and was confirmed by116 LEAN : TETRAHYDROFURFURAN-2 : 5-DICARBOXYLIC ACID. determining the actual loss in weight which occurred when the hydrate was exposed over sulphuric acid. 1.1737 gmm of the hydrate lost 0.0638 gram or 5-4 per cent. in 1 day; at the end of 10 days, the weight remained constant, and 0.1235 gram had been lost, or 10.52 per cent. The calculated loss is 10.10 per cent. A determination of the 6asicity of the substance (m. p. 93-95') with a solution of barium hydroxide containing 0.00917 gram barium hydroxide per C.C. confirmed the conclusion that it had the composition 0.4342 gram required 50.39 C.C. or 0.4622 gram Ba(OH), for neutralisation, whether phenolphthalein or litmus was used as the indicator. Calculated for C,H,,O,, 0-4176 gram, and for C6H805, 0.4645 gram of Ba(OH), would be required to form a dibasic salt with this amount of acid, 'GHSo5* The silver sult was prepared and analysed : 0,1752 gave 0.1227 CO,, 0.0295 H,O, and 0.1007 Ag. c6H,05Ag2 requires c = 19-24 ; I€ = 1.62 ; Ag = 57.73 per cent. It follows therefore that the substance C,HSo5 cannot be the &lactone of dihydroxyadipic acid. When a portion of the tetrahydro- furfurandicarboxylic acid melting a t 93-94' was dissolved in a little water and the solution allowed to evaporate over solid potassium hydr- oxide until dry, the product was found to melt at 57-62'. Further, on exposing some of the acid in the open air for 7 days, the melting point was lowered until it became 57-62'. There was not sufficient material for analysis. These results show that this tetrahydro- furfurandicarboxylic acid can be readily converted into its hydrate, C= 19.08; H = 1.88 j Ag = 57.46. A portion of the expense incurred in this investigation was defrayed by a grant awarded by the Government Grant Committee of the Royal Society, for which the author desires to express his thanks. The author's thanks are also due to Mr. F. H. Lees for his very care- f u l and assiduous assistance in the later stages of the work. THE OWENS COLLEGE, MANCHESTER ; AND ACKWORTH SCHOOL

ISSN:0368-1645    

DOI:10.1039/CT9007700103

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

DEAN : TEE ATOMIC WEIGHT OF NITROGEN. 117 XII.-Tlze Atonaic Weiyht of -Nitrogen. By GEORGE DEAN, B.A. CONSIDERING the large number of very definite aud stable compounds in which nitrogen occurs as a constituent, it might have been ex- pected that the atomic weight of nitrogen would be known with the greatest exactness. The readiness and accuracy with which nitrates may be converted into chlorides and wice vem&, the determination of the percentage of silver in silver nitrate by synthetical and by analy- tical methods, the ratio between ammonium chloride or bromide and the silver required for complete precipitation, and many other exact processes seem fully to warrant this supposition, and t o enable us to deduce directly the ratio of the atomic weight of nitrogen to those of both hydrogen and oxygen.A glance a t the summary of results given below, however, will show that much work has still t o be done before we know the atomic weight of nitrogen as accurately as we have every reason t o believe it can be determined with the resources now at our command. The experiments described in the following paper were undertaken with the view of deducing the constant from a combination of elements which had not hitherto been used for the purpose. Before entering upon the account of the method adopted here and the results obtained, it may be of interest to briefly consider the most important work done by previous investigators. Both for variety of method and the number of experiments, the researches of Stas take the foremost place. Making oxygen the standard of comparison, and giving t o it a value of 16, the different numbers obtained by him for nitrogen, with the respective methods employed, are as follows : (1) Comparison of ammonium chloride and metallic silver (3) Conversion of silver into silver nitrate.(Two series of experiments, the atomic weight having, in each series, two values, deduced respectively from the weight of silver nitrate before and after fusion). First series, silver nitrate before Fusion.. ................ > Y Y 9 9 9 after ,, .................. Second ,, ,? before , , 9 9 after ,, P? 7, ,¶ bromide ,, 9 , .................. .................. >9 9 9 (4) Comparison of ammonium chloride and silver ni tmte,. ( 5 ) Conversion of potassium chloride into potassium nitrate (6) ¶? sodium ?) sodium ,) VOL, LXXVII.14.043 14.048 14,044 14.029 14.054 14.042 14.027 14.044 14.046 K118 DEAN : THE ATOMIC WEIGIHT OF NITROGIEN. (7) Comparison of silver nitrate and potassium chloride : First series. ..................................................... 14.083 Second ,, ...................................................... 14-1 05 Third ,, ...................................................... 14.043 The general mean of these values, assigning equal importance to each, is 14.051, the lowest value obtained being 14.027, the highest 14-105. Next in order of importance t o the work of Stas is probably that of Penny (Phil. Trans., 1839, 129, I, 32) ; his various methods and the results respectively deduced from them may be briefly given thus : (1) Conversion of metallic silver into nitrate ...............(2) 9 ) silver nitrate into silver chloride.. ....... (3) ,, p Aassium nitrate into potassium chloride (4) 9 9 ,, chloride ,, nitrate.. (5) (6) (7) (8) 9 , ,, chlornte 99 99 9 , sodium 99 sodium ,, 9 , 9 9 chloride 9 , 9 , 9 9 9 , nitrate ,, chloride 13.996 14.011 14.037 14,039 14-003 14.031 14-025 14.02 1 The mean of these is 14.020, the lowest value beicg 13.996, the highest 14.039. Marignac treated the question less exhaustively ; his methods with their corresponding results were : (1) Comparison of metallic silver and ammonium chloride 13.961 1 , 7, silver nitrate ...... 13-977 (3) ?, silver nitrate and potassium chloride.. . 14.150 (2) the mean being 14.029. Thus the values for the constant, determined by three of the masters in this branch of research, are practically 14.02, 14.03, and 14.05, the separate experiments yielding results varying from 13.961 to 14.150.Other workers have used methods more or less similar with the following results. Pelouze ( C m p t . rend., 1845, 20, 1047) determined the weight of pure silver which, when dissolved in nitric acid, was sufficient for the complete precipitation of a weighed amount of pure ammonium chloride. The atomic weight of nitrogen calculated from his numbers is 13.975. Hardin (J. Amer. Chem. Soc., 1896, 18, 995) electrolysed small weighed amounts of silver nitrate, and weighed the silver deposited. His data lead to the value 14.042. Turner (Phil. Trans., 1833, 123, 11, 537) converted a weighedDEAN : THE ATOMIC WEIUHT OF NITROGEN. 119 amount of silver nitrate into silver chloride, and determined the mass of chloride produced.Hibbs (J. Amer. Chem. SOC., 1896, 18, 1044) heated known masses of potassium nitrate in a stream of hydrogen chloride, and weighed the amount of chloride obtained. Moreover, the same process was applied to the sodium compound, the results being 14.032 and 14.026 respectively. Thomsen (Zeit. physikccl. Chem., 1894, 13, 398) determined the ratio of the weights of hydrogen chloride and ammonia which combine with each other. He passed pure, dry hydrogen chloride into a weighed apparatus containing distilled water, and weighed again. Then pure ammonia was led in until it was present in slight excess, and the in- crease in weight observed, the excess of ammonia being finally deter- mined by titration with standard acid, His mean result, 2.13934, leads to the value 14.021 for nitrogen.Excluding the value deduced by Thomsen-to which little weight can be assigned as his experiments also lead to the conclusion that the ratio of H : 0 is 1 : 16 instead of 1 : 15.88 or 1 : 15.89 as estab- lished by the laborious researches of Rayleigh, Leduc, Morley, Scott, Noyes, and others-the mean is 14.034, if equal importance is given to the result of each separate series of experiments. So far the results considered have been those which are based upon purely chemical methods. In the various determinations of the density of nitrogen, we have, on the other hand, a series of values obtained by physical means.The work of the earlier experimenters, Biot and Arago, Thomson, &c., was carried on without the refinements of accuracy brought to the aid of later research, and may be passed over here. More exact estimations have been made by Dumas and Boussingault, Regnault, von Jolly, Leduc, and Rayleigh, but chiefly with residual atmospheric nitrogen, and therefore still containing argon. In consequence of the admixture of this substance with the nitrogen, these results also are of little value for our present purpose. The most recent numbers obtained for p w e nitrogen, both by Lord Rayleigh and M. Leduc, however, are almosb identical. Taking oxygen as the unit, Leduc, from his own experiments, gives to nitrogen a density of 0.87508, and from Rayleigh’s data, 0937507 (Compt.qqend., 1898, 126, 415). Lord Rayleigh refers his results to the density of air as unit, and obtains for nitrogen and oxygen the densities 0.9673’7 and 1.10535 respectively; hence the relative densities are 14.003 : 16 (Proc. Roy. SOC., 1897, 62, 209). Now the great similarity in behavioiir of oxygen and nitrogen, with regard to changes in temperature and pressure, renders it almost impossible that any deviations from Avogadro’s lam mould be able t o reconcile the two values of 14,034 as found by chemical methods and His experiments give the value 14.013. K 2120 DEAN : THE ATOMIC WEIGHT OF NITROGEN. 14.003 by physical methods. This view is supported by D. Berthelot’s recalculation of the atomic weight of nitrogen from the densities of nitrogen and oxygen, on the assumption that Avogadro’s law is strictly accurate at low pressures.After applying a correction for the differences in compressibility of the two gases, tlhe ratio is only raised to 14.007 : 16 (Compt. rend., 1898, 126, 954). It was therefore thought to be of the greatest importance to redetermine this constant by some new method involving as few atomic weights as possible, and only those which are known with the highest degree of accuracy. itfethod Employed. Some years ago, when discussing the probable cause of the differ- ences between Stas’ numbers deduced from the weights of fused and unfused silver nitrate respectively, Professor Dewar suggested the use of silver cyanide in order to obtain an independent value. By deter- mining the amount of silver in a known weight of cyanide, the equi- valent of cyanogen could be estimated; by subtracting from this the atomic weight of carbon, that of nitrogen is obtained.Many preliminary experiments were made before the final method of treatment was decided upon. Of course, the simplest plan, which at once suggested itself, was to heat a weighed amount of cyanide, and weigh the silver left. Unfortunately, the formation of para- cyanogen and a carbide of silver in the mass of metal, and the appreciable volatility of silver when heated for a fair length of time in the air, led to an utter lack of agreement among the results obtained. Attempts were made, on the other hand, with varying degrees of success, to dissolve weighed amounts of the cyanide in nitric acid alone, in nitric acid with some other oxidising agent (for example, potassium permanganate), and in nitric acid under pressure, and to estimate the weight of silver in solution.Ultimately this difficulty was overcome, and the method resolved itself into the follow- ing steps : I. Preparation of pure silver sulphate ; 11. 99 ,, hydrocyanic acid ; 111. 9 , ,, silver cyanide, free from sulphuric acid ; IV. Y, nitric acid, free from haloid acids ; V. Drying of the cyanide until its weight remained constant ; VI. Conversion of the weighed cyanide into some soluble silver salt ; VII. Estimation of the amount of silver in solution. These objects were obtained in the following manner. First, ordinary silver nitrate was dissolved in water and precipitated by means ofDEAN : THE ATOMIC WEIGHT OF NITROGEN.121 redistilled sulphuric acid. The fine crystals of silver sulphate were drained, recrystallised twice from a large volume of distilled water, and finally made up into a dilute solution. Next, a weak solution of hydrocyanic acid mas prepared by the following method. Potassium ferrocyanida was recrystallised in a fine state of division, and distilled with dilute sulphuric acid, in an apparatus so arranged that any liquid thrown up in the act of ebullition was reflected back into the flask. The distillate was finally redistilled over a little magnesium carbonate, which was used to prevent ‘‘ bumping ” chiefly, but also to combine with any traces of sulphuric acid which might be present. The silver sulphate solution was placed in a stoppered bottle, dilute hydrocyanic acid added, and the whole well shaken, to render the pre- cipitate flocculent.More acid was added, and the process repeated until all the silver was precipitated as cyanide ; the clear liquid was then poured off, and more sulphate solution added ,and precipitated in a similar manner. When a suitable quantity of cyanide had been obtained, it was repeatedly washed with cold, and finally with hot distilled water, and allowed to stand for some weeks, the water being occasionally renewed. Any traces of sulphate of silver enclosed in the flocculi would thus have the opportunity of diffusing out. The cyanide was finally dried, as described later. Nitric Acid-The “pure” acid of commerce, sp. gr. 1-42, was twice redistilled, the first time with a few drops of silver nitrate solution, precautions being taken to avoid spirtings being carried over into the distillate.The acid finally collected, on being tested in the Stas chamber, was absolutely free from either hydrochloric acid or silver. Potassium Bromide, used in determining the amount of silver in solu- tion.-For this I am indebted to the kindness of Dr. Scott, Superin- tendent of the Davy-Faraday Research Laboratory. It is part of the sample used by Dewar and Scott in their determination of the atomic weight of manganese (Proc. Roy. Soc., 1883,35,44), and was prepared from potassium carbonate, obtained by decomposing carefully recrystal- lised potassium bitartrate, and pure hydrobromic acid, obtained from the distillation of potassium bromide and sulphuric acid somewhat diluted.Drying of the Silver Cyanide. The carefully washed precipitate was placed in a clean porcelain basin and as much as possible of the water poured away. After heating for about 12 hours in a steam oven, the basin was placed over concentrated sulphuric acid in a vacuum desiccator, which was then exhausted. The salt was left drying in this manner for a week, the surface of the acid being renewed by occasional agitation. A portion was then transferred to two platinum boats, which were enclosed in thin122 DEAN: THE ATOMIC WEIGET OF NITROGEN. glass tubes, sliding the one over the other, and fitting fairly tightIg, to prevent moisture being absorbed from the air. The whole-case, boats, and cyanide-was then weighed. The actual numbers obtained throughout in one determination are given below.July llth, 1898. Boats +tubes + cyanide. 67,947 grams. The boats were afterwards placed in a wide glass tube, drawn out at one end, and connected there with a series of U tubes, Bc., con- taining calcium chloride, phosphoric oxide, solid caustic potash, &c. Over the other end fitted a slightly wider tube, also drawn out at one end, and connected through a drying tube with a water pump. By means of this arrangement, a slow, steady current of pure, dry air (freed from traces of carbon dioxide and sulphuretted hydrogen by passage through a series of potash bulbs) could be drawn over the cyanide. The tube containing the boats was kept a t a fairly high temperature by means of an annular heater containing boiling xylene (b.p. 135'). c The boats were heated in this way in dry air, constantly renewed,, for 17 hours, allowed to cool all night in the heater, transferred next day to the tubes, and weighed. July 13th. Boats + tubes +cyanide. 67-9466 grams. The cyanide had lost 1.1 milligrams in 17 hours. The boats were again placed in the tube and heated for 18 hours, allowed to cool as before, and weighed. July 15th. Boats + tubes +cyanide. 67.94665 grams. After 18 hours heating, the weight was thus practically unaltered.DEAN: THE ATOMIC WEIGHT OF NITROGEN. 123 Solution of the Silver Cyanide. This was effected in a glass bulb of about 300 C.C. capacity, pro- vided with a long neck. The end of the neck was turned out slightly, and had a small lip in order to make it easier to pour accurately.A small glass condenser was ground to fit into the neck of the bulb, the upper end of the condenser being again fitted with a set of three small bulbs, also ground in. By taking these precautions, all loss of liquid by spirting was effectually prevented. The bulb was disconnected from the condenser, set up vertically over a sheet of paper, and a funnel placed in the neck. To transfer the cyanide, the boats mere carefully lifted over the funnel and gently tapped. any granules remaining on the sides of the funnel being finally washed in by means of pure nitric acid. The boats and tubes mere then weighed. Boats + tubes ........................ 55,8347 grams. Weight of cyanide taken ......... 12.11195 ,, In all 60 C.C. of nitric acid were added, the bulb then attached to the condenser, and the contents kept gently simmering on a sand-bath until the solid had completely dissolved.This took place in about 40 hours, thorough conversion into nitrate being marked by the ‘‘ bumping ” of the liquid. It was found that fuming nitric acid did not dissolve the silver cyanide nearly as readily as the 68 per cent, acid, on account of the insoluble nitrate being precipitated upon it, and protecting it against further action. Determination of the Xilvw. For this, the bulbs and condenser were carefully rinsed into a large stoppered bottle by means of distilled water and the contents of the large bulb added. The latter was repeatedly washed by boiling a little water in it and allowing the condensed water to run down the sides, the different washings being added to the main portion of the liquid.Next the amount of potassium bromide necessary for the theoretical weight of silver present was calculated, and weighed out into a small beaker. I n the particular experiment the weights were those given below : July 20th. 6eaker .............................. ,, +bromide ............... Weight of potassium bromide taken.. . under consideration, 11.8087 grams. 2205716 ,, 10.7629 ,,124 DEAN : THE ATOMIC WEiGHT OF NITROGEN. I n order to protect the silver bromide, when precipitated, from the action of the light, the bottle containing the silver solution was wrapped in red paper. The weighed amount of potassium bromide in the beaker was dissolved ir, a little distilled water, and the solution transferred with the utmost care to the silver solution.Finally, the bottle was vigorously shaken a t intervals in order to procure a perfectly clear liquid above the precipitated silver bromide, and allowed to stand for a day. The next step was the estimation of the amount of silver or potassium bromide present in excess. Standard solutions of these substances were employed (1 gram of the former containing 0.001 17 gram of silver, and 1 gram of the latter being equivalent to 0.00094 gram of silver) and small quantities added from weighed stoppered burettes until the end point was determined, that is, until further addition produced no turbidity. The weight of solution added furnished the weight of silver or bromide needed, and this, with the weight of bromide originally added, gave the means of determining the exact weight of silver in the weight of silver cyanide taken.The titration was performed in a dark room, a double box similar t o that used by Stas being employed to hold the vessel and lamp. Yellow light was passed through the upper portion of the clear liquid in the bottle, and a few drops of the standard solution of silver or potassium bromide, as the case might be, were added to determine which was in excess. Then five or six drops of solution were run in at a time until it was known that a slight excess had again been added. This excess was carefully titrated by means of the other solution, added a drop or so at a time. I n the experiment cited above, the weights of the solutions used before complete precipitation was ensured were : July 23rd.Potassium bromide 1.175 grams = 0.00110 grams silver. Silver . . . . . . , . , . . . . . 0.30 ,, = 0*00035 19 Cwrections. Having now obtained all the experimental data, the various cor- rections for buoyancy and for discrepancies between the actual masses of the weights used and their face values had to be applied. The former were obtained by means of the following densities : Silver cyanide, 3.94 ; potassium bromide, 2.69 ; brass, 8.4 ; air, 0.0012 ; silver, 10.6 ; the latter, by careful comparison of the set of weights among them- selves and reduction to expression in terms of one of them. (The weight thus adopted as unit was the third gram weight,, which is rarely used, and hence suffers little loss from abrasion, &c.) TheDEAN : THE ATOMIC WEIGHT OF NITROGEN.125 balance used was by Bunge of Hamburg, and the weights, a fine set of platinised brass weights, by Sartorius. Silver cyanide as weighed a t first ............... Correction for buoyancy of cyanide + 0.00368 12.11195 grams. I? ?? weights - 0.00175 ?, weights ............... - 0.001 71 Total correction ........................ + 0.00023 ,) Corrected weight of cyanide ..................... 12.1 12 13 ,, -- Potassium bromide as weighed at first.. ....... 10.7629 grams. Correction for buoyancy of bromide + 0-004 8 ?S 9 ) weights - 0.00153 ¶ I weights ............... - 0*00182 Total correction ........................ + 0.00145 Corrected weight of bromide ..................... 10.76435 ,, CcdcuZation of Equivulent of Cpnogen .Having obtained the exact weight of cyanide taken, the amount of silver contained in the cyanide is calculated from the weight of potassium bromide used; by simple proportion, the weight of silver cyanide which would contain the atomic weight of silver is estimated. This is its molecular weight. On subtracting the atomic weight of silver, the equivalent weight of cyanogen remains. The atomic weights used were those found by Stas, namely, Ag= 107.93, 0 = 1 6 . I n addition, it was necessary to know the weight of the potassium bromide employed which would completely precipitate 100 parts by weight of silver ; this was found to be 110.313 parts. The experiments con- ducted in order t o ascertain this fact will be referred to later.Weight of potassium bromide = 10.76435 grams. 100 x 10,76435 Its equivalent of silver = 110.313 = 9*75800 grams. Equivalent in silver of the potassium bromide solution needed for complete precipitation ... = 0.00075 .. Total silver present ............... = 9.75875 ), Weight of silver cyanide = 12.11213 grams. ?? I9 containing 107.93 grams of silver = 12*112*3 107*93 = 133.958 grams. 9.75875 Equivalent of cyanogen = 133.958 - 107.93 = 26.028.126 DEAN : THE ATOMIC WEIGHT OF NITROGEN, Series of Experiments. In the following list are briefly given the leading data and the results of the different determinations. In experiment 6, the method of procedure was varied somewhat, the cyanide being converted in this case into 8zcZpAate instead of nitrate of silver.For this purpose, sulphuric acid, the (' pure for analysis " of commerce, was redistilled in a vacuum! the first runnings being rejected. The cyanide was heated for some hours with the acid, diluted to nearly twice its volume with water, gas being gradually evolved and silver sulphate deposited. More of the concentrated acid was added and the heating repeated in order to bring the sulphate into solution, but although the crystalline salt seemed to disappear completely, there was a slight brownish, flocculent residue, possibly pqracyanogen, still undissolved. The solution was ultimately transferred t o a large volume of redietilled water, heated in a water- bath in order to have the sulphate in solution before adding the potassium bromide, and titrated in the usual way.The slight in- soluble residue still remained on heating the diluted liquid, The value deduced from this experiment is almost identical with that obtained in the one preceding it, which was performed by means of nitric acid. Expt. Wt. of AgCN. 6'2671 grams 17.60585 ,I 17'1049 ,, 179210 ,, 12.11215 ,, 14.6672 ,, 85'67820 grams Equiv. of Ag. 5.0490 grams 14.18496 ,, 13.7801 ,, 14'43881 ,, 11'81727 ,, 9'75875 ,, 69.02889 grams Mol. wt. of AgCN. 133.969 133'956 133.979 133.960 133'958 133,959 133.962 Equiv. of cyanogen. 26.039 26-026 26.049 26 *030 26.028 26'029 26'032 The mean value deduced from these experiments for the equivalent of cyanogen, calculating from the total weight of cyanide used and that of the silver found in it, is thus 26,032. Before we can use this result in determining the atomic weight of nitrogen we must know that of carbon.F. W. Clarke, in his BecaE cdation of the Atomic Veights, gives, as the mean of all the important numbers determined by different experimenters, the value 12-01 1. Since then, however, Scott has shown that certain serious errors have hitherto been neglected, which render some of the experiments con- sidered in that work useless for the time being. The best resultsDEAN : THE ATOMIC WEIGHT OF NITROGEN. 127 which are available, namely, those deduced from the combustion of a known amount of carbon and weight of the carbon dioxide formed, have been recalculated by him, and give a mean value of 12.001 practically (Trans., 1897, 71, 557). Subtracting this, then, from the cyanogen equivalent, we obtain for nitrogen an atomic weight of 1 4 '0 3 1.The accuracy of this number is, of course, strictly dependent upon the value for the atomic weight of carbon, and can only be relied upon to the same extent. The equivalent of cyanogen, however, is quite an independent value, cyanogen in the above experiments having been directly compared with silver, and, as far as method a t least is con- cerned, its equivalent is of the same order of accuracy as those of chlorine, bromine, &c., and mill be equally available for nitrogen or carbon as soon as the other constituent is evaluated. Remccrks on the Titration. On titrating the excess of silver or bromide with the standard solution, the turbid cloud produced in the illuminated layer of liquid became less pronounced as this excess diminished.Moreover,'after the excess had been totally precipitated and more of the solution added, a slight turbidity was produced on standing for a few minutes, which interfered with the accurate determination of the end point. With practice, however, it was possible to distinguish, to a drop or two, the point at which the excess had disappeared, as there was a difference in the appearance of the two turbidities. I n order, however, to check the first determination, the addition of solution was continued in some cases until it was in excess, and the other solution added until the end point was again obtained. In one experiment, the numbers given for the equivalent by successive end point determinations made in this way were (1) 26,0329.(2) 26.0344. The experience derived from many titrations has led to the same conclusion as that of Stas, namely, that titration of excess of silver by means of the bromide solution is more reliable than the converse process, and in most cases I have taken the result of the correspond- ing end point. From the numbers here quoted, however, an idea may be obtained of the magnitude of the maximum error likely to arise from this uncertainty. In some of the earlier experiments, the titration was proceeded with on the same day as the potassium bromide was added. On repeating the addition of the standard solutions on the following day in order toDEAN: THE ATOMIC WEIGHT OF NITROGEN, verify the end point, it was found necessary to add an extra amount of silver before precipitation was again complete.On following days, however, the liquid was quite free from either salt. It would appear that when the silver bromide is thrown down, the flocks enclose small quantities of potassium bromide which diffuse into the bulk of the liquid in the course of a day or so. I n the later researches, provision was made for this, and the titration of the excess postponed for a day at least. Remarks on the Weighings. It was found that the weighings could be made quite easily to a tenth of a milligram provided that the final weighing was not made until half an hour after the tubes and weights had been placed on the pans of the balance. Consecutive weighings, even after an interval of 12 hours, remained then absolutely constant. That the half-hour interval needed was not on account of a certain constant amount of hygroscopic moisture absorbed from the air by the material, is shown by the fact that the weighings taken immediately were always greater than those taken later.Estimation of the Silver Vulue of the Potassizcm Bromide used in the I’its.ations. In order to calculate the weight of silver present in solution from the weight of potassium bromide added, the amount of the latter equivalent t o 100 parts of silver given by Stas, namely, 110.346, was at first made use of. As the results so obtained uniformly gave values for cyanogen which seemed abnormally high, 1 suspected that the bromide used in my research might contain small quantities of the sodium salt. A given weight of the bromide would thus be equivalent t o a greater weight of silver than the pure salt, and the application of a corresponding correction would lead to lower molecular weight for silver cyanide and consequently a lower equivalent for cyanogen.The uncer- tainty arising from this cause was removed by obtaining directly the silver val e of the bromide used. Varying quantities of carefully pre- pared silver were dissolved in nitric acid, purified in the manner described above, and titrated with the bromide in question in the usual way. I n experiment A, the silver used had been obtained by the reduction of a solution of silver and copper nitrates by means of ammonium sulphite, Stas’ directions concerning the method being scrupulously followed. Before the final weighing, the silver was heated in a covered porcelain crucible over a Bunsen burner. In experiment B, a portion of the last fraction of silver prepared by the same method, but obtained on heating the solution, was taken,FORMATION OF a- AND ,8-ACROSE FROM GLYCOLLIC ALDEHYDE. 129 heated to redness for some hours in a current of dry hydrogen (evolved by dropping water upon sodium), and allowed to cool, the gas still passing. This precaution was taken in order that all possible occluded oxygen might be removed from the silver, I n experiment C, the same sample of pure silver was used as in experiment B, but instead of being heated in hydrogen was simply heated in the flame of an alcohol burner in a covered crucible. The bromide used was heated in a current of dry air in a tube provided with a ground cap before being weighed, to insure its thorough freedom from moisture, Wt. of KBr Equivalent of Wt. of KBr per taken. 4. 100 of Ag. A. 9040336 grams 8.52439 grams 110.311 B. 8.63900 ?, 7.83213 ?? 110.316 c. 9.84450 ,, 8.92422 ,, 110,312 Mean ...... 110,313 The author has much pleasure in expressing his indebtedness to Professor Dewar for much kindly criticism and advice, and for the great interest he has taken throughout this investigation.

ISSN:0368-1645    

DOI:10.1039/CT9007700117

出版商:RSC    

年代:1900

数据来源: RSC

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FORMATION OF a- AND 6-ACROSE FROM GLYCOLLIC ALDEHYDE. 129 XII1.-Formation of a- and 6-Acrose from GZycoZZic A Zdehyde. By HENRY JACKSON, B.A., Fellow of Downing College, Cambridge. GLYCOLLIC aldehyde, first obtained in a dilute aqueous solution by Fischer and Landsteiner (Bey., 1892, 25, 2549), was shown by these authors to lose its power of reducing Fehling's solution in the cold after treatment with 1 per cent. aqueous caustic soda at 0" for 15 hours. If the condensation product, after acidification with acetic acid, was heated with phenylhydrazine acetate on the water-bath for 8 hours, a crude osazone separated out which, after purification with ether and crystallisation, first from hot water and finally from dry benzene, gave a pure osazone which melted at 166-168' and had a composition very similar to that required for tetrosazone.I n 1897, Fenton found (Trans., 71,375) that when glycollic aldehyde in the form of a syrup is heated at 100" under very diminished pres- sure, it undergoes condensation, and by fractional solution with absolute alcohol he obtained a sparingly soluble portion which, on treatment with phenylhydrazine acetate, gave a normal hexosazone.130 JACKSON : FORMATION OF a- AND P-ACROSE In a communication to the British Association this year, it wag shown by Fenton and the author that if a dilute aqueous solution of glycollic aldehyde, prepared from dihydroxymaleic acid ( Fenton, Trans., 1895, 67, 778) or glycol (Fenton and Jackson, Trans., 1899, 76, 2), is treated with dilute sohitions of sodium or calcium hydr- oxides at the ordinary temperature of the laboratory (about 15O), it quickly undergoes condensation, losing its power of reducing Fehling’s solution in the cold and of restoring tha colour to an alcoholic solu- tion of magenta, which had been decolorised by sulphur dioxide.After neutralising the product with acetic acid and warming on the water-bath for 3-4 hours with phenylhydrazine acetate, a beautiful, yellow osazone separated out on cooling, which, after crystallisation from boiling water,and afterwards from benzene and from ethyl acetate, melted sharply at 158O, and on analysis was found t o be a normal hexosazone. Its melting point and action towards solvents pointed to its identity with p-acrosazone which Fischer and Tafel obtained from the condensation product of ‘‘ glycerose ” (Bw., 1887, 20, 3384).Considering the readiness with which the condensation by alkalis took place at the ordinary temperature, it appeared to the author that it would be interesting to repeat the experiments conducted by Fischer and Landsteiner, and, with .Mr. Fenton’s .approval, this has been done. Action of Dilute Caustic Soda Solution ut Oofoq* 15 Hours. The details of the experiment were briefly as follows :-Pure glycollic aldehyde was diluted with distilled water until a solution containing 3 per cent. of the aldehyde was obtained, the strength being determined by Fehling’s solution, as the reducing power of tho pure aldehyde is known (Trans., 1899, 75, 579). To the solution, cooled to Oo, dilute caustic soda solution of known strength was added until the mixture contained 1 per cent.of the alkali. The combined solutions were then kept at 0’ for 15 hours, when i t was found t h a t the liquid, whioh was originally colourless, had become orange-yellow. It still had the power of reducing Fehling’s solution in the cold, although not so strongly as glycollic aldehyde, and also of restoring the colour to decolorised magenta solution. After neutralising the condensation product with acetic acid, phenyl- hydrazine acetate was added in excess, and the mixture allowed t o stand for 12 hours. The solution was then filtered and heated on the water-bath at 100’ for 4 hours; longer heating was not found to materially increase the yield, whilst the osazone was far more resinous. After cooling and standing, a bulky, dirty yellow osazone separated out, which, after removal by filtration and drying in the air, wasFROM ULYCOLLIC ALDEHYDE.131 rubbed with small quantities of dry benzene to remove the resinous matter, arid then warmed with 50 times its weight of dry benzene. As only about half was soluble, the solution was quickly filtered on the pump from the sparingly soluble portion. The benzene solution, on standing, deposited a flocculent mass of yellow needles, which were collected and examined. Part soluble in Benzene.-After being recrystallised from hot water and dried in the air, this fraction was crystallised twice from the least possible amount of boiling dry benzene. It was thus obtained as a mass of fine needles which melted sharply at 167", and on analysis gave the following numbers, proving it to be tetrosazone : 0.1230 gave 0.2893 CO, and 0,0672 H,O.C = 64% ; H= 6.07. 0.1452 ,, 0.3409 CO, ,, 0.0785 H20, C=64*03 ; H=6.01. 0.1710 ,, 27.5 C.C. nitrogen a t 19O and 758 mm. N= 18.50. C16H,,0,N, requires C = 64-43 ; H = 6-04 ; N = 18.9 per cent. These numbers agree closely with those obtained by Fischer aEd Landsteiner, and it would appear that tetrose is undoubtedly one of the condensation products of glycollic aldehyde. Part sparingly soluble in Benzene.-This portion was again boiled with small quantities of dry benzene t o remove all traces of tetr- osazone. The osazone was dried in the air, and finally at 100"; on analysis, it gave the following numbers : 0.1484 gave 0.3270 CO, and 0.0854 H,O.C =: 60.23 ; H = 6.37. 0*1120 ,, 15.06 C.C. nitrogen a t 14" and 749 mm. N=15*80. C,,Hz20,N4 requires C = 60.33 ; H = 6.15 ; N = 15.64 per cent. It was evident from these numbers that the substance was either a hexosazone or a mixture of hexosazones. It was therefore warmed with 10 times its weight of ethyl acetate, when only a portion dis- solved ; the insoluble part was removed by filtration, and on standing a mass of yellow needles crystallised out from the solution; this was recrystallised from hot water and finally from ethyl acetate. The osazone melted sharply at 158". On analysis, the following numbers were obtained : 0°1380 gave 0.3042 CO, and 0.0746 H,O. C = 60.12 ; H = 6-02 per cent. The osazone dissolves sparingly in ether or benzene, but easily in ethyl acetate, and is soluble in hot water.The analytical results, melting point, and action towards solvents point to its identity with P-acrosasone. The portion sparingly soluble in ethyl acetate was left as a greenish- yellow powder. This was washed with small quantities of hot absoIufe 0,1660 ,, 0.3655 CO, ,, 0.0893 H,O. C=59*91 ; H=5*98.132 JACKSON: FORMATION OF a- AND P-ACROSE alcohol, and then crystallised from 95 per cent. alcohol. The osazone which separated out was next crystallised from 98 per cent, alcohol, and finally from hot absolute alcohol, in which i t was sparingly soluble. It was thus obtained aR a mass of yellowish needles, which were dried in the air and melted at 208-2109 On analysis, it was found to be a normal hexosazone : 0.1120 gave 0.2814 CO,.The melting point and sparing solubility towards solvents would point to the substance being a-acrosazone, obtained by Fischer and Passmore from '' formose " (Ber., 1889, 22, 359), and by Fischer and Tafel from the condensation product of '' glycerose " (Rev., 1887, 20, 3384). It would therefore seem that the condensation of glycollic aldehyde by dilute soda at Oo, if continued for a short time, results i n the formation of tetrose and of a- and p-acrose. The power which the product has of reducing Fehling's solution in the cold is probably due to tetrose, as i t has been shown that the dilute aqueous solution of tetrose obtained by the oxidation of erythritol is able to effect the reduction in the cold (Fenton and Jackson, Trans., 1899, 75, l ) , whereas the two hexoses only bring this about on warming.C = 60.42 per cent. Action of Dilute Caustic Soda Solution at 0" fop* 2 Days. In the next experiment, the condensation was allowed to go on for 2 days; the solution was then found to reduce Fehling's solution in the cold, but only to a F-ery slight extent. It was neutralised with acetic acid, heated with phenylhydrazine acetate a8 before and the crude osazone rubbed with dry benzene. On heating with a large quantity of benzene, only a very small portion dissolved, the major portion being very sparingly soluble in this solvent. From t h e benzene solution, a small quantity of a bright yellow, crystalline osazone was obtained which, after drying, melted at 157O, and gave on analysis the following numbers, indicating that it was a mixture of tetrosazone with a hexosazone : 0.1635 gave 0.3725 GO, and 0.09 H,O.C = 62.12 ; H = 6.11 per cent. By fractionation with dry ether, i t was separated into two portions, tetrosazone being readily soluble whilst pure p-acrosazone is only very sparingly soluble in this solvent. The portion soluble in ether melted at 166q and on analysis gave numbers corresponding t o those required for tetrosazone : 0.0930 gave 0.2175 CO,. C=63.86 per cent.FROM GLYCOLLIC ALDEHYDE. 133 whilst the sparingly soluble portion melted at 157' and on analysis gave numbers corresponding to those required for a hexosazone. 0.1103 gave 0.2233 CO,. The major portion of the condensation product, namely, that spar- ingly soluble in benzene, mas found on analysis to be a hexosazone, and was separated in the manner previously described into p-acrosazone melting at 1 5 8 O , and a-acrosazone melting at 208'. C = 60.7 per cent.Action of Dilute Caustic Soda Xolution at 0' for 6 Days. I n the final experiments, the condensation was allowed to proceed until the solution did not reduce Fehling's solution after standing for half an hour in the cold. This was found to be case after the dilute aqueous solutions of glycollic aldehyde and caustic soda (1 per cent.) had remained at Oo for 6 days, The solution was neutralised with acetic acid and warmed with phenylhydrazine acetate as before. On boiling with benzene, only a small quantity dissolved, and this crystallised out as a mass of yellow needles which melted at 1 5 8 O , and on analysis was found to consist of P-acrosazone mixed with a trace of tetrosazone. 0.1185 gave 0,2614 CO,. The major portion was, as before, separated into a- and p-acros- azones. It would therefore seem that the tetrose formed by the con- densation of glycollic: aldehyde is unstable in the presence of dilute alkalis, and this view is emphasised by the fact that in the condensa- tion at the ordinary temperature no tetrose could be found. C=6Oo60 per cent. Gclycollic aldehyde is the last member of the series of aldehydes from which synthetical hexoses can be obtained ; the formation of a- and p-acrose by its condensation is of much interest, as Fischer and his pupils have previously shown that the same sugars are formed by the condensation of formaldehyde and of glycerose. UNIVERSITY CHEMICAL LABORATOEY, CAMBRIDGE. VOL. LXXVXI

ISSN:0368-1645    

DOI:10.1039/CT9007700129

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年代:1900

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134 CHATTAWAY AND ORTON : XIV.-Substituted Nitrogen Chlorides and their Relation to the Substitution o f Halogen i n Anilides and Anilines. Part 11. The Trichlorophen yl Acyl Nitrogen Chlorides. By F. D. CHATTAWAY and K. J. P. ORTON. IT has recently been shown by the authors (Trans., 1899, 75, 1046 ; Ber., 1899, 82, 3573)" that substitution of chlorine and bromine in formaailide, acetanilide, and benzanilide is not a direct process, but that nitrogen chlorides and nitrogen bromides are first formed and subsequently undergo isomeric change, Thus, 2 : 4 : 6-tribromo- acetanilide, the ultimate product of the bromination of acetanilide, is the result of the following series of changes : C,H,*NH* COdCH3 - C,H5*NBr*CO*CH, -z C6H,Br *NH* CO*CH, - C,H,Br *NBr*CO*CH, 3 C,HaBr,*NH* CO*CH, 3 C6H3Br2*NBr*CO*CH3 3 C,H,Br,*NH* CO*CH,.The tribromophenyl acyl nitrogen bromides are formed with great ease from the corresponding tribromoanilides, and we find that the same is the case mith the nitrogen chlorides, The present paper contains an account of the latter compounds and of p-chlorophenyl benzoyl nitrogen chloride, which previously we were unable to obtain pure. These complete the series of nitrogen chlorides directly derivable from acetanilide. The trichlorophenyl nitrogen chlorides show in most particulars the characteristic properties of the nitrogen halogen linking. They are well crystallised solids of low melting point, and dissolve readily in chloroform, but only sparingly in light petroleum, from which they can best be crystallised.They are, however, more stable than the corresponding mono- and di-chloro-derivatives, and the halogen can no longer be transferred to the ring, as this transference apparently occurs only when a para- or ortho-position relatively to the nitrogen is unoccupied. When these compounds are heated, isomeric change does not take place, but a t a somewhat high temperature decomposi- tion ensues and a tarry mass is formed. * Since the publication of these papers, we find that we have overlooked a paper by Slosson (Ber., 1895, 28, 3265), in which he has repeated Bender's work and also prepared the nitrogen chlorides of form- and benz-anilide and the nitrogen bromides of form- and acet-anilide by a method similar in principle to ours. He has, how- ever, only obtained one compound, phenyl formyl nitrogen chloride, CGH,-NCl'CHO, in a pure state.We extremely regret omitting to refer to this work in what we thought was a complete list of papers on the subject.TRICHLOROPHENYL ACYL NITROGEN CRLORIDES. 135 The ease with which the hydrogen attached to nitrogen is replaced by chlorine or bromine is in no way affected by the accumulation of halogen in the phengl residue, and the conversion of 2 : 4 : 6-trichloro- acetanilide, for example, into 2 : 4 : 6-trichlorophenyl acetgl nitrogen chloride takes place as readily as the corresponding replacement of the hydrogen attached to nitrogen in acetanilide itself. As a further proof that formation of a nitrogen chloride or brom- ide in every case precedes substitution of halogen in the ring, it is interesting to note that the degree of ease with which the trans- formation of any substituted nitrogen bromide or chloride is effected corresponds with the ease or difficulty with which this transformation prcduct is directly formed.As is well known, substitution by chlorine in anilides and anilines is never so easy as that by bromine" and our experiments shorn that the bromides are always transformed with much greater readiness than the corresponding chlorides. For ex; ample, the transformation of 2 : 4-dichlorophenyl acetyl nitrogen chloride can only be effected by heating under pressure in a sealed tube, whilst that of 2 : 4-dibromophenyl acetyl nitrogen bromide takes place easily when the compound is heated on a water-bath. On warming a substituted nitrogen chloride with any dilute acid on which hypochlorous acid has no action, a certain amount of hydrolysis always takes place, resulting in the regeneration of the anilide, libera- tion of chlorine, and formation of chloric acid.R*NCl*COR + H,O = R*NH* COR' + HOCI. 15HOCI = lOHCl + 5HC10, = 6C1, -I- 3HC10, i- 6H,O. This hydrolysis is much more marked with all the nitrogen bromides. It is also very noticeable in the case of the trichlorophenyl acyl nitrogen chlorides, but isomeric change takes place in most other nitrogen chlorides too readily to allow of this action proceeding to any large extent. The fact that the halogen is directly attached to nitrogen in both the substituted nitrogen chlorides and bromides is shown by the exact correspondence of all the reactions which these compounds undergo with those which nitrogen iodide exhibits under similar con- ditions, as in the latter halogen can only be attached to nitrogen.The reactions of nitrogen iodide are, in fact, typical of the linking between nitrogen and halogens. * As an illustration we may point ont that 2 : 4 : 6-trichloroscetanilide cannot be obtained under ordinary conditions by the direct chlorination of acetanilido, whilst 2 : 4 : 6-tribromoacetanilide is the chief product when an acetic acid solution of acetanilide is heated with an excess of bromine. L 2136 TRICHLOROPHENYL ACYI, NITROGEN CITT~ORIDES. 2 : 4 : 6-FrichZorophet8yZ PormyZ Nitrogen Chlovide, C,H,CI,*NCl*CHO. This compound is easily prep ared by adding a slight excess of 8, solution of bleaching powder to 2 : 4 : 6-trichloroformanilide dissolved i n warm acetic acid, and separates as an oil which quickly solidifies.It is readily soluble in chloroform or light petroleum (b. p. 8O-l0O0), and crystallises from the latter in clusters of brilliant, white prisms with domed ends; it melts a t 7 8 O , and has all the characteristic properties of this group of compounds. 0.3227 liberated I = 24.92 C.C. N/10 iodine. Cl, as :NCl, = 13-68. C,H,ONCI, requires C1, as :NCI, = 13.69 per eent. 2 : 4 : 6-T~*ichZorophenyZ AcetyZ Nitrogen ChZoride, C,H,CI,*NCl*CO*CH,. This compound is prepared from trichloroacetanilide exactly as the last-mentioned substance, It forms small, white, glistening, prismatic crystals resembling cubes in appearance, and melts at 749 0.1982 gave 0.4146 AgC1.C1= 51.72. C,H,ONCI, requires C1= 51 -94 per cent. It is a comparatively stable substance, and when heated in a capillary tube does not show any sign of decomposition up to 190°. When heated, however, for many hours at 140' in a sealed tube, decomposition takes place, and acetyl chloride, 2 : 4 : 6-trichloroaniline, and 2 : 4 : 6-trichloroacetanilide can be recognised among the products. 2 : 4 : 6- Z'l*ichZorophenyZ Benxoyl Nitrogen Chlwide, CGH,CI,*NCl*CO*CGH,. This substance is prepared from trichlorobenzanilide by the method described above. It crystallises singularly well in short, thick, Iustrous prisms terminated by pyramids, and melts at 89'. As in the pre- ceding cases, a nearly theoretical yield -of this chloride is obtained.0,3062 liberated I= 18.3 C.C. N/10 iodine, C1, as :N*Cl, = 10.59, C1,H70NCI, requires C1, as :NCI, = 10.58 per cent. When warmed with alcohol, this nitrogen chloride behaves like all the others (compare Zoc. cit.), and passes quantitatively back into 2 : 4 : 6-trichlorobenzanilide, ethyl hypochlorite which decomposes into aldehyde and hydrochloric acid being also formed. p- Chloropheny 1 Benxoyl Nitrogen Ch Zoride, CBH,CI* NC1. CO*C,H,, The preparation of this compound is rendered difficult by the sparing solubility of p-chlorobenzanilide, and at first (Zoc. cit,) we wereSODEAU : THE DECOMPOSITION OF CHLORATES. 137 not able to obtain it except mixed with 2 : 4-dichlorophenyl nitrogen chloride. It can, however, be prepared by using a hot alcoholic solution of the anilide, and allowing this to run slowly into a large excess of a solution of potassium khypochlorite containing potassium bicarbonate well cooled by a freezing mixture. Under these conditions, the nitrogen chloride suffers no transformation or decomposition, provided an excess of hypochlorous acid is always present, and the temperature not allowed to rise above Oo until the product is filtered off from the solution containing the alcohol. p-Chlorophenyl benzoyl nitrogen chloride forms glistening, short prisms with domed ends, and melts a t 79.59 0.3574 liberated I = 26.65 C.C. N/10 iodine. On allowing a solution in glacial acetic acid to stand for some time well formed crystals of 2 : 4-dichlorobenzanilide slowly separate. This is often a very convenient method of effecting the transformation of nitrogen chlorides into the isomeric chloroanilides, C1, as :NCl, = 13-24. C,,H,ONCl, requires C1, as :NCl, = 13-34 per cent. CHEMICAL LABORATORY, ST. BARTIIOLOMEW’PI HOSPITAL, E. C.

ISSN:0368-1645    

DOI:10.1039/CT9007700134

出版商:RSC    

年代:1900

数据来源: RSC

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X SODEAU : THE DECOMPOSITION OF CHLORATES. 137 V.-The Decomposition of Chlorates, with Special Reference to the Evolution of Chlorine and Oxygen. Part I. By WILLIAM H. SODEAU, B.Sc. THE ultimate object of this investigation is to ascertain the mechanism of the changes which take place when various chlorates are heated. These changes yield (in general) perchlorate, chloride, oxide, oxygen, and chlorine, but the relative proportions are known to vary very greatly with the nature of the base and with the mode of decom- posit ion. The present paper contains an account of experiments with barium chlorate and potassium chlorate, but other chlorates are being inves- tigated, as also the mode of action of certain substances which facilitate decomposition. Throughout the paper, experiments are numbered in the order in whioh they were performed.138 SODEAU : DECOMPOSITION OF CHLORATES, WITH SPECIAL( EXPERIMENTAL.I. Evolution of Chlorine f+om Barium Chloru~s. " Pure" barium chlorate of commerce was found to be neutral and free from strontium and calcium, but contained traces of dust and of chloride ; after separating barium with sulphuric acid, the filtrate left only a trace of residue on evaporation. The salt was purified by careful recrystallisation, drained on a perforated porcelain plate (to avoid fibres of paper), and dried a t 135' after powdering. Barium chlorate, unlike the potassium salt, has but little tendency to creep or spirt when decomposed ; some care is necessary in order to ensure its regular decomposition, as a rise of temperature may render the action violent, the mass becoming red hot.The influence of variations of temperature upon the rate of decomposition of the salt at atmospheric3 pressure has been investigated by Potilitzin (J, Russ. Chem. Soc., 1887, [l], 339; Ber., 1887, 20, Ref. 769). Mode qj Decomposition at va&m Pressures.-A weighed quantity of the substance, usually 1 gram, was placed either in a soda-glass tube of 15 mm. bore closed at one end, or else in a platinum crucible con- tained in a closely fitting tube of about 28 mm. bore. The tube was then sealed on to a narrow one bent twice a t right angles and ground into an absorption tube. When practicable, the gas was thus passed through pure potassium iodide solution (to which traces of iodine had been added until starch gave a faint coloration), and the liberated iodine was titrated with thiosulphate." In the later experiments at 1 mm.pressure, the chlorine was retained by potassium iodide dis- solved in glycerol and distributed over glass beads. It will be shown that the amount of free chlorine must be found by examination of the residue. Two decomposition tubes and a thermometer were usually clamped side by side in a bath of melted pewter, one tube being at atmospherio pressure and the other connected to a Geissler mercury pump having a bulb of 630 C.C. capacity, the upper neck of this being calibrated, in order that the pump might be used as a McLeod gauge; the mercury manometer was only relied on when the pressure amounted t o several mm. The evolved oxygen was always roughly measured by displace- ment of water in order t o observe the progress of the decomposition.Before raising the temperature to the decomposition point, the last traces of water were removed by heating the chlorate to about 300' for some time, the tube was then twice exhausted, dry air free from carbon dioxide being admitted. It was not found practicable to * The potassinm iodide did not become alkaline ; there was thus uo evidence of the formation of ozone or of oxides of chlorine.REFERENCE TO THE EVOLUTION OF CHLORINE AND OXYGEN. 139 employ a constant temperature, for in order to avoid violent action at the commencement and yet complete the decomposition in the course of a few hours, it was necessary to gradually raise the temperature of the bath through 70" or more.The decompositions under reduced pres- sure took place, in general, a t lower temperatures than those at atmospheric pressure, as equality in temperature would have necessi- tated a great difference in the duration of the experiment, owing to the marked manner in which reduotion of pressure facilitates the decomposition, as shown in section 111. Absorption of small amounts of Chlorine by Heated Gkasa.-This wag discovered by comparing the results of a few decompositions at 10-15 mm. with those at atmospheric pressure. Each decomposition lasted about two hours, and afterwards the residue and the contents of the absorption tube were titrated with hydrochloric acid and thiosulphate respectively, The original substance was perfectly neutral, and the standard solutions had been compared with each other by means of iodide and iodate of potassium. Whether the substance was in a platinum crucible or placed directly in the tube, the amount of oxide in the residue, that is, its alkalinity, was but little influenced by the pressure, hence about the same amount of chlorine is evolved a t 10-15 mm.and a t atmospheric pressure. A t 10-15 mm., the amount of chlorine reaching the potassium iodide was rather less than that lost by the residue, but a t atmospheric pressure the contents of the absorption tube indicated no free chlorine, although sensitive to 1 drop N/1000 iodine; on the other hand, the residue neutralised, for example, 6 C.C. of N/lOOO acid. It is thus evident that the chlorine had been absorbed by the heated glass.This absorp- tion is lessened by reduction of pressure, or by passing a current of air, free from moisture and carbon dioxide, through the tube; treat- ment of the glass with steam is not an effective remedy. Examination of the Residues. -Some experiments were conducted in order t o ascertain the best method for titrating the oxide in the residue, this appearing to be the only reliable measure of the chlorine evolved. Phenolphthalein in the cold was found to be the most suitable indicator, as the large amount of barium chloride prevented the utilisation of the reaction between a slight excess of acid and a mixture of iodate (the iodine) and iodide of potassium to be titrated. As the total alkalinity is extremely small, it is important to avoid un- necessary dilution and to carefully guard against the presence of carbon dioxide.All the water used was boiled in a vacuum, and after this treatment 10 C.C. gave a pink coloration with phenolphthalein and 0.1 c,c. of N/lOOO baryta; the burettes were provided with guard tubes containing soda lime. Decinormal hydrochloric acid was diluted to N/500 as required for use, the dilute baryta being titrated140 SODEAU : DECOMPOSITION OF CHLORATES, WITH SPECIAL against this in the cold and then boiled with excess in order to ascer- tain the slight correction for carbonate present. In an estimation, the residue was dissolved in a slight excess of N/500 acid, boiled, quickly cooled in a desiccator containing soda-lime, and the excess of acid titrated with baryta; more acid was then added and Bhe process repeated, in order to ensure the complete decomposition of any car- bonate formed.This method was carefully tested and found to work well ; owing to the dilution, there was no loss of acid on boiling nor were the titrations affected by addition of barium chloride or of neutralised barium peroxide. To ascertain whether the presence of a trace of moisture during decomposition would introduce any considerable error, about 5 grams of finely powdered neutral barium chloride were introduced into a glass tube, a few drops of distilled water added, and the neck drawn out ; this tube was placed in the bath during a slow decomposition (expt. 35) and the barium chloride heated in water vapour mixed with air for about 4 hours a t 360-400° and then for 2 hours a t 400-480° The alkalinity corresponded to the loss of only 0.035 per cent.of the chlorine present, so that the precautions adopted to remove moisture appear to have been more thorough than was really necessary, the effect being small in comparison with the amount producing it. Portions of several residues were examined for barium peroxide by adding 1 C.C. of N/lOOO permanganate to the solid, then a sufficiency of iV/lOO hydrochloric acid, and some potassium iodide. On titrating the liquid with thiosulphate, the volume required was usually rather less than in blank experiments, but the difference was too small to afford satisfactory evidence of the presence of barium peroxide ; the proportion in the final residue must therefore be exceedingly small ; this may, perhaps, be accounted for by the high temperature a t the end of the decomposition.Decomposition of the Chlonxte (see Table I).-Experiments made simultaneously in the same bath have been distinguished from each other by the letters a, b, and c. Those ‘< in contact with platinum ” took place in narrow platinum crucibles, each enclosed in a glass tube and covered with an overlapping split cone of platinum foil, the object of the cover being to prevent surface cooling and to retain any splashes; each crucible was used a t atmospheric and reduced pressures alternately, in order to eliminate any possible differenoe between the pair. In 31a, some pieaes of glass tube were placed in the crucible, but neither in this experiment nor in the decompositions in glass tubes was there any indication of action between the chlorate and glass.It was necessary that the decompositions should last some hours when the pressure was t o he kept at 1-2 mm. by means of theREFERENCE TO THE EVOLUTION OF CHLORINE AND OXYGEN. 141 mercury pump. At this pressure, the substance decomposed SO much more readily that the temperature was at no stage raised to the fusing point of the mixture then present; a t higher pressures, the mass always fused. Where the duration is given as 0.5 minute, the decomposition was of a violent character, the mass becoming red hot. I n expt. 47, the substance was dropped little by little into the already heated crucible (without the cone) ; the temperature would not rise SO high as in the experiments just referred to, so this comes between the two other classes of experiments a t atmospheric pressure.I n the rapid decompositions, the amount of chlorine reaching the potassium iodide was comparable with that lost by the residue. This ssries of experiments indicates that the proportion of free chlorine increases with the temperature, but is probably not affected by variations of pressure, as some allowance has to be made for the accompanying change of temperature (see theoretical part). Decomposition of cc Mixture of B a h m Chloride and ChJoyate.- El, SchuIze (J. p ~ . Chem., 1880, [ ii], 21, 407) found that barium TABLE 1.-Barium c?Jorate. - NO. 29c 31b 46 47 - 33 34a 36a 29a 32a - 29b 34b 35b 45 31a 44b - 44a 42 43 - In contact with Glass Platinum 2 ) 9 ) Pla tinnm 9 , Y9 11 Glass Platinum 9 ) 9 ) 9 9 Pt.and glass Glass Slass and BaCl Pt. and BaCl, 9s Pressure. I atmosphere 9 9 > 9 9 ) 1-2 mm. 2 mm. 1 mm. 10-15 mm. 10-15 mm. 1 atmosphere 9 9 9 9 9 9 9 9 )) 1 atmosphere 9 . 9 9 Duration :minutes). 0.5 0.5 0.5 * 200 230 270 140 345 140 250 340 50 90 120 120 300 180 AT/ 10 0 0 HCl C.C. jer gram 48 73 41.3 49'2 32'3 4'0 4 '9 4 '2 5.0 4.7 __ 5.5 6.1 7'4 5-0 7 -3 6 *O c1 evolved (total = 100). 0.74 0 *63 0.75 0-50 0.061 0.074 0,064 0.076 0'073 0'082 0'093 0.112 0.076 0.111 0.091 0,085 0.097 0'073 - Mols. chloride Mols. oxide. 134 158 132 199 1640 1340 1560 1310 1400 - 1190 1080 890 1310 902 1090 1170 1030 1370 * Rapid decomposition in small portions,142 SODEAU : DECOMPOSITION OF CHLORATES, WlTH SPECIAL chloride remained perfectly neutral when heated to redness in dry oxygen, but supposed it to be partly converted into oxide by ‘‘ nascent oxygen ” when heated with potassium chlorate ; the latter conclusion is traversed at the end of section 111.The employment of barium chlorate avoids the possibility of double decomposition. Some recrystallised barium chloride was roughly dried, finely POW- dered, and then dried a t 155-160°, still remaining neutral. Mixtures having the composition Ba(C10J2 + 2BaC12 were decomposed at at- mospheric pressure in the same manner as the chlorate alone. It will be seen from Table I (p. 141) that the amounts of chlorine (or oxide) obtained from such mixtures agree with those obtained without added chloride, although the average amount of chloride present was then only one-fifth.It is thus evident that the added barium chloride was not attacked by the decomposing fused chlorate or by any of the products, 11. Decomposition Products Q Potassium Chlomte. Several chemists have shown that pure potassium chlorate yields no free chlorine when decomposed in a platinum vessel under atmo- spheric pressure. On the other hand, Williams has stated (Proc., 1889, 5, 26) that the theoretical amount of oxygen was not obtained by heating the chlorate in a vacuum, that a gas, presumably chlorine, was given off which attacked mercury, and that the residue, there- fore, probably contained peroxide. The potassium chlorate used for the present work was obtained by repeated recrystallisation of the ‘( pure ” salt of commerce ; special precautions were taken to avoid dust, &c., and the substance was finally dried at 1 1 5 O after powdering, All the experiments with the substance in contact with glass were made before barium chlorate had been studied.Preliminary experiments indicated the absence of any considerable evolution of chlorine even when the pressure was reduced to a small fraction of a millimetre. Decomposition. w$th Chlorate in contact with Glass.-Portions weigh- ing from 1 t o 1.5 grams were decomposed in tubes of soda glass, Bohemian (combustion) glass, and Jena glass ; the arrangement re- sembled that used for barium chlorate, but the tubes were heated either by radiation from an empty crucible or directly by means of a Bunsen burner provided with a chimney.The decompositions took place one at a time, and the results me given in Table I1 (p. 144). I n all these experiments, the amounts of free chlorine were very small. Before the decomposition of barium chlorate had been investigated, i t was thought that the differences in experiments 19-22 indicated an evolution of chlorine under reduced pressure ;REFERENCE TO THE EVOLUTION OF CHLORINE AND OXYGEN. 143 they are now regarded as showing that, at atmospheric pressure, the heated glass absorbs about 90 per cent. of the chlorine liberated by the action of the glass. The reabsorption of chlorine would (cceteih paribus) vary with the time of contact multiplied by the pressure (concentration) of the gas; this factor is given in the fifth column of Table 11.The amount of chlorine evolved seems to vary with the nature of t'he glass and with the mode of heating ; the largest amount is obtained with Jena glass, its highly silicated nature probably causing a greater expulsion of chlorine and less reabsorption. It will be noticed that the heat of a flame seems to give rise to more action on the glass than the more evenly distributed radiation from a crucible ; in either case, the greater part of the chlorine was evolved towards the end of the de- composition, when the temperature was sufficient t o soften soda It has been repeatedly shown that potassium chlorate yields no free chlorine when decomposed a t atmospheric pressure, yet in this series the largest amount was obtained in experiment 14; i t is thus clear that the experiments of this series lead to fallacious results as regards the evolution of chlorine in the decomposition of the chlorate. Decomposition in Platinum.-Except as indicated, the apparatus was identical with that used for barium chlorate.I n the first pair of decompositions, the substance was decompcsed in two narrow platinum crucibles each enclosed in a tube of Jena glass, one being kept a t 10-15 mm. and the other a t atmospheric pressure. The residues in the crucibles were neutral t o phenolphthalein, but in each case some of the substance had reached the glass; this will account for the gas liberating a trace of iodine from the potassium iodide solution, On account of the tendency for potassium chlorate to creep and spirt, this series was not completed until after barium chlorate had been investigated and the best conditions ascertained.I n the final two pairs of decompositions, 40 and 41, each crucible contained 1 gram of potassium chlorate, and was covered with a piece of platinum foil bent round so as to form an inverted cone. The bath was kept a t just over 400' for half an hour to drive off the last traces of moisture, and the tubes were then twice exhausted to 4 mm., dry air being admitted. The residues gave no pink colour with phenol- phthalein even after boiling and cooling. A similar volume of water gave a very distinct pink with phenolphthalein and 0.1 C.C. of N/500 sodium carbonate, corresponding to 0.007 milligram of chlorine or 0.002 per 100 parts present. If, therefore, chlorine is evolved either at atmospheric pressure or at 1 mm., the amount cannot exceed this proportion.Determinations of free chlorine are evidently fallacious when the substance comes in contact with glass, glass.144 SODEAU : DECOMPOSITION OF CHLOHATES, WITH SPECIAL o. In contaci with -1- 13 23 15 18 16 22 19 20 21 l4 Jena glass Sodiklass Bohemian Y J 9 ) 9 ) Y ) Y 9 Y Y TABLE 11.-Potussium chlorute. Pressure. 10-15 mm. 1 atmospherl Y ) Y ) J9 9 ) Y 9 10-15 mm. 9 ) J J 1-2 mm. 1 mm. atmosphere $ 9 Duration [minutes). 120 35 50 10 25 12 100 100 150 150 240 330 240 330 Duration x pressure. 1.9 35 50 10 25 12 100 1.6 2.4 2 '4 0.5 0'4 240 330 - Mode of heating. Flame Cruiible Flame Crucible Flame Crucible $ 9 Y S 9 ) Melted pewter t A7/1000 c. c. per gram. Na2S203 1.4 6 '0 0-5 0.6 0'12 0-4 0.15 1'6 1'2 1 '3 c1 obtained per 100 parts prssent.0-017 0'074 0-006 0.007 0'0014 0.0047 0'0018 0.019 0.015 0'016 Much less than 0*002 liberated When either Bohemian combustion or soda glass was used, the first half of the gas contained only an infinitesimal amount of chlorine. 111. Experiments connected wit?& the Rate of Decomposition. The mode of working was similar t o that described on p. 138, potassium nitrate being occasionally substituted for metal in the bath on account of its transparency. The evolved oxygen was measured by displacement of water, or by collection over water in a graduated tube; in most experiments, the loss of weight was also determined. Potassium Cldorate under Reduced Presswe.-Veley (Phil. Tpans., 1888, Pt. I. 282) hag Shown that theearly stages of the decomposition are not influenced by reduction of the pressure t o 20 mm., and the experiments described in section I1 appeared to indicate that variations of pressure had no influence upon the rate at any stage of the decomposition.This was more exactly proved by decomposing equal weights in a pair of similar bulbs, and, although one was at 1 mm. and the other at atmospheric pressure, the volumes of oxygen evolved from either agreed as well as oould be expected during the whole of the six hours required for complete decomposition. This would seem to indicate that the formation OF perchlorate is not greatly affected by variation of pressure, as otherwise a marked difference would be expected in the latter part of the decomposition.REFERENCE TO THE EVOLUTION OF CHLORINE AND OXYGEN.145 At 1 atm. I Barizcm Chlorute under Reduced Pressure.-In this case, the previous experiments (section I) had indicated a very considerable facilitation in the evolution of oxygen, resulting from reduction of pressure. This has been confirmed by decomposing equal weights in paired bulbs. The temperature was kept fairly uniform during the first part of the decomposition, but was afterwards raised ; readings were taken every five minutes, The general character of the results is indicated in the table, 10-18 nm. At 1 atm. 6-2 13.6 22.9 31 -7 49 '1 67 -5 1 mm. 22 -2 41.5 55-7 59'2 60 -5 85 5 Minutes. 30. 1 40. 50. 60. 65. 70. -~ ------ Ba(C10,), ...... . ........ 9'0 25.4 35.6 45.9 50.7 51.6 Ba(C10a),+2BaCI, .._ 4.9 6.6 10.7 13.2 26'2 50'0 Time.85. 1 100. 110. 120. 56'6 73.8 95'9 100 52.5 70.5 96'7 100 --- 0 evolved (total = 100). 1 -6 4.7 10.1 20 *2 39 '9 43'7 45 '9 24 7 37-7 41'9 45'6 49 '1 52.6 70.3 The temperature of the bath was progressively raised ; during the first part of the decomposition, the mixture did not reach a, given146 SODEAU : DECOMPOSITION OF CHLORATES, WITH SPECIAL stage until the temperature was about 20' higher than when the pure chlorate attained the same degree of decomposition. It will be noticed t h a t the chloride had very little effect after about half the oxygen had been evolved ; a fair amount of chloride had then been formed by decomposition, and the temperature was much higher. Facilita- tion by reduced pressure and retardation by the addition of chloride may perhaps indicate a n inverse action.Efeect of Potassium Chloride on the Decomposition of Potassium Chloraiei -The two specimens of chloride used in these experiments were each prepared by decomposing some of the chlorate in a platinum crucible heated by a spirit flame. Equal weights of potassium chlorate, with and without addition of chloride, were decomposed in similar tubes the volume of oxygen was noted at intervals of 1 to 2 minutes. A very slight facilitation was observed ; taking the average of four pairs of decompositions, about one-third more oxygen was evolved in a given time when one molecular proportion of chloride had been added. Action of Heat on a Mixture of Yotussiurn Chlorate and Bariuqn Chloride.-In this series of experiments, potassium chlorate and mix- tures having the composition represented by 2KC10, + BaCl, and Ba(C10,), + 2BaC1, were heated in similar tubes, the quantities em ployed containing equal amounts of oxygen.I n comparing potassium chlorate with the mixture 2KC10, + BaCI,, the latter lost 59.1 per cent. of its oxygen in 35 minutes, but only 3.1 per cent. had been evolved from the pure chlorate; in another experiment, the mixture lost 10.7 per cent. of its oxygen with more gentle heating for 45 minutes, but the pure chlorate had then under- gone no appreciable loss. Except in the early stages, the temperature required to produce a given rate of decomposition in this mixture is more or less comparable with t h a t required for the mixture Ba(CIO,), + 2BaCl,, and about 50-60' lower than with potassium chlorate alone, although potassium chloride has but little effect and barium chloride markedly retards the decomposition of barium chlorate.Fused barium chlorate has but little solvent action upon barium chloride, but potassium chlorate readily '' dissolves '' half an equivalent of it; hence, when the mixture BaC1, + 2KC10, is heated, about half the barium chloride a t once goes into solution. Under these circum- stances, double decomposition must occur to a greater or less extent, and the ease with which the mixture is decomposed points to the continuous formation of barium chlorate, from which the oxygen is derived.REFERENCE TO THE EVOLUTION OF CELORINE AND OXYGEN. 147 ~~ ~~~ Totdl c1=100 Duration Duration x (minutes).pressure. C1 as chloride Fres C1. (bydiffer- ence). THEORETICAL. The proportion of chlorine liberated during the decomposition of chlorates by heat depends mainly on the nature of the base and the modeof heating. In order to explain this, two theories have been suggested. Schulze (Zod. cit. ) supposed the chlorate to decompose entirely into chloride and oxygen, the chlorine resulting from the action of ‘‘nascent oxygen” upon the chloride. W. Spring and Prost (Bull. Xoc. Chim , 1889, [iii], €, 340), on the contrary, suggested that the chlorste decomposes entirely into oxide and chloric anhydride, C1,0,, the latter immediately breaking up into chlorine and oxygen, more or less of the chlorine then reacting with the oxide to form chloride with the liberation of more oxygen.It will be noticed that these explanations are in direct opposition, but in neither of the papers does there appear to be evidence that the suggested second action actudly takes place under the conditions obtaining ill the decomposition, nor does either deal with possible alternatives, of which there mould seem to be two, namely, (1) the simultaneous formation of both oxide and chloride as dbect products and ( 2 ) the simultaneous action of chlorine and oxygen upon the residue first produced. For the purpose of discussion, it is convenient to classify the different reactions which might give rise to the formation of oxide and chloride (evolution of chlorine and oxygen) during a decomposition. (a) Chlorate giving chloride and oxygen. ( b ) Chlorate giving oxide, chlorine, and oxygen, ( c ) Chlorate acting upon chloride with liberation of chlorine.(d) Oxygen and chloride giving chlorine and oxide, apart from (e) Chlorine and oxide giving oxygen and chloride, apart from d f ) Simultaneous action of oxygen and chlorine, as in ( d ) and (e) Decomposition of Bwiurn Chlorate.-Averaging three of the series of reverse action (e). reverse action ( d ) , combined. experiments given in Table I, we obtain the following : ~ ~ _ _ _ _ _ _ bIols. chloride Mols. oxide 1-2 mm. 233 0 -5 0-066 99.934 1513 99’907 I 1077 1 ativolphprsl 16id5 1 l6iB5 1 0‘093 9 9 0’704 99’296 141148 SODEAU: DECOMPOSLTIOM OF CRLORATES, WITH SPECIAL The action between a gas and a solid is usually increased by rise of temperature, and increases with the time of contact and the con- centration of the gas; the two latter factors are included in the numbers given in the third column (duration multiplied by pressure in atmospheres).According to Spring and Prost, the chloride is pro- duced by the action of chlorine upon the oxide first formed. Com- paring the slow decompositions at 1-2 mm. and at 1 atm., we find that a slight fall of temperature combined with a reduction of the time-concentration factor from 165 to 0.5 has very slightly increased the amount of chloride from 99.90’7 to 99.934 per cent. of the possible amount, instead of very greatly decreasing it. Hence the chloride must be formed inanother way, and 8pring and Prost’s theory does not hold for this chlorate. Any reabsorption of chlorine which occurs is evidently not com- plete at atmospheric pressure, and would be much less so when the concentration of the gas is reduced by expansion (compare the experiments proving reabsorption by heated glass) ; such reabsorp- tion therefore necessitates an increase of free chlorine on reduction of pressure, but none occurs at 1-2 mm., hence reaction (e) cannot occur to an appreciable extent.It may be noted that both oxide and chlorine are very greatly diluted with chloride and oxygen respectively. Comparing the effect of rapid decomposition at atmospheric pressure with that of reduction of pressure to 1-2 mm., we see that in either case the time-concentration factor has been reduced to about 0.5, yet this change has been accompanied by a slight decrease of chlorine in the latter case, but by a sevenfold in- creatw in the former.The increase with rapid decomposition must therefore be due to the great rise of temperature instead of to rapidity of removal of the gaseous products as supposed by Spring and Prost. The increase does not really seem a necessary conse- quence of this theory, as the rapid formation of oxide would partly compensate for the decrease in the time, and the great rise of tempera- ture might even cause more complete absorption by accelerating the reaction between oxide and chlorine, It seems probable that the propor- tion of free chlorine is not affected by variations of pressure and that the slight decrease at 1-2 mm. is due to reduction of temp_erature. Schulze’s hypothesis cannot apply to barium chlorate, for it has been shown that no ohlorine is expelled from barium chloride by barium chlorate or any of its decomposition products under the con- ditions actually obtaining during a decomposition.It has also been noticed that the first bubbles of gas contained about the average proportion of chlorine, although only traces of chloride had then been formed. The chloride experiments exclude reactions ( c ) and (d), and show that, in this case, ( f ) coincides with (e), which has also been excluded j as chloride and oxide are actually formed, i t is concludedREFERENCE TO THE EVOLUTlON OF CHLORINE AND OXYGEN. 149 that reactions (a) and (b) occur during the decomposition, the average velocity of (a) being about 1000 to 1590 times that of ( b ) when the decomposition proceeds slowly, but at a higher temperature, when the decomposition is rapid, the ratio is only about 140 : 1.These average velocities represent the number of molecules of chloride t o each molecule of oxide. From the heats of formation, we obtain : (a) 2Ba(C103), 2BaC1, + 60, + 438K. 2Ba(C103), = 2Ba0 -t. SC1, + 50, - 972K. (b) { 2Ba(C10,), = 2Ba0, -t 2C1, + 40, - 624K. The result of rapid decomposition thus appears to be merely a n example of an endothermic reaction ( b ) g.tiuing upon an exothermic one (a) when the temperature is increased. Decomposition of Potassium ChZorute.-In this case, the evidence is of a somewhat negative character, but as leas than 0.007 milligram of chlorine is present in the 400 litres of gas (measured at about 530° and 1.5 mm.) from 1 gram of the substance, it seems extremely improbable that any appreciable amount is evolved a t first.The last stages of the reabsorption would be exceedingly slow, as the oxide would then have been all but completely transformed into chloride; in the final residue, less than 0.002 per cent. of the potassium can remain as oxide. The improbability is increased by the fact t h a t no such reabsorption was detected in the decomposition of barium chlorate at atmospheric pressure when the proportions of oxide and of free chlorine were respectively a t least 50 times and 25,000 times those just given for potassium chlorate. It appears that the direct decomposition into chloride and oxygen is the only one which need be considered, this proceeding a t a rate at least 50,000 times as great a s any reaction yielding chlorine.Genera I Consides.ations. The experiments in t h i s paper, and some already performed with lead chlorate and calcium chlorate but not yet published, tend to indicate the general conclusion that when a chlorate is heated it undergoes two simultaneous and independent decompositions, (u) into chloride and oxygen, ( b ) into oxide, chlorine, and oxygen ; it remains t o be shown that this view will harmonise with the results of Schulze’s and of Spring and Prost’s experiments. In each of these papers, a point is made of the increase of chlorine with increase of weakness of the base; now as the affinity for oxygen approaches that for chlorine, there would be more tendency for oxygen t o attack the chloride, less for chlorine to react with the oxide, and more tendency for the oxide to be directly produced; this point therefore accords VOL.LXXVII. bl150 ADIE AND BROWNING: TEE INTERACTION OF equally with each of the three theories. The increase of chlorine with rapid decomposition has already been dealt with under barium chlorate; the only remaining point brought forward by Spring and Prost is the suggestion that the proportion of free chlorine is in- creased by addition of an acidic oxide because it combines with the liberated basic oxide and so prevents reabsorption of the chlorine first liberated. This cannot, however, be a generally correct explana- tion, for many such substances cause this action with potassium chlorate when 50--200' below t h e temperature at which this salt undergoes appreciable decomposition when heated alone (Baudrimont, J. Pharm., 1871, [iv], 14,81 and 161 ; Fowler and Grant, Trans., 1890, 57, 272) ; the '' liberated oxide " would then be non- existent. It does not seem remarkable that these substances should expel chlorine and oxygen (chloric anhydride) from chlorates, as many expel sulphuric anhydride from sulphates. Schulze also shows that the amounts of free chlorine obtained by the decomposition of the chlorates of sodium, barium, and strontium agree with those resulting when equivalents of the chlorides are heated with potassium chlorate, and that comparable results would probably be obtained with other metals. Double decomposition, however, would be expected to take place with the formation of a chlorate more readily decomposed than that of potassium; these ex- perimen ts would thus be decompositions of the respective chlorates rather than a study of the action of " nascent oxygen." In section 111 this has been shown to be the case with barium chloride, and there seems little doubt that the same will apply with Gther metals, as reaction takes place at a relatively low temperature. It thus appears that the theory of two independent decompositions is in harmony, not only with the present investigation, but also with the results supposed to support the two older theories. The author desires to express his thanks for facilities afforded him in the Davy-Faraday Research Laboratory.

ISSN:0368-1645    

DOI:10.1039/CT9007700137

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

150 ADIE AND BROWNING: TEE INTERACTION OF XVI.-The Interaction of Sulphuric Acid and Potassium Ferrucyanide. By RICHAED HALIBURTON ADIE, M.A., B.Sc., and KENDALL COLIN BBOWNING, B.A. THE interaction of concentrated sulphuric acid and potassium ferro- cyanide seems to have been first investigated by Dobereiner (Schweig- ger’s Journ,, 1820, 28, 107), who stated that pure carbon monoxide is formed (compare Berzelius, ibid., 1820, 30, 57).SULPHURTC ACID AND POTASSIUM FERROCYANIDE. 151 Fownes (Phil. Mag., 1844, [:iii], 24, 21), apparently in ignorance of Dijbereiner’s previous work, to which hedoes not allude, found that nearly pure carbon monoxide is formed, accompanied a t first with traces of hydrocyanic acid and carbon dioxide. The residue consisted chiefly of ferrous, ammonium, and potassium hydrogen sulphates.Towards the end of the reaction, ferric sulphate and sulphur dioxide were formed, and crystals of anhydrous iron ammonium alum deposited. Merk (Repert. .P?mrm., 1839, 68, 190), by rapidly distilling potassium ferrocyanide with sulphuric acid, obtained a distillate con- taining a litt,le prussic acid, ttiiocyanic acid, and formic acid; he also obtained a sublimate of needle-shaped crystals of ammonium sulphite. Everitt (Phil. Mug., 1835, [iii], 8, 9’7) first showed that, with dilute sulphuric acid in slight; excess, hydrocyanic acid is given off and a new salt, Everitt’s salt :K,Fe2(CN),, left. Wittstein (VierteZjahr. PAurrn., 1854, 4, 515), Aschoff (Arch. Phurm., 1860, [ii], 106, 257), and Williamson (Anncden, 1846,57, 225, and Memoirs Chem.Soc., 1848. 3, 125) also investigated the reaction, Considering the differences between the conclusions of these in- vestigators and the almost complete absence of quantitative results, the authors have investigated the decomposition of potassium ferro- cyanide by sulphuric acid of concentrations varying from that of the approximately pure acid containing 98 per cent. H2S0,, to that of the acid represented by H,SO4,l8H,O. The potassium ferrocyanide used was recrystallised until no impurity could be detected. It was dried at 104-105° until its weight was constant, and kept in a desiccator over phosphoric oxide. The sulphuric acid used was freshly distilled and was free from dissolved sulphur dioxide. Estimation of Carbon Monoxide. A weighed amount of ferrocyanide was introduced into a small flask or wide test-tube, which could be heated in an oil-bath, and the apparatus compIetely filled with dry carbon dioxide.The sulphuric acid was then run in by means of a tap-funnel and the vessel heated, a, slow current of carbon dioxide being maintained, The carbon monoxide was collected over aqueous caustic potash (1 : 2). Tempera- tures were taken during the reaction by means of a thermometer immersed in the acid. Estimation cf Hydrocyanic Acid. The anhydrous salt was placed in a flask and the apparatus filled with hydrogen, free from oxygen. The acid was run in and the mixture distilled into two sets of potash bulbs. I n order to keep the concentration of the acid constant, a small double surface condenser was used, and at the end of each estimation its temperature was M.2152 ADlE AND BROWNING: THE INTERACTION OF raised t o 100' t o expel all traces of hydrocyanic acid * from the apparatus.The solutionwas then washed out of the potash bulbs, diluted, and the hydrocyanic acid estimated by standard silver nitrate, using sodium chloride as indicator. Action of 98 per cent. Sulphuric Acid. When mixed with excess of 98 per cent. sulphuric acid, potassium ferrocyanide, dried as described, turned white and then dissolved. Although a trace of hydrocyanic acid was evolved at first, no carbon dioxide was given of'f and no measurable quantity of carbon monoxide was obtained, even after heating for two hours at 100'. When the temperature was raised t o 130°, decomposition set in, but mas slow even at 200°, at which temperature the acid fumed strongly, and sulphur dioxide was evolved.Quantitative experiments showed that the reaction was very slow and incomplete, Carbon monoxide is only formed in m y appreciable quantity at a temperature above 200', and approximating to that of the formation of fumes. The action increased slowly on further raising the temperature, but even after 2& hours at 200-210' the yield of carbon monoxide amounted only to about 4 per cent. of the theoretical, being dependent on the temperature and time of heating. The authors confirm Fownes' observation of the formation of crys- tals containing potassium and ammonium ferric sulphates towards the end of the reaction. To ascertain the nature of the reaction taking place in the solution, dry potassium ferrocyanide was dissolved in 48 per cent.sulphuric acid a t 100' in an atmosphere of carbon dioxide, the solution cooled in a freezing mixture, and ether added. The white precipitate obtained was collected by the aid of a Pasteur filter in an atmosphere of hydrogen, dried, dissolved in absolute alcohol, and reprecipitated by ether. This process was repeated three times, and the white, crys- talline product dried in a vacuum over phosphoric oxide. Its properties and determinations of the iron by means of mercuric oxide, and by sul- phuric acid showed it to be hydroferrocyanic acid, Action of H,SO,,H,O. The reaction was carried out on similar lines to the foregoing, and, although more rapid, was still slow; gas bubbles appeared at about 170°, simultaneously with slight fuming.The action became more rapid at 195-200°, but was not complete at the end of an hour, even with a large excess of the acid. Thus 0.2832 gram of anhydrous * Blank experiments showed that hydrocyanic acid was completely expelled from the condenser by this means,SULPHURIC ACID AND POTASSIUM FERROCYANIDE. 153 potassium ferrocyanide gave 85.8 C.C. (corr.) of carbon monoxide in 1 hour, the calculated volume being 103.4 C.C. Action of H,S0,,2H20. The reaction was steady, the salt dissolved completely, and carbon monoxide began to be slowly evolved at about 130'. At 175-180", the evolution mas rapid, and the reaction was complete in about 35-40 minutes. The yield of carbon monoxide accounted quantitatively for the amount of carbon in the ferrocyanide, and no measurable quantity of hydrocyanic acid could be detected.CO at 0" and 760 mm. Found. Calc. 0.1388 gram K,Fe(CN),,3:K20 gave.. .... 44.6 C.C. 44.2 C.C. 0.2125 ,, K4Fe(CN),,3H,O ,, ...... 77.6 ,, 78.0 ,, Action of H2S0,,4H,0. With increased dilution, the reaction began to change, hydrocyanic acid being formed in quantity, as well as carbon monoxide, and a small quantity of a solid substance was precipitated. A small quantity of formic acid was also detected, both in the absorption bulbs and in the flask. The carbon monoxide was given off below 120°, but the hydrocyanic acid only came off slowly, even with brisk boiling, at this temperature, as shown by the following three experiments: HCN [calc. as 6HCN Time.per mol. KdFe(CN),]. 14 hours ..................... 3& ,, ..................... 6-02 ,, 7 ,, ..................... 8.80 9 ) 2.6 per cent. Taking the highest of these numbers, we obtain Vol. CO at O* HCN CN Mass and 760 mm. per cent. per cent. K,Fe( CN)6. (found). (found). (calc.). 0.8964 ,, -- 8.83 8.43 The sum of these two amounts of cyanogen does not account for the whole of this radicle, the theoretical percentage being 36.96, so that the amount of formic acid obtained had t o be estimated. As it is difficult to estimate formic acid in presence of Everitt's salt, &c., by ordinary methods, it was determined from the amount of ammonia formed in the hydrolysis of the cyanide groups, as in the Kjeldahl method, The total ammonia obtained represents carbon monoxide as well as formic acid, hence the amount of the latter is obtained by subtracting the ammonia corresponding to the carbon monoxide from the total and calculating the difference as formic acid.The amount of formic acid which was at a maximum with this 0.2241 gram. 6.99 C.C. - 3-7154 ADIE AND BROWNING: THE INTERACTION OF strength of acid" was represented only in milligrams, and conse- quently was too small to affect the result. The solid residue consisted of Everitt's salt, which is only slowly decomposed, mixed with a certain amount of ferrous and other sul- phates in solution. Hence, in this case, the main products of the reaction are carbon monoxide and hydrocyanic acid, mixed in about the ratio 3.7 : 8.43. Action of H,S0,,6H20. With acids of less concentration than H2S0,,4H,0, for example H2S0,,6H,O, the reaction showed a marked change in character, Acid.H2S04,4H20 (Everitt's salt left) H2S04,6H20 (Everitt's salt left) H2S04,8H,O (Everitt's salt left) H.#O4,1OH20 (No Everitt's salt left) (No Everitt s salt left) H2S O4, f 2 H 2 0 H2SO4,14HzO 0.7326 grams. 0.6997 ,, 0.8964 ) ) 0'9722 ,) 0.9432 ), 0-8088 ) ) 2.2074 ,) 0'8463 ), 1'1114 ), 0'8536 ,, 1-3180 ,, 1,1356 ,, 0.9382 ,, 1.0285 ,, 1'7694 )) 1.0912 ) ) 0.8574 ,) 0.8642 ), 0.7440 ,, 1,7230 ,, 1*0900 ) ) 0,9796 ,, 1'0848 :, 2.0532 ), 0'8896 )) 1'5426 ,) 1'1634 ) ) 0'9646 ), 0.7461 ) ) 0'9894 ,, 1.0766 ), 1'1212 )) 0'7394 ,, HCN [calc. as 6HCN per mol. K4Fe(CN)61* 2'7 per cent. 6-3 8 '8 10-3 16'8 39 24.5 36'6 47 71 30 98.7 99.2 75 81 100 47'2 57.0 65-0 80.5 86'0 94-8 71 '0 7G.6 84.9 91.5 94.0 98'0 99 '1 99.3 98 *7 98.2 99.0 Time.* A number of experiments were made to see if formic acid could be prepared in quantity by modifying the action of H,S04,4H20 on potassium ferrocyanide, with, however, no satisfactory results.SULPHUBIC ACID AND POTASSIUM FERROCYANIDE. 155 hardly any carbon monoxide being obtained. Thus, 0.57 gram of potassium ferrocyanide heated for one hour with a large excess of H2S0,6H,0 in an atmosphere of carbon dioxide, gave less than 0.5 C.C. of carbon monoxide. The reaction began a t about 1 zoo. The table on p. 154 contains a summary of the results obtained, using as neariy as possible the same weight of potassium ferrocyanide and a large excess of sulphuric acid, so as to keep the concentration of the acid nearly constant.The reaction in every case was carried out in an atmosphere of hydrogen as far as possible free from air. I n all cases, traces of formic acid could be detected. These results show that the theoretical yield of hydrocyanic acid was obtained by using acid of a concentration not exceeding that re- presented by H,SO,, 1 OH,O. A t first, difficuIty was experienced in obtaining comistent results. This was found to be due to (1) The rate at which the mixture was boiled. (2) The presence of traces of air. (3) The mass of potassium ferrocyanide used, the massof acid being kept constant. The effect due to the first cause is seen in the preceding table, by comparing, for example, the results obtained with H2S0,,10H20 and H2S04, 14H,O respectively. The mixture was boiled much more rapidly in the case of the former. The effect of the second cause is seen in the following table con- taining the results of experiments in which a very slow stream of air was used : Acid, H2S0,,6H2O HSSO,, 8H2O H2S04, 14H@ K,Fe( CN)@ 0.9432 grams.o-aoaa ,, 0.9770 ,) 1'1114 ,) 1-9992 7 7 1,1031 ,, 0,7793 ,) 0'7440 ,) HCN [calc. as 6HCN per mol. K,Fe(CN),I. 54.5 per cent. 39 7 , 61.2 ), 47 9 9 71'2 ,, 75'2 ,, 98'1 7 7 65 J > Time. The influence of the third cause, namely, that of mass, is seen in the following table, and becomes less with increasing dilution of t h e acid :156 ADIE ANb BROWNING: THE INTERACTION OF Acid. H,SO,, 8H,O €€,SO,, 12H,O H,SO,, 16H20 H,SO,, 1 8H20 K,Fe( CN),. 2.2074 grams. 0-8463 ,) 2.2826 ,, 2.1354 ,, 1.6285 ,, {:;;g ;; {;:; ,7 9 7 1.1412 ,, 0'7394 7 7 HCN [calc.as GHCN per mol. KE;,Fe(CN),I. 24.5 per cent. 36'6 ,, 60.2 ,) 66'6 ,. 75.5 7 , 70.6 ,) 84.9 ,, 91-5 7 7 98.3 ,, 98-2 ,, 99'0 ,, Time. Explanation of the Reaction. Hydro- ferrocyanic acid is first obtained, and can be isolated and examined. With st'rong sulphuric acid, it decomposes very slowly, evolving carbon monoxide, and forming ferrous and ferric sulphates, &c. With an acid of the concentration H,S0,,2H20, it decomposes quantitatively, forming carbon monoxide and ferrous, &c., sulphates. With sulphuric acid of less concentration, the following reactions occur. (i) The hydroferrocyanic acid reacts with the potassium sulphate, forming Everitt's salt (Aschoff, Zoc. cit.) : The reaction is probably explained in the following way.2H,Fe(CN)6 + 2K,S04 = BKHSO, + GHCN + K,Fe,(CN),. (ii) At the same time, the hydroferrocyanic acid decomposes, form- ing FeSO, and HCN. H,Fe(CN)6 = 4HCN + Fe(CN),. Fe(CN), + H2S0, = FeSO, + 2HCN. This second reaction becomes more marked the greater the dilution, and predominates with an acid of the concentration H,SO,,lOH,O; or with more dilute acids. The second mode of decomposition explains the fact that with, for example, H2S0,,18H,O, the whole of the cyanogen is evolved as hydrocyanic acid rapidly and completely. If Everitt's salt were formed, the decomposition mould take much longer, as this compound is only slowly decomposed by acid of this composition. Ifiteruction of Hydroferrocyanic Acid and Potassium Xdphate.I n order to investigate the reaction between hydroferrocyanic acid and potassium sulphate, aqueous solutions of v arying strengths ofSULPHURIC ACID AND PO'I'ASS[UN FERROCYANIDE. 157 hydroferrocyanic acid were boiled with potasium sulphate solution i n an atmosphere of hydrogen, a double surface condenser being used to keep the concentration constant. The water used had been boiled and also cooled in hydrogen to remove dissolved air. I n one case, a 10 per cent. solution of hydroferrocyanic acid with excess of potassium sulphate gave a precipitate of Everitt's salt on boiling. On warming the precipitate with dilute sulphuric acid at 60' * and filtering, no ferrous sulphate mas found in the filtrate, hence no ferrous cyanide was formed. A 0.7 per cent.solution of' hydroferrocyanic acid was similarly treated, and a precipitate obtained. It was, however, merely ferrous cyanide, as it rapidly and comple tely dissolved in dilute sulphuric acid at 60°, forming ferrous sulphat e and evolving hydrocyanic acid. The precipitate obbained from the strong (10 per cent.) solution was collected in absence of air, washed repeatedly, placed in a desic- cator in an atmosphere of cArbon dioxide, and dried in a vacuum at 100' over phosphoric oxide. The pale bluish-yellow precipitate contained potassium, iron, and cganogen, and was analysed by (ij evaporating down with strong sulphuric acid and a little am- monium sulphate and igniting ; (ii) boiling with mercuric oxide, filtering, igniting, and weighing ZLS ferric oxide.0.3086 gave 0.1457 Fe,O,. Fe =33*1. K,Fe,(CN), requires Fe = 32.4 per cent. Decomposition Gf Irydyoferrocyanic Acid. A number of experiments mere made with the object of studying the decomposition represented by the equation : H,Fe(CN), = Fe(CN), + 4HCN. Fe(CN), + H,SO, = FeSO, + BHCN. According to Berzelius (Zoc. cit.) the decomposition with boiling water is represented by the equation : H,Fe(CN), = 4HCN + Fe(CN),. Reemann and Carius (Annalen, 1860,113,39), and h a r d and Bbmont, (Compt. rend., 1884, 90, 1024), on the other hand, express it by the equation : 2H,Fe(CN)6 = 6HCN + H,Fe,(CN),, but, in their papers, give neither analyses nor details. To examine this question, a quantity of hgdroferrocyanic acid was prepared by Possell's method, and purified by repeatedly dissolving in absolute alcohol and reprecigitating by ether until spectroscopically * Ferrous cyanide dissolves completely and rapidly a t 60" in dilute sulphuric acid.158 ADIE AND BROWNING: THE INTERACTION OF free from potassium.oxide at 60°, this was analysed. After drying in a vacuum over phosphoric Determination of the iron gave : I. IT. 111. Calc. Fe 25.8 26.0 25.85 26.04 per cent. On heating with water in an atmosphere of hydrogen, hydro- cyanic acid began to be evolved at 60°, and a pale yellow-green solid separated out, thus proving Berzelius’ statement to be correct. The hydrocyanic acid evolved was estimated as above. 0.4970 H,Fe(CN), gave 0.2605 HCN. HCN = 52.4. 0.3863 H,Fe(CN)6 ,, 0.2035 HCN. HCN= 52.7. The excess of hydrocyanic acid is undoubtedly due to hydrolysis of the ferrous cyanide, as on further boiling hydrocyanic acid is slowly evolved, and the precipitate, after drying in a vacuum, was found to contain ferrous oxide.In presence of air, a coppery-blue precipitate was formed, but in too small a quantity for analysis, It was undoubtedly Williamson’s blue, KFe,(CN),, as this is formed from Everitt’s salt in presence of air and sulphuric acid (Williamson, Zoc. cit.). That Everitt’s salt in presence of air is converted more or less completely to Williamson’s blue, which, in the presence of dilute acid and oxygen, decomposes as fast as it is formed, was confirmed by preparing a quantity of the latter. On boiling this with dilute sulphuric acid in presence of air it dissolved, forming hydrocyanic acid and ferric sulphate.3HCN requires 37.5 per cent. 4HCN requires 50 per cent. 2KFe2(CN), + 8H,SO, + 0 = 2KHS0, + Fe2(S0,), + H20 + 12HUN. Summary. The preceding results may be epitomised : (i) Concentrated sulphuric acid, H,SO,, dissolves potassium ferro- cyanide and shares the potassium with the hydroferrocyanic acid. The ratio must be primarily determined by the active masses and relative affinities of the acids. The following equation represents the initial change : K,Fe(CX), + €€,SO, = 4KHS0, c H,Fe(CN)6. The solution is only very slowly decomposed by rise of temperature. Carbon monoxide is given off, but even a t 200’ the rate of evolution is low and the decomposition proceeds only when the sulphuric acid can dissociate or decompose into water, sulphur trioxide, and sulphur dioxide, (ii) With the addition of water, marked decomposition occurs, and large quantities of carbon monoxide are formed. This reaction in- creases with dilution until the concentration H2S0,,2H20 is reached ;SULPHURIC ACID AND POTASSIUM FERROCYANIDE.159 at this strength, the whole of the cyanogen appears as carbon mon- oxide a t 180’. The equation which represents this change is : K,Fe(CN), + 8(H2S0,,2H20) = 4KHS0, + S(NH,),SO, + I n this case, there is evidently hydrolysis, and it seems probable that it may be directly due to the molecules of water which are dissociated by solution in the solvent H,SO,. On the other hand, it is possible that sulphuric acid of the concentration H2S0,,2H20 may really act as orthosulphuric acid, S(OH),, in which case the above reaction may be evidence of its existence. (iii) With further dilution t o the concentration H2SO,,4H,O there is another definite change in the reaction, since, in addition to carbon monoxide, Everitt’s salt, K,Fe,(CN),, and hydrocyanic acid make their appearance.That this is a definite change is shown by the fact that warm acid of the strength H,S0,,2H20 immediately decomposes Everitt’s salt. The Everitt’s salt appears to be formed from hydroferrocyanic acid by the action of potassium sulphate solution, thus : EeSO, + 6CO + 1 OH,O. 2H,Fe(CN),Aq + 2K2S0,Aq = K2Fe,(CN), + 2KHS0,Aq + 6HCNAq. Some hydroferrocyanic acid is decomposed at the same time, form- ing hydrogen cyanide and ferrous cyanide, With increasing dilution, this becomes the more important and eventually, with acid of the concentration H,SO,,lOH,O, the sole reaction.The equation which may represent this stage is : H,Fe(CN),Aq = 4HCXAq + Fe(CN),. I n presence of the sulphuric acid, the ferrous cyanide dissolves with the formation of ferrous sulphate and hydrocyanic acid, and the change as a whole may be considered as due to the molecules of s u b phuric acid dissociated by solution in the solvent water. The final equation now becomes : K,Fe(CN), + 5(H2S0,,10H20) = 4KHS0, + FeSO, + 6HCN + 50H20. (iv) The final decomposition is hindered by increasing the mass of the salt, but helped by increase of temperature and the presence of air. This last condition is important, and assists in the rapid decomposi- tion of the salt. It also explains the use of porous brick or the passage of an air current to assist in the preparation of hydrocyanic acid on the manufacturing scale. When air is present, Williamson’s blue, KFe,(CN),, is formed in small quantity, and the solution contains ferric salts ; it is probably formed from Everitt’s salt, and then decomposed by the action of the oxygen of the air, as explained above.160 SMILES : AUTlON OF' ATJKYL IODIDES ON THE These results, therefore, confirm the oldest account of the hydrolysis of hydroferrocyanic acid, namely, that due to Berzelius (Zoc. cit.). The authors are engaged in further investigations of changes of the character of that described under (ii) produced by sulphuric acid, to see if they admit of further elucidation, ST. JOHN'S COLLEGE, LBBORATORY, CAMBRIDGE.

ISSN:0368-1645    

DOI:10.1039/CT9007700150

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

160 SMILES: ACTfON OF ATAKYL IODIDES ON THE XVI1.-Action of AEkyl Iodides on the Mercuk Iodide Su,lphides OJ the Fatty Series. By SAMUEL SMILES, B.Sc. SOME years agol Kriiger (J.pr. Chem., 1876, [ii], 14,207) investigated the action of methyl iodide on methyl ethyl sulphide, and of ethyl iodide on dimethyl sulphide, and found that in each case a different dimethylethylsulphine iodide was produced. This work was repeated by Nasini and Scala (Gaxzettcc, 1888, 18, 67) a few years later and confirmed. Klinger and Masssen (Annulen, 1888, 243, 193), however, in a careful series of experiments, obtained by the two methods identical sulphine iodides which gave rise to identical series of double salts. At the same time, they pointed out that Kruger's method of preparation was at fault and that his substances mere impure.From the facts that conflicting results have been obtained, and that the bulk of the evidence in these researches is based upon the behaviour of certain double salts, it seemed possible that an inves tiga- tion of these substances might throw some light upon the matter. The following research has therefore been undertaken, firstly, to attempt to determine the constitution of the double salts of the sulphine bases, and, secondly, to ascertain whether, by varying the methods of preparation, stereoisomeric compounds could be obtained. I n acetone or alcoholic solution, t h e sulphides unite with mercuric iodide to form compounds of the general formula R,SHgI,. These are analogous to such substances as R2SI,, R2SBr2, R,SRI, &c., and their constitution must therefore be represented in a corresponding manner, that is, as containing yuadrivalent sulphur : E>S<pl.Mercuric iodide and the nlkyl iodides might be expected to react in a similar way with the mercaptans forming substances such as H R>S<&gI and g>S<i. These, however, do not appear aspro- ducts of the reaction, and may bo assumed to he unstable com-MERCURIC IODIDE-SULPI-IJDES OF THE PATTY SERIES, 161 pounds, formed at an intermediate stage, and readily splitting off hydrogen iodide as follows : RSH + HgI, 4 g>S<F1 - RSHgI + HI. RSH + RI - g>S<F - RSR + HI. Regarded from this point of view, the acid nature of the al- cohols and mercnptans appears to be dependent on the tendency of oxygen and sulphur to become quadrivalent, and since oxygen shows this tendency to a less degree than sulphur, it follows that the alcohols show weaker acid properties than the mercaptans.That; this is the case is illus- trated by the fact that ethyl mercaptan, dissolved in an alcoholic solution of sodium ethoxide, shows all the reactions of sodium mercaptan; for example, on treating with alkyl iodides, the sulphides are formed. The alkyl iodides react with the mercuric iodide compounds of the sulphides t o form stable yellow substances, which are found to be identical with those produced from the corresponding sulphine iodides and mercuric iodide. Accordingly, their formation must be repre- sented as follows : Dobbin and Masson (Trans., 1885,47,56) have already investigated the products of addition of the halogens to the sulphine halides, and conclude t h a t they are not molecular compounds, but owe their formation t o either sexavalent sulphur or tervalent iodine.From their stability and from the fact that the sulphine sulphates give similar compounds, these authors incline to the former hypothesis. I n support of this view, I have found that dimethyl sulphide bromide, (CH,),SBr2, reacts with methyl iodide to give the same sub- stance, (CH,),SBr,I, as is produced from trimethylsulphine iodide and bromine in molecular proportion. The following series of reactions were carried out with the object of investigating the stereochemical properties of sexavalent sulphur. As yet, only negative evidence has resulted. It has been found that the same compound of trimethylsulphine iodide with mercuric iodide is produced in the following three different ways.From dimethyl sulphide-mercuric iodide and methyl iodide : From trimethylsulphine iodide and mercuric iodide :162 SMILES,: ACTION OF ALKYL IODIDES Oh' THE From dimethyl sulphide iodide and mercury methyl iodide : The following two reactions also give identical products. Triethylsulphine iodide and mercuric iodide : Diethyl sulphide, mercuric iodide, and ethyl iodide : c2H5\ /Hgl C2H5>S<y1 + C,H51 - C 2 H 5 ~ S r I C2*5 C,Hg '*\I . The same process has been applied to derivatives containing only The following reactions give identical products. Dimethylethylsulphine iodide and mercuric iodide : two of the three alkyl groups alike, Methyl ethyl sulphide-mercuric iodide and methyl iodide : Dimethyl sulphide-mercuric iodide and ethyl iodide : Also the same compound of diethylmethylsulphine iodide with mercuric iodide is produced by the following reactions, Diethylmethylsulphine iodide and mercuric iodide : Diethyl sulphide-mercuric iodide and methyl iodide : Methyl ethyl sulphide-mercuric iodide and ethyl iodide : CH,\ /w CH3>S<p1 = C,H,I C,H,TST-;-I C2H5 c, EX,.MERCURIC IODIDE SULPHlDES OF THE FATTY SERIES. 163 From these results, no definite conclusion can he drawn as to the relative directions of the six valencies of sulphur.Even the simplest arrangement, that in which the valencies are directed towards the six angles of an octahedron, allows of three possible isomerides in the case of (CH3)3SIHgI,.Where the alkyl groups differ, the possible number becomes still larger. As, however, Wedekind (Bey., 1899, 32, 517) and others have shown that quaternary ammonium compounds containing two or more:small groups, such as methyl and ethyl, are not obtained in isomeric forms, and that the presence of more complex groups, as phenyl or benzyl, renders this isomerism possible, it is desirable to repeat these experiments with derivatives containing larger radicles. It is a noteworthy feature of these reactions that the presence of mercuric iodide appears to render the addition of alkyl iodide far easier of accomplishment than is the case in its absence. Thus, for example, the action of ethyl iodide on dimethyl sulpbide-mercuric iodide is complete in 10 t o 15 minutes with the formation of (CH,),(C,H,)SIHgI,, whilst, on the other hand, the production of dimethylethylsulphine iodide from ethyl iodide and dimethyl sulphide is scarcely complete in 3 days.It is hoped, therefore, that this method of preparation will be of use in obtaining sulphines containing higher radicles and possibly those of the aromatic series, which do not appear to be readily formed by the ordinary methods. EXPERIMENTAL. Action of Mercuric Iodide on Alkyl J’ulphides. The sulphides of the fatty series dissolve mercuric iodide with slight evolution of heat and formation of the mercuric iodide-sulphides. These substances are best prepared by shaking up a warm concentrated solution of the sulphide in acetone with mercuric iodide, which dis- solves, the solution acquiring a yellow colour. After filtering or decanting from excess of mercuric iodide, the solution is either left to crystallise or, if the product is very soluble, evaporated in a vacuum.These substances are yellow, unstable compounds, the lower members of the series crystallising well in long prisms. They are soluble in acetone, but only sparingly so in alcohol or ether. When exposed t o the air or gently warmed, they are decomposed, leaving a residue of mercuric iodide, the same decomposition occurring when they are boiled with water or acids. Potassium hydroxide solution converts them to yellow substances, from which acids regenerate the original mercuric iodide sulphides. On account of their tendency to decompose, and the conse- quent difficulty in obtaining them sufficiently pure for analysis, their composition was determined as follows.A weighed quantity of164 SMILES: ACTION OF ALKYL IODIDES ON THE sulphide dissolved in acetone or ether was shaken with a known amount of mercuric iodide in excess. The remaining mercuric iodide was removed by filtration, washed with ether, and, after drying, weighed. Owing to the slight solubility of mercuric iodide in acetone or ether, the numbers obtained were generally a little low. Dimethyl subhide-mercwric iodide, ( CH,),SHgI,, crystallises from acetone in long, yellow needles and melts at 75'. Estimation of the amount of mercuric iodide which entered into combination with the sulphide gave the following results : 0.183 requires 1.322 HgI,.HgI,= 87%. 0.235 ,, 1.70 HgI,. HgI,=87.8. Methyl ethyl subhide-mercuric iodide, CH,(C,H,)SHgI,, crystallises On analysis, C,H,T,SHg requires HgI, = 87.9 per cent. from acetone in pale yellow prisms and melts at 59". the following result was obtained : 0.356 requires 2.166 HgI,. C,H,12SHg requires HgI, = 85.6 per cent. Biethyl suljohide-mercuric iodide, ( C2H&3HgI,, crystallises from acetone, in which it is very soluble, in pale yellow prisms and melts at 52'. It was analysed by weighing the residue of mercuric iodide ob- tained by gently heating a known quantity to a temperature slightly above its melting point. HgI, = 85.9. 0.3026 gave 0.2516 HgI,. HgT2= 83.14. 05505 ,, 0.4565 HgI,. HgI, = 82.92. C,H,,I,SHg requires HgI, = 83.45 per cent. Amyl subhide-mercuric iodide, (C,H,,),SHgT,, is obtained as a yellow On analysis, it gave the oil which easily decomposes on heating.following result : 0.5 requires 1 *24 HgI,. C,,H,,I,SHg requires HgI, = 72.2 per cent. Bibenxyl suZphide-mercui*ic iodide, (C,H,),SHgI,, is very soluble in acetone ; i t crystallises in pale yellow, transparent plates and melts at 37-38'. It is exceedingly unstable in the solid state and decom- poses on being pulverised, but is more stable when i n solution. On analysis, the following numbers were obtained. 1.1435 requires 2-53 HgIy HgI,= 68.8. 0.926 ,, 2.05 HgI,. Hgl',=69.0. C1,H,,T,SHg requires HgI, = 67.9 per cent. Of the foregoing derivatives, some are stated to have already been obtained. Loir (Amnalen, 1858, 107,234) claims to have prepared the dimethyl (m.p. 67') and the diethyl derivative (m. p. 110') by the HgI, = 71.3.NERCURlC IODIDE SULPHIDES OF THE FATTY SERIES. 165 action of ethyl iodide on dimethyl sulphide-mercuric chloride and diethyl sulphide-mercuric chloride respectively, and describes them as stable yellow substances. These are evidently derivatives of sulphine bases, since, as shown below, such substances are produced from alkyl iodides and the mercuric iodide sulphides. C'ompounds of iYuJpT&e Iodides with Mercuric Iodide. Action of Alh$ Iodides on the Mes.cui.ic Iodide Sulphides. The alkyl iodides dissolve the mercuric iodide sulphides, and on allowing the solutions t o stand for a few minutes they become warm, gradually acquiring a bright yellow colour. Precipitation with ether yields yellow, crystalline products, identical with those produced from the corresponding sulphine iodides and mercuric iodide.These are stable, yellow, crystalline substances, and, especially in the case of the lower members of the series, can be easily obtained in large, mell- defined crystals. They show a slight tendency to split off mercuric iodide, although t o a far less degree than the mercuric iodide sulphides. When suspended in water in the finely divided state and boiled, only a very slight decomposition occurs. With potassium hydroxide solution, they yield a white substance soluble in acetone. The substance was decomposed by treatment with nitric and hydrochloric acids, and the solution evaporated to dryness. The resulting mercuric chloride was dissolved in water, and from the solution, after neutral- ising with sodium carbonate and then acidifying with hydrochloric acid, the mercury was precipitated as sulphide and estimated in the usual manner.It may be noted that all the following reactions appear to take place quantitatively. TyimethyZsulphine iodide-mercuric iodide, ( CH3),SIHgI,, was prepared in three ways. 1. The calculated quantities of trimethylsulphine iodide and mercuric iodide were shaken up with acetone. From the yellow solution, ether precipitated a crystalline substance melting at 163*, which, after recrystallisation from acetone, melted at 165'. By allow- ing a cold solution in acetone to evaporate spontaneously, it was deposited in large, yellow prisms often half a centimetre across. 2.Dimethyl sulphide-mercuric iodide was dissolved in an excess of methyl iodide ; interaction took place with slight evolution of heat, and was complete in two minutes. On cooling, a substance separated out which melted a t 163-164', and from the mother liquor a further quantity was obtained by precipitation with ether. After precipitat- ing twice from acetone with ether, it melted at 165O. 3. The substance was also produced from dimethyl sulphide VOL. LXXVII. N The mercury in these compounds was estimated as follows.166 SMILES: ACTION OF ALKYL IODIDES ON THE iodide and mercury methyl iodide, but whether the reaction may be regarded as an additive one is a matter of doubt. 0.6 gram of dimethyl sulphide and 2.5 grams of iodine were dissolved in 6 C.C. of acetone and 3.4 grams of mercury methyl iodide added.In about 15 minutes, the reaction was complete, and on cooling the mixture in ice a crystalline precipitate was obtained melting at 140-145'. After precipitating twice from acetone with ether and cryst.allising once from acetone, it melted at 163-164'. Together with this sub- stance there was formed another, which may be obtained from the mother liquor ; it melted at 68-70', and on analysis showed rather a high percentage of mercury (31.05 per cent.). Analyses of the sub- stances prepared by the above three methods were made, with the following results : I. 0.3686 gave 0-1 289 HgS. Hg = 30.1 7. 11. 0,3513 ,, 0.1235 HgS. Hg=30*29. 0.2129 ,, 000756 HgS. Hg=30*56. { 0-241 0 ,, 0-0855 HgS. Hg= 30.58. III. C,H,I,SHg requires Hg = 30.39 per cent.It is evident from these results that the substance obtained by the third method still contained a small quantity of the compound of lower melting point. Triethylsulphine iodidemercuric iodide, (C2H5)3SIHg12, was obtained by two methods. It was found that concentrated acetone solution of trimethylsulphine iodide, when saturated with mercuric iodide and precipitated with ether, formed a yellow, crystalline substance which melted a t 116', and on analysis the following result was obtained : 0°5372 gave 0.2143 HgS. Hg = 34-38. (C,R,),SI,2HgI2 requires Hg = 34.66 per cent. 1. The following method was therefore used for the preparation of the required compound. An acetone solution of triethylsulphine iodide was divided into two equal parts, one of which was shaken with excess of mercuric iodide.After filtering, the solution was added to the second part and the whole concentrated by spontaneous evaporation. By precipitation with ether, a substance was obtained which melted at 107-108°, and after purification crystallised in bright yellow leaflets melting at 112'. 2. Diethyl sulphide-mercuric iodide was dissolved in excess of ethyl iodide and the interaction, which took place with evolution of heat, was complete in about fifteen minutes. On the addition of ether, a substance was precipitated which melted a t 109-110' and after recrystallisation at 112'.MERCURIC IODIDE SULPHIDES OF THE FATTY SERIES. 167 Analyses of the products of the above reactions were made, with the following results : I. 0.2462 gave 0.0810 HgS.Hg= 28.35. II. 0.2593 ,, 0.0857 HgS. Hg= 28.48. C,HI,I,SHg requires Hg = 28.5'7 per cent. Dirnethyletl~yl~uline iodide-viaemuric iodide, (CH,),(C2H,)SIHg12, was prepared by three methods. 1. Dimethylethylsulphine iodide was dissolved in acetone and the calculated quantity of mercuric iodide added. From the solution, ether precipitated a substance which melted at 8 5 O and, when pure, crystallised from acetone in long, yellow prisms melting at 87". 2. Dimethyl sulphide-mercuric iodide was dissolved in excess of ethyl iodide, and after standing for 12 to 15 minutes, the interaction was complete. Prom the solution, a yellow, crystalline substance melting a t 85' was precipitated by ether, and this, when recrystallised from acetone, formed long prisms which melted at 86.5'.3. An excess of methyl iodide mas added t o methyl ethyl sulphide- mercuric iodide, and the interaction, which took place immediately with slight evolution of heat, was complete in about 2 minutes. On adding ether, a yellow substance melting at 78-79' was obtained, which, after reprecipitating twice from acetone, melted at 87O. When the mixture of methyl iodide-and methyl ethyl sulphide- mercuric iodide was allowed to stand longer than about 15 minutes, an impure product was obtained. I n one experiment, the mixture mas allowed t o stand for 2 hours, and a crystalline substance was then obtained which melted at 160-161°, and was evidently the trimethyb derivative. Analyses of the products of the above three reactions were made,. with the following results : The solution contained a mixture of other substances.I. 0.43 gave 0.1483 HgS. Hg=29-72. 11. 0.5981 ,, 0.2050 HgS. Hg= 29-54. 111. 0.4512 ,, 0.1545 HgS. Hg=29*51. C4Hll13SHg requires Hg = 29 *76 per cent. Methy Zdiethylsulphine iodide-mercuric iodide, CH,( C,H,),SIHgI,, was also obtained in three ways. 1 , 2.5 grams of methgldiethylsulphine iodide were dissolved in acetone and 4-9 grams of mercuric iodide added. From the solution, ether precipitated a yellow, crystalline substance which melted at 64-65O, and after reprecipitating twice from acetone by ether, at 67'; itsacetone solution, when allowe3 to evaporate spontaneously, deposited large, transparent, yellow plates. 2. A concentrated solution of 6 grams of diethyl sulphide mercuric168 MERCURIC IODIDE SULPHIDES OF THE FATTY SERIES.iodide was treated with an excess (3 grams) of methyl iodide. After standing for 3 minutes, the solution was precipitated with ether, giving 5 grams of a yellow, crystalline compound melting at 63-64'. After purification, the product melted at 67', and could be easily obtained in large plates. 3. Methyl ethyl sulphide-mercuric iodide was dissolved in ethyl iodide, and in a quarter of an hour the reaction was complete. The product obtained by precipitation melted at 60-62', but when purified by solution in acetone and precipitation with ether, at 66.5'. When the substances prepared by these methods were analysed, the following numbers were obtained : I. 0,6543 gave 0.2213 HgS. Hg = 29-15, 11. 013950 ,, 0.1330 Hg8. Hg=29*02. 111. 0.3051 ,, 0.1027 HgS. Hg=29*01. C,H,,13SHg requires Hg = 29.15 per cent, It appears, then, so far as these experiments go, that no isomerism exists among the compounds which the sulphine iodides form with mercuric iodide. Although the supposition that these substances contain sexavalent sulphur allows of its possibility, isomerism does not follow as a necessary consequence, for, as already pointed out in the introduction, similar isomerism among the nitrogen compounds is non-existent in the lower members of the series, and only appears when the nitrogen is united to larger and more complex radicles. In connection with this work, attempts have been made to resolve methyl ethyl thetine, CH ~ s < C H 2 * ~ o , into optically active com- C P 5 ponents, but without success. It was found that any attempts to prepare a strychnine or cinchonine salt of the hydrobromide of the thetine, ~ ~ > S < ~ ~ 2 * Co2H, resulted in the formation of its an- 2 5 hydride and the hydrobromide of the active base. Silver malate and the thetine hydrobromide gave similar results. Experiments were also made with PeniciWium ghucwm, but it was found that only a very slight growth of the mould took place after standing for some weeks with a 2 per cent. solution of the anhydride, the solution being inactive. In conclusion, I wish to express my thanks to Professor Ramsay for the interest he has taken in the work described in this paper, and the help he has afforded me in carrying it out. UNIVERSITY COLLEGE, LONDON.

ISSN:0368-1645    

DOI:10.1039/CT9007700160

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

169 VICTOR MEYER MEMORIAL LECTURE, (DELIVERED ON FEBRUARY 8th, 1900). By T. E. TRORPE, Ph.D., D.Sc., LL.D., F.R.S., President of the Chemical Society. BY the untimely death of Victor Meyer, on August Sth, 1897, under circumstances of peculiar sadness, and at the comparatively early age of forty-nine, our sister Society in Berlin lost her President of the year, and, at the same moment, we were deprived of one of the most brilliant of that band of eminent men whom we distinguish as our Honorary Foreign Members. The Council have deemed it fitting that the attempt should be made to put on record our appreciation of the remarkable services Victor Meyer rendered to the science which he cultivated, during the all too short period of his activity, with such striking assiduity and success.As a friend of nearly thirty years’ standing, and as one who worked, literally, side by side with him in the famous laboratory which he lived t o direct, and died whilst directing, I have charged myself with the execution of this duty. Of Meyer’s early life-that is, of the period before I first knew him at Heidelberg as a girlish-looking, bright-eyed youth, quick of movement and active in thought, ready and fluent of speech, full of zeal, and intensely interested in the higher work of the place-I know little, beyond that he was born in Berlin and was the son of a calico manufacturer.* Once, in the course of some discussion on the characteristic differenues in the school training of English and German lads, he made reference to his own experiences in the gymna- sium, from which I gathered that his inclination towards science was in nowise shaped by what he saw or heard i n early youth.Nor, so far as can be determined, was there anything in his home life which inclined him to take to chemistry. I n the case of many who have become eminent in physical science-and doubtless also in the case of more who have not-their first love has sprung from the passion of experimenting. But at this time Meyer, apparently, had neither the opportunity nor the desire to make experiments. Indeed, the home atmosphere tended to make him literary or artistic. There can be no doubt that he owed to this environment, and more especially to the example and precept of his mother, herself a woman of considerable intellectual power, certain strongly marked features of character which * The date of his birth was September 8th, 1848. VOL.LXXVII. 0169 VICTOR MEYER MEMORIAL LECTURE, (DELIVERED ON FEBRUARY 8th, 1900). By T. E. TRORPE, Ph.D., D.Sc., LL.D., F.R.S., President of the Chemical Society. BY the untimely death of Victor Meyer, on August Sth, 1897, under circumstances of peculiar sadness, and at the comparatively early age of forty-nine, our sister Society in Berlin lost her President of the year, and, at the same moment, we were deprived of one of the most brilliant of that band of eminent men whom we distinguish as our Honorary Foreign Members. The Council have deemed it fitting that the attempt should be made to put on record our appreciation of the remarkable services Victor Meyer rendered to the science which he cultivated, during the all too short period of his activity, with such striking assiduity and success.As a friend of nearly thirty years’ standing, and as one who worked, literally, side by side with him in the famous laboratory which he lived t o direct, and died whilst directing, I have charged myself with the execution of this duty. Of Meyer’s early life-that is, of the period before I first knew him at Heidelberg as a girlish-looking, bright-eyed youth, quick of movement and active in thought, ready and fluent of speech, full of zeal, and intensely interested in the higher work of the place-I know little, beyond that he was born in Berlin and was the son of a calico manufacturer.* Once, in the course of some discussion on the characteristic differenues in the school training of English and German lads, he made reference to his own experiences in the gymna- sium, from which I gathered that his inclination towards science was in nowise shaped by what he saw or heard i n early youth.Nor, so far as can be determined, was there anything in his home life which inclined him to take to chemistry. I n the case of many who have become eminent in physical science-and doubtless also in the case of more who have not-their first love has sprung from the passion of experimenting. But at this time Meyer, apparently, had neither the opportunity nor the desire to make experiments. Indeed, the home atmosphere tended to make him literary or artistic. There can be no doubt that he owed to this environment, and more especially to the example and precept of his mother, herself a woman of considerable intellectual power, certain strongly marked features of character which * The date of his birth was September 8th, 1848.VOL. LXXVII. 0170 THORPE : VICTOR MEYER MEMORIAL LECTURE, are not usually associated with men of science. According to his friends Liebermann and Jacobson, his own wish was to become an actor, and that he would have succeeded in such a profession is highly probable. He had, indeed, all the natural gifts of the born actor- dramatic sense, emotional power, a fine voice, an impressive manner, and a handsome presence. When he became a teacher of chemistry, these attributes were turned to good account. His early love of declamation, combined with his elocutionary ability, eventually made him one of the most striking and effective lecturers in Germany.The traditions of the University lecture-theatre no doubt exercised their restraining influence, but Meyer was too much under the sway of his artistic temperament and too impatient of conven- tionality to repress altogether his natural bent. Moreover, he was not insensible to the effect he created, or unmindful of the influence he gained, when, t o use the common phrase, he (‘let himself go,” and by his trenchant, impressive language, and the brilliancy of his illus- tration, communicated something of his own enthusiasm to even the most listless of back-bench men. This power of exposition was quickly perceived, and no doubt its early recognition served to bring him the more speedily to the front.At Heidelberg, as in many other centres of chemical instruction, there was a small Chemical Society, composed of the Extraordinary Professors, the Privat-docenten, and assistants, together with the senior or more active students i n the various laboratories who were elected into it by favour of the teachers. I n my time it numbered amongst its members Erlenmeyer, Ladenburg, Horstmann, Ludwig, Cohen (the mineralogist), Rose, and Emmerling. Its president was Bunsen, and the occasions on which he took the chair were the red-letter days of the session. We invariably sent him home happy, his pockets filled with all the good champagne corks we could collect. The formal business of the Society-if formal it can be called-was preceded by an Abend- essen, and if not accompanied, at least succeeded, by a considerable mani- festation of ‘‘ das gemuthliche Element.” No man was more popular at these gatherings than Meyer.His nimble mind and retentive memory, his gift of ready speech, his sense of humour and genial manner combined to make it pleasant to listen to him no matter whether he was, in accordance with the rules of the Society, called upon to give an account of some work which had just been published, or whether he was discussing and criticising a communication from a fellow member. From time to time we had reports of the condition of such investigations as were in progress in the Heidelberg laboratories, or of which the results were to appear in the forthcoming issue of the Annalen, for, at the period of which I write, the Berichte was a thin and puny pub- lication, hardly out of its swaddling clothes, and with little sign of theTHORPE : VICTOR MEYER MEMORIAL LECTURE.171 vitality which has since enabled it to assimilate practically the whole outcome of German chemical activity. Of his own laboratory work, we had nothing from Meyer, for there was little or nothing a t the time to be told. He had entered the University in the autumn of 1865, when barely seventeen years of age, and apparently with no very definite conception of a career. Suddenly he elected to study chemistry, and attached himself to Bunsen with the idea of ultimately becoming a teacher. I t is not improbable that his choice was in a measure determined by the cir- cumstance that he had attended some of Hofmann’s lectures in Berlin in the preceding summer, and had thus been influenced by that great teacher, then in the fulness of his intellectual vigour.Those were the palmy days of Heidelberg-the days of Bunsen, Kopp, Kirchhoff, Helmholtz-and Meyer came under the spell of them all. His pro- gress as a student was exceptionally rapid, and the brilliant manner in which he gained his doctorate-without the adventitious aid of a thesis-strongly impressed the wholo philosophical faculty. Bunsen, especially, was greatly struck with the power and promise of the young Jew, then one of the youngest students in the University, and soon selected him as one of his assistants. It was in this capacity that I first made the acquaintance of Meyer. Bunsen for some years previously had been engaged in the examination of the mineral waters of South Germany, and Meyer a t the time I entered the Heidelberg laboratory was acting as water analyst.However great the disciplinary value of such work might be (and no one who has practised Bunsen’s method of water analysis, with its system of check and control, can doubt that it is one of the most rigorous quantitative exercises possible), I fear i t was not altogether con- genial to the active mind of the young assistant, who was yearning to try his ’prentice hand a t original research. Accordingly, towards tho end of 1868 he threw up the position, arid entered Baeyer’s little laboratory a t the Gewerbeakademie in Berlin. Although in a sense overshadowed by the more magnificently appointed University laboratories of Hofmann in the Georgenstrasse, and of Kekulb in Bonn, both a t that time comparatively new, the modest laboratory of the Gewerbeakademie, with its twenty workers, was already one of the most famous schools of organic chemistry in Europe.Baeyer himself had recently published his brilliant investigation of mellitic acid ; and Graebe, at first alone, and subsequently in conjunction with Liebermann and with Caro, was a t work on those remarkable sorim of inquiries which served to establish the true chemical nature and relationships of alizarin, and led eventually, with the independent collaboration of Perkin, to its artificial production on a commercial 0 2172 THORPE : VICTOR MEYER MEMORIAL LECTURE. scale. I well remember the interest and excitement which these dis- coveries created in Germany : they unquestionably gave an enormous impetus to the study of organic chemistry and attracted eager aspir- ants for chemical fame from all parts of the world, quickened, no doubt, by the perception of the rich promise of material benefit thus suddenly opened up.Heidelberg at that period was pre- eminently a school of inorganic chemistry : organic chemistry was represented by Delffs and was mainly studied by prospective apothe- caries. Erlenmeyer had been called to the Polytechnic at Munich, and the influence of KekulB’s teaching was as yet hardly felt by any of the Privat-docenten. Baeyer quickly recognised the power and ability of his pupil, and t o Baeyer was undoubtedly due the impulse which started him on his career.As a Vorgeruckter ” he attended no more lectures, and thus it happened that he who became one of the greatest organic chemists of his time never followed a course on organic chemistry. Shortly after his entrance into the laboratory, he began the series of half-dozen investigations which characterised his activity during his three years’ stay in Berlin. His first paper, published in the Berichte, was a note on the action of trimethylamine upon monochlorhydrin, which sub- stances form a basic condensation product, the chloride and the gold salt of which he described (Ber., 1869,2, 186). This was quickly followed by a short paper on diethyl thiodicarbonate, S(CO,Et),, which he obtained by the action of ethyl chloroformate upon sodium sulphide (Ber., 1869,2, 297).A far more ambitious production appeared in the following year, dealing with the constitution of the disubstituted benzenes (Annuden, 1870, 156, 265). I n this memoir, Meyer described a new method of introducing a carboxyl group into the molecule of aromatic compounds, no matter whether the substance already contained a carboxyl group or not. This was effected by the action of sodium formate upon the potassium salt of the aromatic sulpho-acid. Of the acids prepared synthetically by this method, isophthalic acid was the most important on theoretical grounds, as its production under these conditions led to a revision of the views then held with respect t o the orientation of the radicles in the “ortho” and “meta” (salicylic) series.Isophthalic acid had been shown by Baeyer to be a 1 : 3-derivative. “ Ortho ”-sulphobenzoic acid, obtained from benzoic acid, was thought t o have its radicles in contiguous positions. Meyer’s experiments showed that isophthalic acid was the only di- carboxylic acid formed from the sulpho-acid by interaction with a formate, whence he argued that ‘‘ ortho ”-sulphobenzoic acid, and the chloro-, bromo-, nitro-, amido-, and hy droxy-benzoic acids corre-THORPE : VICTOR MEYER MEMORIAL LECTURE, 173 aponding with it in constitution, must, like the isophthalic acid, be 1 : 3-derivatives. It followed that the meta ” (salicylic) series of compounds are the 1 : 2-compounds, The main facts of this paper have long since taken their place in the history of our knowledge of aromatic compounds, but the memoir has an especial interest as being Meyer’s first excursus into the realm of chemical theory.I n a subsequent extension of the work, in conjunction with Ador (Annuden, lS71, 159, l), he showed that in sulphanilic acid the substituent groups S@,H and NH, were in the 1 : 4 positions. The phenolsulphonic acid from sulphanilic acid he proved to be identical with Kekuld’s paraphenolsulphonic acid, and hence to have the position 1 : 4. Potassium monobromobenzoate fused with sodium formate yields isophthalic acid ; hence this bromobenzoic acid belongs t o the 1 : 3 series. At the conclusion of their memoir, the authors gave a list of the disubstituted derivatives of benzene then known, arranged in columns according to whether the second substi- tuent element or radicle is attached to the second, third, or fourth carbon atom, as deduced from the experimental evidence put forward.Their views as to the orientation of the substances there named, except in the case of the dihydroxybenzenes, have not been materially modified by subsequent inquiry, Pending the publication of this work, Meyer essayed to solve that cwcanurn of aromatic chemistry, the constitution of camphor (Ber., 1870,3, 116). He sought to show in the first place that camphoric acid is a dicarboxylic acid, C,H1,(CO,H),. Since camphor yields, by the action of dehydrants, an homologue of benzene, namely, cymene, he reasoned that it must contain the benzene nucleus, and hence the remaining four carbon atoms must exist in the side-chains.But by the oxidation of camphor to camphoric acid, the side-chains apparently are not attacked; the action would seem to be on two of the carbon atoms in the benzene ring. The carboxyl groups cannot be attached t o one and the same carbon atom, otherwise camphor would not yield an homologue of benzene by abstraction of water. therefore that, in all probability, camphor ought stitution expressed by one or other of the following (1) COHO C,H, 4: CH. (2) ?(OH) :C,H,,:QH. (3) YH:C,H,,:YH. 0- - It would follow to have the con- formulze : The first, or aldehydic, formula, suggested by Berthelot, was practically disproved by the work of Fittig and Tollens. The second formula, which contains the hydroxyl group, was rendered improbable by174 THORPE : VICTOR MEYER MEMORIAL LECTURE.Berthelot, and the improbability was further strengthened by Meyer, who found that acetic chloride was without action on camphor. The third formula then would seem of the three to be the most probable. The constitution of the group C8H,, can only be inferred from that of the camphor cymene. This, as shown by Fittig and his pupils, is probably for the most part methylpropylbenzene," Hence camphor would appear to have the constitution yH:C(CH,) * CH,*CH,* C(C,H,):CH, o------' and camphoric acid CO,H*Q(CH,)* CH,*CH,* 7(C,H7)*C0,H. Borneo1 would be CH(OH):C,H,,:CH,. These views have now only an historical interest. All that is certain in them is that Meyer's conception of camphoric acid as a dicarboxylic acid is correct. The work of Claisen and Manasse has rendered it practically certain, as long surmised, that camphor has the grouping C,Hl4<YH2, It has, co however, required the labour of a generation of workers, and the accumulation of a literature which, as regards its bulk, is without a parallel in any other department of chemistry, to unravel the true relations of camphoric acid to camphor, and hence to get an insight into the constitution of a substance which has been known in Europe and prized as a medicine since the twelfth century.Meyer acquired some experience in tuition, even in the early Heidelberg days, as a "coach," and in Berlin he added to his means, which were slender enough, by similar work. His success as a teacher induced Baeyer to recommend him to Fehling, who sought assistance, especially in modern organic chemistry and in laboratory teaching, in connection with his duties at the Stuttgart Polytech- nic.His departure from Berlin was a great loss to the little circle in the Gewerbeakademie, where his high spirits and geniality made him universally popular. He was an omnivorous reader and the power of his memory was astonishing, so much so that on his leaving, Baeyer exclaimed '( Jetzt werden wir ja wieder die Literatur nachschlagen mussen." How he came to leave it has already been told by Professor Liebermann. Johannes Wislicenus had just been called from the Zurich Polytechnic to Wiirzburg, and the President of the school, Kappeler, was engaged in searching for a successor. He came to Stuttgart and, unknown to * Widman (Bey., 1891, 24, 450) subsequently proved that cymene is methyliso- propylbenzene, but this does not affect Victor Meyer's argument, He remained in the Wiirtemberg capital barely a year.THORPE : VICTOR MEYER MEMORIAL LECTURE.175 Meyer, attended one of his lectures. Although Kappeler, as he him- self relates, knew little of chemistry, he was so struck with Meyer’s power of lucid and stimulating exposition that the decision to invite him to Zurich was immediately made. At the close of the lecture, he communicated tc the unsuspecting young teacher his idea, expressing, however, his fear that in comparison with his future students he might prove to be still too young. As Meyer laughingly promised to do his best, day by day, to repair this fault, the invitation was given, and thus, when barely 24 years of age, he found himself Ordinarius and Director of the chemical laboratory of the Zurich Polytechnic.The Zurich Polytechnic has enjoyed a succession of distinguished teachers, and Meyer worthily sustained and, indeed, greatly extended the fame of its chemical chair. He was now in possession of a well equipped laboratory and surrounded by eager, active students, stimu- lated and encouraged by the enthusiasm of a teacher as active and eager, and, it may be added, as high-spirited as themselves. The thirteen years of Meyer’s stay at Zurich constitute the most fruitful and the most brilliant period of his career : before its close, he had brought himself within the foremost rank of contemporary investi- gators. Some idea of his wonderful power of work, and of the stimulus he gave to others, may be gleaned from the fact that during that period the Zurich laboratory, under Meyer’s direction, gave close upon 130 papers and memoirs to chemical literature.It is, of course, impossible here t o do more than indicate, in the briefest possible out- line, the outcome and significance of the more important of them. During his short stay at Stuttgart he sent some half dozen papers to the Berichte, some of them in continuation of work which had occupied him in Berlin. The chief of these were put together in a memoir, in conjunction with Stuber, on the aromatic amines, which appeared in 18’43 (Annalen, 1873, 165, 161). The main objeet of the work was to gain further evidence in favour of Meyor’s view, that in the case of the chloro-, bromo-, iodo-, and nitro- derivatives of aromatic amines, obtained by direct substitution, it is always the hydrogen immediately contiguous to the amido-group which is replaced, or, in other words, that the NH, group exercises an attractive influence on the substituent.It was assumed byKekul8 that Riche and BBrard’s dibromaniline, obtained by the reduction of dibromonitrobenzene, was identical with the dibromaniline from acetanilide. Meyer and Stuber proved that such was not the case. It was found that Riche and B6rztrd’s dibromaniline yields, or is derived from, a l i p i d dibromobenzene, which boils at 219*4O, and remains liquid at -28’. Riese had previously obtained a liquid dibromobenzene boiling at 224O and crystallising below - lo.All the three possible dibrornobenzenes were thus made known. Meyer’s176 THORPE : VICTOR MEYER MEMORIAL LECTURE. surmise that the new dibromobenzene was the 1 : 3 variety has since been established, The authors also made known the existence of a new tribromobenzene melting at 119O, the symmetric or 1 : 3 : &derivative. The isomerism of the liquid dibromo benzenes was subsequently con- clusively demonstrated (Ber., 1874, 7, 1560) by the crystallographia examination of their mononitro-derivatives by Grot h and Bodewig. In this connection may be mentioned a short paper, in conjunction with Wurster, ‘‘ On some derivatives of solid Dibromobenzene ” (Annalen, 1874, 172, 57). In the attempt to prepare a nitrated phenylenediamine by acting upon di bromonitrobenzene with alcoholic ammonia, in the same manner that Walker and Zincke obtained nitraniline from monobromonitrobenzene, they found that only a moiety of the bromine could be displaced, the resultant product being a new substance, bromonitraniline, in which the NO, group is next to the NH, group, By converting this substance into bromo- phenylenediamine, the two NH, groups would be in close proximity ; on debrominating this compound, the resulting phenylenediamine was found to be identical with that discovered by Griess (m.p. 99O), whose surmise that the NH, groups were united to contiguous carbon atoms was confirmed. Meyer began also an inquiry on the chemical nature of chloral hydrate, a substance which, in consequence of Liebreich’s discovery of its anaesthetic action, had by that time become of considerable industrial importance, and was readily procurable.By the action of acetic chloride upon chloral hydrate, tetrachlorethyl acetate, CCl,*CHCl*O=CO*CH,, is obtained, identical with the product formed by the condensation of chloral and acetic chloride, or by the action of acetic chloride on acetaldehyde. Chloral alcoholate with acetic chloride yields C C 1 3 * C H < ~ ~ ~ ~ ~ c H l indicating that the alcoholate, as already shown by Henry on other chemical grounds, is the ethyl ether of trichlorethylidene glycol. By dissolving chloral hydrate in glacial acetic acid, Meyer obtained a white, crystalline substance, melting at BOO, which he regarded as isomeric with ordinary chloral hydrate (m. p. 55’). The chloral hydrates may have respectively the constitution (I) CCI,*COH + H,O.(2) CCl,*CH(OH),. It is not proved, however, that they are not polymeric (Annaten, 1874, 171, 66). It is possible that the substance thus obtained is identical with the uniaxial form observed by Pope which slowly changes into the biaxial modification stable at ordinary tempera- tures (Trans., 1899, 75, 458). Meyer does not definitelyTHORPE : VICTOR MEYER MEMORIAL LECTURE. 177 decide which of the two formula represents the constitution of ordinary chloral hydrate, but he inclines to regard it as trichlorethyl- idene glycol, which Perkin’s observations on its magnetic rotation definitely indicate that it is. Wallach’s observation of the conversion of chloral into dichloracetic acid was shown by Meyer to be in accordance with a general property of aldehydes in alkaline solutions to take up the elements of water, one molecule of aldehyde being thereby reduced, whilst another is oxidised.Meyer, in conjunction with his pupil Haffter, devised a very simple and rapid method of estimating the actual quantity of pure chloral in the commercial product, founded on the fact that chloral hydrate is rapidly decomposed by an aqueous solution of an alkali into chloroform and an alkaline forrnate (Ber., 1873, 6, 600). Although Meyer’s papers up to this time had amply demonstrated his power of investigation, and aEorded to critics like Kekuld and Baeyer abundant proof of the clearness and keenness of his vision, he had hitherto worked upon somewhat conventional lines.His memoir ‘( On the Nitro-compounds of the Fatty Series ” (Artmaten, 1874, 171, l), which appeared shortly after his removal from Stuttgart to Zurich, at once stamped him as an original investigator of a very high order. I n anticipation that two series of alkyl nitrites would be found to exist, denoted in hhe methyl series by CH,*NO, and CH,-O*NO, Meyer, whilst still at Stuttgart, had studied the action of amyl iodide upon silver nitrite and had obtained a colourless liquid, having the ordinary smell of amyl compounds, boiling between 150’ and 160°, which on analysis was found to have the composition C5H,,N0,. Hence it was isomeric with amyl nitrite, a yellow liquid of a peculiar, disagreeable smell, which boils a t 99”. To the new compound Meyer gave the name of nitropentane.The reaction was found t o be general. He now entered upon an elaborate investigation of the nitro-compounds of the alkyl series and their derivatives, and of questions incidental to the main subject, which, in conjunction with his pupils, among whom may be mentioned Stuber, Rilliet, Chojnacki, Wurster, Clonstam, Janny, Lecco, Locher, Tcherniac, Ceresolc, Niiller, Demuth, Keppler, and Zublin, continued to occupy him a t intervals for upwards of twenty years. One peculiarity which distinguishes aromatic from aliphatic com- pounds consists in the ease with which ‘nitration,’-that is, the replacement of hydrogen by the group NO, with the elimination of water-may be effected in the first-named substances. A reaction analogous to that by which nitrobenzene is formed from benzene was scarcely known among fatty compounds, the most familiar instance being the production of chloropicrin by the action of strong nitric178 THORPE : VICTOR MEYER MEMORIAL LECTURE.acid upon chloroform. The constitutional difference between the nitroparaffins, as the new group came to be called, and the alkyl nitrites consisted in the fact that, in the first-named substances, the NO, group is directly connected with a carbon atom, as in nitro- benzene, whereas in the alkyl nitrites the NO group is intermediately linked with the hydrocarbon radicle by means of oxygen. The alkyl nitrites are true esters capable of being resolved isto alcohols and nitrous acid by the hydrolytic action of alkalis or acids, The nitro- paraffins, on the other hand, are incapable of hydrolysis.By reduction, they yield alkyl hydroxylamines and then the corresponding amine. By reduction, however, the alkyl nitrites lose their nitrogen and form the corresponding alcohol. Heyer’s view that the nitroparaffins were veritable nitro-compounds mas not a t once accepted. Geuther, and subsequently Gotting, as- sumed that nitroethane was acetamidoxide, CH,*CO*NH,O, whilst Kissel regarded it as aeethydroxylamine, CH,*CO*NH(OH). It is true, as found by Meyer, that nitroethane, under the hydrolytic influence of strong acids, splits up into hydroxylamine and acetic acid, but since phosphoric chloride is without action upon nitroethane, an hydroxyl group must be assumed to be absent. As for Geuther’s view of the constitution of these substances, Meyer had little difficulty in showing that it wholly failed to explain all their known reactions.The general characteristics of the nitroparaffins, namely, the power of forming salts possessed by the primary and secondary compounds, the absence of this power in the tertiary series, together with the re- markable differences in the behaviour of bromine, and of the action of acids upon the primary and secondary nitroparaffins, were carefully studied by Meyer and his pupils. He found that when a solution of a primary nitroparaffin in potash is mixed with an alkaline nitrite and treated with sulphuric acid, the liquid acquires a blood-red colour which disappears on the further addition of acid. On shaking the whole with ether, there is obtained a solution of a new acid, known N* OH as a nitrolic acid, of the general formula C,R2n+~*C<No .case of nitroethane, the formation of the ethylnitrolic acid represented as follows : 2 I n the may be N* OH CH3*C<Eb + ON* OH E= H20 + CH,* C<NO, That such is the constitution of ethylnitrolic acid is indicated by its formation by the action of hydroxylarnine on dibromonitroethane, CH,. CeBr2 + H,N*OH = 2HBr + CH,. CcN0, N* OH . NO2 The nitrolic acids are colourless, sweet-tasting substances of a strongTHORPE : VICTOR MEYER MEMORIAL LECTURE. 179 acid reaction, readily soluble in water, and for the most part easily crystallisable. In alkaline solution, they give an intense blood-red coloration and form characteristic precipitates with salts of the heavy metals.They slowly decompose on standing, and on heating are quickly resolved into the corresponding fatty acid, nitrogen, and nitrogen dioxide. On treating the nitrolic acids with sodium amalgam, substances known as azaurolic acids are formed, They are strongly coloured, sparingly soluble substances, and differ from the corre- sponding nitrolic acid by containing two atoms of oxygen less. The best known member of the series is ethylttzaurolic acid, C,H,N,O, or more probably C,H,N,O,. On heating, it yields, together with forma- tion of nitrous oxide and water, ethylleucazone, C4HrN,0, a substance possessing both acid and basic properties, and in its general charac- teristics resembling an amido-acid. The secondary nitroparaffins, when treated with nascent nitrous acid, behave quite differently from the primary compounds.On adding sulphuric acid to the mixed solutions, a deep blue colour is produced and insoluble substances are formed, isomeric with the nitrolic acids, but which have no acid character. They were called by Meyer pseudo- nitroles, and have been regarded as nitrosonitro-compounds. ;g;>c<&@ Their formation may be thus represented (CH,),CH*NO, + OH*NO = 1T20 + (CH,),C(NO)*NO,, Scholl subsequently discovered that these substances may be obtained by the action of nitrogen peroxide upon the ketoximes: thus with acetoxime : 4(CH,),C:N*OH + 3N,04 -" 4(cH3)&<~0 + 2H,O + 2N0, a mode of formation which, as Meyer pointed out, indicated that they may be regarded as the nitrates of the oximes, (CH,),C:N-O*NO,.Their formation from the secondary nitro-compounds may be supposed to occur in the following phases : NO 2 (CH3),CH*N<? + HNO, = (CH,),CH*N<OH O*NO, , 0 (CH,),CH*N<ggo2 - H,O = (CH,),C:N*O*NO,. Meyer was inclined to give the preference t o the latter view of their constitution, as it is generally very doubtful whether compounds containing a nitroso-group (NO) directly linked to a carbon atom are capable of existence.180 THORPE : VICTOR MEYER MEMORIAL LECTURE, Tertiary nitro-compounds are unchanged by the action of nascent nitrous acid. Meyer pointed out how the characteristic colour reactions afforded by the behaviour of nitrous acid with the primary and secondary nitro- paraffins, and its inability to act upon the tertiary compounds, offered a ready means of distinguishing primary, secondary, and tertiary alcohol radicles.The iodido to be tested is distilled with silver nitrite, the distillate shaken with a solution of potassium nitrite in strong potash, diluted with water, and mixed drop by drop with dilute sulphuric acid. If the liquid acquires a red colour (formation of nitro- lic acid) which disappears with excess of acid and reappears on the addi- tion of alkali, we are dealing with a primary radicle : should the liquid give a blue colour (formation of pseudonitrole) soluble in chloroform, the compound is derived from a secondary alcohol radicle ; the non-forma- tion of colour indicates a tertiary radicle. The test ceases to be of much practical value beyond the 5 carbon series (compare Meyer and Jacobson, L e h h c h der Orgarkchen Chemie, 1893, 253, et seq.).The same line of inquiry was extended to the other main groups of aliphatic substances, and resulted in the discovery of new types of compounds. Thus, by the reduction of the isonitrosoketones and the isonitrosoacetoacetic esters, Meyer, in conjunction with Treadwell, obtained a series of volatile bases having apparently the generic formula C,H2, - 4N2, which they termed ketines and subsequently aldines. This group of substances is now generally known as the azines, and the substance first described by Meyer and Treadwell is dimethy lpyrazine, ,C(CH,): CH BCH,*CO*CH:N*OH + 6H = N ‘N + 4H,O. \CH :c~H,)/ Meyer had the faculty of keeping more irons hot a t a time than any man of his period.Although much of his thought and energy was directed in the first years of his sojourn in Zurich to the development of the new field of inquiry which his discovery of the nitroparaffins opened out, he continued his work on aromatic compounds, partly in defending positions he had already secured, and partly in breaking new ground. I n the latter connection, reference may be made to his discovery, with Michler, of diazoxybenzoic acid, and to the new class of azo-compounds which he described in conjunction with Ambuhl. A point of some little interest a t the time (1875) was his discovery that hydroxylamine and nitrous acid together yield nitrous oxide and water, NH,O + NO,H = 2H20 + N,O, in the same manner that nitrous acid and ammonia form nitrogen and water. The production of nitrous oxide by mixing together concentrated aqueous solutions ofTHORPE : VICTOR MEYER MEMORIAL LECTURE.181 hydroxylamine sulphate and sodium nitrite constitutes a noat and striking lecture experiment. He also showed, with Locher, that hydroxylamine may be obtained by a number of new reactions, as, for example, by acting on dinitropropane or ethylnitrolic acid with tin and dilute hydrochloric acid, when, in the one case, the amine is liberated in conjunction with acetone, and, in the other, together with acetic acid. (1) CH,. C(NO,),* CH, + 8H = CH,* Coo CH, + 2NH,O + H,O. (2) CH,. C(N*OH)*N02 + 4H + H2O = CH3* CO,H + 2NH3O. These reactions showed that the rule, hitherto regarded as universally true, that nascent hydrogen reduces nitroxyl to amidogen, has its exceptions.But perhaps the most important of Meyer’s discoveries a t this period was that of the oximes. He hadobserved that dibromonitroethane, under the action of hydroxylamine, passes into ethylnitrolic acid, and he antici- pated that the analogous nitrosoacetone would be formed in like manner from unsymmetrical dichloracet one. Experiment showed, however, that the chlorine in dichloracetone was replaced by a hydroxylamine rest, whilst the ketonic oxygen was replaced by the oximido-group, forming a compound termed by Meyer acetoximic acid, but now known as methylglyoxime, CH,. C(:N* OH)*UH(:N*OH). The fact that hydr- oxylamine would thus react upon carbonyl oxygen induced him, in conjunction with Janny, to study the action of this reagent upon ordinary ketones and aldehydes, and thus led to the discovery of the ketoximes and the aldoximes.This discovery has a two-fold signifi- cance. The reaction not only serves to indicate the existence of carbonyl oxygen in compounds, and hence is of value as a mode of determining constitutional problems, but it brought into existence a number of substances yielding derivatives of considerable interest. Further, it is not too much to say that the stereochemistry of nitrogen takes its rise from the discovery of the oximes. With Janny, he likewise obtained a-nitrosopropionic acid by the action of hydroxylamine on pyroracemic acid, a reaction which is almost quantitative and capable of being used as a test for pyro- racemic acid. Although it was quickly recognised as an exceedingly reactive substance, its use was greatly curtailed by the difficulty and expense of preparing it in quan- tity, Much of it, prior to 1883, was obtained by Dumreicher’s process, namely, by reducing ethyl nitrate by means of stannous chloride and hydrocliloric acid.Meyer showed how the irksomeness of the method, entailed by the necessity of removing the tin by sulphuretted hydrogen, and of dealing with the large volume of liquid produced, Lossen discovered hydroxylamine as far back as 1865.182 THORPE : VICTOR MEYER MEMORIAL LECTURE. might be materially lightened, and considerable quantities of hydroxyl- amine salts were made by the modified process in the Zurich laboratory. The position which hydroxylamine occupies between ammonia and nitric acid, which a t that time were held to be the main nitrogenous foods of plants, as well as its great; chemical activity when compared with the inertness of the other substances, seemed to Meyer to point to a possible formation of hydroxylamine within the plant, and to its playing an important part in the assimilation of starch and in the formation of albuminoids.In conjunction with Schulze, he therefore made comparative experiments on the action of hydroxylamine, ammoniacal salts, and nitrates upon plants, when it was quickly found that hydroxylamine acted as a poison to vegetable organisms. Meyer, however, points out that it may still be possible thah hydroxylamine may be formed in transition products, and yet act as a poison when taken up by the roots, just as peptone behaves as a poison when in- jected into the veins of animals.Reference may here be made to Meyer’s attempts to elucidate the constitution of ammonium salts. It was found that the di- methyldiethylammonium iodide, obtained by the action of ethyl iodide on dimethylamine, is identical with that produced by acting with methyl iodide on diethylamine, and no difference can be detected in the character of their salts. As the substances, although identical, were obtained by different reactions, it was inferred that they could not be ‘ molecular ’ compounds, that is, combinations of a tertiary base with an alkyl haloid, but must contain pentavalent nitrogen, whence, by analogy, ammonium chloride would be This assumption is only sound on the supposition that, in tho forma- tion of the salts, no change had taken place in the position of the alcohol radicles.The main conclusion would be invalidated if, for example, ethyl iodide, when reacting on trimethylamine, did not com- bine directly with it but was decomposed, as Lossen had suggested, as follows : N(CH,), + C,H$ = CH$ + N(CH3)2C2H5. To ascertain if such an interchange occurred, Meyer, in conjunction with Lecco (~nnahn, 1876, 180, 173), studied the action of ethyl iodide upon tetramethylammonium iodide. If Lossen’s contention were sound, the reaction should be N(CH3),$ + C,H,I = CH31 + N(CH,),C,H,I.THORPE : VICTOR MEYER MEMORIAL LECTURE. 183 No action, however, was found t o occur either with ethyl or methyl iodide alone at any temperature up to 180”, or in presence of methyl alcohol or water.Ladenburg and Struve tested Meyer’s conclusion by making similar experiments with benzyl iodide and triethyl- amine, and with ethyl iodide and benzyldiethylamine, and were dis- posed to regard the resultant compounds as isomeric, although closely alike in most of their properties. On repeating the observations, Meyer found that no difference existed ; the substances prepared in the two ways were absolutely identical. Suggestive and fruitful in ideas as Meyer was, he was seldom at a loss in devising means t o put them to the test of trial. I n many of his mental characteristics not unlike Davy, as an experimentalist, he had all Davy’s resourcefulness with far more than his patience. As I knew him i n Heidelberg, he was an excellent manipulator ; still his temperament would never have permitted him to better the example of the great master under whom he was trained.We could all look on and marvel at the patient, concentrated power with which Bunsen would devise, elaborate, and perfect some new form of apparatus, or some new method of analysis. The first steps were very simple-so simple indeed that it was frequently impossible to divine their ultimate purpose. It was from such small beginnings that we obtained the whole process of gasometric analysis, the burner, the photometer, the various voltaic batteries, the spectroscope, the filter-pump, the ice-calorimeter, the flame reactions, &c. Before Bunsen gave a piece of apparatus t o the chemical world, he left it practically perfect ; the striving after perfection was a veritable passion with him, and numerous were the forms or modifications through which the apparatus or the method passed before he rested satisfied with it.Although bleyer’s genius was of a different order, the influence of the Heidelberg training is to be recognised in the various forms of laboratory apparatus with which his name is connected. Chief among these are his modes of determining vapour densities. The elegant modification of Gay Lussac’s method intro- duced by Hofmann left nothing to be desired in the case of compara- tively volatile substances unacted upon by mercury, but many bodies were known, and their number was being rapidly increased, in which this method was inapplicable. Meyer accordingly, in 1876, devised his displacement method (Ber., 1876, 9, 1216).This in principle was similar to the method suggested by W. Marshall Watts as far back as 1867, from which it differed in that Wood’s metal-an alloy of bismuth, lead, tin, and cadmium, melting below 70°-replaced the mercury, and that the volatilisation was effected at the temperature of boiling sulphur, that is, at 444’. This process allowed of the determination of the vapour density of many substances which could184 THORPE : VICTOR MEYER MEMORIAL LECTURE, be vaporised at temperatures below the boiling point of sulphur, and compounds like diphenyl, methylanthracene, triphenylamine, paradi- bromobenzene, and paradiphenylbenzene, had their vapour densities ascertained for the first time by means of it, The method was further modified in the following year (Ber., 1877, 10, 2068), mercury being used instead of Wood’s metal and the vapours of boiling water, aniline, ethyl or amyl benzoate or diphenyl- amine-depending on the temperature required-were employed tts a bath instead of sulphur vapour.The t6 Luftverdrangung Methode ”-the simple and extremely con- venient process-which will for all time be associated with the name of Victor Meyer, was devised in 1877 (Bey., 1877, 11, 1867). The apparatus is now one of the commonest articles of laboratory furniture, and i t is not too much to say that, thanks to the ease with which the whole operation may be carried out, more vapour densities have been determined by its aid than by any other means. The apparatus is usually constructed of glasg, but by making it of glazed porcelain, determinations can be effected a t very high tempera- tures.Except for special reasons, neither the temperature of the heated bulb nor its volume need be known : all that is required is that the temperature should be sufficiently high to gasify the substance under examination. Avariety of liquids-water, xylene, aniline, ethyl benzoate, amyl benzoate, diphenylamine-depending on the temperature needed t o effect complete vaporisation, may be used as media for heating the bulb. For temperatures exceeding 300°, a bath of molten lead may be employed, the glass bulb of the apparatus being coated, as suggested by Watson Smith and Davis, with a moderately thick film of soot before immersion in the bath so as to diminish the risk of fracture.Mr. Watson Smith, who was with Meyer at Zurich, and who has kindly sent me some reminiscences of him a t this period, writes: “It was somewhat singular that just as Victor Meyer, with Carl Meyer (no relation), had completed their vapour density apparatus for bodies of very high boiling point, I had just obtained in the pure state specimens of the three isomeric dinaphthyls, all of which urgently awaited the determination of their vapour densities. They mere the first new high boiling substances with which the apparatus and method were tried. Victor Meyer was immensely pleased and interested with this circumstance, and we practically all three worked the de- termination together, the results amply proving the reliability and accuracy of the new method. Of course in these cases the lead bath was used ” (compare Trans., 1879, 35, 226 ; 1880, 3’7, 491).The molecular weights of a number of substances were quickly ascertained by this method, for example, phosphorus pentasulphide, indium chloride, cuprous chloride, stannous chloride, arsenious oxide,THORPE : VICTOR MEYER MEMORIAL LECTURE. 185 antimonous oxide, cadmium bromide, &c. Volatilised in an at mo- sphere of hydrogen chloride, ferrous chloride yielded values between FeCI, and Fe2Cl,. Ferric chloride a t no temperature showed a vapour density corresponding with Fe,Cl,, whilst a t 750” and 1077”, its mole- cule would seem to be FeC1,. Potassium iodide at 1320’ in an atmo- sphere of nitrogen had a density corresponding with KI. Arsenic and phosphorus at a white heat had densities approaching the values for As, and P,, whilst zinc a t 1400°, and bismuth at 1700”, were found to be monatomic, and thallium at 1700” diatomic.In 1879, the two Meyers, Victor and Carl, astonished the chemical world by announcing (Bey., 1879, 12, l426), as the result of de- terminations of their vapour densities a t high temperatures, that the halogens were capable of undergoing dissociation or possibly decom- position. As regards chlorine, this announcement at once threatened to re-open a question which had been regarded by most people as practically settled since July 12th, 1810, when Davy read to the Royal Society his classical memoir on oxymuriatic acid. Davy, it is true, had never stated that chlorine was an element i n the absolute sense of that term.What he inferred was that it was a substance which ‘‘ has not as yet been decompounded,” and therefore is “ ele- mentary as far as our knowledge extends.” The very name chlorine, which he suggested, inculcated this view, “ To call a body which is not known t o contain oxygen and which cannot contain muriatic acid, oxymuriatic acid, is contrary to the principles of that nomen- clature in which it is adopted. . . , After consulting some of themost eminent philosophers in this country, it has been judged most proper to suggest a name founded upon one of its obvious and characteristic properties-its colour, and to call it chlorine, or chloric gas. Should it hereafter be discovered to be compound, and even to contain oxygen, this name can imply no error, and cannot necessarily require a change.” Had chlorine then been ‘decompounded’? Did it contain oxygen? Were Berzelius and Murray right after all? Was there such an entity as murium? The pages of the popular scientific periodicals of the time show how these questions agitated the minds of chemists.The indications of the spectroscope were advanced as confirmatory of Meyer’s results, and there was much exercise of ‘ the intelligent anticipation of events before they occur ’ which occasioned him some annoyance at the time. However sanguine he might be that he had decomposed chlorine, and however freely he might talk with his colleagues, he never committed himself in print to any statement of the kind. To begin with, the amount of oxygen he had obtained was very small, and there was uncertainty as t o the action of the chlorine upon the silica or alumina of the VOL.LXXVII. P186 THORPE : VICTOR MEYER MEMORIAL LECTURE. porcelain at the high temperature, and whether the materials em- ployed were wholly free from moisture. I have it, on the authority of Professor Lunge, whose knowledge was derived from daily inter- course with him, that Meyer himself refused to consider the fact as es- tablishad until he had worked in an apparatus made of material devoid of oxygen, and to this end he obtained a special grant from the Zurich authorities to defray the cost of a vessel of platinum; Meanwhile Meyer’s observations on chlorine were repeated, and their validityimpugned by Crsf ts (Compt. vend., 1880,90,153 et sea.) who found, by a modification of Meyer’s method, that the gas, even at the highest temperature of the Perrot furnace, showed no change indica- tive of diseociation or decomposition.Meyer, in conjunction with Ziiblin, at once repeated Crafts’ determinations on preformed chlorine and confirmed their accuracy. As regards bromine and iodine, however, the observers were in substantial agreement. Thus with iodine : Victor Meyer. Crafts and Meier. Temp. Density. D’lD. Temp. Density. 0’10. 450° 8.85 - 445O 8.74 - 686 8-72 0.99 830--880 8’07 0-92 842 6.76 0’77 1020-1050 7.01 0 ‘80 1030 5.75 0.66 1275 6-82 0.66 1670 5.70 0.65 1390 5.28 0.60 Naumann showed from these results, on the assumption that the molecule I, splits up into two atoms 191, that the course of the dissociation is in accordance with the result required by the mechanical theory of gases, namely, that the increments of decomposition corre aponding to equal differences of temperature increase gradually from the temperature at which dissociation begins up to that at which 60 per cent.of the vapour is decomposed, and then decrease in a similar manner up to that temperature at which dissociation is complete, In conjunction with Lnnger, Meyer greatly extended these observa- tions, and subsequently published them as a monograph, entitled ‘‘ Pyre chemische Untersuchungen ” (Braunschweig : Vieweg u. Sohn, 1885). As regards bromine, they found that the gas, when sufficiently diluted with air, had a normal density, namely, 5 5 2 even at the ordinary temperature, and no sensible change occurred up to 900° even when diluted with eleven times its volume of nitrogen.At 1200°, the density had diminished to 4.3 on dilution with five volumes of nitrogen, At a white heat, the density of the diluted bromine fell to 3.6. Experiments at higher temperatures were not possible,THORPE : VICTOR MEYER MEMORIAL LECTURE. 187 as at above 1600' the platinum apparatus is rapidly attacked by both bromine and chlorine. The alteration in density of bromine vapour a t high temperatures has recently been studied by Dr. Perman and Mr. Atkinson, who have found that no sensible diminution occurs up to about 750" a t atmospheric pressure, at which point dissociation becomes just ap- ppeciable, especially at low pressures, and gradually increases with increasing temperature (Proc.Roy. Xoc., 1900, 66, 10). In the case of chlorine, it was found by Meyer and Langer that no analogous change occurred below 1200°, no matter whether pure or highly diluted chlorine was employed, At 1 400', however, the density of the diluted chlorine fell from the normal value 2.45 to 2.08. Similar observations with carbon monoxide seemed to show that at 1690' this gas is partially decomposed into carbon dioxide and carbon, 2CO = C -I- CO,. Carbon dioxide itself experiences no change in density at this temperature in a platinum apparatus, although when passed through a porcelain tube filled with broken pieces of porcelain it undergoes dissociation, as already shown by Deville. This pheno- menon may be connected with the remarkable observation of Menschutkin and Konowaloff that dissociable vapours are far more rapidly broken up in presence of asbestos, or pieces of glass, or even of the roughened sides of glass, than when the interior of the glass vessel is perfectly smooth.Nitrous oxide, heated in a porcelain tube, is entirely resolved into oxygen and nitrogen a t goo', and in a platinum tube at 1690'. Nitric oxide remains unchanged up to 1200'; at 1690', it is com- pletely decomposed into its elements. Hydrogen chloride also appears to be partially, whilst sulphuretted hydrogen is entirely, decomposed at the latter temperature. Cyanogen has a normal density up to 800" ; at 1 ZOO', it suffers decomposition. Meyer made his pyrochemical investigations under very unfavour- able conditions, The magnificent chemical institution which Zurich now possesses was not then built, The old laboratory was a low building to the east of the main block of the Polytechnicum, and the only room which could be spared for the purpoge was so small that, in spite of the best ventilation possible, +he temperature not unfrequently rose to 50'.Moreover, both he and hi3 assistants suffered greatly from the strenuous ardour with which the wotk was carried on, and he himself eventually broke down under the strain of it. I saw him in Zurich in the autumn of this year (lS79), and was surprised and shocked to notice, although it was at the endof the vacation, how nervous and jaded he seemed. I believe the distressing insomnia from which he suffered at times throughout the rest of his life began at about this period.I n reference t o this time, Mr. Watson Smith writes : Meyer had a most excitable P 2188 TRORPE : VICTOR MEYER MEMORIAL LECTURE. mind and was a tremendous worker. His assistant, Carl Meyer, told me that on several occasions he was so overworked, not by compulsion, but through the mere influence of Meyer’s presence, his mental power, and enthusiasm, that he came very near committing suicide during the fits of depression following exhaustion after long-continued spells of work.” Pyrochemical problems continued to interest Meyer to the end, and he was quick t o take advantage of any hint which seemed t o promise the possibility of their solution. I n a lecture before the Nntur- forscher Versammlung in Heidelberg, he regretted that the lack of vessels of sufliciently refractory material prevented him from working at the higher limits of temperature even then attainable.‘‘ There can be no doubt,” he said, ‘‘ that new and undreamt-of discoveries will manifest themselves-that a new chemistry will disclose itself, when we are furnished with vessels that will enable us to work a t tempera- tures at which water can no longer exist, and at which oxy-hydrogen gas becomes an uninflammable mixture.” Shortly before his death, he returned to the subject with new appar- atus made of a platinum-iridium alloy capable of withstanding a far higher temperature than pure platinum, and he was in hopesof being able to construct vessels of magnesia which would allow of the application of temperatures over 2000O.Meyer, at the time he announced his discovery of the dissociation of the halogens, was thirty-one pears of age. He was now on the flood- tide of his prosperity. His published work had shown him to be an investigator of uncommon power and originality, and students flocked to him from all parts, to participate in the pioneering work which his astonishing energy and enthusiasm opened out. In its triumphs it was indeed a time of “joyous yesterdays and confident to- morrows.” He was happily married to the friend of his youth, Fraulein Hedwig Davidson, whose ‘ Verlobungstag ’ was the very day on which he received his call to Zurich. What she was to Meyer only those who were privileged to know his home circle can fully realise. Meyer’s first great grief came to him with the death of his eldest daughter, and in 1882 he lost his friend Wilhelm Weith, Professor of Chemistry in the University.How close and intimate was their friend- ship was evident to all who frequented the meetings of the Zurich Chemische Gesellschaft, where the two professors were generally to be found seated side by side at the head of the table; it is reflected too in the obituary notice of his colleague which Meyer wrote for the Berichts. In the autumn of 1882, Meyer was requested to undertake the delivery of the series of University lectures on benzene derivativesTHORPE : VICTOR MEYER MEMORIAL LECTURE. 189 which had been interrupted by Weith’s death. I have already attempted to indicate what Meyer was as a teacher. No one could possibly take greater pains in the preparation of his lectures, or study more to make them instructive and interesting. It is generally supposed that organic chemistry does not lend itself to effective lecture illustration.“I well recollect,” writes Mr. Watson Smith, ‘‘ that the word most fre- quently used in Zurich in defining the opinions of Victor Meyer’s students of his lectures was ‘ brilliant I ’ ” Another of our Fellows, Mr. John I. Watts, who attended his course in 1879-80, writes :- Such was not the case when Meyer had to teach it. (‘What particularly struck me about his lectures was their finished style. He made fairly constant use of notes, speaking with great rapidity. Yet his treatment of the subject was very clear, and his language perfect. The experiments were always well prepared and exceptionally suocessful.Indeed, his lectures were most popular, and both at his work and outside the Polxtechnic there was no professor who was inore respected and admired by all students than Victor Meyer. Young, handsome, well-dressed-for a German professor, with a quick wit and a genial manner, he was a welcome addition to any gathering. When, in 1881, he had a ‘ call ’ to Aachen and elected to remain at Ziirich, the students treated him to a torchlight pro- cession and a grand ‘ Kommers.’ Meyer watched the ‘ Fackelzug’ of over 1000 students from a balcony, and later, sitting as the honoured guest in a still greater throng, he seemed indeed a happy man.’’ Si>milar testimony is given by Dr. Sudborough, who was with him in Heidelberg, and who writes :- “As a lecturer, Meyer was clear, concise, and extremely lucid, and his delivery was easy and natural. His lectures were given by the aid of care- fully written notes, and were fully illustrated by experiments, the table being always crowded with apparatus both in the organic and inorganic lectures.It was very rare indeed for an experiment to fail ; this was firstly due to Meyer‘s own dexterity as a manipulator, and also to the care which wag bestowed upon the preparation of the experiments.” It was in the course of these lectures on benzene derivatives that Meyer came upon what is perhaps the most brilliant of all his dis- coveries-that of thiophen. How he lighted upon it is well known, but the story bears repetition. He desired to show his class the SO.called indopheain reaction of Baeyer, a t that time held to be indicative of benzene, but to his astonishment not a trace of the characteristiu blue colour made its appearance, although, as was his wont, he had rehearsed the experiment just prior to the lecture, It appeared that his assistant, Sandmeyer-himself one of Meyer’s ‘discoveries’-had handed to him a sample of the benzene made in the lecture course by heating benzoic acid with lime, and a t once drew his attention to the fact that the rehearsal had been made with the ordinary laboratory supply-190 THORPE : VICTOR MEYER MEMORIAL LECTURE. the Benxot prissim. crystallisaturn of the dealers, and, of course, derived from coal-tar. Meyer, at the moment, was so fully occupied t h a t he might well have put aside the incident, or have given no immediate heed t o its significance.But that was not his way. Fortune scatters her chances indifferently, and every man may have his share, but it is not given to each t o perceive when he is favoured, or to know when to grasp (4 the skirts of happy chance.” Madame de Wtael once said that a most interesting book might be written on the important consequences which spring from little differences, and it was the little difference that riveted itself on Meyer’s mind. H e at once began the investigation of the cause. All kinds of benzene to be found in Zurich were tested, and it was soon definitely established that it was only coal-tar benzene that gave the indophenin reao- tion. Meyer’s first idea was that it might be ocuasioned by an isomeric-a second benzene found in coal-tar, Within less than a month he had -ascertained that the reaction was due t o some sulphuretted product accompanying coal-tar benzene, and that Baeyer’s indophenin was probably a sulphur compound.Meyer’s action was characteristic of him. Before communicating with Baeyer, he carefully repeated his experiments, and only when all ground for doubt was removed did he inform his friend of his obser- vations and of the inferences he had formed. Baeyer at once sent him a specimen of his indophenin, and the fact that it actually was a sulphuretted compound mas then established. Meyer found that coal-tar benzene, after repeated shaking with oil of vitriol, no longer reacted with isatin, and hence he determined t o search among the sulphonic acids so formed for the reactive substance.By distilling the product obtained by shaking 10 litres of benzene with oil of vitriol, he obtained a few cubic centimetres of a clear, thin, mobile liquid containing sulphur, which boiled at about 83a and remained liquid in a freezing mixture of ice and salt. It gave a most intense reaction for indophenin. The amount of the new substance present i n coal-tar benzene was very small, a t most not more than 0.5 per cent. Thanks to the co-operation of his friends, Messrs. Bindschedler, Busch and Go., of Basle, he was enabled to repeat this experiment on a large scale, as much as 250 litres of coal-tar benzene being operated upon at a time, and the sylphonic acids converted into the lead salts, which were then mixed with sal ammoninc and distilled.The crude produot, which contained about 28 per cent. of sulphur, was found t o react strongly with bromine, forming a heavy, colourless, highly refractive liquid, boiling a t 2 1 lo, greatly resembling dibromobenzene, but showing on analysis the composition C,H,Br,B The new com- pound was the dibromo-substitution product of a substance whichTHORPE : VICTOR MEYER MEMORIAL LECTURE. 191 Meyer was at first inclined to call thianthren, then thiophan, next thiol, and lastly thiophen, to denote that it was a sulphur-containing substance giving derivatives analogous to those of phenyl. I n the early part of the following June, that is, within about six months of his first observation, he had obtained a considerable quantity of thiophen, and was in a position t o show to the Swiss Naturforscher Versammlung, which met during that summer in Zurich, that its chemistry was hardly less extensive than that of benzene itself.Thus it was that a chance observation-the observation of a little difference-added a new section to organic chemistry. It would be quite impossible within the limits at my disposal to show how this section was developed by Meyer and his pupils. In 1888, he published, in the form of a monograph, dedicated to his friend and patron, President Kappeler, (‘ dem hochherzigen Forderer wissenschaftlicher Bestrebungen,” an account of its condition at that time (Die Thiophengruppe. Braunschweig : Vieweg u. Sohn), from which it appears that during the preceding five years no fewer than 106 contributions t o its history had been made from his own labora- tory, and some 40 from those of others.How fertile the field still continues may be gleaned from the circumstance that upwards of 50 papers on the same subject have since made their appearance in various journale. Meyer’s restless energy had now begun to read most seriously upon his general health. At times he was almost prostrated by nervous exhaustion ; he had frequent spells of insomnia, and his friends viewed with alarm the signs of physical decay which now set in, in spite of the occasional holidays, mainly among the Alps, which he gave himself. In 1884, he again broke down, and although at the moment he was im- mersed, with his colleague Lunge, in the plans for the new chemical laboratory of the Polytechnic in which, as he states, he had hoped ultimately to resume his pgrochemical labours under more favourable conditions, he was obliged to relinquish, for a time, all idea of work, and towards the end of the year was ordered away to the Riviera, where he wintered.I n the following spring, he received a ‘call’ to Gattingen as the successor of Hubner. This he eventually decided to accept, and entered upon his duties there in the summer session of 1885. He was not able, as he had hoped, to take leave of his Zurich students at the time, but what they thought of him-with what affection and respect he was regarded-was seen in the terms of the Address they sent to him on the occasion of his opening lecture at Gottingen. It was seen, too, in the way he was received by them during a visit t o Ziirich some months later, on the occasion of the seventieth birthday of his friend Kappeler.Professor Goldschmidt,192 THORPE : VICTOR MEYER MEMORIAL LECTURE. who was present, thus describes the sceno : ‘( I see him even now before me as he spoke t o the students at the ‘ Kommers’ in the evening. The ‘Ziircher Polytechnikers’ have, as a rule, but little opportunity of knowing the professors outside their special faculty, and have, therefore, but little interest in those who are not their own teachers. As Victor Meyer’s slender form appeared on the platform, and as his bright blue eyes glanced round the assembly, there broke forth a shout of welcome from all-engineers, machinists, architects, as well as from his old students the chemists-to beended in a whirl- wind of applause a t the close of a speech, sparkling and witty as ever.’ ’ With renewed health and vigour, he now set about the plans for the new laboratory which the authorities had decreed should adorn the ‘ Georgia-Augusta,’ for Wohler’s old place no longer sufiiced to con- tain the chemical workers which Gottingen had now to receive. Whilst it was being erected, he continued his pyrochemical work, and his investigation of the thiophen derivatives, and began with Paul Jacobson the admirable “Text-book of Organic Chemistry,” which, in the critical selection and arrangement of its material, is still unsur- passed. With Auwers, he resumed the study of benzil and its derivatives which he had begun with Wittenberg and Goldschmidt. With Miinchmeyer, he began the study of the behaviour of phenylhydrazine towards various groups of oxygen compounds, and he sent a short paper t o the Bsrichte on thiodiglgcol compounds, and on an easy method of preparing /3-iod opropionic acid from glycerol.With Demuth, he undertook the investigation of the sulphuranes, a group of disulphides of the general formula C,H,*S*C,H,* SR. Other papers were on the densityof nitric oxide, which showed no evidence of asso- ciation or molecular duplication even at - looo; on isophthalaldehyde ; on the negative nature of the phenyl group; and on isodibromo- succinic acid. It was characteristic of his receptivity that Meyer should be among the earliest workers in Germany to perceive the value of Raoult’s method of ascertaining molecular weights; it was first used in the Gottingen laboratory to determine the molecular weight of some derivatives of benzil which yielded two series of isomeric compounds, both series having the same constitution, in the ordinary sense, but which were yet distinct from one another and yielded different derivatives. Other papers of this period were on the thio-derivatives of deoxy- benzoin and its analogues (desaurins), and, with Riecke, on the carbon atom and valency. The latter paper is of interest as an example of Meyer’s (‘ scientific use of the imagination,” and mayTHORPE : VICTOR MEYER MEMORIAL LECTURE, 193 be studied in connection with an earlier paper in 1876 (AmmaZen, 1876, 180, 192) on the same subject, as showing how he grafted the theoretical conceptions of van’t Hoff upon the teaching of KekulB.According to Meyer, the carbon atom is surrounded by an ethereal shell which, in the case of an isolated atom, has a spherical form ; the atom itself is the carrier of the specific affinities, the surface of the shell is the seat of the valencies ; each affinity is determined by the existence of two opposite electrical poles, which are situated a t the end-points of ft straight line small in comparison with the diameter of the ethereal shell. Such a system of two electric poles is called a double- or di-pole. The four valencies of a carbon atom would be re- presented by four such di-poles, the middle points of which are situated on the surface of the ethereal shell, but freely movable within it.The di-poles themselves can rotate freely round their middle point. The carbon atom has a greater attraction for positive than for negative electricity, and the positive pole of a valency is slightly stronger than the negative pole. This hypothesis explains why the four valencies take up the position of a regular tetrahedron ; why they can be diverted from this position ; why the valencies of one and the same carbon atom cannot combine together, whilst the valencies of different carbon atoms can do so ; why there are two kinds of single-binding, one stable, and the other allowing free rotation; and lastly, why free rotation ceases in cases of double- or treble-binding (Be?., 1888, 21, 946 ; compare Abstr., 1888, 549). Stereochemical questions-we owe the phrase to Meyer-were indeed at this time occupying much of his thought.In a paper with Auwers (Be?., 1885, 21, 784), he pointed out that the existence of the two isomeric dioximes of beazil, discovered by him in conjunction with Goldschmidt, would, if for both the formula C,H,*C(N*OH)* C(N*OH)-C,H, were established, be in direct contradiction to the hypothesis of van% Hoff that two carbon atoms united by a single affinity are free to rotate, the axis of rotation being the bond of union, and that isomerism is only possible for those substances of the type EC-C!, which cannot, by rotation round the common axis, be converted into the same form. The two dioximes were carefully compared as regards their melting points, solubilities in water, alcohol, ether, or acetic acid, and the conditions under which the a-form is converted into the P-modification were ascertained.To further remove all doubt as to the possibility of merely physical isomerism, and to prove that the oximes are not only different from one another, but yield different derivatives reconvertible into their respective oximes, the propionic and isobutyric derivatives were prepared and compared. The result showed that the dioximes were of identical chemical oompasition, and194 THORPE : VICTOR MEYER MEMORIAL LECTURE. hence it appeared that van’t Hoff’s hypothesis must be so altered as to admit of cases in which free rotation round the axis cannot take plaoe, as otherwise no explanation of the isomerism of the a- and P-dioximes is possible (compare Abstr., 1888, 597).He subsequently showed how the work of Bethmann, Graebe, and Baeyer confirmed these views. Wislicenus’ theory as to the free rota- tion of singly-bound carbon atoms would appear to be limited to certain cases ; absolutely free rotation is probably possible only when the substituting atoms or groups are identical ; where, as is the case in the majority of compounds, the atoms or groups are not identical, there will be some definite position of equilibrium ; only in cases where the substituting atoms or groups are equally negative will there be several positions of equilibrium (Bey., 1890, 23, 2079 ; Abstr., 1890, 1083). Meyer’s perspicacity and critical insight are well illustrated in a lecture which he gave to the German Chemical Society in 1890 ‘( On the Results and Aims of Stereochemical Research.” It is of interest to the student as giving a fairly complete historical account of the development of space formulze, and more especially for its criticism of the work of Baeyer and Wislicenus on the stereochemical formule of single-, double-, and treble-linked carbon compounds, and of the stereo - chemical conceptions of Hantzsch and Werner in the case of nitrogen compounds.With regard to the assumption that the nitrogen atom may be represented as a tetrahedron, and that the isomerism of the benz- aldoximes may be similar to that of fumaric and maleic acids, it is pointed out that the structure of the oximes is in all probability not identical, Two isomeric forms of each of the unsymmetrical oximes of the formula OH-N:CXI’ are indicated by the hypothesis of Hantzsch and Werner, but they do not appear to exist.If the tetrahedral representation of the nitrogen atom were tenable, we should have to assume that substituted ammonias can exist in the isomerio forms N-a /= and N l ? , but such bodies are not known. 1 6 \a We must therefore assume that in ammonia the hydrogen atoms are placed symmetrically with regard to the nitrogen atom, and this can only find expression in a plane formula (Ber., 1890, 23, 567 ; compare Abstr., 1890, 719). Reference may be made here to the short paper on isomeric oximes of unsymmetrical ketones and the configuration of hydroxylamine, in conjunction with Auwers (Bar., 1890, 23, 2403), in which the authors advance further evidence that the isomerism of the oximes cannot depend upon structural dissimilarity, but must be sought for in theTHORPE : VICTOR MEYER MEMORIAL LECTURE.I95 nature of the hydroxyIamine group. Assuming the correctness of the theories of van’t Hoe and Wislicenus regarding the arrangement of atoms in space, the combined effect of the attraction of the nitrogen and oxygen on the hydroxylic hydrogen of hydroxylamine would cause it to be in a plane dieerent from that occupied by theremaining atoms in the molecule. This hypothesis suffices to explain all observed facts : unsymmetrical oximes would therefore exist in two forms, C:N*6 and a R b c1 C:N*?. b H Werner is shown by the two formulae, The difference between this theory and that of Hantzsch and QH C:N and H C:N--b (Hantzsch and Werner). (humers and Meyer).The formation of an oxime by the action of nitrous acid is readily accounted for on the graund that i t is a substituted hydroxylamine; morwver, the fact that no case of geometrical isomerism has ever been observed in the azo-, azoxy-, and imido-compounds tells in favour of this theory (compare Abstr., 1890, 1263). To this period belongs also the work on the azines ; on deoxybenzoin ; on the aromatic nitriles; on tetramethylsuccinic acid; and on the oximes of phenanthrsquinone. Meyer was not destined t o remain long in Gdttingen. The new laboratory was barely finished, when, in 1889, he received a 6 call ’ to Heidelberg. Bunsen, full of years as of honours-the Nestor of Chemistry, as his friends were wont to call him-had expressed a wish to retire, and of all his many students there was none, he said, whom he wished more to take his place than he who, twenty-one years before, had vorked with him in the modest little room of some four or five places, which had constituted his private laboratory.To Heidelberg accordingly Meyer vent, with the coveted title of Geheimrath, and the promise of a new and enlarged laboratory. Although only forty years of age, he was now, so far as worldly position was concerned, a t the summit of his career ; he had returned to his Alma Mater and the rest of his days were to be given to her service. During his four years’ stay in Gdttingen he had in great measure recovered hiB health and with it the elasticity of his active, buoyant temperament.I saw him in Heidelberg in the spring of 1891, when he was busy with the enlargement of the old laboratory, and it was196 THORPE : VICTOR MEYER MEMORIAL LECTURE, with a glance of pride-a pardonable pride-that he pointed out the places where he and I had worked with ‘ Papa ’ Bunsen, ‘ So kindly modest, all accomplished, wise,’ in the corner place near the window, towering above both of us. It was strange, too, to hear the sound of children’s voices and their laughter; and the bustlo of servants in what were formerly the silent, half-deserted rooms overlooking the Wrede-platz ; and stranger still to me was it, as we together called upon Bunsen, sitting solitarily in his rooms overlooking the Bunsen-strasse, t o behold the meeting and to listen to the greeting of these two men-the memory of whose names and fame Heidelberg will cherish so long as Heidelberg exists, To all of us life has its dramas, and in some of these the incidents are as moving as those ever conjured up by playwright or poet.How well I remember it ! He was as bright, as active, as mentally vigorous as of old, although i t was but too obvious that his physical strength was not the equal of his nervous energy. Meyer’s earliest experimental work at Heidelberg was mainly concerned with the continuation of investigations begun a t Gattingen. But he was perpetually breaking new ground or seeking to clear up doubtful points in ground already partially explored. The classical labours of Frankland on zinc ethyl might be thought to have definitely established the chemistry of that substance, but even on such a comparatively simple matter as the action of oxygen on zinc ethyl there was room for still further inquiry.The white compound obtained by Frankland, as the result of the oxidation of zinc ethyl, was regarded by him as a mixture of zinc oxide, ethoxide, and acetate. It was found, however, by Meyer and Demuth to con- tain no acetate, but to be mainly composed of a peroxide, ZnEt*O*OEt, as proved by its power of liberating iodine from potassium iodide. The explosive character of the substance is thus explained. Zinc ethouide, in fact, does not appear to have been prepared (Ber., 1890, 23, 394). In conjunction with a number of his pupils-Krause, Freyer, Askenasy, and others-Meyer in 1891 began the investigation of 8 subject already associated with the name of his predecessor, namely, on the conditions determining both the gradual and the explosive combustion of gaseous mixtures, Although a considerable amount of experimental work was done, the results obtained, ourious and interesting as they were in some particulars, led to no very definite general conclusions.It was found that the temperature at which combination occurred This wits the last occasion on which I saw Meyer.THORPE : VICTOR MEYER MEMORIAL LECTURE. 197 varied with the nature of the vessel, and depended upon whether the gases were confined or not. Ignition takes place at a lower tempera- ture when the mixture is in a closed vessel than when passing freely through an open tube. If, however, an open vessel containing the mixture is heated suddenly, explosion takes place at the lower temperature.I n the cases of gradual union, no relation between time and amount of combination could be perceived. As showing the influence of the nature of the surface, it was found that, when the bulbs were silvered inside, the union of oxygen and hydrogen was rapidly effected at a temperature of about 200°, whereas in an un- silvered bulb the gaseous mixture had to be heated to above 530' before any sensible amount of water was produced, The principal quantitative results are embodied in the following table in which tlie mixture did not explode a t the lower temperature in each column, but did so at the higher : Equivalent mixtures. Free current. Hydrogen, oxygen .................. 650--730° Methane, oxygen ..................650-730 Ethane, oxygen ..................... 606-650 Ethylene, oxygen .................. 606-650 Carbon monoxide, oxygen ......... 650-730 Hydrogen sulphide, oxygen ...... 315-320 Hydrogen, chlorine .................. 430-440 Closed bulbs. 530-606' 606-650 530-606 530-606 650-730 250-270 240-270 I n a subsequent paper with Munch (Ber., 1893, 26, 2421), the temperatures of explosion of gaseous mixtures were determined by placing the vessel containing the gases inside the bulb of an air thermometer immersed in a metal bath. The mixture of a gas with the amount of oxygen theoretically necessary for its complete com- bustion was passed through a 6ne tube to the bottom of the internal vessel, and lighted as it issued from the mouth of the exit tube.At a certain temperature, the flame ran down the tube and the con- tents of the vessel exploded. This temperature-the temperature of explosion-was determined by displacing the air contained in the air thermometer by means of hydrogen chloride, collecting it over water, and measuring it. I n 38 experiments with a mixture of hydrogen and oxygen (pure electrolytic gas), the temperature of explosion varied from 620' to 680°, being about 650' in mean, The tempera- ture is not affected by variations in the rapidity with which the gaseous mixture enters the glass vessel, or by the presence of frag- ments of glass or sand. I n presence of platinum, the gases com- bine quietly, and if the glass vessel is very small no explosion occurs. The temperatures of explosion of a number of aliphatic hydro-198 THORPE : VICTOR MEYER MEMORIAL LECTURE.carbons, mixed with equivalent amounts of oxygen, were then determined as follows : Methane ...... 656-678O Propane . , , , , . 545-548 Ethane ...... 605 - 622 Propylene ... 497-5 1 1 'Ethylene ...... 5'77-590 isoButane , . . 545-550 Acetylene ... 509-515 isoButylene , . . 537-548 Coal-gas with 3 times its volume of oxygen ... 647-649 It would thus appear that the temperature of explosion falls as the number of the carbon atoms in the molecule increases; that it is probably lower for ppimary than for corresponding secondary hydro- carbons ; and is less for hydrocarbons containing a double bond than for those containing only single bonds, and still less for those containing a triple bond (compare Abstr., 1894, ii, 11).Mention may here be made of the work done, in conjunction with Bodenstein, on the decomposition of gaseous hydrogen iodide by heat, This gas was selected for the reason that the action of heat upon it is reversible, and hence it might be expected that the establishment of a condition of equilibrium will be in no way influenced by the many disturbing circumstances which were found to occur in the case of other gaseous mixtures. Combination of hydrogen and iodine vapour takes place even at 444' (b. p. of sulphur), and the hydrogen iodide formed is far more stable, at all events in the dark, than has hitherto been supposed. It is, however, very sensitive to light, In bulbs which were exposed for 10 days to direct sunshine, 59 per cent. of the gas was decomposed, and when exposed throughout the summer, practically the whole of the gas is resolved into its constituents.Experiments on the relation of the amount of decomposition to temperature gave the following results i Relative amount of HI decomposed, as determined Temperature of boiling By decomposition. By direct union. Sulphur ............ 444' 0.2150 0.2104 Retene ............... 394 0.1957 4 Mercury ............ 350 041731 0,1738 At 310' (b, p. of diphenylamine) the relative amount of HI decoma posed was 0.1669, instead of 0.1550 as calculated from the above numbers. The difference between the observed and calculated result8 is due to the circumstance that the heat of formation of hydrogeh iodide is, at ordinary temperatures, negative ( - 1600°, Thomsen), but from the fact that the decomposition at temperatures such as 350-444' increases with rising temperatures, it follows from van't Hoff's prin- ciple (Principe de l'equilibre mobile) that the heat of formation at theseTHORPE : VICTOR MEYER MEMORIAL LECTURE.199 temperatures is positive. There must, therefore, be a temperature at which the heat of formation is zero, and at which also the decom- position is at a minimum, This point, as the experiments show, lies between 310' and 350°, and calculation by van't Hoff's formula showed t h a t it is at 324'. As it was found that two bulbs heated under the same conditions always gave the same result, it was possible to study the decomposition as a time reaction, and by the formula given by Nernst.The constancy in the values actually obtained for each of the foregoing temperatures showed that, in the case of the decom- position af hydrogen iodide by heat, the change occurs in a perfectly regular manner ( B e y . , 1893, 26, 1146 ; compare Abstr., 1893, ii, 369). This short account of Meyer's labours in physical chemistry may conclude with a brief reference t o the determinations of the fusing pointn of salts melting only at relatively high temperatures, which he made in concert with his pupils. These he was able t o obtain by the aid of the platinum air-thermometer he described in conjunction with Freyer. The following is a list of his final values : Sodium chloride ...... 816' Sodium bromide.. . . , . 757 Sodium iodide ......661 Potassium chloride., . 800 Potassium bromide.. . 722 Potassium iodide ... 684 Potassium carbonate 878 Sodium carbonate ... 849 Sodium biborate ... . . , 878' Sodium sulphate . , . . . 863 Potassium sulphate 1078 Caesium iodide .".... 621 Calcium chloride ... 806 Strontium chloride.. . 833 Barium chloride.. . . . . 92 1 Rubidium iodide ... 641 (Compare Heycock and Neville, Trans,, 1895, 67, 190). In 1892, Meyer and Wachter made known the possibility of the existence of a class of aromatic derivatives, known as the iodoso- compounds, in which the monovalent group I0 replaces hydrogen. The first representative of the series was iodosobenzoic acid, C,H510,, which they obtained by the action of fuming nitric acid or a boiling and acidified solution of potassium permanganate upon orthoiodo- benzoic acid.It is a crystalline, solid substance, melting a t about 200°, sparingly soluble in water or ether. It liberates iodine from potassium iodide, and chlorine from hydrochloric acid, forming orthoiodobenzoic acid. It is an extremely feeble acid, and its silver salt when dry is highly explosive. No iodoso-derivatives could be obtained from meta- or para-iodo- benzoic acida. Of the two iodoparatoluic acids, the one in which the iodine atom occupies the ortho-position t o the carboxyl group yields an iodoso-derivative similar t o iodosobenzoic acid, but the200 THORPE : VICTOR MEYER MEMORIAL LECTURE. isomeric acid does not yield a corresponding compound, If, however, paraiodobenzoic acid be previously nitrated, it may be converted by the further action of fuming nitric acid into an iodoso-derivative, 10*C6H,(N02)*C02H.In like manner, the iodoparatoluic acid may be made t o yield an iodoso-compound by previous nitration (Ber., 1893,26, 1354). By the further action of oxygen on an alkaline solution of iodoso- benzoic acid, iodoxybenzoic acid, I0,*C6H,*C02H, is formed, a white, crystalline substance, turning red on exposure to light, and decom- posing with explosion at 233'. It is a much stronger acid than the iodoso-derivative, forms moderately stable salts, and gives character- istic colour reactions with aniline and phenol (Ber., 1893, 26, 1727 ; compare Abstr., 1893, i, 577). Hartmann and Meyer found that when iodosobenzene, C6H,*I0, is dissolved in strong sulphuric acid, the solution, on dilution with water, yields the sulphate of a base, phenyliodophenyliodoniurn hydroxide, I-C,H, ' ~ ~ 5 > 1 -OH.A similar change occurs with paraiodosotoluene. The free bases have a strong alkaline reaction, and form characteristic crystalline salts. Meyer was thus led to the discovery of a remarkable group of substances known as the iodonium compounds, the simplest aromatic representative of which is diphenyliodonium hydroxide, /%H5- I-C,H,. \OH. These bases are compounds in which two of the valencies of the iodine atom are satisfisd by aromatic radicles whilst the third is satisfied in the free base by hydroxyl, and in the salts by an acid radicle. The iodonium bases are readily soluble in water, are strongly alkaline, and in their behaviour, as in that of their salts, show a remarkable similarity with the derivatives of silver, lead, and, more particularly, thallium, These bases are formed by the decomposition of the iodoso- and iodo-hydrocarbons under various conditions ; for ex- ample, by the action of moist silver oxide upon an intimate mixture of equivalent proportions of iodosobenzene and iodoxybenzene, O H C6H5*I0 + I02*C6H, + AgOH = C6H,*I<C + AgIO,.6 5 By the addition of potassium iodide to the aqueous solution, diphenyl- iodonium iodide is precipitated. This compound stands i n the same relation to iodobenzene that trimethylsulphonium iodide does toTHORPE : VICTOR MEYER MEMORIAL LECTURE. 201 methyl sulphide, and as tetramethylammonium iodide does to tri- methylamine. It cry stallises from alcohol in long, pale yellow needles, and decomposes on heating almost quantitatively into iodobenzene, c,,H,,T, = ~c,H,I.If the decomposition is started at one point, it proceeds through tho whole mass with development of heat. The existence of these remarkable bases and salts, which recall the sulphonium-, ammonium-, arsonium-compounds, &c., shows that a complex which is composed of one iodine atom and two molecules of phenyl, that is, of constituents which are otherwise negative, possesses strongly basic properties, From the general behaviour o? the iodonium compounds, it is evident that the complex -I<C6H5 or C6H5 in general -I<;, (where R and R, are aromatic radicles) possesses I the function of a metal analogous to thallium (compare Lehrbuch der Organischen, Chsmie, Meyer and Jacobson, 2, 127).It is interesting to note that the physiological action of the diphenyliodonium chloride resembles that of ammonium salts on the one hand, and of heavy metals, such as lead and thallium, on the other. Doses of 0*02-0*03 gram produce total paralysis in frogs, both the motor nerve-ending and the muscle substance being affected, A dose of 0.08 per kilo, proves fatal to rabbits, the spinal chord and medulla oblongata being also affected. A study of the condition8 determining the formation and hydrolysis of ethereal salts of aromatic acids occupied Meyer, in conjunction with his pupils, and more especially Sudborough, from 1894 up to the year of his death. It was found that benzoic acid and its substituted pro- ducts, as a rule, readily yield practically the theoretical quantity of an ethereal salt when treated with methyl alcohol and hydrochloric acid in the cold.On the other hand, the symmetrical trisubstitution pro- ducts of benzoic acid yield no ethereal salts whatever under these conditions. This rule holds absolutely for all 1 : 3 : 5-trisubstitution derivatives of benzoic acid (Me, NO,, C1, Br, I, and CO,H), except those containing one or more hydroxyl groups. The same is true of all substituted benzoic acids in which the 2 : 6-hydrogen atoms (C0,H = I) have been replaced by other atoms or groups. The acids which do not yield ethereal salts when treated with alcohol and hydrochloric acid can readily be converted into these substances by the action of methyl iodide on their silver salts, or of methyl alaohol on the acid chlorides.This remarkable difference in behaviour may be ascribed t o a gtereo- chemical cause, the substituent groups being supposed to hinder the VOL. LXXVII, Q202 THORPE : VICTOR MEYER MEMORIAL LECTURZ. introduction of the alkyl group to such an extent that under the prescribed conditions the reaction does not proceed." Acids in which the carboxyl group is linked with the benzene nucleus by one or more carbon atoms readily undergo etherification. The constitution of a substituted benzoic acid may, therefore, be ascertained in this way, and the method may also be used for isolating or purifying those acids which will not undergo etherification. The nitrophthalic acids behave similarly : dinitrophthalic acid [NO, : C0,H : C0,H : NO, = 1 : 2 : 3 : 41 gives no ethereal salt, whilst the acid [NO, : CO,H : CO,H : NO, = 1 : 3 : 4 : 51 yields monalkyl salts.1 : 2 : 6-Dinitrobenzoic acid gives no ethereal salt (Abstr., 1895, i, 93). Chloronitrobenzoic acid [CO,H : NO, : C1= 1 : 2 : 61 yields no ethereal salt, showing that the rule applies when the substituents are dissimilar. Diortho-substituted benzoic acids are not etherified at low temperatures when one of the substituents is hydroxyl. Meyer was of opinion that etherification, in the case of analogous compounds, is diversely influenced by substituents of different relative mass. He imagined that those radicles which prevent etherification at high temperatures have a much agreater relative mass than those which only hinder it at low temperatures, but it is probable that the methyl group and its normal homologues will produce almost identical effects, since the action is chiefly due to that carbon atom which is directly linked to the benzene nucleus.According to theory, those ethereal salts which are formed with greatest difficulty should be hydrolysed least readily, and such Meyer found to be generally the case.? These conclusions have been tested by Kellas (Zeit. phys. Chern., 189'7, 24, 221), who has measured the velocity of etherification for a large number of monosubstitution derivatives of benzoic acid. From a study of the influence of temperature, and of the nature of the substituent, he has more precisely indicated the limits within which they may be regarded as generally true, Considerations of space preclude more than a bare reference to the work on the derivatives of ethyl dinitrophenylacetate; on the in- doxazen group ; on the laws of substitution in the aliphatic series ; on the synthesis of triphenylacrylonitrile and on the isomerides of tri- phenylacrylic acid ; on the modes of introduction of acetyl groups into aromatic hydrocarbons ; on the substitution of the hydrogen * This supposition has been modified by Wegscheider, who introduces Henry's conception of the formation of an additive compound between the alcohol and the acid.According to Wegscheider, the ortho-substituents prevent the formation of such additive compounds (compare, however, Davis, Trans., 1900, 77, 33). t This is approximately true for the benzoic series of acids,1 but does not obtain for the acetic and probably other series (compare Sudborough and Lloyd, Trans., 1899, 75, 467).THORPE : VICTOR MEYER MEMORIAL LECTURE.203 in trinitrobenzene by alkaline metals j on the fusibility of platinum ; on the formation of tetriodoethylene from diiodoacetylene ; on the durenecarboxylic acids ; on the action of potassium permanganate on hydrogen, methane, and carbon monoxide ; on the slow oxidation of hydrogen and carbon ; on the evolution of oxygen during reduction ; on hexahydrobenzophenone and its oximes ; and on diphenylamine from orthobromobenzoic acid. Meyer contributed to the literature of chemistry, either alone or in conjunction with his pupils, upwards of 300 memoirs and papers. No account of Meyer’s scientific activity would be complete with- out some allusion to the various pieces of apparatus with which he enriched operative chemistry. Reference has already been made t o his methods of determining vnpour density, and to his mode of ascertaining the melting points of substances fusible only at high temperatures.H e also greatly improved the methods of accurately determining the solubilities of substances a t various temperatures. His form of water-bath is to be met with in many modern laboratories, surmounted, it may be, with the funnel-shaped cover which he devised to prevent access of dust to the evaporating liquid. Particularly neat and convenient are the drying ovens he constructed in which constant temperatures are obtained by means of liquids of different boiling points, for example, toluene, xylene, anisoil, &c.Analytical chemistry had little attraction for Meyer, and, beyond his mode of diagnosing primary, secondary, and tertiary alcohols and alcoholic radicles by colour reactions (see p. 180); and the method he devised, with Jannasch, for the simultaneous determination of carbon, hydrogen, and nitrogen in the elementary analysis of organic substances, he made no contribution to this department of the science. As the director of a large chemical laboratory, and as a laboratory teacher, Meyer worthily followed in the footsteps of Bunsen. In proof of this, I may here quote the testimony of some of our Fellows who have worked under him. Mr. John I. Watts thus refers to him in the Zurich days : ‘‘ Victor Meyer as a teacher had a wonderful faculty of infusing enthusiasm into his students.He was constantly in the laboratory, and whether the pupil was engaged upon the analysis of some simple, well-known substance, or was pursuing oziginal investigation, he seemed somehow to succeed in making him feel how interesting was his work. Possessed of a very quick and active intelligence, he would point out the reason of the difficulties almost before the student had finished recounting them. He was himself a constant worker, and when engagedin his work he always appeared to be in a high state of pleasurable excitement.” LJimilar testimony is afforded by English chemists who were with him at Heidelberg. Dr. J. T, Hewitt writes : Q 2204 THORPE : VICTOR MEYER MEMORIAL LECTURE.“ Professor Meyer was universally liked by the men who had the privilege of working under him. He had an extraordinary capacity for hard work, and his example, together with the interest he took in his men, induced in them a more or less similar love of work. After the morning lecture, which in the summer semester was at eight, he would come round the lriboratory and see how every one was getting on, though of course he spent more time with those who were doing joint work with him than with those who were working with the other professors. We used very often to see him again during the moriiing, and at least once in the afternoon. I n 1891, when I first went to Heidelberg, the most important work being done was on the slow combustion of electrolytic gas, and, not only those who were actually working on this subject, but every one else in the laboratory; used to take great interest in what was going on.Meyer’s way of taking up old pieces of his work again and again meant that a very varied sort of work was clone in the laboratory ; for example, in consequence of Nef s criticism, nitro-fatty compounds were again examined, the result on the students being excellent, in that their general interest in chemistry was aroused. Meyer, as you well know, was an excellent speaker, not only in the lecture room, but in taking the chair at meetings of the Heidelberger Chemische Gesellschaft, when he was seen to great advantage.” Dr. Sudborough, who served him as an assistant when in Heidelberg, writes : ‘‘ As organiser and director of the laboratories, Meyer undoubtedly exhibited great business qualities, and everything worked extremely smoothly, owing probably to the fact that his staff had been with him for a number of years and were all on intimate terms of friendship with him, During the time I was an assistant, I had opportunities of observing with what care he entered into even the minutest financial details in connection with the department.I‘ In the laboratories he was extremely genial and pleasant, always having a kindly word for the students, and taking a great interest in their work. Characteristic, too, was the hopeful way in which he alwayslooked forward to the successful termination of each piece of work, and by this means endeavoured to keep up the interest of the student.Every student who worked under him respected and honoured him as a scientific leader of the first rank, but in addition they felt a deep friendliness towards him on account of the kindly interest he took in them and in their work. A goodly percentage of those carrying out ‘ Arbeits ’ under him were either English or American ; in fact, Meyer appears to have had a predilection for English and American students. ‘‘ Mention must also be made of Meyer’s connection with the Heidelberg Chemical Society, of which he was an ardent supporter-in fact, may be said to have been its soul : he and Bernthsen (of the Badische Anilin- u. Soda-Fabrik) were the two presidents in my time and both were frequent contributors.” Dr, Jocelyn F. Thorpe writes : (6 Perhaps that which impressed one most about Victor Meyer, besides his power and ability as an exponent and lecturer, was the faculty he possessed of conferring some of his enthusiasm upon the students who worked under him, Be his interest ever so slight and his knowledge of the subject ever 80 small,THORPE : VICTOR MEYER MEMORIAL LECTURE.205 no student could work long with Victor Meyer without feeling that he had a part in a system ; that he was, in fact, one of the instruments by which the plans and ideas of a master mind were being shaped. Noticeable, too, was his wonderful power of grasping and remembering every little detail of the re- searches upon which he was at the moment engaged. At times, as many as thirty men would be working under him on subjects widely varying in character, yet in no case would he forget what each individual had been doing when he last visited him ; occasionally he would astonish the student by aaking him what had become of some (by the student) long-forgotten snb- stance, the properties of which he could remember most distinctly.“ Every morning after his lecture he would enter the laboratories and personally not only visit the students who were working directly under him, but also those who were engaged in research with the other Professors and Privat-docenten of the department. ‘‘ Not only will Victor Meyer live inithe memory of those who worked under him as a leader in chemistry, but many will remember him as the genial and kindly host. On many evenings during the semester he would give either supper parties or small dances, and occasionally a ball, t o which his students were welcomed, and when his camaraderie and great tact were especially noticeable to those of us who, being foreigners newly arrived, were unacquainted with the language and social customs of his country, I remember meet- ing him inHeidelberg the year before his death and asking him something, I cannot now remember what, bnt at any rate he was unable to answer me a t the time, and asked me to call and see hin; the next day.He, however, stopped and tied a knot on his pocket handkerchief, saying, with a sad smile, ‘ my memory is not what it was.”’ “ Towards the last his wonderful memory began to fail, Meyer’s literary ability, combined with his power of lucid exposi- tion, made him an admirable writer of what are called popular science articles. He was a frequent contributor t o t h e Natu~- wissenschaftlichen Rundschau, and a number of his essays appeared under the title of (‘ B u s Natur und Wissenschaft ” (Heidelberg, 1892). His love of natural scenery and his power of graphically describing it may be seen in his “Marztage in Kanarischen Archipel ’’ (Leipzig, 1893), a record of travel, written during tho enforced rest following upon one of his too frequent periods of nervous prostration. One who had studied him carefully and knew him well t h u s writes of his personal qualities and of the influence and attraotion he exerted upon all who came in contact with him : ‘‘ Victor Meyer had 8 remarkable power over men. Where he entered, there he soon becsine the centre ; each one listened to him, all collected round him. I n the fascination he exercised there was nothing intentional or self-conscious ; it was far lesg the influence of a commanding strength than the working of an incomparably attractive and many-sided nature. To this, too, his appearance contributed : the finely chiselled head with the splendid blue eyes might, at first sight, betoken the artist, were it not that there was in the expressive206 THORPE : VICTOR MEYER MEMORIAL hECTUSE, features a rare blending of the lively temperament with the contemplative calm of the philosopher. “ In the circle of his fellows he captivated all by the eagerness with which he followed anything new, discussing and elucidating it in a manner peculiarly his own ; by the joyous, often enthusiastic, recognition of other men’s work, and by the warm-hearted interest he displayed in the scientific struggles of his juniors. In society, he showed himself an accomplished convei3sationalist and raconteur, an intelligent and warmly appreciative connoisseur of the arts of music and literature. As a host, he studied the comfort of every guest in his house. At the ‘ Biertisch his sunny humour and overflowing wit diffused a general harmony ; and his enthusiastic love of natural scenery made him the most delightful of travelling companions.” (Paul Jacobson, in Ntrtuywiss. Rundschau, 12, 43 and 44, p. 19). Meyer’s merits were recognised in every land where science is cultivated. He was a corresponding member of the Academies of Munich, Berlin, Upsala, and Gottingen, and an honorary member of many learned societies. The University of Konigsberg made him an Honorary Doctor of Medicine. The Royal Society gave him the Davy Medal in 1891. H e was elected an Honorary Foreign Member of our Society in 1883, and attended the celebration of our Jubilee in the spring of 1891. Many of our Fellows will no doubt recall the rstirring speech, instinct with a true eloquence, which he made at the banquet in responding t o the toast of ‘( Our Foreign Members,” with its striking peroration :-‘‘ Moge die Chemical Society, neben allen ihren anderen schonen Aufgaben auch in Zukunft ihre volkerverbindenden Ziele in so erfolgreicher Weise anstreben wie bisher, m6ge Sie bluhen und gedeihen als eine Pflegstatte der Wissenschaft, f u r ihr Vaterland vorerst, aber nicht minder fur alle Volker welche sich im friedlichen Wettbewerb wissenschaftlicher Arbeit verbundet wissen.” May the Chemical Society, in the years t o come, continue, as in the past, to recognise, with a full and generous appreciation, the work of those across the seas who engage with us in the friendly rivalry oE scientific labour ! And may our action i n thus recording the services in our own annals of the gifted man whose May this aspiration be fulfilled! prosperous labour fills The lips of inen with honest praise,’’ tend i n some degree, however small, t o that consummation for which he so earnestly and so eloquently pleaded 1

ISSN:0368-1645    

DOI:10.1039/CT9007700169

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

SZARVASY : ELEGTROLYTIC PREPARATION OF INDULINE DYES. 207 XVII1.-Electrolytic Preparation of Induline Dyes. By EMERIQUE CHARLES SZARVASY, Ph.D. IT has long been known that different colouring matters are formed when the electric current is allowed to pass through solutions of aniline salts. The first experiments bearing on this subject were made by Letheby in 1862 (this Journ., 15, 161), who electrolysed a solution of aniline sulphate between platinum electrodes, the cathode being immersed in dilute sulphuric acid in a porous cell, and observed the formation of a bluish-green dye on the anode. aoppelsroder (Farbenelektrochemishe Mittheilungen, Muhlhausen) electrolysed neutral or acid solutions of aniline salts; the dyes formed varied according to the salts, solvents, electrodes, and current densities employed.On electrolysing a solution of aniline hydrochloride for several hours, he obtained aniline-black mixed with small quantities of aniline-violet and ‘6 anilein.” If the aniline con- tained tolnidine, then mauvaniline, rosaniline, and leucaniline were also formed, Besides these colouring matters, he prepared a large number, the nature of which was not determined. Voigt (Zed. angew. Chena., 1894, 107), on electrolysing concentrated solutions of aniline sulphate, obtained rosaniline, saffranine, chrys- aniline, and paraleucaniline. Complex mixtures of colouring matters are evidently obtained by these methods, but no explanation has been given of the reactions which lead to their formation. In all probability, the production of dyes from aniline in this way is traceable primarily to the formation of azo-compounds by the action of electrolytic oxygen which may result either in the dehydrogenation of the amino-group and sub- sequent condensation, or in oxidation of the base to nitrobenzene and interaction of this with the excess of aniline. This view is supported by Rotondi’s experiments (Jahres6er., 1884, 270), as azo-, diazo-, amidoazo-, and diazo-amido-compounds were found among the pro- ducts of the electrolysis of solutions of aniline.These secondary effects necessarily complicate the reactions, but by far the greatest influence on the nature and quantity of the final products is exerted by the solvent, which, being ionisable, takes part in the electrolysis introducing new factors, which cause further secon- dary reactions.On studying the electrolytic preparation of colonring matters, it occurred to me that the process could be essentially simplified by electrolysing the aniline salts in a fused state; the secondary reactions, due to the ionisation of the solvent, being eliminated, there208 SZARVASY : ELECTROLYTIC PREPARATION OF INDULINE DYES. was good reagon to hope for end products of a more homogeneous character. The present paper gives an account of the principal results I have obtained by electrolysing fused mixtures of aniline and aniline hydro- chloride, this salt being chosen as it has the advantage of melting comparatively easily and without decomposition. The preliminary experiments were made in glass tubes bent at right angles, the carbon electrodes being adjusted in the limbs of the tube, which was filled with aniline hydrochloride and kept a t tho desired temperature.When a current of 0.5-1 ampere was passed through the fused salt the mass soon turned blue. The colouring matter was formed on the anode, and could be better observed, when F I of suitable dimensions was connected loose asbestos, was packed in the bend of the tube forming a diaphragm. I n this case, the dye was only formed in the limb contain- ing the anode, that contain- ing the cathode remaining colourless. When the direc- tion of the current was re- versed, the other side be- came coloured, and a t the same time the blue colour on the cathode was slowly destroyed. I n the experiments on a larger scale, the substance was placed in a graphite crucible, A, which acted as the positive electrode.An- other graphite crucible, B, with the negative pole by a copper wire, fastened to the inner wall of the crucible and passing through the glass tube, C, which served as a rotating axle. The upper part of B was closed with plaster of paris, B, to fix the axle and to protect the metallic connections. The contact between i he two wire ends in P was effected by means of a mercury connection. With the aid of a motor and the wheel, E, the inner crucible was slowly turned round and the melted mass kept in motion during the electrolysis, so that fresh portions of the mixture came into contact with the electrode. The large crucible was heated with a Bungen burner, which was regulated t o keep the fused mass a t the desired temperature,SZARVASY : ELECTROLYTIC PREPARATION OF INDULINE DYES.209 The active surface of the anode is about twice as large as that of the cathode, so that a higher current density on the cathode is attained and also the reducing action of the latter, which naturally tends to diminish the yield, is restrained, The main advantage of this apparatus is that comparatively large quantities of the electrolyte form a thin layer between the two electrodes, and thus the resistance is very low. Graphite being a good conductor of heat, the temperature of the fused mass is uniform, this being an important condition in these reactions. I may mention that this apparatus is very suitable for electrolysing substances of high melting points, the only alteration to be made in this case being that the glass tube forming the axle is replaced by one of porcelain. After the electrolysis was completed, the product was poured into a flask, diluted with water, the excess of aniline hydrochloride decom- posed with sodium carbonate and the aniline removed by distillation with steam.The coloured substance remaining in the distillation flask was purified by subsequent washing with water and ether, and then extracted with methyl alcohol, in which it was very soluble. After extraction, a black powder remained, which consisted chiefly of aniline black, mixed with small quantities of graphite from the electrodes. The quantity of aniline black varied according to the conditions under which the electrolysis was carried out, as high current density and high temperature tend to increase the amount, whereas, under other conditions, very little is formed.This method, which merely separates the indulines from aniline black, was employed in determining the quantities of the products formed and ascertaining the most favourable conditions under which the current efficiency is the highest. The results obtained are arranged in the table on p. 210. I n columns D, and Do respectively, the current densities on the anode and cathode are given, the numbers being calculated in amperes per square decimetre of electrode surface. Experiments 1-7 were made to determine the influence of current density, 8-11 that of the duration of the action, a,nd 12-15 that of temperature. It will be seen that when z), is approximately 0.8, the efficiency of the current is at its highest, but at the same time the temperature must be maintained a t about 160'.The experiments also show that as the electrolytic action is prolonged, the product per unit of electric energy becomes less, so that only 20 per cent. of the original material can be profitably transformed into the dye, but aa the aniline is recovered almost quantitatively, when separating the products, the yield amounts to 86-90 per cent, of that actually used. The colouring matter extracted with methyl alcohol consists of o210 SZARVASY : ELECTROLYTIC PREPARATION OF INDULINE DYBSa ~- 2'9- 3'2 3 - 3'2 3 - 3.5 3.2- 5 4.5- 5 5.4- 7 LO -12 3 - 3-5 3 - 8 ' 5 3 - 3.5 3 - 3'5 5 - 7 4 - 5 2 - 3 2 - 3 Series.- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 16 0.57 0-7 0-8 1-03 1.12 2'2 3-2 0.8 0 '8 0.8 0.8 0.8 0.8 0.8 0 '8 1 '2 1'48 1.7 2-2 2 5 4.5 5.5 1.7 1.7 1.7 1.7 1 *7 1.7 1.7 1 *7 Duration of sxperiments in hours. 3 3 3 3 3 3 3 2 5 8 16 3 3 3 3 Cemperature, 160" 160 160 160 160 160 160 160 160 160 160 120 150 180 210 Product in grams per 1 amp. hour. 1 *64 2'0 2'5 2 *1 1 *86 1.54 1 *45 2'1 1.9 1 *3 0.61 1.8 2'3 1.67 1.1 mixture of hydrochlorides of bases of the induline class, and in acid solution dyes silk or wool, but has no affinity for cotton. It may be remarked that this mode of preparation resembles the well known " induline process," inasmuch as a mixture of indulines is produced, the nature of which, as well as the proportions existing between the constituents obtained, depends largely upon the temperature at which the reaction takes place and the manner in which it is conducted.Separation of the Dyes. When electrolysing with low currenh density a t a comFaratively low temperature, several colouring matters are formed, which are soluble in water ; from these I succeeded in separating (' induline " and '' B,,4 anilinoinduline," first described by 0. Fischer and Hepp (Artmlen, 256, 262, 266, 272, 286). The colouring matter was dissolved in 50 per cent. acetic acid, and concentrated hydrochloric acid was added to the violet solution. After some time, a crystalline precipitate, A, separated, which was removed by filtration. Sodium chloride was then added to the filtrate, and a precipitate, B, obtained consisting of a mixture of several dyes which dissolved in hot water forming a dark blue solution. Ppecipitccte B.-The aqueous solution, on the addition of caustic soda, gave a precipitate which was soluble in benzene, and from the solution after concentration small crystals were obtained.After recry st allisiag several times from a mixture of light petroleum and benzene, the product wag obtained in reddisb-brown needles ; itSZARVASY : ELECTROLYTIC PREPARATION OF INDULINE DYES. 211 melted at about 206O, and dissolved in concentrated sulphuric acid with a violet colour. On analysis, it proved to be induline. Found C = 79.37 ; H = 4.21 ; N = 15-35 per cent. Cl,Hl,N, requires C = 79.70 ; H = 4-79 ; N = 15-49 per cent. Precipitate A.-This precipitate was examined in the same way, the crystalline powder which separated from the solution in benzene being recrystallised several times from this solvent.When pure, the product formed small prisms with a metallic lustre, and melted at about 150’. It dissolved in strong sulphuric acid with a dark blue colour, which, on the addition of water, became violet. On analysis it gave numbers agreeing with those required for “B2,4 anilino- induline.” Found C = ‘79.73 ; H = 5.30 ; N = 15.22 per cent, C,,H,,N, requires C = 79.55 ; H = 4.98 ; N = 15.47 per cent. When the conditions of experiment were varied by increasing the current density, and the temperature was maintained at 160-170’ during the electrolysis, it was found that only small quantities of soluble indulines were formed, and that the ‘( induline 6B,” described by Witt and Thomas (Trans., 1883, 43, 112), occurred among the products.This separated in a crystalline form when the fused mass was allowed to cool very slowly, and was freed from soluble indulines by filtration and subsequent washing with alcohol, in which it is almost insoluble. It was then treated with alcoholic caustic soda, and the resulting base, after washing with water and then with dilute alcohol, was purified by repeated recrystallisation from aniline, from which it separated in greenish, glistening crystals. On analysis, it gave numbers agreeing with those required for ‘‘ induline 6B.” C,,H,7N, requires C = S1.66 ; H = 5-1 1 ; N = 13.23 per cent. Found C = 81-78 ; H = 5-23 ; N = 13.10 per cent. Theory of the Process-Etectrolytic Pveparation of Axophenine. Induline dyes are formed by the action of azo- and amidoazo-com- pounds on the hydrochlorides of aromatic amines; as an intermediate product, azophenine is formed, which plays a most important part in the formation of indulines.The formation of this compound is in all probability due to the oxidising effects of the azo-compounds, which decompose into p-phenylenediamine and aniline with the elimination of ammonia. With these bases, the azophenine reacts yielding indulines. Only small quantities of the azo-compounds are found in the pro- ducts of electrolysis, as immediately after their formation interaction with the aniline hydrochloride takes place. However, it is certain212 SZARVASY : ELECTROLYTIC PREPARATION OF INDULINE DYE13. that azo-compounds are the primary products, and are present in the early stages of the reaction.Their formation may be explainec! as follows. By the electrolytic decomposition of the aniline hydrochloride, chlorine is liberated a t the anode, and reacting with the aminic hydrogen of the aniline effects dehydrogenation with the production of hydrogen chloride, hydrazobenzene, and azobenzene. So far as I am aware, only one instance of a similar reaction has yet been re- corded, namely, the formation of azobenzene by the action of bleaching powder on aniline dissolved in chloroform (Schmitt, J. pr. Chem., 1878, [ ii], 18, 196). As a rule, the halogens, when reacting with aniline, give rise to the formation of substitution products. Azophenine can be detected in the product of the electrolysis of a mixture of aniline hydrochloride and aniline, and may be obtained in considerable amount if the temperature is kept at 70-90° during the reaction.In one experiment, after the electrolysis had continued for 2-3 hours, the product, after treatment with sodium carbonate and re- moval of the excess of aniline, formed a brownish powder, which, after being washed with hot water and alcohol, was dissolved in aniline. From this solution, brownish-red crystals separated, which, after re- crystsllisation from benzene, melted a t 239O. On analysis, it gave numbers agreeing with those calculated for azophenine. Found C = 82.05 ; H = 5.67 ; N = 12.73 per cent. C,,H,,N, requires C = 81.36 ; H = 5.46 ; N = 13-18 per cent. The substance formed a violet solution in concentrated sul phuric acid, gave a violet mass when heated with p-phenylenediamine hydro- chloride, and, on reduction with tin and hydrochloric acid, formed a mixture of bases, among which aniline and p-phenylenediamine were detected. Briefly summarised, the results prove that (1) the chlorine produced by the electrolytic decomposition of aniline hydrochloride effects de- hydrogenation of aniline ; (2) under certain conditions, the azo-com- pounds thus formed interact with the aniline hydrochloride, forming (3) primarily azophenine, and (4) ultimately indulines. I propose to extend these investigations to the homologues of aniline and some other aromatic amines, and the results will, in due course, be communicated to the Society. This research has been oarried on in the Dnvy-Faraday Research Laboratory of the Royal Institution, and I take this opportunity of tendering my thanks to the Directors and to Dr, 4. $cott far the facilities they have given me. DAVY-FARADAY RESEARCH LABORATORY, ROYAL INSTITUTION.

ISSN:0368-1645    

DOI:10.1039/CT9007700207

出版商:RSC    

年代:1900

数据来源: RSC

摘要:

ELLIOTT : 0-AMINOBENZOIC ACID, 213 XIX- Action qf Chloroform and Potassium Hydroxide on o-Arninobenxoic Acid. By WALTER J. ELLIOTT, M.A. IN a previous communication (Trans., 1896, 69, 1513), it has been shown that when chloroform and potassium hydroxide act on rn-amino- benaoic acid under certain conditions, a compound is produced which condenses with phenylhydraxine, but does not yield a hydrazone. The results of analysis pointed t o the formation of a compound of the formula NH,= C,H,(CO,H)*CHO. The study of the action taking place when o-aminobenzoic acid is substituted for the meta-derivative has afforded further evidence of the formation of aldehydes, a hydrazone and semicarbazone having been isolated. Unfortunately, the yield is so small and the substance SO soluble that the pure aldehyde has not been obtained, but de- rivatives have been prepared and analysed.Numerous attempts have been made to increase the yield with but slight success. The product, however, is more stable than that obtained from the meta- acid. It has been shown (Trans., 1898, 73, 145) that o-nitrobenzoic acid is far more stable towards chloroform and potassium hydroxide than the meta- and para-acids j the o-amino-acid has also proved to be more stable towards these agents than its isomerides. The compound obtained from the meta-acid readily decomposes when boiled with water, yielding m-aminobenzoic acid again, and it was suggested (Trans,, 1896,69, 1517) that the decomposition was preceded by oxidation to aminophthalic acid, which, according to Miller (AmmaZen, 1881, 208, 245), decomposes with the formation of m-aminobenxoic acid.The greater stability of the compound formed from the ortho- acid can be understood if the aldehyde group does not enter the molecule in the ortho-position relatively to the carboxyl group as it does probably in the product from the meta-acid. Experiments have been carried out with p-aminobenzoic acid which promise interesting results bearing on this point, and I hope shortly to resume the work. EXPERIMENTAL. The method adopted in the case of m-aminobeneoic acid (Zoc. cit.) Was tried. 10 grams of o-aminobenzoic acid were added to a, solution of 20 grams of potassium hydroxide in about 200 C.C. of water, and the eolution was boiled with 14 grams of chloroform for 45 minutes.214 ELLIOTT: ACTION OF CHLOROFORM AND After acidifying with acetic acid, no precipitate was a t first obtained, but on standing, crystals separated, which proved to be unchanged o-aminobonzoic acid (m.p. 144'). Numerous similar experiments were made with varied proportions of the reacting substances and of water, but with similar results. When concentrated solutions were boiled for a long time, a small quantity of a reddish, resinous substance was precipitated by acetic acid; the amount, however, was too small to admit of further examination. As no insoluble product had been obtained, dilute sulphuric acid was substituted for acetic acid, and the product, after acidification: was shaken with ether. The residue, after distilling off the ether, was crystallised from water ; o-aminobenzoic acid separated out a t first, but on concentrating the mother liquor, crystals were obtained having a melting point considerably below that of this substance. A solution of phenylhydrazine in acetic acid gave, with the mother liquor, a yellow precipitate at once.All attempts to isolate the aldehydo-acid from the ether extract have failed, as no medium has been found to separate it from o-aminobenzoic acid. The phenyl- hydrazone, however, has been prepared in sufficient quantity for ex- amination and analysis, although the task has been laborious, the yield being very small. Phenylhydraxone of AZdehydo-o-dmirnobernzoic Acid, NH,. C,H,(CO,H)*CH:N*NH* C,H,. The method finally adopted for the preparation of the phenyl- hydrazone was as follows: 10 grams of o-aminobenzoic acid were dissolved in a solution of 30 grams of potassium hydroxide in 150 C.C.of water, and the solution heated to a temperature of 60' in a flask fitted with a reflux condenser ; 16 grams of chloroform were added gradually, and the mixture heated for 3 hours. When cold, the product was acidified with excess of acetic acid, allowed to stand for an hour, filtered from crystals of the original acid, and treated with a solution of phenylhydrazine in acetic acid. The phenylhydrazone separated on standing as a bulky, yellow precipitate. It was washed with hot water, and crystallised twice from alcohol. The filtrate from the phenylhydrazone, when evaporated to a small bulk, treated with dilute sulphuric acid, and shaken with ether, yielded a large quantity of the original o-amino-acid.The recrystallised phenylhydrazone separated in small, yellow needles which melted at 230'. It was insoluble in water, but fairly easily soluble in alcohol. The yield of the pure substance obtained from 10 grams of the acid never exceeded 0% gram, On analysis, the following numbers were obtained :POTASSIUM HYDROXIDE ON 0-AMINOBENZOIC ACID. 21 5 0.1445 gave 0.3476 CO, and 0.0700 H,O. 0.1.092 ,? 14.9 C.C. moist nitrogen at 13O and 763 mm. N=16.04. 0.1134 ), 16.2 C.C. ,, ,, 15" ,? 752 mm. N-16.37. Numerous attempts have been made to obtain the aldehydo-acid from the hydrazone but without success. When boiled with dilute hydrochloric or sulphnric acid, the hydrazone dissolved, but was xeprecipitated unchanged on carefully neutralising the solution.Decomposition apparently occurred with concentrated hydrochloric acid, but no definite product could be isolated, possibly owing to the small quantity of hydrazone available. One remarkable property of this substance is its power of forming salts sufficiently stable for analysis. The barium and silver salts have been prepared and analysed. Barium Salt.-A dilute solution of ammonia was neutralised by excess of the hydrazone, filtered and treated with barium chloride solution. A yellow, crystalline precipitate separated, which was washed well with water and dried in a vacuum. It was found impossible t o recrystallise the salt, as decomposition occurred on heating with water. C = 65.60 ; H = 5.09. 0.1997 ,, 0.4827 CO, ,, 0.0946 H,O.C=65*91 ; H=5*25. C,,H,,0,N3 requires C=65*88 ; H= 5.09 ; N= 16.47 per cent. 0-2574 gave 0.0957 BnSO,. (Cl4Hl2O2NJ2Ba requires Ba = 21.24 per cent. Silver Salt.-This salt is unstable but can be isolated if care is taken to exclude light during the preparation and to use cold solu- tions only. The hydrazone was dissolved in dilute ammonia solution, very dilute nitric acid was added until a precipitate just appeared, the solution was then filtered and silver nitrate solution added. The light yellow precipitate obtained was washed well with cold water and dried in a vacuum. Ag = 30.38. C,,H1,O,N,Ag requires Ag = 29.83 per cent. Ba 5 21.86, 0.1244 gave 0.0378 Ag. h%micurbaxone of Aldehyde-o-un~inobenzoic Acid. When a solution of semicarbazide hydrochloride was added t o the filtrate obtained after acidifying the condensation product, as already described, a yellow precipitate separated on standing, which proved on analysis to be the semicarbazone of an aldehydo-o-aminobenzoic acid. The yield is even smaller than that of the phenylhydrazone, The semicarbazone is insoluble in water, and only sparingly soluble in alcohol, from which it separates in greenish-yellow, microscopic crystals melting at 246'.216 MALLET : ANHYDROUS SULPHATES OF THE FORM 2M”S0,,R’,S04 0.1462 gave 33.5 C.C. moist nitrogen at 22’ and 757 mm. N = 25.39. C9H,,,O3N4 requires N = 25 9 2 per cent, All attempts t o prepare the aldehyde-acid from the semicarbazone have failed. I hope to be able to publish in due course the results of an investi- gation of the action of chloroform and potassium hydroxide on p-aminobenxoic acid.

ISSN:0368-1645    

DOI:10.1039/CT9007700213

出版商:RSC    

年代:1900

数据来源: RSC