|
1. |
Abstracts of the Proceedings of the Chemical Society, Vol. 2, No. 26 |
|
Proceedings of the Chemical Society, London,
Volume 2,
Issue 26,
1886,
Page 215-228
Preview
|
PDF (1000KB)
|
|
摘要:
ABSTRACTS OF THE PROCEEDINGS OF THE CHEMICAL SOCIETY. No. 26. Session 1885-86. --~ _ _ _ June 17th, 1886. Dr. Hugo >fuller, F.R.S., President, in the Chair. Certificates were read for the first time in favour of Messrs. Alfred R6e, Apperley Bridge, near Leeds ; Vivian Phelps Richards, 28, Bos- combe Road, Shepherd’s Bush, W. ; Laurence Hislop, Saltney, Chester ; Frank Thomas Shutt, B.Sc., Rosedale Cottage, Toronto, Canada. The following were duly elected Fellows of the Society :-Thomas Akitt ; James Blake, M.D.; Alfred Chaston; A. W. H. Chapman; Angusto CEesar Diojo ; Charles A. R. Jowitt; Charles Alexander Kohn ; John Temple Leow ; William Ray ; Joseph Price Remington ; William Richards ; Fuibes Rickard ; William Saunders ; Charles A.Smith. The following papers were read :--60. “ The Electrolysis of aqueous solutions of Sulphuric Acid, with special reference to the forms of Oxygen obtained.” By Professor H. McLeod, F.R.S. The experiments were instituted to determine the quantity of ozone that can be obtained by electrolysis. The negative electrode consisted of a small platinum plate, and the positive of a, tube con-taining mercury and with fine platinum wires of 0.045 mm. and 0.027 mm. in diameter fused into the glass. Several wires were used, the total length being about 6 mm. The electrolysis was carried out in ft U-tube surrounded by ice and water; the hydrogen was collected over water, and the ozonised oxygen passed through a tube containing a, solution of potassic iodide, the oxygen being afterwards collected.The quantity of ozone was determined by acidifying the 216 potassic iodide solution and decolorising by a standard solution of sodic thiosulphate. In the electrolysed acid an oxidising substance is present which is not hydroxyl, but is probably Berthdot’s per- sulphuric acid. The amount of this “ active oxygen ” was found by adding potassic iodide to the liquid and decolorising by the solution of thiosulphate. The electric current was measured by a tangent galvanometer, and the dimensions of the wires of the positive pole were determined; from these daka the intensity of the current was calculated. Acids were used of relative densities varying be- tween 1.025 and 1.7. The maximum quantity of ozone was obtained with solutions about 1475 or 1.1in density, the electrolytic oxygen containing about 16 or 17 per cent.of its weight of ozone. The maxi- mum quantity of “ active oxygen ” in the oxidising substance referred to was produced with acids about 1.2 to 1-25 in density, the proportion being 16 or 17 atonis to 100 atoms of hydrogen. The solubility of ozone was determined by one experiment and found to be much greater than that of oxygen. A note is added to the paper detailing some experiment’s on the action of oxygen on chlorhydric acid under the influence of light : it was found that a considerable quantity oE chlorine was liberated. DISCUSSION. Mr. FRISWELLsaid that Professor McLeod’s observation explained a fact that had come under his notice years ago; viz., the constant presence of chlorine in muriatic acid.The PRESIDENTsaid that he also had noticed this, and had found that chlorine was always contained in the acid if it had been exposed to the air. Mr. LAURIEsuggested trying aluminium electrodes ; he had noticed a very distinct smell of ozone on electroljsing dilute sulphuric acid with poles of this metal. 61. “ Essential Oils (Part 111) : their Specific Refractive and Dispersive Power.” By Dr. J. 11. Gladstone, F.R.S. Since the appewance of the author’s former papers on essential oils in 1863 and 1872, ma,ny investigations have been published ; but important divergences of opinion still exist among chemists as to the rational constitution of these compounds. He now brings forward arguments founded on the phenomena of refraction and dispersion, believing that in the conflict of opinions such arguments ought to have considerable force.For this purpose he employs the refraction equivalent for the solar line A, as compared with that calculated from the known values of carbon and hydrogen and the known increase on 217 account of the double linking of carbon-atoms. But he also intro- duces a new conception, that of dispersion equivalents: being the difference between the refraction equivalents for the lines A and H, or PCLH-FLA) where p and d are the refractive index and relative d density and P the atomic weight. It is found that the dispersion equivalent of carbon may be taken at 0.25, and that of hydrogen at 0.045, as a first approximation, while in the case of benzenoid com-pounds the addition to be made to the dispersion equivalent on account of each double linking of carbon-atoms is fully 0.8.The paper deals mainly with the C,&& hydrocarbons. These are divisible on account of their physical and chemical properties into two large groups, the terpenes and the citrenes. There are also the solid camphenes and the cedrenes or C H2* hydrocarbons. The optical properties of the terpenes are in close accordance with what may be expected from a compound in which one pair of carbon-atoms is double-linked; those of the cihrenes indicate two pairs; while camphene has a slightly slower specific refraction and dispersioii, however, than a terpene.The cedrenes appear to be strictly pols-meric with the terpenes from an optical point of view. The optical properties of caoutchouc. were also examined. Its principal constituent resembles the citrenes ; so also does the liquid hydrocarbon, CI0Hl6, that is produced by its dry distillation. Isoprene, C5H8,also, must have two pairs of its carbon-atoms double- hiked, a result which agrees with Tilden’s conclusions from its chemical properties. Refraction equivalent. Dispersion equivalent. Culculatecl. Observed. Calculated. Terpenes, natural ......... artificial.. ..... 73’0 72.9 73 -0 73.0 4‘0 3.9 4.02 4‘02 Camphene. ............. Cedrenes .............. 71 -9 109* 8 73’0 109 -5 3.7 G-1 4 -02 6.03 Uitrenes, natural .......... artificial .......75.0 75.1 75 *2 75’2 4.5 4.6 4’82 4*82 Caoutchene. ............ 75.3 75 *2 5 -0 4.82 Isoprene ............... 40.3 39.8 3.2 3 *21 Arnistrong’s cymhydrene, CIOH20,Atkinson’s menthene, C:10H18, citreiie, C10H16, and cymene, CloH,d,form a serias : the first being a saturated compound, and the others having respectively one, two and three pairs of cai-boil-atonis double-linked. 218 DISCUSSION. Prof. TILDEN asked whether Dr. Gladstone had made any special attempt to determine the composition of the cedrenes; they were commonly regarded as C15H211hydrocarbons, but the difference in com- position between CI,H,l and C,H,, was so slight that it was conceivable that the cedrenes were in reality homologues of the terpenes.Dr. GLADSTONEsaid that this suggestion was novel to him. Dr. ARMSTRONGthought that while Dr. Gladstone's observations agreed with the chemical evidence in assigning the terpenes to a posi-tion intermediate between the camphenes and citrenes, the chemical evidence did not harmonise with the assumption that the terpenes contained only a, single pair of " double linked '' carbon-atoms ; in this respect the terpenes and citrenes must be classed together. In point of fact the C10Hf16hydrocarbons manifest peculiarities which at present do not admit of satisfactory representation by a symbolic expression. 62. " The Formation and Destruction of Nitrates and Nitrites in Artificial Solutions and in River and Well Waters." By J.M. H Munro, D.Sc. Most of the experiments recorded in this paper were made in the years 1883 and 1884, the method followed being that adopted by R. Waring-ton and described in his Second Report on Nitrification (1879). Many of the general conditions of nitrification, as stated by Schloesing and Riluntz, and by W arington, have been confirmed. For example, in no case has nitrification occurred in a solution sterilised by boiling after being seeded with soil and left unopened until tested after an interval of as much as three years. Mercur:c chloride, lead acetate and chloroform are all equally fatal to nitrifi- cation. As an instance of the slowness of the process in some cases, a solution of 2 grams per litre of ammonium chloride seeded with 2 grams of soil commenced nitrifying only after an iiicubation of three months, and required two years and ten months €or complete nitrification ; but when a fresh solution of 1gram per litre of ammo-nium chloride was added bodily to this nitrified solution, it com-menced to nitrify after an incubation of only five days.Amongst nitrogenous bodies other than ammonium salts, ethyl-amine hydrochloride, gelatin,, potassium and ammonium thiocyanate and urea are all easily susceptible of complete nitrification in contact with soil. In all these cases ammonia is first formed, and nitrite appears at a subsequent stage, finally passing into nitrate. Thiourea has resisted repeated attempts to nitrify it.Several experiments are cited to show that the organic carbon 219 required in a solution prepared for nitritication is infinitesimal in pro- portion to the quantity of ammonium salt nitrified. Thus 63 mgrms. ammonium chloride have been completely nitrified to nitrite without any added organic carbon. When an alkaline tartrate or any similar organic matter is included in a solution prepared for nitrification (as has been the case in all published experiments), it delays nitrification, and even brings about a destruction of any nitrate that may pre-exist in the solution unless all other germs than those of the nitrifying organism are rigorously included. It does this because it encourages a, growth of denitrifying bacteria, the germs of which exist in the air, in soil, in natural waters and generally even in the few drops of nitrifying solution employed as seed.Until these bacteria have run their course and died, nitrification does not commence, and hence there is a period of apparent incubation even in solutions otherwise ready for immediate nitrification. By using soil as seed ahd ex-cluding all other added organic matter, a first solution of ammonium chloride may be caused to commence nitrifying in three or four days ; if after nitrification this is poured off and replaced by a second solu-tion, nitrification commences in 24 hours ;and a third solution employed in a similar manner may (under favourable circumstances) be seen to have commenced nitrifying in seven hours. Well and river waters, since they contain organic matter not fer- mentible by denitrifying bacteria, form suitable media for the study of nitrification. The salifiable base (calcium carbonate) and the traces of necessary minerals are also present in suitable proportions and in such a form as not to interfere with the perfect transparency of the solutions.Such waters, boiled and filtered and seeded with a little soil, or a few drops of a nitrifying solution, will nitrify added ammonium chloride to the full saturating capacity of the calcium carbonate contained in them. The process usually takes 30-40 days at the ordinary temperature. The question as to how far these natural waters contain the nitrifying organism independently of added soil has also been care-fully tested.A suitable quantity of ammonium chloride solution (5 C.C. = 5 mgrm. NK,) is boiled in a sterilised flask plugged with cotton-wool ; on cooling, the plug is removed for a moment while the flask is half filled with the water to be examined. A cap of paper is then tied over the flask, which is placed in a warm place (not over 85°F.) for 18-30 days and then opened and tested. If the water possess any nitrifying power some nitrite will almost certainly be found at; the end of this period by the nietaphenylenediamine test. Eleven waters tested in this way were found to possess nitrifying powers in different degrees : they inclnded river-water, seven well-waters, water from a coal-pit level, rain-water from a brick cistern and water from t<he 220 Bristol Waterworks Company's main.The wells with sewage con- tamination, present and past, nitrified readily : probably because the nitrifying organism has already undergone a period of incubation and is in full ,activity. River water commences nitrifying after 9 days, and finishes on the 46th day, nitrite being present as late as the 42nd day. The addition of 1per cent. of soil hastens the process and lessens the production of nitrite. The only water which failed to produce nitrification after an incubation of 18 days at 80-85°F. was rain-water caught from the clouds in a sterilised beaker and added to boiled well-water. Well-water will produce a purely nitrous or a purely nitric fermentation, according to circumstances, and the nitrite may persist for at least two years without further oxidation.The nitrifTing power of a well-water is not removed by filtration through Swedish paper, and is even increased by filtration through a charcoal filter in common use. The waters remain practically clear throughout, and the deposit is extremely slight ; as they encourage the growth of the nitrifying organism almost exclusively (in the dark) they are probably well suited for microscopic observation of this organism. Denitwjcatiow-An alkaline tartrate, acetate, or oxalate, sugar, glycerol, or in fact any fermentible organic matter, if added to well-water, produces a bacterial reduction or destruction of the nitrate pre-existing in the water.The tartrate, acetate, or oxalate is de-stroyed with formation of an alkaline carbonate. The water becomes opalescent in 3-4 days, and consistently with this a trace of nitrite is found. In a few more days all the nitrate may be reduced to nitrite. In good waters the reduction may go no fui-ther. In many polluted waters, the nitrate and nitrite are totally destroyed, iiitrogen gas being evolved. The same effect is produced by the addition of a few drops of sewage to the water, if the uater contain any fermentible oyyanic matter. Even salicylic acid and phenol lend themselves to this reduction, althougb they are fatal to nitrification. NM. Gayon and Dupetit, in a memoir published since this paper was in MSS.,have examined this phenomenon in great detail by the culture of the denitrifying bacteria in highly artificial solutions.The bacteria which effect the reduction to nitrite in presence of organic matter are common in the air, waters and soil. Those which destroy the nitrate or nitrite with evolution of nitrogen gas were obtained by MM. Gayon and Dupetit from sewage. 63. " Water of Crystallisation." By W. W. J. pu'icol, M.A., D.Sc., P.R.S.E. The paper is a reply to Professor Pickering's criticism of thc author’s experiment on the molecular volumes of salts in solution. (Trans., 1886, 411-432.) The author maintains the accuracy of his experiment’s and of the conclusions derived from them, which are that when a salt is dissolved water of crystallisation is indis- tinguishable from solvent water, both having the same volume ; and that water of constitution has in solution a volume markedly different from that of solvent water.Hence it seems certain that water of crystallisation does not exist in solution, but that the whole of the water present is in the same relation to the salt, no hydrate definite or indefinite existing in solution. This is supported by experiments on supersaturation, the author having prepared supersaturated solu- tions from dehydraked salt and coZd water : the salt dissolving with evolution of heat but without the formation of a hydrate. DISCUSSION. Mr. PICKERINGsaid that he did not wish for one moment to call in question Dr. Nicol’s results, and he even agreed with him so far as to admit that the work showed no difference between combined water and water of solution ;but this was a very different thing to saying that it proved that no water was combined with the salt. He had ample reason for considering that this was a case in which negative evidence proved nothing.He considered that Dr. Nicol’s experiments on the magnesium sul- phates afforded the strongest evidenee which we have of one of the water molecules contained in them being different from the rest. At the same time he thought that that evidence was far too slight to warrant any positive conclusion being drawn ; and even if it proved that such a difference did exist, it would not prove that this one mole- cule was so-called constitutional water.A discussion of the thermal phenomena attending dissolution would open the whole question of the nature of solution, into which it was impossible then to enter. Although Mr. Pickering could not accept Dr. Nicol’s theory of solu-tion, he by no means adhered to what is ordinarily understood by the “ hydrate theory.” It was impossible he thought to draw any general conclusions as to the nature of solution from the behaviour of one of the most exceptional salts which we know, sodium sulphate. Dr. NICOLsaid that he was glad to hear that Mr. Pickering had no wish to call in question the accuracy of his results, for that was not the impression to be gathered from Mr. Pickering’s paper. As to negative evidence proving nothing, he thought that it should have at least as much weight as an affirmative statement, unsupported by any evidence other perhaps than the colour of cobalt and copper chlorides.In using the term constitutional water, he had no intention of corn- mitting himself to more than the statement that one water molecule was differently related to the salt in solution from the remainder of the water. With regard to the dissolution of a dehydrated salt without the intermediate formation of' a hydrate, he had wed sodium sul- phate as the most convenient, but had performed similar experiments with sodium thiosulphate, magnesium sulphate and other salts. He was of the opinion that such experiments are conclusive evidence against the existence in solution of hydrates of these salts, Dr.ARMSTRONGcalled attention to T. Thornsen's recent observations on the supposed division of the water between two bodies in solution (c7. pyaChem., 1885, 32,211 ; Chem. Xoc. Abs., 1886, 12). 64. " A Method of investigating the constitution of AZO-, Diazo- and analogous CompoundB." By R. Meldola, F.R.S., and F. W. Strea tf eild. The method described consists in displacing the hydrogen in such compounds by alkyl radicles and then decomposing by heating with acids or by complete reduction. The compound described in the ?resent paper is paradinitrodia,aoamidobenzene obtained by treating paranitraniline dissolved in chlorhydric acid with the necessary quantity of sodium nitrite. The formula of this substance is that of a true diazoamidoazo-compound, vie., N0,*C,H,*N2*NH*CGHa*N0,.On reduction by tin and hydrochbric acid it gives only paraphenylene- diamine.It is a strongly acid substance, the H of the *N,.NH-group being displaceable by metals with the formation of crystalline salts. It is remarkably stable in the presence of alkalis, buB is decomposed on heating with acids. Its differs from other diazoamido- compounds, however, in not furnishing a phenol as a, product of decomposition by acids. With dilute sulphuric acid it gives para- nitraniline and a, tarry substance, and with chlorhgdric acid, para- nitraniline and paranitrochlorbenzene :-NO,*C,H,*N,*NH.CcH*eNO, + HC1 = N, + NO,-C,H,Cl+ NO2.C~H,~NH;,-By acting with ethyl iodide upon the sodium salt the ethyl-deriva- ti ve, N0,*C6H4*N2*N(C,H6)C,H4*N02,is obtained.The original sub-stance forms small yellow needles, melting with decomposition at 223". The ethyl-derivative melts at 191-192". The last compound does not form salts ; it is decomposed by dilute sulphuric acid into ethyl paranitraniline and resinous products, and by chlorhydric acid into paranitrochlorobenzene and ethylparanitraniline. The ethylpara- nitraniline forms a nitroso-derivative (m. p. 119*5O), which is described in the paper. The authors point out that the decomposition of the 223 ethyl-derivative into ethylnitraniline and nitrochlorbenzene is conclu- sive evidence against the symmetrical formula+- NO,*C6aN-N*C,H,*NO, ; NO?*C~Ha~N-N~CsH,*NO~, \/\N/H N(Cab) for this compound and the original substance.They propose to extend the investigation to other diazo-, azo- and oxyazo-compounds. 65. ‘‘ The Estimation of free Oxygen in Water.” By Miss K. I. Williams and Professor W. Ramsay. The authors have instituted a comparison of Schutzenberger’s methods of estimating free oxygen in wat,er with each other and with the gasometric method with favourable results. Schuteenberger’s first method, which consists in adding sodium hyposulphite to a measured quantity of water, using indigo-carmine as an indicator, is stated by him to estimate only half the amount of free oxygen; his second method in which water containing free oxygen is added to indigo- white, turning it blue, and the amount of oxidised indigo-white is estimated by hyposulphite, was regarded by him a8 the only accurate one.The authors disprove the assertion, and show that there is a preliminary stage in the first process when colonr disappears; but that on standing for some time a blue colour appears, to destroy which permanently requires such an addition of hyposulphite as to make the total amount equal to that employed in operating according to the second method. The proportion of hyposulphite used during the first stage of Method I to the total amount used is 3 to 5; but they believe that this proportion was conditioned by the temperature and dilution prevailing during the experiments. It is also shown that hyposulphite of soda reacts to some extent with hydrogen dioxide, thus negativing the statements of Schutzenberger’s of Konig.66. “Note as to the Existence of an allotropic modification of Nitrogen.” By Miss K. I. Williams and Professor Ramsay. Attention was some time ago directed to the existence of an allotropic modification of nitrogen by Mr. 5. Stillingfleet Johnson, who stated that an ac tive modification of this element could be prepared by heating a mixture of potassium nitrite and ammonium chloride solutions ; and that 011 passing the evolved gas over heated platinum sponge along with hydrogen, ammonia was formed. The support lately given to this statement by the experiments of Professors J. J. Thomson and 224 Threlfall has suggested the propriety of testing Johnson's state-ments by further experiments ; the results, however, have been nega- tive.The hydrogen used in the experiments was prepared by the action of chlorhydric acid on granulated zinc. It was collected in a gasholder and dried by passing it first through sulphuric acid and then over phosphoric anhydride. In preparing the nitrogen, 85 grams of potassium nitrite was dissolved in distilled water and added to it solution of 53.4 grams of ammonium chloride ; some ammonia and then some crystals of cupric chloride were introduced. On the nddi- tion of a sufficient proportion of this latter compound a steady stream of gas came off and was collected in a gasholder. In order to dry it and remove any oxides of nit'rogen or ammonia present in the gas, it was first passed through a tube containing pumice-stone soaked in an acid solution of ferrous sulphate, next through a wash-bottle partly filled with sulphuric acid, over pumice-stone soaked with Nessler's reagent, then over pumice-stone soaked wit,h sulphuric acid, and then through a tube filled with phosphoric anhydride.At this point the two streams of gas were brought together bya T-tube, and the mixture passed over heated platinum sponge into bulbs containing chlorhydric acid. At the end of each experiment the contents of the bulbs was washed into an evaporating basin and eraporat8ed over a water-bath ; the residue was then dissolved in distilled water and tested for ammonia with Nessler's reagent. The first experiment was made with about 4-38 litres of nitrogen prepared at a temperature of about 100" ; the result being that the Nessler's reagent was coloured merely a faint yellow.In a second experiment, the nitrogen used was evolved at first from the mixed solution by external application of heat, but on adding more cupric chloride the reaction went on alone and the temperature was lower than in the first experiment. To get accurate results the capacity of the nitrogen gasholder was gauged; when full of water it con-tained 8.481 litres, equal to 7.7031 litres at 0" C. and 760 mm. After using the whole of this nitrogen, at the end of the experiment the same tint vas obtained as that given by 1.10 C.C.of ammonium chloride solution in 100 C.U. of distilled water with Nessler's reagent, 1C.C.of the ammonium chloride containing 0*00019107gram NH,C1 01' 0.00005 gram N. Therefore the amount of " active nitrogen" was only 0.000055 gram in the 7.7031 litres. To obtain better results, if possible, during the preparation of the next gasholder full of nitrogen, the flask from which it was evolved was carefully kept below 50" C., the temperature being watched by means of a thermometer placed in the cork of the flask. In this case the ammonia formed produced the same tint with Nessler's reagent as that given by 1.14 C.C. of the standard ammonium chloride solution, 285 proving the presence of only 0.000057 gram “ active nitrogen ” in rn/*do31litres. It is evident, therefore, that these experiments fail to corroborate Mr.Johnson’s results. 6‘7.“The Presence of a reducing agent, probably Hydrogen Per- oxide, in Natural Water.” By Professor Ramsay. Distilled water, as well as ordinary tap water, has a reducing action on potassium permanganate. The amount of the reducing agent is increased by evaporation, even when all possibility of oon-tamination with solid organic impurity is excluded. The amount of reduction is far too great to be ascribed to the nitrites present in the water. The experiments described in the paper show under what circumstances and to what extent this substance-which is probably hydrogen dioxide-is produced. If this supposition be correct and the active substance in natural water be really hydrogen peroxide, it becomes of importance to ascertain its action on organic impurities contained in many natural waters.Experiments were therefore made quantitatively on the action of dilute solutions of peroxide of hydrogen on urea, and it was found that the urea is slowly oxidised on standing ; the rate of this action has also been measured. (Comp. H. B. Dixon, Chem. SOC.Trans., 1886, p. 108.) 68. “Evaporation and Dissociation. Part 1V. A Study of the thermal properties of Acetic Acid.” By W. Ramsay, Ph.D., and Sydney Young, D.Sc. This paper contains a record of measurements of the relative density of liquid acetic acid at 13-11’(water at 4”= 1*0),the number obtained being 1.05682 ; its expansion up to a temperature of 280”, at which the volume of 1 gram is 1.5172 C.C.; its vapour-pressures, which reach 24600 mm. at 280” ; and the density of its saturated and unsaturated vapour at different tcmperatures and pressures. The minimum value of the density of the saturated vapour is at 150°, and is equal to 50.06 (H = 1.0) ; it increases both with rise and with fall of temperature. The values of drp have also been calculated, and dt from them and from the other data the heats of vaporisation have heen deduced. Here, asgain, there is a maximum value at 110.6”;the latent heat at this point is 92.8 C., and decreases both with rise and fall of temperature. Diagrams are appended contrasting the be- haviour of acetic acid with that of alcohol and of ether. 69. “Note on the Vapour-densities of Chloral Eth~-l-Alcoholate.” By William Ramsay, Ph.D., and Sydney Young, D.Sc.This paper contains an account of determinations of the densities of the saturated and unsaturated vapour of chloral ethyl-alcoholate. The amount of dissociation is always very great, the percentage number of molecules decomposed being never less than 75. Owing to the very small variation of vapour-density under different condi- tions of pressure and temperature, to the impossibility of obtaining very concordant results with such a substance, and to the fact, noticed to a smaller extent with acetic acid, that on decreasing the volume condensation begins before the pressure has reached its maximum, it is impossible to draw any very definite conclusion re-garding the relation of the density of the saturated vapour of this body to the temperature, but it may be stated that a rise in the density of the saturated vapour with fall of temperature could not be detected.The density of the unsaturated vapour diminishes with iise of temperature at constant pressure, and with fall of pressure at constant t'ernperature. 70. " The Nature of Liquids as shown by a study of the thermal properties of stable and of dissociable Bodies." By William Ramsay, Ph.D., and Sydney Young, D.Sc. After Deville advanced the theory of dissociation, its opponents endeavoured to explain the abnormality of the vapour-density of unstable bodies by ascribing it to a deviation from Avogadro's law supposed to occur in many liquids at temperatures and pressures near their condensation points.No complete research having been made to compare the behaviour of stable and of dissociable bodies in this respect, the authors have investigated the thermal properties of alcohol, ether, acetic acid and chloral alcoholate. In all cases, they have fouud abnormality at high pressures. But whereas with alcohol and with ether the density of the saturated vapour becomes and remains normal below certain temperatures, with acetic acid the density when at its lowest is abnormally high and increases with fall as well as with rise of temperature. The two theories alluded to above, bg which attempts have been made to explain this abnormal density, are (1) that the gaseous molecules exercising attraction on one another are thereby drawn closer together, and (2) that gaseous n~olecules combine to form more complex molecules such as are by iiiany supposed to exist in liquids.It appears to t'he authors incon- ceivable that this effect should be produced by the same cause under conditions so totally different : for at low temperatures the stability of a saturated vapour is greater while the rnolecules are necessarily f'urther apart; and at high temperatures, owing to the high pressure, the niolecules are in closer proximity, while the stability is necessarily decreased. With acetic acid, it appears therefore that the ilbllo1*- 227 mality at high temperatures is due to a physical cause, common to all liquids, but at low temperatures must be ascribed to some sort of chemical combination between the gaseous molecules.71. “ The Electromotive Forces developed during the combination of Cadmium and Iodine in Presence of Water.” By A. P. Laurie, B.A., B.Sc. The author has determined by means of a Thomson electrometer the electromotive forces of cells consisting of a cadmium and a platinum plate immersed in a solution of cadmium iodide containing free iodine. In one set of experiments, t,he amount of cadmium iodide in solution was constant and the amount of iodine was varied ; in another. the amount of cadmium iodide varied, the solution being in each case saturated with iodine ; in a third, a constant amount of iodine, but varying amounts OP cadmium iodide were used. The result of the experiments is to show that if cadmium and water.containing cadmium iodide and free iodine are brought toge-ther, a considerable electromotive force is developed, which steadily falls. This depends on the facts (1) that as the free iodine is diminished, the electromotive force falls gradually at first, but’ more rapidly the less iodine there is present ; (2) that as the cadmium iodide solution increases in strength, the electromotive force falls off very rapidly while very small quantities of khe salt are present but more and more slowly as the amount of salt present becomes con-siderable. In both cases the change may be represented by a con- tinuous curve. The actual values are given in the paper. 72. “Detection and Estimation of Iodine, Bromine and Chlorine,’’ By 31.Dechan. To separate iodine from a mixture of chloride, bromide and iodide, the author distils with a concentrated solution of potassium bichro- mate (40 grams KICr20,to 100 C.C. water) ; on repeating the distilla- tion, after adding a small quantity of sulphuric acid, the bromine only passes over, provided that the solution be not too concen-trated. The apparatus is therefore so arranged that by means of a stopcock funnel water may be added whenever necessary. The fol-lowing results are quot,ed :-Iodine. Bromine. Chlorine. -1Taken. Found. Taken. Found. Taken. Found. -__---. -----------0‘01443 0-01441 0*0126 0.01254 0.0123 1 0.y0*0288 0-02833 0-0252 0’0250 0*056 0’0576 0,05628 0*0504 0-05009 0*194 228 73.“The Analysis of Alloys and Minerals containing the heavy Metals, Selenium, Tellurium, &c.” By Thomas Bayley. The metals precipitable as sulphides are commonly divided into the two groups of those forming sulphides insoluble in alkaline sulphides, and those whose sulphides are Roluble; the method of extraction with an alkaline sulphide is often applied in qualitat’ive but less often in quantitative analysis, owing to the dif€iculty of completely removing the soluble sulphides when once they have been precipitated in admixture with the other sulphides. Instead of precipitating both classes together, it is better, the author finds, to prevent the precipi- tation of the thio-salt forming elements altogether, experience having shown that the process conducted on this principle is at once accurate and very easy of execution.The process recommended consists in passing sulphuretted hydrogen in to a boiling solution containing the substance together with citric and tartaric acids and caustic soda. ADDITIONS TO THE LIBRARY. I. Donations. Select Methads in Chemical Analysis (chiefly Inorganic) : by W. Crookes : second edition, re-written and greatly enlarged : London, 1886 : from the Author. Notes on Analytical Chemistry for Students in Medicine: by A. J. Bernays : second edition : London, 1886 : from the Author. New Commercial Plants and Drugs : by T. Christy : No. 9 : London, 1886 : 11. By Purdiase. Electro-deposition : a Practical Treatise on the Electrolysis of Gold, Silver, Copper, Nickel, and other Metals and Alloys; with several chapters on Electro-metallurgy : by A. Watt : London, 1886. Spectrum Analysis in its Applications to Terrestrial Substances and Physical Constitution of the Heavenly Bodies, familiarly ex-plained by the late Dr. H. Schellen: translated from the third en-larged and revised German edition by Jane and Caroline Lassell, edited with notes by W. de W. Abney: London, 1885. Die Chemie des Steinkohlentheers : von G. Schultz : Zweite Auflage, Zweite Liefernng : Braunschweig, 1886. HAREISON AND 80~8, PRINTERS IN ORDINARY TO HER MAJESTY, ST.MABTIN’G LANK.
ISSN:0369-8718
DOI:10.1039/PL8860200215
出版商:RSC
年代:1886
数据来源: RSC
|
|