摘要:

Mr. E. Schunck on Lecanorin &. XI. On some $ the Substances contained in the Lichens em-ployed for the preparations of Archil and Cudbear. By EDWARD* ESP.,Munchester. SCHUNCK Read January 4 1842. OUR knowledge concerning that department of organic chemistry which embraces the colouring matters and other principles nearly allied to them is of the most iniperfect kind. Though many other branches of organic chemis- try have been so thoroughly and accurately investigated that little or nothing remains to be known coiicerning them this may be called an unexplored field. Most of the coa louring matters are so little known as regards even their most essential characters as not to allow 11s either to justify or to question the propriety of throwing them together into one general class; a class distinguished from those nearly allied to it merely by the (as far as we know) adventitious cir- cumstance of the substances belonging to it being endowed with certain more or less vivid colours.,4mong all the co-louring matters there are none the study of whose properties and reactions is calculated to throw more light on the nature of the whole class than those which are prepared by an arti- ficial process from certain kinds of lichens and on this account Mr. E. Schunck on Lecanorin it is desirable that they should be carefully examined. It was the circumstance of these substances being prepared artificially from plants perfectly devoid of coldur that first attracted to them the attention of chemists and led to a series of investi-gations by which a number of highly interesting substances was brought to light and a process elucidated which belongs to the most remarkable and unparalleled in the whole range of organic chemistry.RoQiquet first discovered a colourless crystallizable sub- stance in them (orcin) capable of being converted by the joint action of ammonia and oxygen into a true colouring mat- ter which contains neither the original substance nor ammo- nia as such. This interesting discovery was followed by others. The researches of Heeren made us acquainted with a series of substances contained in the RocceZZa tinctoria pos-sessed of the same property and another substance phlorid- zin was shown by Stas to bear a complete analogy to orcin in this respect.The subsequent labours of Dumas who sub- jected orcin and the bodies derived from it to an accurate examination and of Kane who has determined the compo- sition of the substances discovered by Heeren and of the co- louring matters contained in archil and litmus seemed to have sufficieritly elucidated the subject. Some obscurities however in a part of Dr. Kane’s late paper seemed to make it desirable that some of his results should be confirmed befork being finally adopted and at the suggestion of Professor Liebig I undertook the re-investigation of this subject and performed it in his laboratory. Instead of the EocceZZa tinctoria I employed in my experi-ments the lichens that grow on the basalt rocks of the Vogels-berg in Upper Hessia where they are collected for the pur- pose of preparing a dye from them.These lichens were all crustaceous and belonged to the genera Lecanorn Urceo-Zaria F‘arioZaria &c. From them I extracted the following substances :-1. A white crystalline substance soluble in alcohol and aether but insoluble in water bearing in its properties $reat resemblance to the substance called by Heeren ETythrin and by Kane ErythriZin but different in composition and giving other products of decomposition. This substance I call Le-canorin. 2. A crystallizable substance identical in properties and composition with Heeren’s PseudeTythrin and Kane’s Erythrin. 3. A fatty substance of acid properties soluble in alcohol but insoluble in aether and water.The method by which these substances were extracted and and other Substances derivedfrom Lichens. separated from one another was the following. The lichens were reduced to a coarse powder and then treated with aether in an apparatus of displacement until the aether dissolved no- thing more. The aethereal extract which had acquired a green tinge from chlorophyll in solution was distilled off leaving as a residue a greenish yellow mass consisting for the Freater part of lecanorin. This mass was brought into a glass tunnel and washed with small quantities of aether until it had lost its green colour in part. It was then treated with boiling water in order to remove every trace of pseuderythrin and lastly purified by dissolving it in a small quantity of boiling alcohol which deposited on cooling a snow-white crystalline mass consisting of lecanorin in a state of purity.The dark green Ethereal fluid obtained by washing the impure lecanorin contained besides lecrriiorin the greatest part of the pseudery- thrin which liad been extracted by the aether. The fluid was evaporated to dryness and the residual mass treated with boil- ing water which deposited on cooling a inass of shining plates and needles of pseuderythrin which was purified by re-cry-stallization. More of this substance was obtained by treating the lichens which had been exhausted with Ether with boil-ing alcohol and filtering rapidly. The alcohol was distilled off and the residue treated with boiling water which dissolved all the pseuderythrin and deposited it on cooling.The mass left undissolved was washed with aether which dissolved all the chlorophyll and left behind the fatty substance mentioned above which was purified by re-dissolving in alcohol. 1 will now proceed to a more minute description of the properties of these several bodies. Lecunorin. This substance when pure is perfectly white. If prepared in the manner described above it has the appearance of a white mass composed of acicular needles. When its solutions are slowly evaporated it crystallizes in silky needles grouped together in star-shaped masses. It is insoluble in boiling water but soluble easily in alcohol and aether. Its solutions redden litmus paper. It is soluble in alkaline liquors from which it is precipitated unchanged by acids provided the so-lutions be not boiled and be not left to stand too long.It is insoluble in all weak acids with the exception of acetic acid. Strong nitric acid converts it ultimately into oxalic acid. It combines with metallic oxides by double decomposition. Heated on platinum foil it melts emits a dense vapour and burns off leaving but little carbonaceous residue. When heated in a tube closed at one end it melts and under violent Mr. E. Scliunck on Leeanorin ebullition gives off a dense vapour which condenses in the upper part of the tube into a thick liquid which after some time solidifies forming a crystalline mass. The nature of this sublimate will be explained further on.The action of the alkalies on this substance is of course the most interesting point connected with its history. A solution of lecanorin in ammonia when exposed to the air acquires after some time a beautiful deep purple colour from this solution acids precipitate a red colouring matter. A solution in potash under the same circumstances becomes of a deep red colour. Being desirous of ascertaining whether the leca- norin was immediately converted into the red colouring mat- ter or whether it passed first through any intermediate state which was not improbable I dissolved some of the substance in ammonia excluding the solution from contact with the air. After a lapse of some hours the solution though perfectly colourless was found. no longer to contain any lecanorin ; for acids instead of producing a thick gelatinous or flocculent precipitate as they do when applied immediately after solu- tion has been effected merely caused a brisk effervescence of carbonic acid plainly showing that the substance had been completely decomposed without a colouring matter having been formed.The same effect was brought about instanta- neously when the solution was boiled. In order to observe the process more clearly I dissolved a quantity of lecanorin in baryta water in the cold. The solution on being boiled or allowed to stand deposited a great mass of pure carbonate of baryta. The liquid was filtered rapidly and the excess of caustic baryta precipitated by a stream of carbonic acid on slow evaporation it yielded large prismatic crystals of a sub-stance which possessed characters in every respect iden tical with those of orcin.It had an extremely sweet taste was ca- pable of being voiatilised without change and without leaving any residue gave a deep blue colour when dissolved in am4 monia and exposed to the air struck a blood-red colour with nitric acid and precipitated a solution of basic acetate of lead. Lecanorin this is converted by the action of alkalies into orcin and carbonic acid in the first instance this decompo- sition always preceding the form:rtion of colouring matters. The same decomposition is produced by the carbonated alka-lies by long boiling with water and by dry distillation the heavy vapour mentioned above as being produced by heating lecanorin to decomposition being vapour of orcin.The composition of Iecanorin is expressed by the formula C, H 0,. The results of the combustions which I rriade of it admit of no other interpretation. All attempts to determine ‘rind other Substances derivedfrom Lichens. 7*5 its atomic weight by means of combining it with metallic oxides failed. These compounds can only be prepared by double decomposition ; but the ficility with which lecanorin is decomposed when alkalies are added to its solutions always renders the purity of the compounds fixmed liable to doubt. The compound with oxide of silver formed by adding nitrate of silver to an alcoholic solution of lecanorin and then pre- cipitating by means of a few drops of ammonia though it changed colour but slightly in drying gave no consistent re-sults.The compound with oxide of lead formed by preci- pitating a solution of lecanorin with basic acetate of lead was so basic and its formula so unusual that I am led to suppose that one or two atoms of basic acetate of lead were precipitated together with it. By decomposing however a weighed quan- tity of lecanorin with caustic baryta and determining the quantity of carboriate of baryta formed I obtained very accu- rate results confirming the formula C H 0, or C, H 0, for lecanorin. In regard to the composition of orcin I have been induced to replace the generally received fortnula for its composition by a new one. Dumas’s formula for anhydrous orcin is C, H O, and for crystallised orcin C, H, 0, which evidently cannot be brought into accordance with the formula for lecanorin as given above.If however the for-mula c16 H 0 be taken for anhydrous orcin and c16 H, 0 for crystallized orcin then the decomposition which lecanorin undergoes with alkalies may be expressed as follows :-1 atom of anhydrous orcin ..C16H 0 2 atoms of water ....... H* 0 2 atoms of carbonic acid ...C 0 1 atom of lecanorin ......CISH 0 Two atoms of water are furnished by the decomposition of the lecanorin itself and three more by the fluid to form from CI6H6 0 one atom of crystallized orcin c16 HI 0,. The combustions which I have made of this substance agree per- fectly with these formulas but Dumas’s analyses of the lead compound of orcin which I have myself not yet examined do not coincide with them unless it be supposed that this cool-pound contains acetate of lead either in chemical combina- tion or mechanicalJy mixed.In regard to the numerical results from which the above formulas have been deduced I shall reserve them for a future occasion when having completed the in yestigat ion of the whole class of substances of which those here described are only a part I shall be able to enter more minutely into de- tails arid exhibit the facts and numbers brought to light in Chem. SOC.Mem. VOL. I. K 76 Mr. 33. Schunck on Lecanmiri &c. their proper connexion and order. I have merely been de- sirous of showing on the present occasion that our know- ledge of' this series of bodies is far from being complete.I have shown above that the action of alkalies on lecanorin is twofold ;it consists first in abstracting from the substance carbonic acid a process not requiring the co-operation of the oxygen of the atmosphere; secondly in inducing in contact with the air the formation of colouring matters. The first action seems to have been overlooked in the case of all the bodies nearly allied to lecanorin. I have found the most com- plete analogy in the case of Heeren's pseuderythrin; and if I am not mistaken in the interpretation of his statements his erythrin also undergoes the same decomposition as lecanorin for the former is converted into erythrin-bitter by the very same agencies by which lecanorin is converted into orcin and in fact there is the same relation in regard to all general pro- perties between erythrin and erythrin-bitter as between leca- norin and orcin.This circumstance is of some importance for in order to arrive at a knowledge of the exact composition of such complex bodies as the colouring matters formed by the action of alkalies on these substances and to understand perfectly the nature of the process by which they are pro- duced it is absolutely necessary to know the exact substance out of which each is in the last instance formed the last link of the chain which precedes its formation. PseuderJthrin. For this substance it would be advisable to substitute another name as in this case the substance by which it is ac- companied is not erythrin but lecanorin.It is contained in very small quantities in the lichens that I examined. It is sparingly soluble in cold water but easily soluble in boiling water from which it crystallizes on cooling in shining plates and needles. If more of the substance is taken than the boil- ing water can dissolve the part left undissolved melts and collects at the bottom of the fluid in oily drops which on the temperature falling a little below 212O congeal and form cry- stalline masses. This is a characteristic property of pseud- erythrin and one distinctly nientionecl by Heeren. It is easily soluble in alcohol and aether and also in alkaline solutions. It gives compounds with metallic oxides by double decom- position. When dissolved in ammonia and exposed to the air it Vives like lecanorin a red colouring matter; but its conversion into the latter is much more slowly effected than that of lecanorin When subjected to dry distillation it also gives n crystalline sublimate accompanied by a copious dis- Mr.Warington ona Ke-awa?agement oJthe Molecules 4.c. 7 7 engagement of gas. When its solution in an alkali is boiled or left to stand some time it imparts carbonic acid to the alkali the decomposition being accomplished however with much more difficulty than with lecanorin. The exact nature of the substance left in solution after this decomposition I was unable to determine on account of the very small quantity of pseuderythrin which I had at my disposal. The coiribustions which I made of this substance confirmed the formula established by Liebig at the time of Heeren’s in- vestiption viz.C, H, 0,. The fatty substance mentioned above I have examined but slightly. It is soluble in alcohol but insoluble in aether and water. From an alcoholic solution it is deposited in small pearly-white scales; if the solution be spontaneously evapo- rated it is obtained in si~,all hard shining transparent cry- stals. It is soluble in alkalies forming soapy solutions and is re precipitated by acids. Its alkaline solutions do not be- come coloured when exposed to the air. It cannot be melted without being decomposed.

ISSN:0094-2405    

DOI:10.1039/MP8410100071

出版商:RSC    

年代:1841

数据来源: RSC

摘要:

Mr. Warington on a Ke-awa?agement oJthe Molecules 4.c. 77 XII. ONa Re-arrangement of the Molecules of a Body affcr Solidz$cation. B-4 ROBERT Esq. WARINGTON Read January 4 1842. HAVING occasion lately to prepare some alloys of lead for the purpose of lecture illustration I was much sur- prised at an alteration taking place in the arrangement of the particles of one of these alloys as shown by the appearance of the surfaces of fracture after the metal had assumed the so!id form. The alloy experimented on was that known as Newton's fusible metal composed of 8 parts of bismuth 5 of lead and 3 of tin. On pouring this alloy in the melted state on a marble slab and breaking it as soon as solid and when it may be readily handled the exposed surfaces were found to exhibit a bright smooth or conchoidal metallic appear- ance ofa tin-white lustre ;and the act of disjunction at one part will frequently cause the whole to fly into a number of frag- ments analogous to the breaking a piece of unannealed glass.The metal after this becomes so hot as to burn the fingers if taken up and when this evolution of heat has ceased the alloy will be found to have entirely altered its characters having lost its extreme brittleness requiring to be bent to and fro several times before it will break and presenting on frac-ture ti fine granular or crystalline surface of' a dark colour and Kg 78 Mr. Warington on a Be-arrangement offhe Molecules &. dull earthy aspect. Similar phaenomena accompany the cast- ing of the fusible alloy of H.Rose composed of 2 parts of bismuth 1 of lead and 1 of tin. The fact of the evolution of heat from the alloy of Newton and its cause are thus noticed by Rerzelius in his Trait6 de Chimie. '' If this alloy is plunged into cold water and quickly withdrawn and taken in the hand it becomes sufficiently hot after a few moments to burn the fingers. The cause of this phenomenon is that during the solidification arid crystalliza- tion of the interiznlpnrts the latent heat of these is set free and communicates itself to the surface before the fixing and cool- ing." The alteration in the internal arrangement of the par- ticles as proved by the surfaces of fracture is not however noticed and the explanation is defective as it supposes the interior not to have assunied the solid state until the evolution of the heat occurs.If such were the case it would be seen on breaking it in tlie first instance. The phenomena can only be accounted for by admitting a certain degree of mobility among tlie particles and that a second molecular arrnnge- ment takes place after the metal has solidified ; this may arise from their not having assumed in the first state that direction in which their cohesion was the strongest. That a very marked and extraordinary alteration in the characters and properties of various substances arises entirely from this change in the position of their component particles effected either by the communication or abstraction of heat after solidification there can be no doubt.And these changes are applied to many very important purposes in the arts and ma-nufactures; such as the hardening and tempering of steel the rolling of commercial zinc and rendering that metal perma- iiently malleable the annealing of glass and a variety of other usest particularly in crystallization which might be adduced. TI he following experiments were made to ascertaiii to what extent the emission of latent heat takes place. The melted alloy was poiired in a perfect!y fluid state on the bulb of a thermometer placed in a small platinum crucible haviiig a capacity equal to about 70 grain nieasures of water aiid stand-ing in a vessel of cold water or mercury. The thermometer surrounded by the solidified metal and crucible was removed from the cooling medium before it had reached its stationary point and the greatest decrease of tetnperature noted.The heat then rose rapidly again and the maximum effect was registered. The fusing point of the alloy was 202' Fahr. the following results were obtained :- Mr. Garrod on the Conversionof Benzoic intoHippuric Acid. 79 DiE Exper. Fahr. Fahr. Fahr. 1. thermometer fell to 97" and then rose to 1.57' 60° 2. ... ... 94 ... ... 149 55 C.. 3. ... 90 ... ... 150 60 4. ... ... 87 ... ... 147 60 0.. 5. ... 104 ... ... 156 52 6. ... ... 97 ... ... 148 51 7. ... ... 92 ... ... 152 60 8. ... ... 104 ... ... 155 51 So that in four out of the eight trials a difference of 60' Fahr. was rendered apparent. In a platinum crucible of larger size the effects were not so marked 34' Fahr. being the greatest difference obtained ; this of course would arise from the greater bulk of the melted metal not exposing comparatively so large a surface to the cooling medium.

ISSN:0094-2405    

DOI:10.1039/MP8410100077

出版商:RSC    

年代:1841

数据来源: RSC

摘要:

Mr. Garrod on the Conversion of Benzoic into Hippuric Acid. 79 XIII. On the Conversion of Bmaoic Acid into Hippuric Acid in the Animal Ecortomy. By Mr. ALFREDBARING GARROD, of University ColZege. Read January 18 1842. PAPER has appeared in the Medico-Chirurgical Trans- A actions for last year and also in the first Number of the Yharniaceutical Transactions by Dr. Alexander Ure in which it is stated that by the internal administration of ben- zoic acid,' or any of its salts hippuric acid is formed in the system and is eliminated from the kidneys in the form of a soluble hippurate and that this hippurate is formed by the benzoic acid uniting with uric acid. It is also stated that no trace of uric acid or any of its salts could be found in the urine after the administration of the benzoic acid.I have repeatedly performed Dr. Alex. Ure's experiment swallowing from a scruple to half a drachm of benzoic acid at a time arid have always obtained a copious crop of crystals of hippuric acid amounting to from fifteen to twenty-nine grains by the addition of hydrochloric acid to the urine passed about three or four hours afterwards (evaporated or not according to its state of dilution). These crystals possessed all the cha- racters of hippuric acid with the crystalline form the small solubility in cold water and aether the ready solubility in al-cohol the evolution of nitrogen and also the odour of the tonquin bean when heated to destruction ; and my experi-ments therefore so far confirm Dr. A. Ure's fundaiiiental ob- Mr.Garrod on the Conversion servation. He also mentions another test of hippuric acid viz. that when evaporated to dryness with dilute nitric acid and ammonia added a beautiful purple colour is produced. This is certainly true of the crystals obtained from the uriiie but it is not a character of pure hippuric acid. The cause of this colour will be shown presently. Dr. A. Ure states that no trace of uric acid could be found in the urine; but on examination I have always been able to obtain a distinct trace of uric acid from a drop or two of the urine by adding a little nitric acid carefully evaporating and holding the capsule containing it over ammonia when a distinct trace of murexide was formed; also when the dish containing the crystals of hippuric acid is carefully exa-mined minute grains are found at the bottom which are uric acid crystals ; and 011 exarniiiing the crystals of hippuric acid with the microscope uric acid crystals are found adhering to them in immense numbers and this is the cause of the pro- duction of th,e purple colour spoken of end which has been given as a test of hippuric acid.When the crystals are dis-solved in alcohol the uric acid is precipitated and the hip- yuric acid crystallized from the alcoholic solution no longer gives the purple colour. On collecting the uric acid from the same quantity of urine formed on successive days the same food being taken oiie containing about twenty-seven grains of hippuric acid and the other none the following results were obtained :-From 4; 02.of urine when no benzoic acid had been taken uric acid 1.07 grain. From 44 oz. of urine after taking 30 grains of benzoic acid uric acid 0’96 grain. Difference in favour of first 0.11 grain. In the second experiment also a small loss might have oc- curred from the greater washing of the crystals necessary in that experiment. Now if we suppose that uric acid is decomposed to afford the elements necessary to be added to benzoic acid to form hippuric acid we find that each equivalent of benzoic acid requires the addition of C H 0 N. To obtain the nitrogen four atoms of benzoic acid would require one atom of uric acid or half a drachm of benzoic acid would require rather more than ten grains of uric acid.Now the quantity of urine in the experiment without the benzoic acid only contained 1-07grain of uric acid and yet that quantity was not mate- rially diminished when twenty-eight grains of hippuric acid were found in the urine. It cannot therefore be from the uric acid that the hippuric acid is formed. If we exaniine the subject theoretically it does not seem of Beizxoic Acid iiito Hz'ppuric Acid. probable that such a body as benzoic acid possessing such feeble affinities and producing no sensible action on the body when taken should be able to break up such a stable com- pound as uric acid; to abstract from the latter the requisite elements for its conversion into hippuric acid. But as hippu- ric acid is really formed in the urine from whence does it obtain the necessary addition? The quantity of urea was noticed in several experiments to be deficient; could this be the source? We can find 110 rational formula for the explana- tion of the conversion if we suppose it to be from urea alone.We can it is true select the elements required ;but as in the last case we should leave some compound in the system which cannot be resolved into any known compounds as am- monia,.water carbonic acid &c. while from the ready con- version of the benzoic acid into hippuric acid we should expect that the change was one which could easily take place with- out the action of any unusual affinities being brought into play. It occurred to me that it might be the lactate of urea instead of pure area which is taken up; and upon comparing the formulae for hippuric acid benzoic acid and the Iactate of urea it appeared that one equivalent of lactate of urea minus three eqs.of water gave exactly the requisite elements for the conversion of 2 eqs. of .benzoic acid into 2 eqs. of hippuric acid. Z-eqs. of benzoic acid +1 eq. of lactate of urea =2 eqs. of hippuric acid +3 eqs. of water. Hippuric acid (anhydrous) C, H 0 N Benzoic acid (Do.) CI4H O3 Difference ........C H 0 N Twice the difference ..C H 0 N2 Lactic acid. ........C H 0 Urea.. ..........C,H40eN Lactate of urea ......C8 H 0 N Lactate of urea -3 H 0 =C H 0 N,. Now the urea has by MM. Cap and Henry been fouiid to exist in human urine as lactate and the separation of the elements of water is a change which might be expected to take place in the system under such circumstances.The ben- zoic acid merely taking up the lactate of urea and throwing off' water is certainly a more probable occurrence than the destruction of such a stable compound as uric acid. In analyses for the quantity of lactate of urea according to the method of Cap and Henry I found that although I could not obtain it in crystals yet the quantity in a syrupy state was much reduced after taking the benzoic acid and the same ap- peared on forming nitrate of urea from it. I obtained 1(k grs. Mr. Graham on the Cunstitzitim oJSulphates less of urea in 44 ounces of urine when the benzoic acid had been taken. In another experiment I obtained I 7 grs.less of urea when 30 grs. of beiizoic acid had been taken; this is a greater loss than can be accounted for by the formation of the hippuric acid ; but this can be referred to the urine from some accidental circumstance being of nearly as high specific gra- vity in this case as when the beiizoic acid had been taken. 30 grs. of benzoic acid swallowed usually increased the spe- cific gravity of the urine from four to six-thousandths. From these results two inquiries suggest themselves :-1st May not hippuric acid be formed artificially out of the body ? Znd If sufficient benzoic acid were swallowed at such a time when least urea was contained in the urine would the benzoic acid not cease to be all converted into hippuric acid part of it then appearing in the urine unchanged?

ISSN:0094-2405    

DOI:10.1039/MP8410100079

出版商:RSC    

年代:1841

数据来源: RSC

摘要:

Mr. Graham on the Cunstitzitiotz oJSulphates XIV. On t4.e Constitution of the Sulphates as illzcstrtrted h~late Thermometrical Researches. By THOMAS Esq., GRAHAM, F.B.S. &c. Read January 18,1842. PROF. Hess and Dr. Andrews both apply the results of their late inquiries respecting the heat evolved in combina- tion" to test the accuracy of a view of the constitution of dou-ble and acid salts which was published by myself and arrive it is remarkable at opposite conclusions. The view in question I may first state taking the example of double and acid sulphates. Crystallized sulphate of magne-sia and the double sulphate of magnesia and potash I have represented thus :-M~ 0 s 0 (H 0)+ 6 H 0 Mg 0 S 0,(K 0 S 03)+ 6 H 0; considering the latter salt to be derived from the former by the substitution of sulphate of potash for that single atom of water which is found to be much more strongly attached to the sulphate of magnesia than the other six.This atom of water which is not basic water was formerly named saline water to indicate that it is replaceable by a salt; its presence being considered a provision in sulphate of magnesia for the formation of double salts. The water and sulphate of potash are therefore looked upon as equivalent in the con-struction of the two salts; and the substitution of the salt for the water might therefore be reasonably expected to occur without the evolution of heat. * Phil. Mag. January 1842. as illustrated by Thermometrical Researches. In accordance with that statement Dr.Andrew finds that no heat is evolved on mixing solutions of sulphates of magnesia and potash nor in the formation of any other dolible salt. On repeating the experiment I found also no heat nor change of temperature on mixing the solutions although a change of &th of a degree Fahr. would have been distinctly indicated by my thermometer. Possibly however the double salt may not immediately be formed and hence 110 change of temperature at the moment of mixing the two solutions nor for some time afterwards. To meet this objection solutions of sulphate of magnesia and of sulphate of ammonia (the last from its greater solubility being preferred to sulphate of potash) were made of such a strength that they might be mixed without the precipitation of the double salt immeditrtely occurring but strong enough to allow a large quantity of the double salt to fall upon stirring the li- quid strongly.The solutions were 1546*88grains of cr. sul- phate of magnesia dissolved in so much water as to form 8000 water grain measures and 613.5 grains oil of vitriol neu- tralized with ammonia and made up to 4000 water grain mea- sures. On mixing one ounce measure of the first with half an ounce measure of the second both exactly at 50° not the small- est change of temperature could be observed; but as soon as the double salt began to deposit the temperature rose and on stirring strongly much salt was depcsited and the temperature rose 5'40' Fahr. On re-dissolving this salt however by substituting for the mother liquor an equal bulk of water the temperature instantly fell 5'85O.Hence the heat which first appeared was produced by the solidification of the double salt and disappears upon its liquefaction. There is no heat referable to combination of the two salts. The cold on dis- solving was always somewhat greater than the heat oil pre- cipitating the double salt in repetitions of this experiment chiefly I believe from the slowness of the precipitation which requires a minute or two? so that a portion of the heat is lost from contact with the atmosphere and the whole not observed while the subsequent solution of the salt being almost instan- taneous the whole fall of temperature is observed. The same experiment was made with a solution of sulphate of zinc of the same strength as the sulphate of magnesia and with simi- lar results only that the fall of temperature on solution was somewhat less than that on solidification namely as go*%? to 9O*67,difference O"45 Fahr.This was principally owing to the time required in re-dissolving this double salt being greater than that occupied in precipitating it three applications of Chem. Soc. Mem. VOL. I. L Mr. Graham on the Constitution of Sulphates. water being required to re-dissolve the double salt completely owing to its sparing solubility. M. Hess's objection is made to the analogous constitution which I have assigned to the bisulphate of potash :-Sulphuric acid of specific gravity 1.78 H 0,S 0 (H 0).Bisulphate of potash . . . . . . . . H 0 S03.( KO SO,). He maintains that heat is evolved in the formation of a bi-sulphate and therefore that the combination is not effected by the equivalent substitution supposed. He mixed sulphate of potash with H 0 S 0 + H 0,and found heat evolved but allows that the result here is fallacious a portion only of the sulphuric acid being converted into bisulphate while the other portion is diluted by the displaced water of the first portion and thus heat evolved. On performing the direct experiment which M. Hess ap-pears to have neglected using a saturated solution of sulphate of ammonia and sulphuric acid of specific gravity 1.256 I obtained on mixing 5.4' of cold instead of any heat. But on diluting the sulphate of ammonia with a volume of water equal to that of the dilute acid a fall of 1.12' occurred.De-ducting this from the former there remains a fall of 3*88Odue to the combination of the two salts sulphate of water with sulphate of ammonia. But this may be explained. The bi- sulphate of ammonia formed is an anhydrous salt unlike the double sulphate of magnesia and ammonia which carries along with it all the water of crystallization of the sulphate of mag- nesia. But the sulphate of water itself as it exists in diluted sulphuric acid is a largely hydrated salt like sulphate of mag nesia. The water of the former on being set free in the last experiment absorbs heat because heat was evolved originally in the combining of this water with the sulphuric acid. Although certain small corrections on these experiments for changes in capacity for heat of the liquids have been neglected yet they are sufficient to demonstrate that no heat is evolved in the formation of double sulphates and also as appears by the last experiment that these compounds are formed at once on mixing the solutions of their constituent salts whether precipitation occurs or not. Sulphate of potash and water are therefore equivalent in the constitution of such salts or equi-calorous if a term may be coined to express this relation.

ISSN:0094-2405    

DOI:10.1039/MP8410100082

出版商:RSC    

年代:1841

数据来源: RSC

摘要:

XV. On the Change qf' Colour in the Biniodide of Mercury. By ROBERTWARINGTON, asp. 'Read February 1 1842. is well known that when a solution of the iodide of po-lTtassium is added to a solution of the bichloride or perni- trate of mercury a yellow precipitate passing rapidly to a scarlet is formed; this is the biniodide of mercury. It is soluble in an excess of either of the agents employed for its production and if this act of solution be assisted by heat the biniodide may be obtained as the solution cools in tine scarlet crystals having the form of the octohedron with the square base or its modifications. If this precipitated biniodide in the dry state be subjected to the action of heat it becomes of a bright pale yellow colour fuses into a deep amber-colouretl fluid and gives off a vapour which condenses in the form of rhombic plates of the same bright yellow ; these crystals by my mechanical disturbance arising from the unequal contraction of their molecules in cool- ing from varying thickness in different parts of the same cry- stal or from partial disintegration return again to the origi- nal scarlet colour of the precipitate the change commencing in the latter case from the point ruptured and spreading over the whole of the crystalline mass; they may however be fre- quently preserved in the yellow state for a great length of time if sublinied slowly and not exposed to the contact of other sub-stances which is readily effected by conducting the sublima- tion in closed vessels and allowing the crystals to remain in them undisturbed.The resumption of the scarlet colour has been attributed to an alteration in the molecular arrangement of the crystals and it was with the view of clearly ascertaining this point that the followiiig microscopic investigations were undertaken. When a quantity of the precipitated biniodide is sublimed the resulting crystals are very complicated in their structure consisting of a number of rhombic plates of varying size su-perposed sometimes overlapping each other and causing con- siderable variableness in their thickness but generally leaving the extreme angle and the two lateral edges clear and well-defined ; the annexed sketch taken by the camera lucida from the field of view of the microscope will give a better idea of their character.The length of these crystals were about '01.5 of an inch in length. On coolin? the first change that is ob-served is usually a scarlet marxiiig coinmencirig at the ex- treme angle and extending gradually inwards always retain-ing a perfectly well-defined liiie in its progress; when thi5 (Ihem. SOC.Mem VOL. I. M Mr. Warington on the Change of change has reached as far as the line ab fig 1 the scarlet Fig. 1. C line will suddenly shoot along one of the lateral edges as shown at c d and instantly t.he whole mass is converted in a most rapid and confused manner which the eye in vain endeavours to fol-low to the scarlet colour the crystal being frequently if de-tached twisted and contorted during the transition.In order to obtain these crystals in a more defined and clearly developed form a small glass cell was constructed of two slips of window-glass leaving a space of about the thickness of cartridge paper between the upper an& under plates in which the subliniations could be readily conducted and the whole of the subsequent changes at once submitted to the microscope ; by this means beautifully well-defined and perfect crystals were obtained having the form of right rhombic prisms as in the accompanying outlines Fig. 2. fig. 2 a and b. The follow- ing interesting phenomena were then observed a de-fined scarlet line of varying breadth would shoot across the crystal as at 1. c d t;,f; fig. 2 and then gradually spreadthroughout thewhole of its structure keeping a straigrht and well-defined line in its onward progress Colour in the BiTiiodide of Mercury.until the whole had undergone the change of colour. Nos. 2,3 4 5 in e and No. 2 inf are the stages which the transition had reached at intervals of observation; in many cases after the crystal has undergone this metamorphosis two angles can be distinctly seen as at e fig. 1 and at times two edges are visible as at c 6 and d 6 fig. 2. This observation must of course de-pend entirely on the position of the crystal to the eye of the observer. These phenomena prove I consider in the most perfect manner that the change in the colour of this compound arises from the plates of the crystal having been separated from each other by the means alluded to in the direction of their clea- vages; and in further confirmation of this view the laminae so separated may by the sudden application of heat be again fused together and the yellow colour reproduced without ma- terially altering the dimensions of the crystal a slight round- ing of the edges from partial sublimation being the only other concomitant.When the temperature is raised slowly and the sublimation conducted with great care a very large proportion of red cry- stals having a totally different form are obtained the octahe- dron with the square Lase Fig. 3. as shown fig. 3 a L c d e. If however the heat is quickly raised the whole mass of the sublimed cry- El+ fl stals are yellow and of the rhonibic form.It is evident $ 75 from these facts that the biniodide of mercury has twa vltpours which are given off at different temperatures and also that it is diniorphous which facts have been sub- stantiated by some experiments of M. Frankenheim who has carefully examined this part of the subject. From the circumstance that the first effect which occurs in the process for preparing this iodide by precipitation is the yro- duction of a yellow powder which passes rapidly through the orange colour to a scarlet I was induced to submit this phe- nomenon also to the test of microscopic examination and with this valuable instrument of research results were exhibited which could not have been anticipated. As I expected the precipitate was in small crystalline grains and the first step of the investigation was to effect its formation in the field of view of the microscope so as to observe directly as they occurred the transitions of colour which have been alluded to and this was effected by the following means :-A slip of common win- M2 88 Mr.Warington on Changeof ColourinBiniodideof Mercury. dow-glass about three inches long by one and B half wide and having a very narrow slip attached on one of its edges so as to act as a ledge was taken and a drop of the salt of mercury employed placed on it; this was then covered with a small piece of extremely thin glass about one inch long by half an inch wide and the whole carefully adjusted to focus in the field of the instrument; the iodide of potassium was then in- troduced by capillary attraction between the glasses.The instant the solutions came in contact a myriad of pale-yellow crystals having the same rhombic form as those obtained by sublimation formed in a curved line across the field of view and extended slowly downwards ; by the strong transmitted light these minute crystals appeared colourless ; but when viewed by reflected light the pale yellow colour was readily apparent. After a short interval a very extraordinary change commenced; the crystals which had been perfectly sharp and well-defined became ragged at their edges as though some dissolving action were going on gradually decreased in size and at last disappeared altogether; but as this act of solution progressed nuni bers of red crystals made their appearance forming across the field and following at a regular distance the yellow crystals as they disappeared and occupying their place.These red crystals which appear to be formed by the disintegration through the medium of solution if I may be allowed the expression from those first produced had the form of the octohedron with the square base exactly similar to those procured by careful sublimation at a low heat only modified in the most beautiful manner Some few of these are sketched in the forms a b c d e,f; g,ir fig. 4. When either Fig. 4. the salt of mercury or the iodide of potassium employed in the production of the biniodide ofo mercury was in excess another curious act of disintegration took :+; place; the red crystals in fig.4 were slowly dissolved aproperty mentioned in the first part ofthis a paper the first act of solution commencing apparently by the 0 BcY disjunction of the crystals a b c,J; g h at the lines of marking these lines being at first bright red and gradually deepening in colour when the act of solution commenced and at last perfect separation taking place so that the light could be seen between the compartments. At times the field would become dry from Mr.Croft on a new Oxalate of Chromium and Potash. 89 evaporation and some of the yellow rhonibic crystals which had not been dissolved prior to the formation of the octohe- dra with the square base were observed with scarlet lines on them similar to the first act of transition in the sublimed cry- stals as shown at g 1 and 2 in fig.2. By polarized light the appearances now described were beautiful beyond all description the yellow crystals present- ing the most superb and brilliant colours varying in hue with the varied thickness of the crystalline plate and in the dark field having the appearance of the most splendid gems the imagination can conceive the red crystals do not appear to be affected by polarized light so far as the display of colour is concerned. The magnifying powers used in these investigations were for the experiments on the sublimed crystals ZOO times linear measurement or diameters ; in the precipitated compound 620 diameters.

ISSN:0094-2405    

DOI:10.1039/MP8410100085

出版商:RSC    

年代:1841

数据来源: RSC

摘要:

Mr. Croft on a new Oxalate of Chromium and Potash. 89 XVI. On n new Oxalaie of Chromium and Potash. By HENRY CROFT,Esp. Read February 15,1842. is well known that in 1830 Wilton Turner accidentally 1 iscovered a salt composed of oxalate of the oxide of chm-mium and oxalate of potash. Its curious optical properties have been examined by Brewster. Gregory also discovered the same salt independently and proposed a much better me- thod for obtaining it than that used by Turner which con- sisted in adding oxalic acid to a solution of bichromate of po-tash until effervescence ceased ; the solution became deep green or black and on evaporation yielded beautiful crystals of the black salt. Gregory supposed it to consist of 3 equi-valents of oxalic acid 2 of potash 1 of oxide of chromium and 6 of water.Its true composition 3 (KO C 0,) + Cr 0, 3 C,O + 6 HO has been shown by Graham and Mitscher- lich who have also prepared a number of salts similarly con- stituted. On attempting to prepare the black salt by Turner’s method I could never completely succeed but obtained in its stead when a very concentrated hot solution of the bichromate was employed a red granular precipitate which proved to be a new salt and forms the subject of the present notice. Perhaps the best method of preparing it is that above de- scribed viz. to employ IS concentrated a solution of the bichro- mate as possible in which case the salt crystallizes out on cooling. The precipitated salt must be redissolved in a small 90 Mr Croft on u new Oxalate of Chromium and Potash.quantity of water and allowed to crystallize. It is however one of the most difficult salts to crystallize that is known in nine cases out of ten it separates in the form of a somewhat granular bldsh gray powder and it appears to be only under particular circumstances that it will crystallize well which however I was not able to discover. It does not seem to crystallize any better by spontaneous evaporation than out of a very concentrated solution; it seems however to form more regularly in warm air as in summer. The best crystals are generally formed on the surface of the solutions they are very minute in the form of triangular plates; when the crystals form a mass at the bottom of the liquid the plates are thicker but their form is indistinguishable.The salt is of a deep red colour by reflected as well as by transmitted light; the solu-tion is green or even black (when concentrated) by reflected and red by transmitted light. The solution when at a boiling temperature remains red as is seen best by candle- light the same is the case with the solution of the black salt which shows that the purple oxide of chromium contained in these salts is not converted by a boiling heat into its green modification; the purple oxide must however as is well known be first brought into combination with the oxalic acid for the black salt can never be obtained by dissolving green oxide of chromium in binoxalate of potash. A solution of caustic potash added to a solution of the red salt turns it bright green but caiises no precipitate until boiled when the greater part of the oxide of chroniiiim is thrown down.Carbonates of the alkalies partly change the colour in the same manner but do not precipitate the oxide so readily. Ammonia causes no precipitate nor does chloride of calcium owing to tbe formation of Dingler's oxalate of chromium and lime ; when ammonia is added a green precipitate containing oxide of chromium is formed. This salt contains a larve quantity of water of crystalliza-tion which can only be driven out by a strong heat as is also the case with the black salt (Graham). It loses about 15-16 per cent. at looocent. and 19 per cent. at YOOo cent. The last portions of water can only be driven out at 300°cent.Near this point the salt begins to be decomposed and conse- quently the determination of the water is rendered somewhat difficult. per cent. 0.9986 gramme of salt lost 0*2638water = 26-42! 8.. 0.748 1 ... 0'1965 ... = 2697 0.8971 ... ... 0-2532 ... = 28.22 The determinations of the oxide of chromium and the po-tash were performed in the following manner. The salt was heated red-hot in this opeattion great care must be taken Mr. Croft on a new Oxalate of Chromium and Potash. 91 for the salt possesses the curious property of decomposing with considerable violence (without explosion) into a green powder which unless the heat is applied very gradually is forced out of the crucible and the analysis is thus lost.When the temperature is raised gradually the crystals retain their form but become of a bright dark green colour as soon as the decomposition of the oxalates commences they fall into a light green pow+r which when stronger heated becomes brown. In closed vessels carbonate of potash is formed; in open ones when the heat is continued for a length of time chromate is produced. This chromate must be extracted by water reduced and the oxide of chromium precipitated by ammonia in this operation however it is better to evaporate the ammoniacal solution to dryness as the ammonia always dissolves a small quantity of the oxide. This method is pre- ferable to that usually employed (Heinrich Rose's Analytical Chemistry) the ammoniacal and potash salts must be dis- solved out evaporated the ammonia driven 06and the potash determined either as chloride or by means of platinum.The oxalic acid may be determined by boiling the salt with sulphuric acid as proposed by Prof. Graham. The salt being excessively difficult to crystallize it seldom happens that a perfectly homogeneous substance can be ob- tained for analysis he method of analysis is moreover some- what complicated and consequently the analyses do not agree so perfectly as could be desired. I. 11. 111. IV. V. VI. Cr 0 21*80 21.83 23-11 22-05 21.10 24-11 KO 13.18 13.11 12% 12-92 c,0 37.00 36'98 40.89 The water as obtained by other experiments is H 0 26'42 26.27 28*22 The most plausible formula is KO C 0 + Cr 0, 3 C 0, + 12HO.c,03 + 1811*50 38'098 Cr,O 1 1003'63 21'10'7 K 0 1 589.92 12'405 HO 12 1349'75 28-390 4754*80 1 OO*OOO This differs from the black salt in containing one atom of basic oxalate instead of three. It may be said to be related to the black salt in the same way as metaphosphates are to phosphates. It is evident therefore that if' we add two atoms of oxalate of potash to one atom of the red salt we ought to obtain the black salt which is indeed the case. 92 Mr. Croft on a new Oxalate of Chromium and Potash. 2.37 gramnies of red salt were mixed with 1 *15gr. of oxalate of potash (these are the atomic proportions) the solution boiled and evaporated they yielded 3.119 grs. of the black salt in good crystals and perfectly pure according to theory it ought to have given 3.070.The weight of the black salt must be equal to that of the red salt pZus two atoms of anhy-drous oxalate of potash ininus six atoms of water. The agreement of the experiment with the calculation speaks for the correctness of the above formula in which one might perhaps otherwise not place so much confidence. The constitution of this salt led me to consider the theory of its formation and also that of the black salt more particu- larly as in employing the known formula? for making the black salt I always obtained it mixed with other bodies. In forming the red salt from bichromate of potassa 7 atoms of oxalic acid are required. K 0 2 Cr 0,and 7 C 0 = K 0,C O3 +Cr 03,s C 0,and 3 C O3 + 3 0 or 6 C 0,.On mixing the two substances in this proportion I obtained perfectly pure red salt. It is evident that seven atoms of ox-alic acid either free or in combination with potash must be used in making the black salt. None of the numbers in the formulae given for preparing the black salt agree with this. Dr. Gregory gives 190 parts bichromate of potash 157*5 parts crystallized oxalic acid aiid 517 parts binoxalate of pot-ash; that is? one atom of the bichromate two atoms oxalic acid and three of binoxalate of potash ; on trying these num- bers I obtained a mixture of black salt with oxalate and chro- mate of potash. Prof. Graham proposes one part of bichromate two of bi-noxalate and two of crystallized oxalic acid. In these pro- portions a large quantity of chromate of potassa remains un- decomposed which requires if 19 grains bishromate 23 grains binoxalate and 16 grains crystallized oxalic acid be taken exactly 36 grains of crystallized oxalic acid to effect its perfect decomposition and making the whole quantity of oxalic acid 52 grains.According to the formula which I would propose there are required 19 grains bichromate of potash 23 ... oxalate of potash 55 ... crystallized oxalic acid. If the salts be taken in these proportions nothing but black salt is obtained; it is however better to evaporate the whole to dryness and then re-dissolve. I have not been able to obtain an intermediate salt namely 2 K 0 C O3 + Cr O, 3 C 0,. This if it exists ought to Mr. R.Warington on Bed Oxalate of Chomium and Potash. 93 be produced fiom two atoms chromate of potash and eight atoms oxalic acid I obtained however oxalate of potash and red salt. A similar salt may probably exist wit,h oxide of iron but it does not crystallize. On dissolving sesquioxide of iron in quadroxalate of potash a solution is obtained which dries to a brown gummy mass without traces of crystallization.

ISSN:0094-2405    

DOI:10.1039/MP8410100089

出版商:RSC    

年代:1841

数据来源: RSC

摘要:

Mr. R.Warington on Bed Oxalate of Chomium and Potash. 93 a c 70' 45' cp 50' 40' an33 2 cm 77 32 cn 37 43 ar61 0 bp 53 13 af 78 30 ck 59 16 a'q 63 50 ap 47 49 bf 37 40 am49 5 Prof. Liebig 011 the Preparation of "The faces a p rf q are all in one zone ; h p b are in one zone ; k q b are in one zone ; a h c k are in one zone. The other zones are sufficiently well indicated by the parallelisms of the edges. " The symbols of the faces are,-a (loo) b (OlO) c (OOl) h (101) p (111) q (lll),f(Oll) m (110) k (101) r (112). " I remain yours faithfully I' W. H. MILLER.'' These crystals submitted to measurement by Professor Miller were ohtained by slow spontaneous evaporation the difficulty of procuring this salt in crystals of any size has been fully pointed out by Mr.Croft. I have only one observation which does not coincide with Mr. Croft's statements but which however confirms in a great measure the results of his analysis; I allude to the statement that these double salts of chromium cannot be formed by the direct combination of their ingredients. The process which I have followed has been to digest the hydrated oxide of chro-mium iri a mixed solution of oxalic acid and oxalate of potash in the proportions indicated by analysis and when it ceases to dissolve the oxide to decant the clear solution and allow it to crystallize. By the same means the analogous salts of soda and ammonia have been obtained but not in crystals suffi-ciently large for measurement as also other double salts of chromium.To prepare the hydrated oxide of chromium the best and most economical process that I have found is to take 150 grs. of the bichromate of' potash and 200 grs. of liquid sulphuric acid oil of vitriol these proportions being iiearly in the ratio of their atomic weights so that the chrome alum sulphate of the green oxide of chromium and potash may be formed; the deoxidation of the chromic acid is easily effected by the addition of a little sugar and boiling the solu- tion. When the deoxidation is coniplete the green oxide may be precipitated by ammonia or by a carbonated alkali and only requires to be well washed to remove all trace of alkali or saline matter.

ISSN:0094-2405    

DOI:10.1039/MP8410100093

出版商:RSC    

年代:1841

数据来源: RSC

摘要:

Prof. Liebig 011 the Preparation of XVIII. On the Prepnration of Cyanide of Potassium and on ifsApplications. %y Prof.LmmGof Giessen. Translated by ll!lr.W. FRANcIS,andcommu?iicated:throughhim by the Author. Read March 1,1842. of the best methods of preparing the cyanide of po-O%siurn is founded on the decomposition of the yellow prussiate of potash at a red heat; it is however attended with much inconvenience and a third part of the cyanogen Cyaiiide of Potasshn and on its Applzkations. contained in the salt is lost. Considered as a compound of two atoms of cyanide of potassium with one atom of proto- cyanide of iron the former undergoes no change on exposure to a red heat while the latter is decomposed into carburetted iron with evolution of nitrogen gas.The carburet of iron like a sponge imbibes the fused cyanide of potassium to ob-tain which free from iron and without loss a solvent such as alcohol is required. As the cyanide of potassium is possessed of properties which render it highly valuable as a means of reductioii and separation in chemical analysis I have endea- voured to simplify the preparation of it. When eight parts of the yellow prussiate are sharply dried (slightiy roasted) on a hot plate of iron then finely powdered and mixed well with three parts of dry carbonate of potash and thrown at once into a Hessian crucible previously heated to redness and kept at that temperature the mixture fuses into a brown magma with a lively evolution of gas. After a few minutes when the fluid mass has become red-hot its dark colour is seen to be- come brighter and on continued fusion the salt becomes clear and of an amber-yellow tint.If from time to time a hot glass rod be immersed in it the adhering mass on cooling is at first brown afterwards yellow and at last towards the close of the operation clear and colourless as water and solidifies into a shining white crystalline mass. During the fusion brown flocks are seen floating in the fluid mixture which subsequently unite into a spongy mass and assume a light gray colour. If the crucible be now re- moved from the fire and allowed to cool somewhat the gray powder generally settles entirely at the bottom; this is faci- litated by stirring once or twice with the glass rod.The fused mass may now be easily poured into a warm porcelain dish without a particle of the sediment accompanying it. This mass consists of two combinations of which the cyanide of potassium forms the chief portion ;the other compound is the cyanate of potash in the proportion of five of the former to one of the latter. The reaction in the fusion of the yellow prussiate with carbonate of potash is as follows :-at the com- mencement the protocyanide of iron of the ferrocyanide is decomposed and forms cyanide of potassium with the potash of the alkaline carbonate and the protocarbonate of' iron which is deprived of all its oxygen at a higher temperature by the cyanide of potassium. In consequence of this reduction cyaiiate of potash and pure metallic iron are obtained.Let us suppose in the mixture two atoms of ferrocyanide of potassium and two atoms of carbonate of potash we then have as sum of the constituents N2 96 Prof. Liebig on the Preparation of Ferrocyanide of potassium. Carbonate of potash. Cy6 Fe2K4 and K2 O2 -+ 2 C O2 = Cy6 Fe2 K6 O2 and 2 C 02. And we obtain after fusion Cpnide of potassium. Cpanate of potash. Iron. Carbonic acid. Cy5 K5 Cy 0 + K 0 Fe2 ZC 02. From two atoms of the fdrrocyanide of potassium we thus obtain five atoms of the cyanide that is one-fourth more than by fusing it alone. The cyanate of potash mixed with it has 110 injurious influence in any one of its applications. The presence of cyanate is readily detected by the effervescence caused from the escape of carbonic acid 011 the addition of an excess of acid and an ammoniacal salt is afterwards found in the liquid.The explanation given above of the formation of the cyanide of potassium under the conditions described is not absolutely correct as the protocarbonate of iron previous to its reductioii is decomposed into carbonic acid carbonic oxide and the proto-peroxide (black oxide) of iron at the expense of' which an undeterminable quantity of' cyanate is formed more than the formula indicates. The metallic iron precipitated and the sides of the crucible are covered by cyanide of potas- sium to obtain which it is best to remove with cold water a11 that is soluble and to warm the solution with some sulphuret of iron which easily dissolves in it.The cyanide of potassium is thus obtained on evaporation again in the form of ferro- cyanide and sulphuret ofpotassium remains in the mother ley. Preparation of Hydrocyanic Acid.-The cyanide of potas- sium of the precedinl; process is much better adapted for the preparation of prussic acid than the ferrocyanide; a larger quantity is obtained and the distillation is easier. It is well known that on distilling the yellow salt with sulphuric acid a bluish-white powder is deposited a combination of cyanogen potassium and iron the composition of which is analogous to that of cyanide of iron and zinc and is represented by the r Tr formula 2 Cfy + itFe; where Cfy = Cy3 Fe. From the formation and composition of this body it results that not more prussic acid can be obtained from five atoms of the ferrocyanide which coritain fifteen atoms of cyanogen than from nine atoms of cyanide of potassium which only con- tain nine; the other six atoms remain in the bluish-white precipitate.When the yellow salt is converted according to the above method iiito cyanide of potassium twelve and a half equivalents of lr ydrocyanic acid are obtained froin five atoms of the ferrocyanide or three and a half equivalents more. Cyanide of Potassium arid on its Applications. It is usual to take so much sulphuric acid to deconipose one atom of the yellow salt as will suffice to form with the alkali the bisulphate of potash on employing cyanide of potassium only one atom of the hydrate of the acid is requi- site.Equal parts of the cyanide of potassium and proto-hy- drate of sulphuric acid are the best proportions for preparing hydrocyanic acid ; that quantity of sulphuric acid exactly suf-fices to form with the whole of the potash a neutral sulphate and with the ammonia originating from the decomposition of the cyanate the bisulphate of oxide of ammonium. The cyanide of potassium is dissolved in double its weight of water and the sulphuric acid diluted with three times its weight of water slowly added in small portions previous to each addition the effervescence must have subsided. Preparation of Cyanznte of Potash.-'I'he cyanide of potas- sium prepared according to the method above described is an excellent means of procuring easily and with very little loss the cyanate of potash.It is most advantageous for this pur- pose to make use ofcommon litharge which has been previously heated slightly. The cyanide of potassiuni is fused in a Hes- sian crucible and the powdered litharge thrown from time to time into it; the oxide of lead is instantaneously reduced to metal which at first remains as a fine powder mixed with the cyanate formed but melts with greater heat into a regulus. The fluid mass is poured out and the salt which is nothing else t,hari cyanate of potash being finely pounded is boiled so long with alcohol as crystals are obtained. The crystalliza- tion of the cyanate of potash salt from alcohol is not requisite in the application of that salt to the preparation of urea.Cyanide of Potassium as a reducing age?tt.-It is difficult to conceive with what extreme facility the cyanide of potassium deprives certain metallic oxides and sulphurets of their oxygen and sulphur for it approaches nearest in that respect to pure potassium. The process of preparation of cyanide of potas-sium and that of the cyanate afford two instances of this re- ducing power ;.the iron remains either as powder mixed with the fused cyanate or its particles aggregate together and form a spongy mass. A process might be founded on this reduc- tion for determining in the dry way the amount of metal in an iron ore. When a weighed quantity of the ore is exposed with a mixture of cyanide of potassium and carbonate of pot-ash in a porcelain crucible to a strong red heat the alumina and silica go into the slag froin which the reduced iron can then be separated by cold water arid weighed.The protoxide of manganese is not reduced by the cyanide of potassium; this when contained in the ore must be determined by a separate operation. When oxide of copper is sprinkled on Prof. Liebig on the Preparation of melting cyanide of potassium it is immediately reduced with evolution of heat and light; after washing a regulus of pure metallic copper is obtained. The reduction proceeds most beautifully with the oxides of tin and antimony. At a low red heat the oxide of tin is converted into a bright regulos which may easily be separated from the slag. The oxide of anti- mony and antimonious acid may be reduced in the same way to the metallic state.All these reductions ensue at a low red heat scarcely visible in daylight which consequently has the advantage that not a trace of the reduced metal is lost by vola- tilization. Sulphuret of tin and sulphuret of antimony are reduced by gently melting them with cyanide of potassium before the blowpipe or in the porcelain vessel with the same ease as their corresponding oxides; the slag then contains the sulphocyanide of potassium. The cyanide of potassium does not only possess this reducing power in the dry way but likewise in a dissolved state mixed with a solution of alloxan a heavy crystalline precipitate scarcely soluble in water of dialurate of'potash is formed in a few seconds.Cyanide of Potassium as an agent of separation in Quanti-tative Analysis.-Nickel cobalt and manganese are so nearly related in their properties that their separation is attended with great difficulties. In one single form of combination only does nickel differ from cobalt to such an extent that this might be used as an absolute'means of separation. The oxide protochloride or any salt of cobalt warmed with cyanide of potassium and an excess of hydrocyanic acid is converted into the percyanide of cobalt and potassium (the cobalti-cyanide of potassium) the aqueous solution of which according to the observation of L. Gmelin does not undergo the slightest decomposition from boiling with hydro- chloric sulphuric or nitric acid. The oxide of nickel and its salts are thrown down by the cyanide of potassium ; this precipitate dissolves in an excess of the precipitating agent of a yellow colour; and the double compound of cyanide of nickel and cyanide of potassium, although not decomposed by acetic acid is perfectly so by dilute sulphuric acid and the cyanide of nickel again pre- cipitated.When a mixture of a cobalt and nickel salt contaiuing free acid is treated with an excess of cyanide of potassium so that the precipitate formed is redissolved there are in so!ution free hydrocyanic acid cyanide of potassium cyanide of nickel and the protocyanide of cobalt ; the latter changes immediately on being slightly warmed into the cobalti-cyanide of potas-sium; if now dilute sulphuric acid be added in the cold three cases present themselves.Cyanide of Potassium and on its Applications. 99 If the cobalt and nickel in solution are in the proportion by weight of two cobalt to three nickel (quantities which cor- respond to their atomic proportions in the cobalti-cyanide of nickel) the precipitate produced is cobalti-cyanide of nickel and is of a bluish-white colour. The filtered liquid contains not a trace of cobalt or nickel. If the solution contains less nickel than corresponds to the above proportions there remains in solution a certain quan- tity of cobalti-cyanide of potassium and the precipitate is still cobalti-cyanide of nickel. If there is more nickel present in the solution the preci- pitate is a mixture of cyanide of nickel and cobalti-cyanide of nickel.In the first and second cases the precipitate produced by dilute sulphuric acid is boiled so long with the acid fluid in a vessel until not a trace of hydrocyanic acid is observed to escape (or it may be evaporated to dryness in a water-bath) and then slightly warmed with an excess of carbonated or caustic potash ; the cobalti-cyanide of nickel is decomposed by this into (1) pure oxide of nickel or the carbonate which is washed on a filter dried and weighed and (2) an alka- line liquid which contains the whole of the cobalt. The lat-ter is evaporated to dryness some nitre being added to it and the residuum ignited. On being treated with water the oxide of cobalt remains behind. This method is applicable in all analyses of cobalt ores in which the amount of cobalt predominates.For nickel ores in which the quantity of cobalt amounts merely to a minimum the following precaution must be attended to :-a somewhat considerable excess of muriatic acid must be taken to preci- pitate the cyanides dissolved in the cyanide of potassiiim and the mixture must be kept boiling at least one hour. The precipitate contains in this case cyanide of nickel inter- mixed which is decomposed by potash into cyanide of potas-sium and oxide of nickel; this cyanide of potassium retains however another portion of nickel in solution. On boiling the precipitate with muriatic acid the cyanide of nickel is de- composed into chloride of nickel and hydrocyanic acid which last is removed by boiling and no longer prevents the entire precipitation of the nickel.The cobalti-cyanide of nickel is not attacked by boiling hydrochloric acid so that a complete solution cannot be expected when any quantity of cobalt is present. When the smell of hydrocyanic acid is no longer perceptible the boiling has continued long enough. Experiments made to separate the solution of the two cya- nides in cyanide of potassium by boiling with peroxide of 100 Mr. Fownes on the Preparation of Art9cinl Yeast. mercury gave less certain results. The following points must be attended to in this process :-as the cyanide of potassium used contains a certain quantity of cyanate of potash apor- tion of an amrnoniacal salt originates on its deconiposition by a mineral acid ; accordingly after boiling and the addition of caustic potash ammonia is set free which retains some oxide of nickel in solution.Thismickel is entirely thrown down by boiling for a few minutes or by a larger addition of potash. The same method may be followed for the separation of manganese from cobalt only in this case a complete solution of the precipitate produced by the addition of the cyanide of potassium to the mixture of the two metallic salts cannot be expected; the greater portion of the protocyanide of manga-nese remains undissolved. The residue is filtered and the liquid treated as if cobalt and nickel were to be separated. The cyanide of potassium is not less applicable with advan- tage for the separation of the oxide of chromium from prot-oxide of iron.A niixture of the two is previously saturated with sulphuretted hydrogen to be certain that the iron is con- tained in the liquid as protoxide (an addition of a few drops of the sulphuret of ammonium answers the same pprpose) and then thrown down by cyanide ofpotassium and an excess of the latter added. The iron then dissolves irnniediately as ferrocyanide of potassium while the oxide of chromium is left behind. In many cases the cyanide of potassium can be em-ployed to advantage in separating iron from alumina (little iron from much alumina) as the protoxide as well as the sul-phuret of iron are so easily soluble in that salt while alumina is perfectly insoluble. The cyanide of potassium well deserves to be studied as a general agent of separation. Unfortunately the composition of the numerous double compounds it forms with other cyanides is only imperfectly known while their relation to mineral and vegetable acids is wholly unknown so that the entire investigation milst necessarily be repeated.

ISSN:0094-2405    

DOI:10.1039/MP8410100094

出版商:RSC    

年代:1841

数据来源: RSC

摘要:

100 MP.Fownes on the Preparation of Art$cial Yeast. XIX. 011 the Preparation of Artgcial Yeast. By GEORGE FOWNES, PAD. 11.‘often becomes a matter of great practical importance to have it in our power to excite the vinous fermentation under circumstances in which ordinary yeast cannot be obtained. In making bread for example although the use of yeast may be avoided by ernploying what is called ‘‘leaven,” or dough which has already become sour and partly putrefied by spon- Mr. Fownes on the Preparation of Az*t$ciaZ Yeast. 101 taneous change-a practice which has been followed from the most remote antiquity and is still occasionally in use-the bread so made is always to be distinguished by apeculiar sour and nauseous taste and smell and can never bear comparison with that fermented by yeast.The object of the present notice is to point out a method by which yeast of the most unexceptionable quality can be artificially produced at will. I am aware that somesiibstitute for ordinary ferment in brewing has long been known to cer- tain persons who go about the country and impart their secret to those who are willing to purchase it of the nature of this preparation I am ignorant and a reference to systematic che- mical works will suffice to show that whatever it be it has never been made public. On turning to Berzelius it will be found stated* that although the reproduction as it were of yeast the conversion of a small into a large quantity is a very easy thing,.yet to roduce that substance from the beginning is very difficult.he describes a process for this purpose on the authority of Dr. Henry and which consists in taking a strong infusion of malt saturating it with carbonic acid and then exposing it for some days to the prcper fermenting temperature when g small quantity of yeast is gradually formed and deposited which may by various contrivances be made to give origin to a larger. I shall have occasion to notice presently the be- haviour of a ma!t infusion when left to itself at a temp. of YOo or 80’ F. for some time and to show that the addition of carbonic acid is wholly unnecessary. The principle of induced chemical action which Liebig has assumed to explain a great number of those extraordinar-y phaenonieiia to which Berzelius gave the term Catalysis,” and which principle has been so fully confirmed and even perhaps extended by the late valuable researches of MM.Boutron and Fremy on the formation of lactic acid serves to solve this difficulty as it will doubtless many others of far greater magnitude and importance. It has been shown that cc the kind of chemical change going on in the decomposing azo-tized body or ferment determines the kind of decomposition which shall occur in the neutral ternary substance subject to its influence ;’’ that diastase for example according to its peculiar condition whether fresh from the germinated grain slightly putrefied or in a still more advanced state of that change possesses the singular power in the first case of changing starch into dextrin and ultimately into grape sugar; in the second of causing the conversion of sugar into lactic * Lehrbuch vol.viii. 89. foot note third edition. Chem. SOC.Mem. VOL. I o 102 Mr. Fownes on the Prepamtiorr of Art@cinl Yeast. acid; and in the third and last of exciting the vinous fernieri- tation. Now if common wheaten flom be mixed with water to a thick paste and exposed slightly covered to spontaneous change in a moderately warm place it will be observed to run through a series of changes which seem very closely to resemble those described by MM. Boutron and Fr6my in the case of diastase. About the third day of such exposure it begins to emit a little gas arid to exhale an exceediiigly disagreeable sourodour much like that of stale milk; after the lapse of some time this smell disappears or changes in character the gas evolved is greatly increased and is accompanied by a very distinct and somewhat agreeable vinous odour this will happen about the sixth or seventh day and the substance is then in a state to excite the alcoholic fermentation.A qiiantity of brewers' wort is next to be prepared in the usual mariner by boiling with hops; and when cooled to 90' or 100° the decomposed dough before described after being thoroughly mixed with a little tepid water is added to it arid the temperature kept up by placing the vessel in a warm si-tuation. After the lapse of a few hours active fermentation commerices; abundance of carbonic acid having its usual agreeable pungent smell is disengaged and when the action is complete and the liquid clear a large quantity of excellent yeast is found at the bottom well adapted to all purposes to which that substance is applied.In one experiment the following materials were used :-a small handful of ordinary wheat flour was made into thick paste with cold water covered with paper and left seven days on the mantel-shelf of a room where a fiie was kept all day being occasionally stirred at the end ofthat period three quarts of malt were mashed with about two gallons of water the infu- sion boiled with the proper quantity of hops and when SUE-ciently cooled the ferment added. The results of the experi- ment were R quantity of beer not very strong it is true but quite free from any unpleasant taste and at least a pint of thick barn] which proved perfectly good for making bread.It appears to me that this simple plan would enable distant residents in the country and settlers in the colonies to enjoy the luxury of good bread when a little rnalt could be got- a very ezsy home manufacture from grain of any kind the hops might probably be omitted when the yeast alone was the object. A moderately strong infusion of malt which has not been boiled suffered to stand in a warm place for some days IVY.Fownes on the Preparation of ArtzJicinl Yeast. 103 speedily becomes sour and turbid and begins to evolve gas; this change rapidly progresses carbonic acid is given out plentifiilly and a deposit of thick insoluble whitish matter formed which readily excites fermentation in a dilute solution of sugar ; the supernataiit liquid contains alcohol acetic acid and I believe lactic acid.When wort which has been boiled and hopped is set aside to decompose spontaneously the change it undergoes appears to depend very much upon its strenqh. When weak three or four days elapse before anything is noticed; a scum then collects upon the surface and a brown flocculent substance is thrown down which is incapable of excitir,g fermentation in a solution of sugar while the liquid gives off a flat offensive smell. If the infusion experimented on be stronger then the change is different the liquid becomes turbid from the sepa- ration of a yellowish adhesive substance a good deal of gas is very slowly emitted alcohol is formed and the deposit at the bottom of the vessel proves a pretty active ferment to sugar.The acidity of the liquid is but trifling and its smell is some- what disagreeable. These differences in the behaviour of boiled wort may also depend upon the quantity of hops added and the length of time during which the ebullition had been continued. The effect produced in a spontaneously fermentable liquid by vegetable acids or acid salts such as cream of tartar is a cu-rious subject of inquiry. From an experiment made upon some wort it appeared not improbable that the result of such addi- tion showed an interference in the formation of lactic acid. We know that when the juice of grapes or currants and goose- berries is exposed to the air the vinous fermentation is set up apparently at once ; whereas in an unboiled infusion of malt which is destitute of these substances lactic acid seems to be first formed although ultimately the two fermentations go on together.I stated when speaking of the spontaneous decomposition of wheaten dough that an acid state preceded that in which it became an alcoholic ferment; and if in this condition it be mixed with a dilute solution of common sugar and the whole kept warm for several days it furnishes a sour liquid which is rich in lactic acid and fi-om which white crystallized lactate of zinc is easily prepared. There is a tendency in the liquid to run into the alcoholic fermentation and to produce vinegar by a subsequent change but still the quantity of lactic acid so formed is very considerable.Common wheat-gluten then in its mode of decomposition Mr. Croft on some Salts of Cndniium. succession through two different dynamic conditions ; it is successively il. lactic acid and an alcohol ferment; is it too much to expect that it might by proper means be detected in a third condition namely as a u sugar ferment,” like diastase itself in the state in which it exists in malt ? Is it not possible that diastase as a definite proximate principle has no more existence than yeast ; that its powers are purely dynamic and that it is in short nothing more than the gluten of the seed in one of its earliest stages of decomposition? This is an in- teresting inquiry but its prosecution will be somewhat difficult from the rapidity with which these changes succeed each other; it must be remembered that no one has yet succeeded in get- ting diastase in a state fit for analysis.

ISSN:0094-2405    

DOI:10.1039/MP8410100100

出版商:RSC    

年代:1841

数据来源: RSC

摘要:

Mr. Croft on some Salts of Cndniium. XX. On some Salts of Cadmium. By HENRY CROFT,Bsq. Read May 17,1842. HLORIDEofcadmium is exceedinglysoluble in water and cannot be obtained in good crystals. If it be treated with a solution of ammonia it is not at first dissolved; but on heat-ing the white powder which is at first formed disappears arid on cooling a granular crystalline powder falls out of the solution. It is a compound of the chloride with ammonia. By heating it loses 16.63 per cent of ammonia; according to the formula Cd C1 + H3N it would lose 15*12; the excess ob- tained is owing to a portion of the chloride being. decomposed when sal-ammonia is evolved. The proof of this is that the heated salt is not perfectly soluble in water. if dry ammonia be passed over piilverised anhydrous chlo- ride of cadmium the powder increases greatly in Idk under evolution of heat.At first there is but little action and the stream of ammonia must be passed over the salt for some time before violent absorption takes place. 1.276 gr. absorbed 0'6835 gr. of ammonia or 100 parts absorbed 53*56;accard-ing to the formula Cd C1 + 3 N H3 it would be 56.47 the difference probably arises fiom the great iricrease in bulk which the salt undergoes and which may prevent the ammo- nia reaching every particle. This compound loses ammonia when exposed to the air ; when it has ceased to smell of ammonia it is converted into the first-mentioned compound viz. that containing one atom of ammonia. Bromide of cadmium crystallizes in long prisms somewhat similar to nitre; it loses its water of crystallization when ex- posed to a dry atmosphere 2.422 grs.lost when heated to Mr. Croft on sum Salts ~JC'udmium. 100° 0'5075 gr. of water ; that is 20.95 per cent. ; accord-ing to the formula Cd Br + 4aq it should be 21.17 it fuses easily and crystallizes on cooling. Bromide of cadmium dis- solves in hot caustic ammonia and gives on cooling a granu-lar crystalline powder ; by slow cooling the salt is deposited in the form of regular octohedrons. It contains 11.69 per cent. of smmonia or 1 atom and is therefore analogous to the chloride. The anhydrous bromide absorbs a large quantity of ainmo-nia like the chloride but the quantity varies between two and three atoms*.All these compounds are decomposed by water and oxide of cadmium is separated. The chloride bromide and iodide of cadmium form very beautiful double salts with the alkaline chlorides bromides and iodides. They may be prepared by dissolving the respective salts in atomic proportions. Cadmio-chloride of potnssiu7nn.-Froin the concentrated so-lution the salts crystallize in silky needles which contain water. If these crystals be allowed to stand in the solution they gradually disappear and large crystals are formed in their stead ; they have the form of regular rhombohedrons ; they contain no water. Their formula is Cd C1 + KC1; the aci- cular salt contains one atom of water. 100 parts of water at 60' F. dissolve 33.45. Cadmio-bromide of potassium is precisely similar to the double chloride it is however much more soluble in water.Formula Cd Br + KBr. The acicular salt contains water. Cndmio-iodide &c. does not crystallize like the bromide snd chloride; the anhydrous salt is Cd I + K I. it is very soluble in water. Cadmio-chloride of sodium does not crystallize in a regular form but in verrucose crystals. The formula is Cd CI + Na C1 + 3 aq. 100 parts of water at 60 dissolve -71-35?. Cadmio-chloride of ammoizium crystallizes like the potassium salt in two forms; the large crystals are anhydrous. All these salts are somewhat soluble in alcohol and wood- spirit but not so much so as the simple chloride iodide and bromide. The analyses of these as well as some other salts of cad-mium will be published in a second paper. * In the last number of the Reports of the Academy of Berlin I find that Rammelsberg has prepared and analysed the crystallized bromide and its compounds with ammonia. That prepared in the dry way contains as he says two atoms of ammonia. Chem. SOC.Mem. VOL. I. P

ISSN:0094-2405    

DOI:10.1039/MP8410100104

出版商:RSC    

年代:1841

数据来源: RSC