摘要:

MEMOIRS AND PROCEEDINGS OF THE CHEMICAL SOCIETY O F LONDON FOB 184.'3-1844 AND 1844-1645. VOL. 11. LONDON PRINTED BY RICHARD AND JOHN E. TAYLOR RED LION COURT FLEET BTRELT. 1845. C 0 NTENT S. Paw 1 9 - On the Products of the Distillation of Meconic Acid. By John Sten- 11OUSP 1’h.I). ................................................................. Further Contributions to the Chemical History of the Products of the Decomposition of Uric Acid. By William Gregory M.D. F.R.S.E. ........................................................................ Additional Observations on Zthogen. By W. H. Balmain Esq. ... 15 O n the Solubility of the Metals in Persulphate and Perchloride of Iron. By Mr. Jarnes Napier .............................................16 Observations on Fermentation. By John N. Furze Esq. ............ 21 Note on a paper on Ferric Acid read May 16 1843. By John Robert Warington Esq. ................................................... On a Class of Double Sulphates containing Soda and a Magnesian Oxide. By A. R. Arrott Esq. ............................................ Experiments on the Heat disengaged in Combinations. By Thomas Graham Esq. F.R.S. &c. ................................................ Note on a Means of Preserving the Crystals of Salts as permanent objects for Microscopic Investigation. By Robert Warington Esq. 71 Observations on the Green Teas of Commerce. By Robert Waring- Denham Smith Esq. .........................................................25 Observations on the Circular Polarization of Light by trailsmission through Fluids. By H. B. Leeson M.D. A.M. ..................... 26 By John Thomas Cooper Esq. ... 45 Observations on Catechuic Acid. On a curious’Change in the Molecular Structure of Silver. By 47 49 5 1 73 Account of a new Cyanide of Gold. By Mr. John Carty ............ 80 On the Cyanides of the Metals and their Combinations with Cyanide 82 92 ton Esq. ........................................................................ of Potassium. By Messrs. Charles F. 0. Glassford and James Napier :- Part I. Cyanide of Gold .......................................... Part 11. Cyanide of Silver .......................................... On the occurrence of Fluorine in Recent as well as in Fossil Bones.On a Spathic Carbonate of Iron. By Mr. John Thomas Way ...... 105 By Charles Daubeny M.D. F.R.S.. ...................................... On some of the Salts of Meconic and Komenic Acids. By John Report &c. ........................................................................ Stenhouse Ph.D. ........................................................... 97 109 113 iv On the Reduction of the Salts of Peroxide of Iron by means of Vege- -g\e table Substances. By John Stenhouse Ph.D. ........................ 120 On the Hydrate of the Oil of Laurel Turpentine. By John Sten- house Ph.D. .................................................................. 121 On East Indian Grass Oil. By J. Stenhouse Ph.D................... 122 Observations on the Pharmaceutical and Chemical Characters of the Peruvian Matico. By John F. Hodges M.D. ........................ 123 On an improved Method for the Detection and Quantitative Deter- mination of Arsenic. By Remigius Fresenius M.D ................... I29 On Fluorine in Recent and Fossil Bones and the sources from whence it is derived. By J. Middleton Esq. .................................... 134 On the occurrence of Mannite in the Laminaria sacchnrina and other Sea-weeds. By John Stenhouse Ph.D .................................. 136 On the Composition of some varieties of South American Guano ; with the description of a new mode of estimating Ammonia and of a process for separating Lime from Magnesia when these earths exist in combination with Phosphoric Acid.By J. Denham Smith Esq. .............................................................................. 140 Observations upon the Decomposition of the Double Cyanides by an Electric Current. By Mr. James Napier .............................. 158 Abstract of a Letter from H. B. Leeson M.D. on the Preparation of Fluoride of Iodine ............................................................. 162 On the Composition of Narcotine and some of its products of De- composition by the action of Bichloride of Platinum. By J. Blyth Fresenius ....................................................................... 179 M.D. .............................................................. .- ............ 163 On the Inorganic Constituents of Plants.By Drs. H. Will and R. Examination of a Specimen of diseased Wheat. By Mr. J. Carty ... 199 Analysis of the Bonnington Water near Leith Scotland. By Edward G. Schweitzer Esq. ......................................................... 201 Description of a Chemical Lamp-Furnace. By Edward dolly Esq 218 Notice of a new Hydrated Phosphate of Lime. By John Percy M.D. 222 On a curious Change in the Composition of Bones taken from the Guano. By Robert Warington Esq. ................................. 223 On a means of detecting Kink Acid. By John Stenhouse Ph.D. ... 226 Remarks upon Chloranil. By Augustus William Hofmann Ph.D.. .. 227 On the Decomposition of Oxides and Salts by Chlorine. By Alex- ander W. Williamson Esq................................................. 234 On some of the Substances which reduce Oxide of Siiwr and precipi- tate it on Glass in the form of a Metallic Mirror. By John Sten- On the Decomposition of Salts of Ammonia at ordinary Temperatures. On some commercial Specimens of Green Glass. By Robert Wa- On certain Processes in which Aniline is formed. By Drs. J. S. Mus- house Ph.D. .................................................................. 242 By H. Bence Jones M.D. ................................................ 244 rington Esq. .................................................................. $47 pratt and A. W. Hofmann ................................................ 249 V Page Observations on the Decomposition of Metallic Salts by an Electric Current.By Mr. James Napier .......................................... 255 On the Distilled Waters of our Pharmacopaeias. By Robert Wa- rington Esq. .................................................................. 261 On the Metamorphoses of Indigo. Production of Organic Bases which Assistant in the Giessen Laboratory .................................... 266 contain Chlorine and Bromine. By Dr. August Wilhelm Hofmann On the Structure of Electro-precipitated Metals. By Warren De la On the true Composition of Chlorindatmit. By August Wilhelm Analyses of Farm-Yard Manure and of Coal-Gas. By Thomas 309 Rue Esq. ..................................................................... 300 Hofmann Ph.D. ............................................................306 Richardson Esq. ............................................................ On a New Phosphate of Magnesia. By Wm. Gregory M.D. ......... 310 Contributions to Actino-Chemistry. By Robert Hunt Esq. Secre- tary to the Royal Cornwall Polytechnic Society &c. ............... 311 On Brown Iron Ore. By Lieut.-Col. P. 1. Yorke. ..................... 321 Observations on the Action of Animal Charcoal. By Robert Wa- 326 Annual Report of the Council ................................................ 329 rington Esq. .................................................................. On Styrole and some of the products of its decomposition. By Dr. John Blyth and Dr. August Wilhelm Hofmann ........................ 334 Note on the useful applications of the Refuse-Lime of Gas-works.By Thomas Graham Esq. F.R.S. ....................................... 358 Contributions to the Knowledge of Conjugate Compounds. By Dr. H. Kolbe Chemical Assistant in the University of Marburg ...... 360 On Toluidine a new OrgaQic Base. By James Sheridan Muspratt Ph.D. and Augustus William Hofrnann Ph.D. ..................... 367 On the Conversion of Cane-sugar into a substance isomeric with Cel- lulose and lnulin. By Thomas Tillep Esq. Ph.D. and Douglas On the Action of Bleaching Powder on the Salts of Copper and Lrad. Maclagan M.D. F.R.S. Edin. .......................................... 384 By Walter Crum Esq. F.R.S .............................................. 387 Note on the Existence of Phosphoric Acid in the Deep.Wel1 Water of the London Basin.By Thomas Graham Esq. F.R.S. ......... 392 On a Crystallized Alloy of Zinc Iron Lead and Copper. By Warren Some Experiments on Ozone. By A. W. Williamson Esq ............. 395 On the Solubility of Oxide of Lead in Pure Water. By Lieut.-Col. De la Rue Esq. ............................................................... 39:; .39!+ Philip Yorke .................................................................. On Atomic Volume and Specific Gravity. By Lyoii Playfair Esq. Ph.D. and J. P. Joule Esq. ................................................ 401 Index .............................................................................. 4 fi :i MEMOIRS AND PROCEEDINGS OF THE CHEMICAL SOCIETY O F LONDON FOB 184.'3-1844 AND 1844-1645.VOL. 11. LONDON: PRINTED BY RICHARD AND JOHN E. TAYLOR, RED LION COURT FLEET BTRELT. 1845 C 0 NTENT S. -Paw On the Products of the Distillation of Meconic Acid. By John Sten-11OUSP 1’h.I). ................................................................. Further Contributions to the Chemical History of the Products of the Decomposition of Uric Acid. By William Gregory M.D., F.R.S.E. ........................................................................ Additional Observations on Zthogen. By W. H. Balmain Esq. ... O n the Solubility of the Metals in Persulphate and Perchloride of Iron. By Mr. Jarnes Napier ............................................. Observations on Fermentation. By John N. Furze Esq. ............Note on a paper on Ferric Acid read May 16 1843. By John Denham Smith Esq. ......................................................... Observations on the Circular Polarization of Light by trailsmission Observations on Catechuic Acid. On a curious’Change in the Molecular Structure of Silver. By On a Class of Double Sulphates containing Soda and a Magnesian Oxide. Experiments on the Heat disengaged in Combinations. By Thomas Graham Esq. F.R.S. &c. ................................................ Note on a Means of Preserving the Crystals of Salts as permanent objects for Microscopic Investigation. By Robert Warington Esq. Observations on the Green Teas of Commerce. By Robert Waring-ton Esq. ........................................................................On the Cyanides of the Metals and their Combinations with Cyanide of Potassium. By Messrs. Charles F. 0. Glassford and James Napier :-through Fluids. By H. B. Leeson M.D. A.M. ..................... By John Thomas Cooper Esq. ... Robert Warington Esq. ................................................... By A. R. Arrott Esq. ............................................ Account of a new Cyanide of Gold. By Mr. John Carty ............ Part I. Cyanide of Gold Part 11. Cyanide of Silver .......................................... By Charles Daubeny M.D. F.R.S.. ...................................... .......................................... On the occurrence of Fluorine in Recent as well as in Fossil Bones. On a Spathic Carbonate of Iron. By Mr.John Thomas Way ...... Report &c. ........................................................................ On some of the Salts of Meconic and Komenic Acids. By John Stenhouse Ph.D. ........................................................... 1 9 15 16 21 25 26 45 47 49 5 1 71 73 80 82 92 97 105 109 11 iv -g\e On the Reduction of the Salts of Peroxide of Iron by means of Vege-table Substances. By John Stenhouse Ph.D. ........................ 120 On the Hydrate of the Oil of Laurel Turpentine. By John Sten-house Ph.D. .................................................................. 121 On East Indian Grass Oil. By J. Stenhouse Ph.D. .................. 122 Observations on the Pharmaceutical and Chemical Characters of the Peruvian Matico.By John F. Hodges M.D. ........................ 123 On an improved Method for the Detection and Quantitative Deter-mination of Arsenic. By Remigius Fresenius M.D ................... I29 On Fluorine in Recent and Fossil Bones and the sources from whence it is derived. By J. Middleton Esq. .................................... 134 On the occurrence of Mannite in the Laminaria sacchnrina and other Sea-weeds. By John Stenhouse Ph.D .................................. 136 On the Composition of some varieties of South American Guano ; with the description of a new mode of estimating Ammonia and of a process for separating Lime from Magnesia when these earths exist in combination with Phosphoric Acid. By J. Denham Smith, Esq. ..............................................................................140 Observations upon the Decomposition of the Double Cyanides by an Electric Current. By Mr. James Napier .............................. 158 Abstract of a Letter from H. B. Leeson M.D. on the Preparation of Fluoride of Iodine ............................................................. 162 On the Composition of Narcotine and some of its products of De-composition by the action of Bichloride of Platinum. By J. Blyth, M.D. .............................................................. .- ............ 163 By Drs. H. Will and R. On the Inorganic Constituents of Plants. Fresenius ....................................................................... 179 Examination of a Specimen of diseased Wheat. By Mr. J. Carty ...199 G. Schweitzer Esq. ......................................................... 201 Analysis of the Bonnington Water near Leith Scotland. By Edward Description of a Chemical Lamp-Furnace. By Edward dolly Esq 218 Notice of a new Hydrated Phosphate of Lime. By John Percy M.D. 222 On a curious Change in the Composition of Bones taken from the Guano. By Robert Warington Esq. ................................. 223 On a means of detecting Kink Acid. By John Stenhouse Ph.D. ... 226 Remarks upon Chloranil. By Augustus William Hofmann Ph.D.. .. 227 ander W. Williamson Esq. ................................................ 234 On the Decomposition of Oxides and Salts by Chlorine. By Alex-On some of the Substances which reduce Oxide of Siiwr and precipi-By John Sten-On the Decomposition of Salts of Ammonia at ordinary Temperatures.On some commercial Specimens of Green Glass. By Robert Wa-On certain Processes in which Aniline is formed. By Drs. J. S. Mus-tate it on Glass in the form of a Metallic Mirror. house Ph.D. .................................................................. 242 By H. Bence Jones M.D. ................................................ 244 rington Esq. .................................................................. $47 pratt and A. W. Hofmann ................................................ 24 V Page Observations on the Decomposition of Metallic Salts by an Electric Current. By Mr. James Napier .......................................... 255 On the Distilled Waters of our Pharmacopaeias. By Robert Wa-rington Esq................................................................... 261 On the Metamorphoses of Indigo. Production of Organic Bases which contain Chlorine and Bromine. By Dr. August Wilhelm Hofmann, Assistant in the Giessen Laboratory .................................... 266 By Warren De la Rue Esq. ..................................................................... 300 By August Wilhelm Hofmann Ph.D. ............................................................ 306 By Thomas Richardson Esq. ............................................................ 309 On the Structure of Electro-precipitated Metals. On the true Composition of Chlorindatmit. Analyses of Farm-Yard Manure and of Coal-Gas. On a New Phosphate of Magnesia. By Wm. Gregory M.D.......... 310 Contributions to Actino-Chemistry. ............... 311 On Brown Iron Ore. By Lieut.-Col. P. 1. Yorke. ..................... 321 Observations on the Action of Animal Charcoal. By Robert Wa-rington Esq. .................................................................. 326 Annual Report of the Council ................................................ 329 On Styrole and some of the products of its decomposition. By Dr. John Blyth and Dr. August Wilhelm Hofmann ........................ 334 Note on the useful applications of the Refuse-Lime of Gas-works. By Thomas Graham Esq. F.R.S. ....................................... 358 Contributions to the Knowledge of Conjugate Compounds. By Dr. H. Kolbe Chemical Assistant in the University of Marburg ......360 On Toluidine a new OrgaQic Base. By James Sheridan Muspratt, Ph.D. and Augustus William Hofrnann Ph.D. ..................... 367 On the Conversion of Cane-sugar into a substance isomeric with Cel-lulose and lnulin. By Thomas Tillep Esq. Ph.D. and Douglas Maclagan M.D. F.R.S. Edin. .......................................... 384 On the Action of Bleaching Powder on the Salts of Copper and Lrad. By Walter Crum Esq. F.R.S .............................................. 387 Note on the Existence of Phosphoric Acid in the Deep.Wel1 Water of the London Basin. By Thomas Graham Esq. F.R.S. ......... 392 On a Crystallized Alloy of Zinc Iron Lead and Copper. By Warren By Robert Hunt Esq. Secre-tary to the Royal Cornwall Polytechnic Society &c. De la Rue Esq. ............................................................... 39:; Some Experiments on Ozone. By A. W. Williamson Esq ............. 395 On the Solubility of Oxide of Lead in Pure Water. On Atomic Volume and Specific Gravity. Index .............................................................................. 4 fi :i By Lieut.-Col. By Lyoii Playfair Esq., Philip Yorke .................................................................. .39!+ Ph.D. and J. P. Joule Esq. ................................................ 40

ISSN:0269-3127    

DOI:10.1039/MP84302FP001

出版商:RSC    

年代:1843

数据来源: RSC

摘要:

9 Dr. Gregory on the Decomposition of Uric Acid. LX XXVI. Fzlrther Contributions to the Chemical History of the Products of the Decomposition of Uric Acid. By WIL- LIAM GREGORY M.D. F.R.S.E. I N 1840 I described at the Glasgow Meeting of the British Association an improved and very productive method of preparing alloxan murexide &c. ; and I showed from the occurrence of urea among the products of the action of hy- permanganate of potash on uric acid that Liebig and Wohler’s view according to which urea pre-exists in uric acid must be admitted in the present state of our knowledge as well- Dr. Gregory on the 10 founded ; thus giving additional probability to the supposition of the existence of the acid supposed by them to be present in uric acid combined with urea and called hypothetically urilic acid= C N 04.Since that period I have been frequently occupied with the subject of uric acid. In 1841 Professor Liebig having en- trusted to me the treatment of upwards of 2 lbs. of urate of ammonia I extracted the uric acid from this and converted nearly the whole of it into alloxan of which I obtained i$ Ib. in large and absolutely pure crystals. 'This not only enabled me to study the preparation of several of the other products but led me to economise as much as possible the very abun- dant mother-liquid of the alloxan which contained a large quantity of that substance but so much mixed with nitrate of ammonia and free nitric acid that the alloxan could not be purified by crystallization even if the liquid could have been concentrated by heat without decomposition.I shall now state the results of my experiments as far as these are to- lerably ascertained. There is still much to be done and se- veral investigations are in an imperfect state in my laboratory. As it may be some time however before I may be able to re- turn to them I think it right in the mean time to describe the results hitherto obtained. 1. Alloxanti7ae. This compound is best obtained from the mother-liquid of alloxan as prepared according to my process*. The acid solution is diluted with two or three parts of water and a cur- rent of snlphuretted hydrogen gas is passed through as long as it produces any effect. Sulphur is first deposited and sub- sequently a large quantity of alloxantine.'rhe mixed pre- cipitate is drained washed with a little cold water and then boiled with water acidulated with hydrochloric acid until all the alloxantine is dissolved which requires from a quarter to half an hour even when enough water is present for the final solution of the whole. The solution is filtered while hot which takes place very rapidly and deposits on coding an abundant crop of crystals of alloxantine. The quantity rexhes its maximum in twenty-four hours and the amount retained in the acidulous mother-liquor is but small. I t may however be obtained by concentration. By this method the mother- liquid of the alloxan above mentioned although some part of it was used for other experiments yielded upwards of 8 oz.of pure alloxantine. * See Turner's Chemistry 7th edition. 11 Products of the Decomposition of Uric Acid. 2. Diabrate of Ammonia. This salt may be also obtained in abundance from the mother-liquid of alloxan as well as from that of alloxantine. Animonia is to be cautiously added in the cold so as to leave a slight excess of acid and hydrosulphuret of ammonia is to be then added in excess so as to redissolve any sulphur that may be at first thrown down. The dialurate is formed in the cold so abundantly as to cause the whole to become thick. It may be dissolved in the liquid by the aid of heat and it is then deposited on cooling in crystals. We ought to see thet nothing is left undissolved by the hot liquid; should this oc- cur it is probably owing to sulphur and in that case a little hydrosulphuret of ammonia clears all up.The crystallized dialurate of ammonia is collected on a filter and washed at first with a weak solution of hydrosulphuret of ammonia then with alcohol to which enough hydrosulphuret has been added to give it a pale yellow colour aid finally with pure alcohol till the latter passes through quite colourless and pure. The salt is quickly submitted while still on the filter to pressure between folds of bibulous paper and is finally dried in vamo over sulphuric acid. Should it not appear pure the process of dissolving it in water with the addition of hydrosulphuret of ammonia of crystallizing,A and washing as above is to be repeated. By this method I have prepared this salt in large quantity and have obtained it dry and quite pure with only a faint tinge of flesh colour in fact almost colourless.If dried in the air without the use of the alcohol and hydrosulphuret in washing and with the aid even of a gentle heat it becomes blood-red. The pure dialurate forms minute prismatic crystals which are united together when dried in light bulky masses of a faint silky lustre. I took advantage of the possession of a large stock of this salt to repeat the analysis of it determining the nitrogen by the process of Varrentrapp and Will. Se- veral analyses made by myself and one made by Mr. Keller yielded results which I shall not detain the Society by re- peating as they agreed entirely with those of Liebig and Wiihler.3. Dialuric Acid. Liebig and Wohler failed to obtain this acid in a separate form owing doubtless to their being compelled to make their experiments on very small quantities. I found that it is easily obtained when the preceding salt is dissolved with the aid of heat in an excess of diluted hydrochloric acid. The liquid deposits 011 cooling a quantity of sparingly soluble crystals Dr. Gregory on the not uiilike those of alloxantine yet quite distinguishable froin them; these crystals are dialuric acid. They have a strong acid reaction and readily neutralize the alkaline bases form- ing with ammonia the preceding salt; with potash a spa- ringly soluble salt in hard crystals; and with baryta an inso- luble or very slightly soluble powder.The latter salts are fornied when dialuric acid is added to solutions of the soluble salts of potash and baryta so that the affinities of the acid are powerful. 12 P Dialuric acid is not however very permanent in its uncom- bined form that is to say when dissolved in water. It gra- dually passes into alloxantine when exposed to the air oxy- aen no doubt being absorbed. The change may be traced i n the colour of the precipitate produced by barytic water. If it be white the acid has not yet undergone a change ; but if it be pale pink reddish-purple or violet this indicates the gradually increasing proportion of alloxantine. Even the crystals of dialuric acid when left in the liquid tiotn which they have been deposited for a day or two are found to be partially changed into alloxantine.I made several analyses both of the acid itself and of its compounds with potash and baryta. The details shall appear hereafter at present I may state that these analyses corre- namely C N H 0 = C N H 0 + HO in which HO spond to the hypothetical formula given by Liebig and Wijhler seems to be capable of replacement by MO in the salts. It is important to observe that urile or urilic acid C N 0 + H4 0, =4 atoms of water contains the elements of dialuric acid. I t is proper to state that Liebig and Wohler did obtain by the same process as I adopted the crystals of dialuric acid which however appear to have been partially converted into alloxantine before they were examined *. Indeed my experi- ments lead me to believe that the substance described by these chemists as dimorphous alloxantine is nothing but dialuric acid more or less completely converted into alloxantine and retaining probably its original form.Or they may have exa- mined a mixture of the crystals of both in which those of dialuric acid happened to be the largest and best formed. Such a mixture if analysed would of course yield results closely approximating to those derived from alloxantine as the latter body consists of the same elements as dialuric acid + 1 at. of hydrogen and 2 at. of oxygen only. Liebig and Wohler have already observed and my experiments confirm the statement that the liquid obtained by boiling dialurate of ammonia with an acid deposits when allowed to stand for.* Ann. deer Pharm. xxvi. 280. 13 Products of the Decomposition of Uric Acid. some time after cooling crystals of alloxantine which will of course be found mixed with the dialuric acid deposited during refrigeration unless the latter be first separated. The salts of dialuric acid in the dry state are quite perma- nent. I am still occupied with the study of this remarkable acid and its salts. 4. Acid Thionurate of Ammonia. This salt from which according to Liebig and Wohler the uramilic acid is best obtained may be prepared in any quantity by dissolving the neutral thionurate of ammonia in hot water and adding exactly as much hydrochloric acid calculated from the specific gravity by means of the published tables of liquid hydrochloric acid as corresponds to 1 eq.of hydrochloric acid for 1 eq. of the salt which contains 2 eq. of ammonia. One of these is removed by the hydrochloric acid and when the liquid is gently evaporated to a small bulk it deposits the acid (monobasic) thionurate of ammonia in soft crusts which frequently fall to the bottom and are composed of very minute prisms. I have not yet succeeded in obtaining uramilic acid either from this salt or in any other way; and Prof. Liebig informs me that neither he nor Prof. Wohler has been so fortunate as to succeed in procuring it again. I t can hardly be doubted however that with an easy and sure method of preparing the acid thionurate we shall soon ascer- tain all the conditions essential to the formation of uramilic acid.The acid thionurate itself as well as all the compounds now- mentioned I have prepared by ounces at a time without once failing. 5. Altoxnno- sulphurous Acid. Liebig and Wohler mention that a solution of alloxan in sulphurous acid when slowly evaporated deposited large ta- bular acid crystals which not only were not thionuric acid (which requires the elements of ammonia besides those of al- loxan and sulphurous acid) but when mixed with ammonia did not produce the thionurate of that base but a totally dif- ferent salt of a gelatinous aspect which has not been further examined. I have not examined those tabular crystals nor indeed have I as yet seen them; but I have by other means obtained a salt the acid of which appears to be composed of alloxan and sulphurous acid.To obtain this salt dissolve alloxan in the smallest possible quantity of cold water and add to the solution a slight excess of a saturated solution of sulphurous acid in water. Then add with care caustic potash in solution till there is the Dr. Gregory on the Decomposition of Uric Acid. 14 slightest possible alkaline reaction. There will be deposited very soon partly even at once in the cold solution a salt in hard brilliant crystals which may easily be obtained by re- crystallization of considerable size and are very beautiful from their perfect whiteness their transparency and brilliant lustre. This new salt may be procured in any quantity and with the utmost facility. I have not yet succeeded in isolating the acid but the analysis of the salt indicates that the acid consists of two atoms of sulphurous acid and one of alloxan.I t thus differs from thionuric acid by the absence of 1 eq. am- monia and probably also in being nionobasic while thioriuric acid is bibasic. The analytical details concerning this new acid which I propose to call the alloxano-sulphurous will appear when I have completed my investigation of its pro- perties. I t is probable that the large tabular crystals above mentioned as obtained by Liebig and Wohler are nothing more than the alloxano-sulphurous acid in a free state. 6. Alloxanic Acid. When pure alloxantine is dissolved in distilled water and the cold solution allowed to stand it slowly loses the property of giving a violet precipitate with barytic water and finally yields a white precipitate.The liquid is now acid and if gently evaporated to dryness yields crystals which are very soluble both in water and al- cohol and which possess all the chemical characters of allox- anic acid. Professor Liebig did me the favour to examine these crystals as obtained by me and considered them to be alloxanic acid as I had previously done. I did not consider them pure enough for analysis and besides their analysis could throw little light on the subject as the crystallized al- loxaiiic acid has the same composition in 100 parts as anhy- drous alloxan ; and differs therefore from alloxantine only by containing 1 eq. of hydrogen less. Should this observation be confirmed it seems difficult to account for the production of alloxanic acid in this experiment.No other compound appears to be formed and the change seems to takeplace as well in tightly corked and filled vessels as in the air. Besides when alloxantine is oxidized it yields not alloxanic acid but alloxan arid there is no base present that might be supposed to give rise to the production of the acid. I t is possible that this acid may not be really alloxanic acid although agreeing with it in its reactions. In that case it appears rnost probable that it may be isomeric with allox- antine as alloxanic acid is with alloxan. At all events it is Mr. W. H. Balmain mi Bthogm. 15 impossible to see how the 1 eq. of hydrogen bas been removed if the acid be really the atloxanic.I am still engaged in re- searches on this part of the subject the results of which I shall forward to the Society at a future period along with those of the other investigations briefly described above. The study of the products of the decomposition of uric acid is still very far from being completed and I hope at no very distant period to follow up this paper with another on the same subject. Dr. Gregory on the Decomposition of Uric Acid. 9 LX XXVI. Fzlrther Contributions to the Chemical History of By WIL-I N 1840 I described at the Glasgow Meeting of the British Association an improved and very productive method of preparing alloxan murexide &c. ; and I showed from the occurrence of urea among the products of the action of hy-permanganate of potash on uric acid that Liebig and Wohler’s view according to which urea pre-exists in uric acid must be admitted in the present state of our knowledge as well-the Products of the Decomposition of Uric Acid.LIAM GREGORY M.D. F.R.S.E 10 Dr. Gregory on the founded ; thus giving additional probability to the supposition of the existence of the acid supposed by them to be present in uric acid combined with urea and called hypothetically, urilic acid= C N 04. Since that period I have been frequently occupied with the subject of uric acid. In 1841 Professor Liebig having en-trusted to me the treatment of upwards of 2 lbs. of urate of ammonia I extracted the uric acid from this and converted nearly the whole of it into alloxan of which I obtained i$ Ib.in large and absolutely pure crystals. 'This not only enabled me to study the preparation of several of the other products, but led me to economise as much as possible the very abun-dant mother-liquid of the alloxan which contained a large quantity of that substance but so much mixed with nitrate of ammonia and free nitric acid that the alloxan could not be purified by crystallization even if the liquid could have been concentrated by heat without decomposition. I shall now state the results of my experiments as far as these are to-lerably ascertained. There is still much to be done and se-veral investigations are in an imperfect state in my laboratory. As it may be some time however before I may be able to re-turn to them I think it right in the mean time to describe the results hitherto obtained.1. Alloxanti7ae. This compound is best obtained from the mother-liquid of alloxan as prepared according to my process*. The acid solution is diluted with two or three parts of water and a cur-rent of snlphuretted hydrogen gas is passed through as long as it produces any effect. Sulphur is first deposited and sub-sequently a large quantity of alloxantine. 'rhe mixed pre-cipitate is drained washed with a little cold water and then boiled with water acidulated with hydrochloric acid until all the alloxantine is dissolved which requires from a quarter to half an hour even when enough water is present for the final solution of the whole. The solution is filtered while hot, which takes place very rapidly and deposits on coding an abundant crop of crystals of alloxantine.The quantity rexhes its maximum in twenty-four hours and the amount retained in the acidulous mother-liquor is but small. I t may however be obtained by concentration. By this method the mother-liquid of the alloxan above mentioned although some part of it was used for other experiments yielded upwards of 8 oz. of pure alloxantine. * See Turner's Chemistry 7th edition Products of the Decomposition of Uric Acid. 11 2. Diabrate of Ammonia. This salt may be also obtained in abundance from the mother-liquid of alloxan as well as from that of alloxantine. Animonia is to be cautiously added in the cold so as to leave a slight excess of acid and hydrosulphuret of ammonia is to be then added in excess so as to redissolve any sulphur that may be at first thrown down.The dialurate is formed in the cold so abundantly as to cause the whole to become thick. It may be dissolved in the liquid by the aid of heat and it is then deposited on cooling in crystals. We ought to see thet nothing is left undissolved by the hot liquid; should this oc-cur it is probably owing to sulphur and in that case a little hydrosulphuret of ammonia clears all up. The crystallized dialurate of ammonia is collected on a filter and washed at first with a weak solution of hydrosulphuret of ammonia then with alcohol to which enough hydrosulphuret has been added to give it a pale yellow colour aid finally with pure alcohol till the latter passes through quite colourless and pure. The salt is quickly submitted while still on the filter to pressure between folds of bibulous paper and is finally dried in vamo over sulphuric acid.Should it not appear pure the process of dissolving it in water with the addition of hydrosulphuret of ammonia of crystallizing,A and washing as above is to be repeated. By this method I have prepared this salt in large quantity and have obtained it dry and quite pure with only a faint tinge of flesh colour in fact almost colourless. If dried in the air without the use of the alcohol and hydrosulphuret in washing and with the aid even of a gentle heat it becomes blood-red. The pure dialurate forms minute prismatic crystals which are united together when dried in light bulky masses of a faint silky lustre. I took advantage of the possession of a large stock of this salt to repeat the analysis of it determining the nitrogen by the process of Varrentrapp and Will.Se-veral analyses made by myself and one made by Mr. Keller, yielded results which I shall not detain the Society by re-peating as they agreed entirely with those of Liebig and Wiihler. 3. Dialuric Acid. Liebig and Wohler failed to obtain this acid in a separate form owing doubtless to their being compelled to make their experiments on very small quantities. I found that it is easily obtained when the preceding salt is dissolved with the aid of heat in an excess of diluted hydrochloric acid. The liquid deposits 011 cooling a quantity of sparingly soluble crystals 12 Dr. Gregory on the not uiilike those of alloxantine yet quite distinguishable froin them; these crystals are dialuric acid.They have a strong acid reaction and readily neutralize the alkaline bases form-ing with ammonia the preceding salt; with potash a spa-ringly soluble salt in hard crystals; and with baryta an inso-luble or very slightly soluble powder. The latter salts are fornied when dialuric acid is added to solutions of the soluble salts of potash and baryta so that the affinities of the acid are powerful. Dialuric acid is not however very permanent in its uncom-bined form that is to say when dissolved in water. It gra-dually passes into alloxantine when exposed to the air oxy-aen no doubt being absorbed. The change may be traced i n the colour of the precipitate produced by barytic water.If it be white the acid has not yet undergone a change ; but if it be pale pink reddish-purple or violet this indicates the gradually increasing proportion of alloxantine. Even the crystals of dialuric acid when left in the liquid tiotn which they have been deposited for a day or two are found to be partially changed into alloxantine. I made several analyses both of the acid itself and of its compounds with potash and baryta. The details shall appear hereafter at present I may state that these analyses corre-spond to the hypothetical formula given by Liebig and Wijhler, namely C N H 0 = C N H 0 + HO in which HO seems to be capable of replacement by MO in the salts. It is important to observe that urile or urilic acid C N 0 + H4 0, =4 atoms of water contains the elements of dialuric acid.I t is proper to state that Liebig and Wohler did obtain by the same process as I adopted the crystals of dialuric acid, which however appear to have been partially converted into alloxantine before they were examined *. Indeed my experi-ments lead me to believe that the substance described by these chemists as dimorphous alloxantine is nothing but dialuric acid more or less completely converted into alloxantine and retaining probably its original form. Or they may have exa-mined a mixture of the crystals of both in which those of dialuric acid happened to be the largest and best formed. Such a mixture if analysed would of course yield results closely approximating to those derived from alloxantine as the latter body consists of the same elements as dialuric acid + 1 at.of hydrogen and 2 at. of oxygen only. Liebig and Wohler have already observed and my experiments confirm the statement that the liquid obtained by boiling dialurate of ammonia with an acid deposits when allowed to stand for. * Ann. deer Pharm. xxvi. 280. Products of the Decomposition of Uric Acid. 13 some time after cooling crystals of alloxantine which will of course be found mixed with the dialuric acid deposited during refrigeration unless the latter be first separated. The salts of dialuric acid in the dry state are quite perma-nent. I am still occupied with the study of this remarkable acid and its salts. 4. Acid Thionurate of Ammonia. This salt from which according to Liebig and Wohler, the uramilic acid is best obtained may be prepared in any quantity by dissolving the neutral thionurate of ammonia in hot water and adding exactly as much hydrochloric acid, calculated from the specific gravity by means of the published tables of liquid hydrochloric acid as corresponds to 1 eq.of hydrochloric acid for 1 eq. of the salt which contains 2 eq. of ammonia. One of these is removed by the hydrochloric acid, and when the liquid is gently evaporated to a small bulk it deposits the acid (monobasic) thionurate of ammonia in soft crusts which frequently fall to the bottom and are composed of very minute prisms. I have not yet succeeded in obtaining uramilic acid either from this salt or in any other way; and Prof. Liebig informs me that neither he nor Prof. Wohler has been so fortunate as to succeed in procuring it again.I t can hardly be doubted however that with an easy and sure method of preparing the acid thionurate we shall soon ascer-tain all the conditions essential to the formation of uramilic acid. The acid thionurate itself as well as all the compounds now- mentioned I have prepared by ounces at a time without once failing. 5. Altoxnno- sulphurous Acid. Liebig and Wohler mention that a solution of alloxan in sulphurous acid when slowly evaporated deposited large ta-bular acid crystals which not only were not thionuric acid (which requires the elements of ammonia besides those of al-loxan and sulphurous acid) but when mixed with ammonia, did not produce the thionurate of that base but a totally dif-ferent salt of a gelatinous aspect which has not been further examined.I have not examined those tabular crystals nor, indeed have I as yet seen them; but I have by other means obtained a salt the acid of which appears to be composed of alloxan and sulphurous acid. To obtain this salt dissolve alloxan in the smallest possible quantity of cold water and add to the solution a slight excess of a saturated solution of sulphurous acid in water. Then add with care caustic potash in solution till there is th 14 Dr. Gregory on the Decomposition of Uric Acid. slightest possible alkaline reaction. There will be deposited very soon partly even at once in the cold solution a salt in hard brilliant crystals which may easily be obtained by re-crystallization of considerable size and are very beautiful, from their perfect whiteness their transparency and brilliant lustre.This new salt may be procured in any quantity and with the utmost facility. I have not yet succeeded in isolating the acid but the analysis of the salt indicates that the acid consists of two atoms of sulphurous acid and one of alloxan. I t thus differs from thionuric acid by the absence of 1 eq. am-monia and probably also in being nionobasic while thioriuric acid is bibasic. The analytical details concerning this new acid which I propose to call the alloxano-sulphurous will appear when I have completed my investigation of its pro-perties. I t is probable that the large tabular crystals above mentioned as obtained by Liebig and Wohler are nothing more than the alloxano-sulphurous acid in a free state.6. Alloxanic Acid. When pure alloxantine is dissolved in distilled water and the cold solution allowed to stand it slowly loses the property of giving a violet precipitate with barytic water and finally yields a white precipitate. The liquid is now acid and if gently evaporated to dryness yields crystals which are very soluble both in water and al-cohol and which possess all the chemical characters of allox-anic acid. Professor Liebig did me the favour to examine these crystals as obtained by me and considered them to be alloxanic acid as I had previously done. I did not consider them pure enough for analysis and besides their analysis could throw little light on the subject as the crystallized al-loxaiiic acid has the same composition in 100 parts as anhy-drous alloxan ; and differs therefore from alloxantine only by containing 1 eq.of hydrogen less. Should this observation be confirmed it seems difficult to account for the production of alloxanic acid in this experiment. No other compound appears to be formed and the change seems to takeplace as well in tightly corked and filled vessels as in the air. Besides when alloxantine is oxidized it yields, not alloxanic acid but alloxan arid there is no base present that might be supposed to give rise to the production of the acid. I t is possible that this acid may not be really alloxanic acid although agreeing with it in its reactions. In that case it appears rnost probable that it may be isomeric with allox-antine as alloxanic acid is with alloxan. At all events it i Mr. W. H. Balmain mi Bthogm. 15 impossible to see how the 1 eq. of hydrogen bas been removed, if the acid be really the atloxanic. I am still engaged in re-searches on this part of the subject the results of which I shall forward to the Society at a future period along with those of the other investigations briefly described above. The study of the products of the decomposition of uric acid is still very far from being completed and I hope at no very distant period to follow up this paper with another on the same subject

ISSN:0269-3127    

DOI:10.1039/MP8430200009

出版商:RSC    

年代:1843

数据来源: RSC

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15 Mr. W. H. Balmain OH Bthogm. By w. H. BALMAIN ESq. LXXXVII. Additional Observations on A3thogen. ON proceeding to make some quantitative experiments on aethogen Iatound that through depending too much upon simple change of property I had been misled upon some points; and I take this the earliest opportunity of pointing out in what respects my conclusions were erroneous. All the compounds described as aethonides are one and the same substance a new compound of boron and nitrogen pro- bably formed by the decomposition of the zthonide of the metal by the nitro-niuriatic acid used at the end of the pro- cess. I t would appear that there are two compounds of boron and nitrogen; one which is not altered by exposure to a white heat is deconiposed by the action of water at ordinary temperatures and also by the action of nitric acid and which does not phosphoresce before the blowpipe; and a second which is not decomposed by any reagents with the exception of water and oxygen at a high temperature and which phos- phoresces beautitully before the blowpipe; The first is formed when mellon and boracic acid are heated together and combines with the metals; the second whenever a com- pound of the first with a metal is decomposed by abstraction ofthe metal which is effected with such difficulty that the traces left induced me to suppose tbat it was an essential ele- ment of the compound.Whether or not these two com- pounds are isomeric remains yet to be ascertained. The simplest method of preparing the phosphorescent com- pound is to heat together 12 parts of cyanide of mercury of boracic acid and 1 of sulphur.The compound of phosphorus and nitrogen (discovered by Rose) probably has similar relations and may perhaps be studied to advantage in connexion with the above; an easy method of preparing it is to place some chloro-amidide of mercury in a flask and add from time to time a portion of phosphorus keeping up a gentle heat all the time and agi- 16 tating now and then; and when the phosphorus ceases to pro- duce any decompositiou raise the temperature nearly to red- ness. Mr. J. Napier on the Solubility of the Mr. W. H. Balmain OH Bthogm. 15 LXXXVII. Additional Observations on A3thogen. ON proceeding to make some quantitative experiments on aethogen Iatound that through depending too much upon simple change of property I had been misled upon some points; and I take this the earliest opportunity of pointing out in what respects my conclusions were erroneous.All the compounds described as aethonides are one and the same substance a new compound of boron and nitrogen pro-bably formed by the decomposition of the zthonide of the metal by the nitro-niuriatic acid used at the end of the pro-cess. I t would appear that there are two compounds of boron and nitrogen; one which is not altered by exposure to a white heat is deconiposed by the action of water at ordinary temperatures and also by the action of nitric acid and which does not phosphoresce before the blowpipe; and a second, which is not decomposed by any reagents with the exception of water and oxygen at a high temperature and which phos-phoresces beautitully before the blowpipe; The first is formed when mellon and boracic acid are heated together and combines with the metals; the second whenever a com-pound of the first with a metal is decomposed by abstraction ofthe metal which is effected with such difficulty that the traces left induced me to suppose tbat it was an essential ele-ment of the compound.Whether or not these two com-pounds are isomeric remains yet to be ascertained. The simplest method of preparing the phosphorescent com-pound is to heat together 12 parts of cyanide of mercury, of boracic acid and 1 of sulphur. The compound of phosphorus and nitrogen (discovered by Rose) probably has similar relations and may perhaps be studied to advantage in connexion with the above; an easy method of preparing it is to place some chloro-amidide of mercury in a flask and add from time to time a portion of phosphorus keeping up a gentle heat all the time and agi-By w. H. BALMAIN ESq 16 Mr. J. Napier on the Solubility of the tating now and then; and when the phosphorus ceases to pro-duce any decompositiou raise the temperature nearly to red-ness

ISSN:0269-3127    

DOI:10.1039/MP8430200015

出版商:RSC    

年代:1843

数据来源: RSC

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16 Mr. J. Napier on the Solubility of the November 20 1843.-Robert Porrett Esq. Treasurer in the Chair. The following works were presented to the Society :- ‘ I Fresenius on Chemical Analysis,” translated and edited by Loyd A New Method of Alkalimetry,” by Drs. Fresenius and Will ; I‘ A Series of Chemical Tables and Labels,” by Messrs. Charles Bullock Esq. from the editor. translated and edited by Loyd Bullock Esq. from the editor. Button and Warren de la Rue from the authors. Taylor’s Calendar of the Meetings of the Scientific Bodies of London,” for 1843 and 1844 from the editor The following papers were then read :- LXXXVIII. On the Solubility of the Metals in Persdphate and Perchloride of Iron. By Mr. JAMES NAPIER. T have HE nished following state for observations some months past been in lying hopes in that an unfi- time would allow me to make more investigations into some of the phaenomena developed ; but owing to urgent duties altogether apart from such investigations I have little hopes of being able to fulfil these intentions; I have therefore collected them together in hopes that it might attract the attention of some one more qualified to give them that investigation which their singularity seems to deserve.I may be allowed in the first place to relate the circum- stances which led me to the observations which follow. Hear- ing of the great quantity of water which is constantly issuing from the Pary’s Mines Anglesea impregnated with copper and the great expense of obtaining this copper I thought it probable that it might be extracted by means of a galvanic current or what is known as the electrotype process.For the purpose of trying experiments upon this subject I was kindly favoured with a quantity of the water with the follow- ing details :-Quantity of water issuing from the mines yearly $oO,OOO,OOO gallons; this is collected in pits into which is put old iron which precipitates the copper. The average pro- duct of copper is from 55 to 60 tons; the iron consumed in obtaining this is 600 tons. The copper found in these waters as indicated from the precipitate obtained varies from 4 to 30 per cent. according to the wetness of the season ; the sam- ple I procured was during the dry season and consequently rich in copper; its specific gravity was 1*055 at 60’ F.The solid contents of one gallon weighed 4960 grains which gave Metals in Persulphate and Perchloride of Irou. peroxide of iron 1680 grains oxide of copper 80 grains sul- phuric acid 3040 grains muriatic acid 38 grains and 122 grains of earthy matters which were not examined. The iron existed in the water as the persulphate. My first operation was one I had found to answer in analysing copper ores namely wrapping a strip of brown paper round a piece of iron attaching this to a piece of copper and immersing them both in the solution of the copper ore in muriatic acid to be examined ; but I found that the first action which took place was the complete reduction of' the persalt of iron to the state of protosalt at the expense of the copper pole after which the electric current began to effect its object the copper being cleposited but from the copper which had been dissolved haying also to be deposited the consumption of iron was 658 grains while the actual increase in the weight of the copper pole was only 64 grains the quantity of copper originally held in solution.The reaction which took place may be expressed as follows :- . - sulphuric acid. oxygen acid acid acid copper Chem. Sue. filein. VOL. 11. protosulphate of iron. sulphate of copper. giving 690.7' grs. + 64 grs. to be ;lepositrd by the electric cur- Copper pole. rent. Different arrangements of batteries were tried; platinum silver and lead were also substituted for the copper but in no case was a deposit obtained from the water until the iron was first brought into the state of a protosalt; but when this was effected I obtained by the method first described 6 3 grains of copper by the loss of 58 grains of iron.Uuring these experiments I found that silver tin lead an- timony bismuth cobalt nickel and several other metals were very soluble in neutral persalts of iron reducing it to the state of a protosalt. In order to repeat these experiments I prepared sonie perchloride of' iron in the following manner adding to the boiling solution of the sulphate as much nitric acid as was necessary to peroxidize tile iron then precipitating by ammonia washing this well with hot water aiid dissolving with hydrochloric acicl evaporating nearly to dryness a i d adding a quantity of distilled water.'The persulphate used was obtained as a dry white powder; both salts were neutral. I was aware that Professor Fuchs had recommended the c 171-5 582.7 17 Mr. J. Napier on the Solubility of the 18 boiling of n piece of clean copper in perchloride of iron as a means of ascertaining the quantity of iron in an ore of that metal and also to ascertain the amount of copper in certain copper ores. For iron ores I have fi)und great difficulty in obtaining uniform results from the great difficulty of knowing the exact period at which the iron is all reduced to the proto state for the copper put in continues to dissolve until the chloride is all converted into a subchloride; this result is effected however much more rapidly when the iron salt is neutral than when it contains free acid a condition specially recommended by Fuchs.The most uniform results are obtained by allowing the copper to remain until the solution hecomes colourless ; on diliiting with cold water the whole of the copper is precipi- tated as a white powder ; the clear solution if the process is completed will contain no copper when there will be two equivalents of copper dissolved from the metal for every equi- valent of peroxide of iron formerly in the solution. I t occa- sionally happens however when neutral salts of iron are used that the copper becomes encrusted with a white deposit upon which crystals of the subchloride of copper collect and thus protect it from further action; this is prevented by boiling or taking out the copper removing the crust washing it and putting it into the solution again when the action goes on as before.When the persulphate of iron is used for this pur- pose instead of perchloride no subsalt is formed and the re- sult is uniform one equivalent of copper being dissolved for every equivalent of peroxide of iron present in the solution. I iiiay mention one especial application of the solubility of copper in perchloride of iron namely the dissolving copper from the surface of silver such as copper that has been used as c? mould in which silver has been deposited; when this so- lution becomes saturated with copper a little ammonia added precipitates the iron as a peroxide and combines with the copper forming a soluble double chloride which may be im- mediately separated by filtration and the precipitate washed the peroxide of iron again dissolved in hydrochloric acid is fitted for a renewal of the same operation.I may here men- tion that ic previous to adding theammonia there be a little perchloride of iron put into the mixture of subchloride of cop- per and protochloride of iron a n immediate change is effected the colour of the solution becomes green and on adding am- monia to this both copper and iron are precipitated. Persulphate of iron cannot be used for the purpose of dis- solving copper from silver both from the easy solubility of silver in solutions of this salt and also from a peculiar de- 19 Metals i7i Persulphate and Perchloride of Iron.structive action which it has upon alloyed silver. Standard silver is completely destroyed. I have used thin sheets weighing from 60 to 70 grains and when only 4 grains were apparently dissolved the remainder had been so much affected that it crumbled between the fingers like a dried leaf. When silver is put into a solution of persulphate of iron an immediate action takes place a yellowish cloud begins to form in the solution; if heated the action is much more rapid a yellow oxide of iron forming upon the sides of the vessel and there is also a brown precipitate deposited; the iron in the solution is converted into the proto state shining particles of metallic silver float through the solution and sulphate of sil- ver crystallizes 011 the vessel but in no case did l find an equivalent of silver for the equivalent of peroxide of iron ; by slow evaporation the solution yielded crystals of protosulphate of iron and sulphate of silver.Tin is very easily dissolved in both the persulphate and per- chloride of iron completely reducing them to the proto state. When the solution is cold this is effected in about an hour; when hot in a few minutes; the iron is reduced to the proto state when only half an equivalent of tin is dissolved for every equivalent of peroxide; my first impression was that the first atoms of protosalt of tin formed reduced a corresponding atom of peroxide of iron and was converted into a persalt; but sa- turating with ammonia and adding it in great excess the pre- cipitated oxide of tin was not redissolved and had every other character of a protosdt.Whether this was owing to the for- mation of a bisulphate or bichloride oytin I did not ascertain; but by boiling or long standing there is an equivalent of tin dissolved for every atom of perchloride of iron but I did not obtain the same result in the persulphate. Cadmium is very soluble in persalts of iron; in the persul- phate an equivalent of cadmium is dissolved for the equivalent of persulphate of iron ; but in perchloride of iron 2 equivalents of cadmium are dissolved for every equivalent of perchloride of iron forming as in the case of copper a subchloride which was not precipitated by the addition of water.Lead is also dissolved in persalts of iron reducing a portion of the iron to the state of a proto salt; the lead becomes co- vered with a thin crust of sulphate or chloride which seems to protect it from further action; when the iron solution is boiled with the lead much more is dissolved and a precipitate of peroxide of iron collects at the bottoni. This action of iron on lead may account for the rapid destruction of leaden tanks noticed by Mr. West at the last Meeting of the British As- sociation that when spring water which had been running c 2 Mr. J. Napier on ihe Solubility of the Netats. 20 into a lead tank for many years without the slightest action upon the lead was conveyed through iron pipes to the tanks the tanks were destroyed in six years.Aiztirnony is not very soluble in persulphate of iron even when heated but it is very soluble in perchloride of iron when hot reducing the iron to a protochloride in a short time the solution becoming of a light brownish colour. I found that if kept boiling slowly for a long time the antimony loses an equivalent of metal for every equivalent of peroxide of iron giviiig us the idea of the existence of'a compound of antimony with chlorine of one to one. l'his solution was not examined further than by dilution with water which precipitated almost all the antimony as a white powder undergoing the usual changes of comnioii chloride except when the dried precipi- tate was boiled in nitric acid in which it dissolved with the evolution of nitrous gas.I Arsenic is very soluble in perchloride of iron reducing the iron to the state of' protochloride losing also with long boil- ing an equivalent of metal for every equivalent of peroxid? of iron in the solution ; but this result is not obtained without long boiling. Bismuth is very soluble in perchloride of iron slightly in persulphate ; the perchloride i s coinpletdy reduced to the state of protochloride a full equivalent of metal being dis- solved for the peroxide of iron present ; this is wholly preci- pitated by dilution. Cobalt is very soluble in perchloride of iron reducing it completely changing the solution to a pink colour ; the co- balt salt tormed crystallizes from this solution very easily.Nickel is also soluble in perchloride of iron giving a pre- cipitate of brown oxide of iron ; the solution becomes green containing protochloride of iron and nickel; a portion of the nickel is precipitated as a fine white powder by dilution. PZatinum in persulphate and perchloride of iron produced no change neither lost anything in weight. Gold boiled for a long time in perchloride of iron in two experiments lost 0.2 and 0-3 of a grain. I n both these in- stances beautiful crimson-red crystals in perfect octahedrons were obtained adhering to the metal and also to the con- taining vessel. I did not try whether they contained any gold. These results were only obtained twice in six different trials; they were procured with iron prepared at different times.Platinum was always tried at the same time with the gold and when there was no gold dissolved I never obtained any crystals. 'I need hardly mention that both zinc and iron when put 21 Mr. J. N. Furze on Fermentation. into the persalts of iron first reduce the persalt to the pro- tosalt which fully accounts for the great consumption of iron for the small quantity of copper ohtained in these waste waters of mines and not as was geiierally supposed from the exist- ence of free acid ; the copper is never all precipitated from the water so long as persalts of iron exist in the solution. The presence of persalts of iron also prevents the deposition of the copper by a galvanic current ; the proportionate quantity of persalts of iron necessary to resist completely the deposition of copper was not ascertained.In no one case did I find any double salt formed between the iron and metal dissolved in it but when the solution con- taining them was evaporated the salts of the two metals cry- stallized separately. In all cases 'where the process is conducted cold the solu- tion of the metal takes place at the bottom of the vessel and progresses upwards; this is beautifully exhibited when a tall glass is used with a solution of perchloride of iron and a slip of copper reaching to the bottom; the solution first becomes green at the lower part and this advances slowly upwards till it reaches the top but before the change of colour reaches the top the bottom has become colourless from the formation of subchloride.I may observe that the whole of these remarks are only the prominent features noted down as they occurred without any idea of bringing them before the Society in this unfinished state; but having no hope of obtaining leisure for making further investigations I have given them as they are thinking that perhaps some one having more time and ability would repeat the experiments and produce something more definite. 16 Mr. J. Napier on the Solubility of the November 20 1843.-Robert Porrett Esq. Treasurer in the Chair. The following works were presented to the Society :-‘ I Fresenius on Chemical Analysis,” translated and edited by Loyd A New Method of Alkalimetry,” by Drs. Fresenius and Will ; I‘ A Series of Chemical Tables and Labels,” by Messrs.Charles Taylor’s Calendar of the Meetings of the Scientific Bodies of Bullock Esq. from the editor. translated and edited by Loyd Bullock Esq. from the editor. Button and Warren de la Rue from the authors. London,” for 1843 and 1844 from the editor, The following papers were then read :-LXXXVIII. On the Solubility of the Metals in Persdphate HE following observations have been lying in an unfi- T nished state for some months past in hopes that time would allow me to make more investigations into some of the phaenomena developed ; but owing to urgent duties altogether apart from such investigations I have little hopes of being able to fulfil these intentions; I have therefore collected them together in hopes that it might attract the attention of some one more qualified to give them that investigation which their singularity seems to deserve.I may be allowed in the first place to relate the circum-stances which led me to the observations which follow. Hear-ing of the great quantity of water which is constantly issuing from the Pary’s Mines Anglesea impregnated with copper, and the great expense of obtaining this copper I thought it probable that it might be extracted by means of a galvanic current or what is known as the electrotype process. For the purpose of trying experiments upon this subject I was kindly favoured with a quantity of the water with the follow-ing details :-Quantity of water issuing from the mines yearly, $oO,OOO,OOO gallons; this is collected in pits into which is put old iron which precipitates the copper.The average pro-duct of copper is from 55 to 60 tons; the iron consumed in obtaining this is 600 tons. The copper found in these waters, as indicated from the precipitate obtained varies from 4 to 30 per cent. according to the wetness of the season ; the sam-ple I procured was during the dry season and consequently rich in copper; its specific gravity was 1*055 at 60’ F. The solid contents of one gallon weighed 4960 grains which gave and Perchloride of Iron. By Mr. JAMES NAPIER Metals in Persulphate and Perchloride of Irou. 17 peroxide of iron 1680 grains oxide of copper 80 grains sul-phuric acid 3040 grains muriatic acid 38 grains and 122 grains of earthy matters which were not examined. The iron existed in the water as the persulphate.My first operation was one I had found to answer in analysing copper ores, namely wrapping a strip of brown paper round a piece of iron attaching this to a piece of copper and immersing them both in the solution of the copper ore in muriatic acid to be examined ; but I found that the first action which took place was the complete reduction of' the persalt of iron to the state of protosalt at the expense of the copper pole after which the electric current began to effect its object the copper being cleposited but from the copper which had been dissolved haying also to be deposited the consumption of iron was 658 grains while the actual increase in the weight of the copper pole was only 64 grains the quantity of copper originally held in solution.The reaction which took place may be expressed as follows :-oxygen . - acid acid acid sulphuric acid. Copper pole. copper protosulphate of iron. 582.7 171-5 sulphate of copper. giving 690.7' grs. + 64 grs. to be ;lepositrd by the electric cur-rent. Different arrangements of batteries were tried; platinum, silver and lead were also substituted for the copper but in no case was a deposit obtained from the water until the iron was first brought into the state of a protosalt; but when this was effected I obtained by the method first described 6 3 grains of copper by the loss of 58 grains of iron. Uuring these experiments I found that silver tin lead an-timony bismuth cobalt nickel and several other metals were very soluble in neutral persalts of iron reducing it to the state of a protosalt.In order to repeat these experiments I prepared sonie perchloride of' iron in the following manner, adding to the boiling solution of the sulphate as much nitric acid as was necessary to peroxidize tile iron then precipitating by ammonia washing this well with hot water aiid dissolving with hydrochloric acicl evaporating nearly to dryness a i d adding a quantity of distilled water. 'The persulphate used was obtained as a dry white powder; both salts were neutral. I was aware that Professor Fuchs had recommended the Chem. Sue. filein. VOL. 11. 18 Mr. J. Napier on the Solubility of the boiling of n piece of clean copper in perchloride of iron as a means of ascertaining the quantity of iron in an ore of that metal and also to ascertain the amount of copper in certain copper ores.For iron ores I have fi)und great difficulty in obtaining uniform results from the great difficulty of knowing the exact period at which the iron is all reduced to the proto state for the copper put in continues to dissolve until the chloride is all converted into a subchloride; this result is effected however much more rapidly when the iron salt is neutral than when it contains free acid a condition specially recommended by Fuchs. The most uniform results are obtained by allowing the copper to remain until the solution hecomes colourless ; on diliiting with cold water the whole of the copper is precipi-tated as a white powder ; the clear solution if the process is completed will contain no copper when there will be two equivalents of copper dissolved from the metal for every equi-valent of peroxide of iron formerly in the solution.I t occa-sionally happens however when neutral salts of iron are used, that the copper becomes encrusted with a white deposit upon which crystals of the subchloride of copper collect and thus protect it from further action; this is prevented by boiling, or taking out the copper removing the crust washing it and putting it into the solution again when the action goes on as before. When the persulphate of iron is used for this pur-pose instead of perchloride no subsalt is formed and the re-sult is uniform one equivalent of copper being dissolved for every equivalent of peroxide of iron present in the solution.I iiiay mention one especial application of the solubility of copper in perchloride of iron namely the dissolving copper from the surface of silver such as copper that has been used as c? mould in which silver has been deposited; when this so-lution becomes saturated with copper a little ammonia added precipitates the iron as a peroxide and combines with the copper forming a soluble double chloride which may be im-mediately separated by filtration and the precipitate washed, the peroxide of iron again dissolved in hydrochloric acid is fitted for a renewal of the same operation. I may here men-tion that ic previous to adding theammonia there be a little perchloride of iron put into the mixture of subchloride of cop-per and protochloride of iron a n immediate change is effected, the colour of the solution becomes green and on adding am-monia to this both copper and iron are precipitated.Persulphate of iron cannot be used for the purpose of dis-solving copper from silver both from the easy solubility of silver in solutions of this salt and also from a peculiar de Metals i7i Persulphate and Perchloride of Iron. 19 structive action which it has upon alloyed silver. Standard silver is completely destroyed. I have used thin sheets, weighing from 60 to 70 grains and when only 4 grains were apparently dissolved the remainder had been so much affected that it crumbled between the fingers like a dried leaf. When silver is put into a solution of persulphate of iron an immediate action takes place a yellowish cloud begins to form in the solution; if heated the action is much more rapid a yellow oxide of iron forming upon the sides of the vessel and there is also a brown precipitate deposited; the iron in the solution is converted into the proto state shining particles of metallic silver float through the solution and sulphate of sil-ver crystallizes 011 the vessel but in no case did l find an equivalent of silver for the equivalent of peroxide of iron ; by slow evaporation the solution yielded crystals of protosulphate of iron and sulphate of silver.Tin is very easily dissolved in both the persulphate and per-chloride of iron completely reducing them to the proto state. When the solution is cold this is effected in about an hour; when hot in a few minutes; the iron is reduced to the proto state when only half an equivalent of tin is dissolved for every equivalent of peroxide; my first impression was that the first atoms of protosalt of tin formed reduced a corresponding atom of peroxide of iron and was converted into a persalt; but sa-turating with ammonia and adding it in great excess the pre-cipitated oxide of tin was not redissolved and had every other character of a protosdt.Whether this was owing to the for-mation of a bisulphate or bichloride oytin I did not ascertain; but by boiling or long standing there is an equivalent of tin dissolved for every atom of perchloride of iron but I did not obtain the same result in the persulphate. Cadmium is very soluble in persalts of iron; in the persul-phate an equivalent of cadmium is dissolved for the equivalent of persulphate of iron ; but in perchloride of iron 2 equivalents of cadmium are dissolved for every equivalent of perchloride of iron forming as in the case of copper a subchloride which was not precipitated by the addition of water.Lead is also dissolved in persalts of iron reducing a portion of the iron to the state of a proto salt; the lead becomes co-vered with a thin crust of sulphate or chloride which seems to protect it from further action; when the iron solution is boiled with the lead much more is dissolved and a precipitate of peroxide of iron collects at the bottoni. This action of iron on lead may account for the rapid destruction of leaden tanks, noticed by Mr. West at the last Meeting of the British As-sociation that when spring water which had been running c 20 Mr.J. Napier on ihe Solubility of the Netats. into a lead tank for many years without the slightest action upon the lead was conveyed through iron pipes to the tanks, the tanks were destroyed in six years. Aiztirnony is not very soluble in persulphate of iron even when heated but it is very soluble in perchloride of iron when hot reducing the iron to a protochloride in a short time the solution becoming of a light brownish colour. I found that if kept boiling slowly for a long time the antimony loses an equivalent of metal for every equivalent of peroxide of iron, giviiig us the idea of the existence of'a compound of antimony with chlorine of one to one. l'his solution was not examined further than by dilution with water which precipitated almost all the antimony as a white powder undergoing the usual changes of comnioii chloride except when the dried precipi-tate was boiled in nitric acid in which it dissolved with the evolution of nitrous gas.I Arsenic is very soluble in perchloride of iron reducing the iron to the state of' protochloride losing also with long boil-ing an equivalent of metal for every equivalent of peroxid? of iron in the solution ; but this result is not obtained without long boiling. Bismuth is very soluble in perchloride of iron slightly in persulphate ; the perchloride i s coinpletdy reduced to the state of protochloride a full equivalent of metal being dis-solved for the peroxide of iron present ; this is wholly preci-pitated by dilution.Cobalt is very soluble in perchloride of iron reducing it completely changing the solution to a pink colour ; the co-balt salt tormed crystallizes from this solution very easily. Nickel is also soluble in perchloride of iron giving a pre-cipitate of brown oxide of iron ; the solution becomes green, containing protochloride of iron and nickel; a portion of the nickel is precipitated as a fine white powder by dilution. PZatinum in persulphate and perchloride of iron produced no change neither lost anything in weight. Gold boiled for a long time in perchloride of iron in two experiments lost 0.2 and 0-3 of a grain. I n both these in-stances beautiful crimson-red crystals in perfect octahedrons, were obtained adhering to the metal and also to the con-taining vessel.I did not try whether they contained any gold. These results were only obtained twice in six different trials; they were procured with iron prepared at different times. Platinum was always tried at the same time with the gold and when there was no gold dissolved I never obtained any crystals. 'I need hardly mention that both zinc and iron when pu Mr. J. N. Furze on Fermentation. 21 into the persalts of iron first reduce the persalt to the pro-tosalt which fully accounts for the great consumption of iron for the small quantity of copper ohtained in these waste waters of mines and not as was geiierally supposed from the exist-ence of free acid ; the copper is never all precipitated from the water so long as persalts of iron exist in the solution.The presence of persalts of iron also prevents the deposition of the copper by a galvanic current ; the proportionate quantity of persalts of iron necessary to resist completely the deposition of copper was not ascertained. In no one case did I find any double salt formed between the iron and metal dissolved in it but when the solution con-taining them was evaporated the salts of the two metals cry-stallized separately. In all cases 'where the process is conducted cold the solu-tion of the metal takes place at the bottom of the vessel and progresses upwards; this is beautifully exhibited when a tall glass is used with a solution of perchloride of iron and a slip of copper reaching to the bottom; the solution first becomes green at the lower part and this advances slowly upwards till it reaches the top but before the change of colour reaches the top the bottom has become colourless from the formation of subchloride. I may observe that the whole of these remarks are only the prominent features noted down as they occurred without any idea of bringing them before the Society in this unfinished state; but having no hope of obtaining leisure for making further investigations I have given them as they are thinking that perhaps some one having more time and ability would repeat the experiments and produce something more definite

ISSN:0269-3127    

DOI:10.1039/MP8430200016

出版商:RSC    

年代:1843

数据来源: RSC

摘要:

21 Mr. J. N. Furze on Fermentation. LXXXIX. Observations on Fermentation. 1 N consequence of the practical inconveniences arising to brewers from want of control over the fermenting tuns By JOHN N. FURZE ESP. and the changes in the worts dependent upon atmospheric temperature I was led to the following experimental obser- va tions. The infusion of malt being made according to the usual practice of brewing the wort or infusion is boiled with the hops and being subsequently cooled yeast to the amount of about one pouiid by weight to the barrel of wort is added and the whole transferred to the fermenting tan The general form of a lwewer’s fermenting tun being that ofa simple open vessel 22 Mr. J. N. Furze 011 Fermentation. the worts lie exposed during their change of state without covering and with free access of air.This as is evident must expose the fermenting mass to the variations of atmo- spheric temperature which in their turn either check or hasten the operation to such an extent that the ultimate suc- cess of the brewing is endangered and not unfreqnently con- siderable loss is sustained. These disadvantages are occa- sionally avoided in some of the larger breweries by the use of fermenting tuns which are so far inclosed as to leave but sufficient space for the escape of the gaseous matters arising from the surface of the worts when the fermentation is in full vigour. Having tried the above method without finding the desired advantage to resiilt from it new measures of proceeding were taken as follows:-A circular tun was erected whose total content was 350 barrels having a door in the side capable of being made air-tight by lining its edges with coarse serge and applying screw-pressure to the centre of it.To the upper part of this tun which was fitted with windows in the top and sides to afford to the brewer an opportunity of viewing the apparent changes in the worts two India-rubber pipes were attached each of I inch internal diameter to convey away the gas generated during the process; and *in order to pre- vent external interference the ends of the pipes were immersed to the depth of about 3 inches in a vessel of water. These arrangements must not be confounded with the at- tempts of some persons both in this country and in France to condense vapours which were supposed to rise in great abundance from fermenting liquids and which are well known to have disappointed the expectations of the projectors.On two occasions when the plan of condensation was tried by me there was not any product after passing the gaseous matter through a worm three quarters of an inch diameter and 35 feet in length surrounded with water at a temperature of 54’ for R period of 36 hours on each occasion. Having arranged the improved tun as before described the gas arising from six fermentations was allowed to escape through the water in the external vessel. After the gas had thus been washed it had lost much of the pungency of smell so characteristic of the usual mode of escape and in a few days the water had so far changed that it had a strong fetid odour similar to that of waste starch liquors and certainly not that of the aroma of the hop This from the great dif- ference between the water in question and that of the same bulk which had not been so treated must have resulted from the absorption of a something passing off i n mechanical sus- Mr.J. N Furze OTJ Fermentation. 23 pension with the gas. I n order to ascertain the contents of tlie water after being charged with the gas and vapour some of it was distilled immediately after the transmission of the gas and the result was that from 36 gallons of the water so em- ployed 9 pints of alcohol were obtained of specific gravity 0.850. I t appeared on further prosecuting the matter that more could have been obtained had a larger quantity of water been used and that the action of the water on the gas de- pended for its efficacy in a great degree upon the apparatus itself.In endeavouring to realize more extended results a tub was made which contained an arrangement of three tin plates perforated with holes set one inch apart f'rorn each other through which the gas passed in small bubbles by which means the.washing of the gas was rendered more ef- fectual. In this manner 3 per cent. of rough spirit was fre- quently obtained of specific gravity 0*850 by distillation from the gas produced by one fermentation. All these distilled products were impregnated with ammonia to a considerable amount which would necessarily affect these results as is shown by tlie following.experiments. 45 gallons of water having received a charge of gas from the fernientation of 350 barrels of porter wort had a specific gravity 0*9988 and the attenuation of the worts during the period was about 1-2 Ibs. per barrel as indicated by the sac- charometer of Dring and Fage. Of this quantity 36 gallons were reduced to one-sixth part by distillation of which 16 02. by measure were again carefully rectified and reduced to 4 oz. which had a specific gravity 0965 being equal to 33 per cent. of alcohol at 0+825. I t therefore follows that the 45 gallons would have yielded 15 imperial pints at 0.965 which would equal 5 pints at 0*825 or about 1.4 per cent. of alcohol by volume. ,5 oz. of the original 45 gallons were distilled with bnryta in excess to combine with any acids that might be present and the product was redistilled with hydrochloric acid ; chlo- ride of platinum and sodium was then added and the whole carefully evaporated to dryness ; the soluble parts having been removed by alcohol left 1.9 gr.of ammonio-chloride of plati- num which indicates by calculation 0- 146 grain of ammonia. I t follows therefore that 4.672 grains of ammonia were con- tained in the original bulk per gallon or 210*24 grs. on the whole volume. The residue after the distillation with barytes was exa- mined for acetic and formic acids but without success. Respecting the volume of carbonic acid eliminated during the process of fermentation I have not yet had the opportu- 24 Mr.J. N. Furze on Fermentation. nity of using an apparatus capable of measuring the amount set free fiorn so large a quantity of wort as 180 barrels. on a small brewing of ale the quantity of gas measured by a very large metre was 7900 cubic feet. The meter having been charged with great care the relative quantities were as fol- lows :-43+ barrels of ale wort attenuated 16.5 lbs. per barrel and gave off 7900 cubic fket of carbonic acid or about 1 1 cubic feet of gas for every pound of attenuation. Again 91 barrels of ale wort attenuated 15 lbs. per barrel and gave off 11,700 cubic feet of carbonic acid or about 11.66 cubic feet of gas for every pound of attenuation. I t being manifestly inconvenient to distil so weak a spirit on a large scale f'rom the necessity of apparatus and arrange- ments totally dicerent from the usual machinery of a brewery the means of preventing the saturation of the gas by the va- pour of alcohol was the next object.This is accomplished in a most simple manner. The tun being air-tight the exit- pipes for the carbonic acid were allowed to dip into a vessel of water to the depth of three feet and by the pressure of the confined gas upon the surface of the fermenting worts the power of holding the vapour of the alcohol in the carbonic acid gas is checked and a very large proportion of spirit thus retained which would otherwise have been .lost. The effect was tested as before by distillation ancl although the retention was not complete a most extraordinary reduction was made amounting in some instances to 80 per cent.of the before- stated produce. The depth of 3 feet is of course an ar- bitrary number but in practice a greater pressure is inconve- nient from the difficulty of keeping large tuns air-tight by common means. The difference of the quantity of vapour dependent upon pressure will be confirmed by the following experiments in addition to the test of distillation. 175 barrels of' porter wort were fermented in a close tun the exit-pipes of which were immersed in water to the depth of3 inches. During the process at three different periods 100 cubic inches of the gas were passed through desiccating tubes 17 inches long ancl half an inch in diameter containing chloride of calcium and on each occasion for every 100 cu- bic inches calculated as dry carbonic acid at a temperature of 5Z0 0.425 grain increase of weight was obtained due to the absorption of watery vapour.181 barrels of porter wort fermented in the same vessel; tlie pipes being immersed 3 feet gave the following result. For every 100 cubic inches calculated as dry carbonic acid at a temperature of 52O only 0.20 grain of vapour was ab- sorbed. I t would appear therefore that the vapour of water 25 @is. Mr. Denham Smith .on Ferric Acid. given OK during the process of' fermentation bears directly on the proportion of alcohol carried away with the carbonic acid If the simplicity of the arrangement is a ground for its recommendation it must be evident that the foregoing appa- ratus would claim the attention of those conversant with the present system as furnishing to the brewer a better control over his fermenting tuns and the production of a stronger beverage from his worts.I have much pleasure in acknowledging the material as- sistance afforded me by my friend Mr. Robert Warington in these investigations. Mr. J. N. Furze on Fermentation. 21 LXXXIX. Observations on Fermentation. By JOHN N. FURZE ESP. 1 N consequence of the practical inconveniences arising to brewers from want of control over the fermenting tuns, and the changes in the worts dependent upon atmospheric temperature I was led to the following experimental obser-va tions. The infusion of malt being made according to the usual practice of brewing the wort or infusion is boiled with the hops and being subsequently cooled yeast to the amount of about one pouiid by weight to the barrel of wort is added and the whole transferred to the fermenting tan The general form of a lwewer’s fermenting tun being that ofa simple open vessel 22 Mr.J. N. Furze 011 Fermentation. the worts lie exposed during their change of state without covering and with free access of air. This as is evident, must expose the fermenting mass to the variations of atmo-spheric temperature which in their turn either check or hasten the operation to such an extent that the ultimate suc-cess of the brewing is endangered and not unfreqnently con-siderable loss is sustained. These disadvantages are occa-sionally avoided in some of the larger breweries by the use of fermenting tuns which are so far inclosed as to leave but sufficient space for the escape of the gaseous matters arising from the surface of the worts when the fermentation is in full vigour.Having tried the above method without finding the desired advantage to resiilt from it new measures of proceeding were taken as follows:-A circular tun was erected whose total content was 350 barrels having a door in the side capable of being made air-tight by lining its edges with coarse serge and applying screw-pressure to the centre of it. To the upper part of this tun which was fitted with windows in the top and sides to afford to the brewer an opportunity of viewing the apparent changes in the worts two India-rubber pipes were attached each of I inch internal diameter to convey away the gas generated during the process; and *in order to pre-vent external interference the ends of the pipes were immersed to the depth of about 3 inches in a vessel of water.These arrangements must not be confounded with the at-tempts of some persons both in this country and in France, to condense vapours which were supposed to rise in great abundance from fermenting liquids and which are well known to have disappointed the expectations of the projectors. On two occasions when the plan of condensation was tried by me there was not any product after passing the gaseous matter through a worm three quarters of an inch diameter and 35 feet in length surrounded with water at a temperature of 54’ for R period of 36 hours on each occasion.Having arranged the improved tun as before described the gas arising from six fermentations was allowed to escape through the water in the external vessel. After the gas had thus been washed it had lost much of the pungency of smell so characteristic of the usual mode of escape and in a few days the water had so far changed that it had a strong fetid odour similar to that of waste starch liquors and certainly not that of the aroma of the hop This from the great dif-ference between the water in question and that of the same bulk which had not been so treated must have resulted from the absorption of a something passing off i n mechanical sus Mr. J. N Furze OTJ Fermentation. 23 pension with the gas. I n order to ascertain the contents of tlie water after being charged with the gas and vapour some of it was distilled immediately after the transmission of the gas, and the result was that from 36 gallons of the water so em-ployed 9 pints of alcohol were obtained of specific gravity 0.850.I t appeared on further prosecuting the matter that more could have been obtained had a larger quantity of water been used and that the action of the water on the gas de-pended for its efficacy in a great degree upon the apparatus itself. In endeavouring to realize more extended results a tub was made which contained an arrangement of three tin plates perforated with holes set one inch apart f'rorn each other through which the gas passed in small bubbles by which means the.washing of the gas was rendered more ef-fectual.In this manner 3 per cent. of rough spirit was fre-quently obtained of specific gravity 0*850 by distillation from the gas produced by one fermentation. All these distilled products were impregnated with ammonia to a considerable amount which would necessarily affect these results as is shown by tlie following. experiments. 45 gallons of water having received a charge of gas from the fernientation of 350 barrels of porter wort had a specific gravity 0*9988 and the attenuation of the worts during the period was about 1-2 Ibs. per barrel as indicated by the sac-charometer of Dring and Fage. Of this quantity 36 gallons were reduced to one-sixth part by distillation of which 16 02. by measure were again carefully rectified and reduced to 4 oz., which had a specific gravity 0965 being equal to 33 per cent.of alcohol at 0+825. I t therefore follows that the 45 gallons would have yielded 15 imperial pints at 0.965 which would equal 5 pints at 0*825 or about 1.4 per cent. of alcohol by volume. ,5 oz. of the original 45 gallons were distilled with bnryta in excess to combine with any acids that might be present, and the product was redistilled with hydrochloric acid ; chlo-ride of platinum and sodium was then added and the whole carefully evaporated to dryness ; the soluble parts having been removed by alcohol left 1.9 gr. of ammonio-chloride of plati-num which indicates by calculation 0- 146 grain of ammonia. I t follows therefore that 4.672 grains of ammonia were con-tained in the original bulk per gallon or 210*24 grs.on the whole volume. The residue after the distillation with barytes was exa-mined for acetic and formic acids but without success. Respecting the volume of carbonic acid eliminated during the process of fermentation I have not yet had the opportu 24 Mr. J. N. Furze on Fermentation. nity of using an apparatus capable of measuring the amount set free fiorn so large a quantity of wort as 180 barrels. on a small brewing of ale the quantity of gas measured by a very large metre was 7900 cubic feet. The meter having been charged with great care the relative quantities were as fol-lows :-43+ barrels of ale wort attenuated 16.5 lbs. per barrel, and gave off 7900 cubic fket of carbonic acid or about 1 1 cubic feet of gas for every pound of attenuation.Again 91 barrels of ale wort attenuated 15 lbs. per barrel and gave off 11,700 cubic feet of carbonic acid or about 11.66 cubic feet of gas for every pound of attenuation. I t being manifestly inconvenient to distil so weak a spirit on a large scale f'rom the necessity of apparatus and arrange-ments totally dicerent from the usual machinery of a brewery, the means of preventing the saturation of the gas by the va-pour of alcohol was the next object. This is accomplished in a most simple manner. The tun being air-tight the exit-pipes for the carbonic acid were allowed to dip into a vessel of water to the depth of three feet and by the pressure of the confined gas upon the surface of the fermenting worts the power of holding the vapour of the alcohol in the carbonic acid gas is checked and a very large proportion of spirit thus retained which would otherwise have been .lost.The effect was tested as before by distillation ancl although the retention was not complete a most extraordinary reduction was made, amounting in some instances to 80 per cent. of the before-stated produce. The depth of 3 feet is of course an ar-bitrary number but in practice a greater pressure is inconve-nient from the difficulty of keeping large tuns air-tight by common means. The difference of the quantity of vapour dependent upon pressure will be confirmed by the following experiments in addition to the test of distillation. 175 barrels of' porter wort were fermented in a close tun, the exit-pipes of which were immersed in water to the depth of3 inches.During the process at three different periods, 100 cubic inches of the gas were passed through desiccating tubes 17 inches long ancl half an inch in diameter containing chloride of calcium and on each occasion for every 100 cu-bic inches calculated as dry carbonic acid at a temperature of 5Z0 0.425 grain increase of weight was obtained due to the absorption of watery vapour. 181 barrels of porter wort fermented in the same vessel; tlie pipes being immersed 3 feet gave the following result. For every 100 cubic inches calculated as dry carbonic acid at a temperature of 52O only 0.20 grain of vapour was ab-sorbed. I t would appear therefore that the vapour of wate Mr. Denham Smith .on Ferric Acid. 25 given OK during the process of' fermentation bears directly on the proportion of alcohol carried away with the carbonic acid @is. If the simplicity of the arrangement is a ground for its recommendation it must be evident that the foregoing appa-ratus would claim the attention of those conversant with the present system as furnishing to the brewer a better control over his fermenting tuns and the production of a stronger beverage from his worts. I have much pleasure in acknowledging the material as-sistance afforded me by my friend Mr. Robert Warington in these investigations

ISSN:0269-3127    

DOI:10.1039/MP8430200021

出版商:RSC    

年代:1843

数据来源: RSC

摘要:

1Mr. Denham Smith on Ferric Acid. The following communications were then read :- .By J. DENHAM SMITH Esq. XC. Note on a paper on Ferric Acid read May 16 1843. 25 Decembe~-4 1843.-The President in the Chair. The following presents were announced since the last meeting :- ‘‘ The Pharmaceutical Journal,” edited by Jacob Bell from the editor. A Specimen of Bitartrate of Potash in Fine Crystals from J. Denham Smith Esq. Mr. Trenham Reekes was elected an Associate Member. T H E paper above referred to which I had the honour of laying before the Society last session* was unfortunately printed before I had proved that two material errors were contained in it. These errors arose partly from the almost invariable presence of manganese in the oxide of iron preci- pitated from the sulphate which I employed,-an hipurity I neither suspected nor guarded against and which usually oc- curs in such minute quantities as to render its detection im- practicable by the ordinary tests ; and partly from the solubi- lity of sesquioxide of iron in potash under certain conditions - a fact noticed by M.Chodnew I-. The first error occurs in pp. 242-3 where it is stated that chlorine gas passed into 6‘ the deep amethystine solution of ferrate of potash keeping the vessel cod during the passage of the gas gives a solution of a lighter colour than the amethystine liquid.” This solu- tion proved to be a very dilute solution of permanganate of potash. I do not however find the intensity of colour altered by the gas and from the permanent nature of this solution I hope eventually to succeed in isolating the potash salt.The second is the more serious error (p. 247) where I an- * See Memoirs vol. i. p. 240. t. Journ. fur Prakt. Chemie Band axviii. D Chem. Soc. Mem. VOL. 11. 26 Dr. Leeson oft fhc Circular Polarization of Light nounced the existence of an oxide of iron forming a green salt with potash; such a salt I now believe does not exist. I pre- pared a quantity of this green solution by boiling ferrate of potash and rapidly filtering the clear green solution; this gradually decomposed and the brown deposit was dissolved in hydrochloric acid affording a yellow solution to which a solutioii of hydrochlorate of ammonia was added and then caustic ammonia ; a small quantity of a reddish-brown floccu- lent precipitate resembling sesquioxide of iron fell ; this col- lected washed and redissolved in hydrochloric acid gave a yellow solution styptic to the taste which diluted and ren- dered as neutral as possible immediately struck the respective colours blue and blood-red with ferrocyanate and sulpho- cyanate of potash evidencing the presence of iron ; the am- moniacal solution was evaporated to expel excess of ammonia and tested with ferrocyanate of potash when the voluminous flesh-coloured precipitate characteristic of manganese was produced potash added to another portion of this ammo- niacal solution gave on the application of heat a small quan- tity of the dark brown oxide of manganese.Having in the paper referred to satisfied plyself that iron did form a salt with potash and also that the green salt con- tained this metal I was too hastily induced to imagine that the colours of the two solutions alluded to arose from iron ses not uioxide of iron.existence to t x anticipating e sesqui and the teroxide Whether and of an manganese possessing oxide of the in iron the qualities intermediate precipitated of an acid really exists I am at present unable to state but hope to be able to decide this point as well as to communicate some new facts respecting ferric acid and its combinations in a fu- ture paper. 1Mr. Denham Smith on Ferric Acid. 25 Decembe~-4 1843.-The President in the Chair.The following presents were announced since the last meeting :-‘‘ The Pharmaceutical Journal,” edited by Jacob Bell from the A Specimen of Bitartrate of Potash in Fine Crystals from J. Mr. Trenham Reekes was elected an Associate Member. The following communications were then read :-XC. Note on a paper on Ferric Acid read May 16 1843. .By J. DENHAM SMITH Esq. T H E paper above referred to which I had the honour of laying before the Society last session* was unfortunately printed before I had proved that two material errors were contained in it. These errors arose partly from the almost invariable presence of manganese in the oxide of iron preci-pitated from the sulphate which I employed,-an hipurity I neither suspected nor guarded against and which usually oc-curs in such minute quantities as to render its detection im-practicable by the ordinary tests ; and partly from the solubi-lity of sesquioxide of iron in potash under certain conditions, - a fact noticed by M.Chodnew I-. The first error occurs in pp. 242-3 where it is stated that chlorine gas passed into 6‘ the deep amethystine solution of ferrate of potash keeping the vessel cod during the passage of the gas gives a solution of a lighter colour than the amethystine liquid.” This solu-tion proved to be a very dilute solution of permanganate of potash. I do not however find the intensity of colour altered by the gas and from the permanent nature of this solution I hope eventually to succeed in isolating the potash salt. The second is the more serious error (p.247) where I an-editor. Denham Smith Esq. * See Memoirs vol. i. p. 240. t. Journ. fur Prakt. Chemie Band axviii. Chem. Soc. Mem. VOL. 11. 26 Dr. Leeson oft fhc Circular Polarization of Light nounced the existence of an oxide of iron forming a green salt with potash; such a salt I now believe does not exist. I pre-pared a quantity of this green solution by boiling ferrate of potash and rapidly filtering the clear green solution; this gradually decomposed and the brown deposit was dissolved in hydrochloric acid affording a yellow solution to which a solutioii of hydrochlorate of ammonia was added and then caustic ammonia ; a small quantity of a reddish-brown floccu-lent precipitate resembling sesquioxide of iron fell ; this col-lected washed and redissolved in hydrochloric acid gave a yellow solution styptic to the taste which diluted and ren-dered as neutral as possible immediately struck the respective colours blue and blood-red with ferrocyanate and sulpho-cyanate of potash evidencing the presence of iron ; the am-moniacal solution was evaporated to expel excess of ammonia, and tested with ferrocyanate of potash when the voluminous flesh-coloured precipitate characteristic of manganese was produced potash added to another portion of this ammo-niacal solution gave on the application of heat a small quan-tity of the dark brown oxide of manganese.Having in the paper referred to satisfied plyself that iron did form a salt with potash and also that the green salt con-tained this metal I was too hastily induced to imagine that the colours of the two solutions alluded to arose from iron, not anticipating the existence of manganese in the precipitated ses uioxide of iron. Whether an oxide of iron intermediate acid really exists I am at present unable to state but hope to be able to decide this point as well as to communicate some new facts respecting ferric acid and its combinations in a fu-ture paper. to t x e sesqui and teroxide and possessing the qualities of a

ISSN:0269-3127    

DOI:10.1039/MP8430200025

出版商:RSC    

年代:1843

数据来源: RSC

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26 Dr. Leeson oft ihc Circular Polarization of Light XCI. Observatiom on the Circutar Polarization of Light 133 transmission through Fhids. By H. B. LEESON M.D. A.M. is with considerable diffidence and not without some re- ITgret that 1 present the followitig observations on the cir- cular polarization of light by transmission through fluids. It is with diffidence because the conclusions which are the result of my own experiments differ from those of others de- servedly considered able and acute observers. It is with re- gret because the tendency of the facts which 1 expect to estttblish before you is to lessen in some degree the value of an otherwise beautiful application of optical science to the exigencies of chemical investigation. b~ transmission through Fluids.27 It is equally important to detect that which is erroneous as it is to establish that which is true in science. Truth being my only aim I trust that whilst endeavouring to remove the veil of mystery and obscurity which has hitherto perplexed and thwarted many who in comnion with myself have assayed to follow out the experiments detailed by Biot and others I may not be considered anxious to throw discredit on their la- bours; but candidly detailing the result of my own experi- ments I can only say to them as well as to others :‘Si quid novisti rectius ids candidus itnperti; si non his cltere mecum.” The point in which the results of my own experiments disagree with those of other observers is in regard to the al- leged possession of opposite rotations by certain fluids which have the property of deviating the plane of polarization of a beam of polarized light transmitted through them some of those fluids being said to produce a right-handed rotation others B left-handed ‘rotation.On examining a great variety of samples of the particular fluids said to possess opposite rotations I found that such fluids deviated the plane of pola- rization in only one direction namely towards the right- hand. The only fluids in which I have hitherto been able to discover a decided Zeff-handed rotation is in the essential oil of lavender arid in that of cubebss. The interesting fact if true that solutions of sugar when obtained from different sources and in different conditions possess in same cases a right-handed and in others a left-handed rotation has not bee11 corroborated by my own observations.When such so- lutions did exhibit any decided rotating influence it was uni- formly right-handed. It is however curious that solutions of cane-sugar differ from those of grape potato and diabetic sugar in this respect; that whilst the former possessed a powerful rotating influence the latter exhibited little or no rotating energy although their solutions were in some cases sufficiently concentrated to furnish crystals after a f’ew days’ repose. It might perhaps be supposed that such result proceeded only from niy own want of information on the subject .or n deficiency of my powers of observation; indeed I long so considered it myself so much so that not satisfied with obser- * The amount of left-handed rotation in oil of ciibebs is much greater than that of oil of lavender.This oil which was colourless and some others contained in the table accompanying this copimunication have been exa- mined since my paper was read the samples having been kindly furnished by Mr. Wwington of Apothecaries’ Hall. Samples of oil of cubebs obtained elsewhere were coloured and possessed much less rotating energy being probably adulterated with oil of peppermint. D 2 Dr. Leeson on the Circttlar Polarization of LighL 28 vations made with apparatus procured in this country I com- missioned a friend to procure for me from Mons. Soleil of Paris an apparatus made according to Biot's own directions.Experinients made with that instrument confirmed the conclu- sioris I before arrived at and I may add that an examination of the apparatus itself has in some degree suggested the pos- sible sources of' error. I do not of course positively assert that the observations of others have been erroneous although strongly inclined to sus- pect they may have been misled. Nothing but an examination of the same sample could indeed establish such conclusion. I have never however been so fortunate as to obtain a solution of sugar possessing a decided left-handed rotation ; and although it is certainly possible that the oil of lemons or oil of turpentine which I have examined may differ from that ex- perimented on by others still I have tried so many samples warrarited genuine and procured from so many different sources that I can scarcely imagine it possible to procure samples possessed of opposite rotating powers; I may also reniark that although I have observed variations as respected the amount I have never noticed any variation as respected the direction of rotation in any of the samples of the same description of fluid.Misunderstanding may perhaps result from the converse use ofthe terms right- and Zecft-handed rotation by cliffitrent writers but this cannot affect the essential fact if true that oil of lemons for instance has an opposite rotation to that possessed by oil of turpentine or the still more interesting fact alleged unfortunately I fear incorrectly that a solution of sugar as existent in the juice of grapes rotates the plane of polarization in an opposite direction to that in which it is rotated by a so- lution of sugar obtained from the cane The direction to which in common with other writers the term right- handed is subsequently applied cannot be mistaken by those who attend to the instructions hereafter given and I would recommend every one previously to experimenting on ff uid substances to study the opposite appearances presented on analysing polarized light when transmitted through speci- mens of right- and left-handed quartz as usually sold for il- lustrating circular polarization and as exhibited in Plates III.IV. V. and VI. With a view to the more explicit understanding of the mode in which the experiments referred to have been conducted and to assist those not coiiversant with the subject in repeat- ing them for thernselves I shall very briefly explain what is meant by the deviation or rotation of the rays of polarized 29 by transmission through FZuids.light when transmitted through fluids said to possess circular polarization. Assuming the general principles of the undulatory theory of light and making use of terms which if not absolutely cor- rect are at least convenient I shall first advert to what is meant by rectilinerrr or as I would suggest it should be teymed rectangular polariz a t' ion. When a beam of oi-diiiary light impinges on a polarizing medium it map be considered as dividing itself into two por- tions the waves of which respectively undulate in directions varying from each other YO' i.e. a right angle in other words they are said to possess opposite planes of undulation and to be rectangularly palarizetl*. This effect may be produced by five different iiiodes viz. refraction reflexion absorption dispersion and double refraction. A number of pieces of thin glass -f superimposed on each other and inclined at a suitable angle to ii ray of light inci- dent thereon polarizes one portion of the light transmitted through it by refraction whilst the other portion reflected from the surf'ace is also polarized but in an opposite direc- tion. That the two portions into which the light is thus di- vided are oppositely polarized or may be supposed to undulate in opposite directions is estaltlished by the fact that if trans- mitted towards a similar bundle of glass the two rajs would comport themselves differently ; that is they would not both be reflected or both traiisniitted by such second bundle if held in the same direction or plane towartls each respectively.Callirig the one portion of polarized light into which the ori- ginal beam of' orcliunry light R (figs. 1 and I p. 30) is divided 0 and the other portion X it will be fuund that the position of the second bundle necessary to reflect X M ~ S L be at right angles to that in which it would reflect 0 and similarly as to refraction or transmission. This second bundle serving to distinguish the two rays is termed the andyser. Figs. 1 and 2 serve to illustrate polarization by refraction and re- flexion.In fig. 1 the bundles of glass are supposed to be all in the same plane or situated parallel to each other whilst in fig 2 the bundles €3 and C are supposed to be situated at right angles to the buiidle A. The beam of light R impinging on the-bundle A is divided into two portions 0 arid X ; and * Consideratinn of the direction in which the waves of light may be supposed to undulate will materiiiily assist the memory in studling the ta- cility of reflexion or transmission of' the respective rags by siirhces opposed to them in different positions. t The very thin glass sold for covering nticrosropic objects is extremely convenient for this purpose. 80 Dr. Leeson on the Circular Polarization of Light it will be observed that 0 proceeding in its original course is transmitted or passes through the second bundle B fig.1 whilst X is reflected from and does not pass through the bundle C. The converse takes place in fig. 2. Hence it will be observed that in fig. 1 the portion 0 is capable of Fig. 1. 0 0 X X transmission but not of reflexion whilst the portion X is ca- pable of reflexion only. I n fig. 2 where the bundles B and C me supposed to be placed at right angles to the bundle A the portion 0 is capable of reflexion only and X of trans- mission. In these figures A forms what is termed the PO- larizer whilst €3 C and D are what are termed analysers serving to test the condition of 0 and X. A tourmaline effects a similar division of a beam of light impinging on it into two portions oppositely polarized trans- mitting one say 0 in one position whilst X is absorbed re- volving the tourmaline goo X will be transmitted and 0 ab- sorbed.FOP experiments on circular polarization as well as for microscopic purposes the green tourmalines may be re- commended as they can be more easily obtained free from flaws. When of a proper thickness and ground truly parallel they form excellent analysers to apply to the eye-pieces of 31 by transmission through Fluids. microscopes ; for experirnen ts on circular polarization they form very useful polarizers. The blue yellow and hair- brown tourmalines are perhaps superior when free from flaws but cannot be so readily obtained perfect. Agates polarize by dispersion but are not suitable for ex- periments on other substances.Iceland spar and quartz polarize light by double refraction. The beam of light transmitted through them is divided into two portions 0 and X polarized in opposite planes but pro- ceeding in paths so closely posited that they may both be the subject of observation at the same time. This is not the case however in what are termed Nicholl’s prisms which are pur- posely so constructed as to allow only one portion to be trans- mitted when held in one direction whilst the other is trans- mitted when the prism is revolved a right nngle. The rhombs of Iceland spar are usually rendered achromatic by cenientirig a piece of glass properly adjusted to them. In order to render quartz available a particular construction is necessary but when well made double refracting analysers of quartz are equally useful for these experiments.It does not matter by what means our polarized beam is first obtained or in what manner the same is analysed or whether one mode be used to polarize the light and another to examine or analyse the same. In all cases the result will be dependent on the relative positions of the polarizer and snalyser and if these are placed in such a direction to each other as that X is not transmitted to the observer’s eye and therefore dark then 0 will be transmitted; but if either the analyser or polnrizer is changed to a position exactly at right angles to its former direction then 0 will be obscured whilst X becomes light.When one portion has obtained its greatest obscuration or is invisible the other will have obtained its condition to the other at the intermediate positions * as re- maximiim of illutnination whilst they pass gradually from one presented in Plates I. and 11. * A most convenient mode of obtaining polarized light which occurred t o me about two years ago and which I have since shown to several friends consists in placing an ordinary looking-glass on the outside of a common window the bottom of the mirror being placed close to the lower portion of one of the panes of glass whilst the top is inclined from the window tc- wards the sky SO as to reflect the paiie of glass into a horizontal position. Standing then within the apartment and looking tbrougli a toiirmaline or other analysing medium at the light of t h e sky reflected from the mirror through the pane of glass it will be found intensely polarized,and on intro- ducing any substatice such for instance as a fluid contained in a glass tube or a crystal &c.between the analyser and the poiarizer it may be readily examined. The great advantage of this mode of obtaining polar- ized light consists not only in the perfection of the polarization but also 38 Dr.. Leeson on t h Cz'rcula?* Polarization of Light On using as an analyser a rhomb of Iceland spar or a prism of quartz constructed as before alluded to the oppositely polarized beams oflight 0 and X may be observed together and they will become alternately light and dark as the analyser i s revolved according to the law already laid down.This may be understood by revolving the outer circle of Plate IT. whilst the lower moveable circle* remains stationary. The ordinary ray being represented by 0 and what is termed the extra- ordinary ray by X the rhomb or prism should be so ar- ranged or posited in its setting as that 0 be central and therefore apparently stationary whilst X revolves around Of- as the analyser is itself rotated as represented in the dif- ferent Plates exhibiting the successive changes in the appear- ance of a polarized ray of light transmitted through a small circular aperture and andysed by double refrwtion. This may be also understood by revolving the outer circle of Plate II. as before stated by which it will be seen that each por- tion 0 and X returns to its original condition after a revo- lution of half a circle or 180° and that it passes from the state of greatest obscuration to that of maximum illumina- tion on a rotation of goo or quarter of a revolution.I n all these cases then of what is termed rectangular po- i n the extent ofthe field of view which is a great advantage in examining large specimens such as unannealed glass although not so important in circular polarization. I may here observe that the sky at all times furnishes polarized light which is more or less intense according to the relative position of the oh- server and the siiti. This circumstance probably influences the chemicsl action of the rays of light and points out the necessity of varying the posi- tion of the camera or the period of exposure in taking Daguerreotypes and other optical investigations according to the tinie of day the state of the sky and the sun's declination.Any person may readily ascertain where the greatest inteiisit~ of polarization exists by using a tourmaline or other analvsing medium and looking through it a t a piece of selenite or a piece of'Iceland spar or other crystal cut to exhibit the cross and rings; of course the colours will be most tivid and the black cross most intense where the greatest polarizing force exists. This polarization is most intense where the sky is t)lue and unclouded. The planes of pola- rization appear to vary at a total distance of 900 or of 4.5' measured each way from t h e suli's position.* In Plates II. V. 2nd VI. the lower moveable circle is introduced as a means of imitating the supposed dcviation in the plane of polarization by moving it to the rightbhnnd or to the left i n Plate II. and by moving it t o the left in Plate V. OF to the right in Plate VI. The outer nioveable circle in ail the Plates represents the rotation of the analyser. + This is very important to prevent confusion arising from a Fevolution ofthe two images aroiintl each other whereby the one map be mistaken for the ather. I n Plates II. V. and VI. it is manifest that the exact cen- trality of the ordinary ray could not be preserved as i n using the appa- matiis. itself. 33 0' X by transmission through Fluids. larization the maximuni of illurninntion takes place when the analyser is placed with its plane of polarization corresponding to that of the rag to be transmitted whilst such ray attains its greatest obscuration when the analyser is placed at right tirigles to such plane.Now this condition is altered when a medium of a certain thickness s possessing what is termed circular polarization is introduced between the polarizer and analyser; for if the polarizer and analyser be placed so that one ray X is at its greatest obscuration or invisible and the other 0 at its maximum of illumination as represented at in Plate I. and as also shown when the indexes of the moveable circles in Plate 11. are both pointed to O' then on introducing a circularly polarizing medium between the an;ilyser and polarizer the plane of polarization will be re- moved to the right-hand or to the left which may be imitated by moving the index of the inner circle (Plate 11.) in either of those directions whilst the outer circle continues sta- tionary and it will be observed that in consequence of such change in the plane of polarization X will become lighter and 0 darker and that the outer circle which may be sup- posed to represent the analyser must be revolved an equal number of degrees in the same direction as the inner circle in order to restore X and 0 to their primary condition.When the rotation of the analyser proceeds in the direction of the T J U ~ - bers in the outer circle of graduation the rotation is terrned right-handed when in that of the inner circle left-handed.Supposing the rotation produced be 30' to the right ; place the index of the inner moveable circle at 30' on the outer circle of graduation ; then the other moveable circle or am- lyser must be also shifted 30' to tlie right-hand in order to obscure X; proceeding onwards it will be observed that X becomes bright at 120' being a further revolution of 90'; again becomes obscured at ZIO' or a revolution of ISO' and again bright at 240'. On registering? then the degrees at which 0 and X are respectively polarized that is most ob- scured we have the following table :- 0 0 1 zoo the degrees being observed on the outer or right-handed circle of graduation and corresponding to 240" * A certain thickness is here stated becanse as will be hereafter shown it is possible in every case to employ a thickness which woi~ld produce no 300' 0 X 210" X 150' 60' 0 on the inner or left-handed circle of graduation.Had we 30' X 3 30' apparent alteration. 0 X 0 240' 150' 34 Dr. Leeson ott the Circula~ Polarization of Light moved the analyser or moveable circle in a left handed direc- tion we might have registered our results as follows :- X 380' 60' by which it will be seen that it would be impossible from the appearance presented at any given position or the direction in which the analyser was revolved done considered to say whether the deviation was 30' to the right or 150° to the left; and this woiild of course be equally true of any other amount of deviation.To add to the difficulty the deviation is in direct propor- tion to the thickness and nature of the circularly polarizing medium. If you find for example a deviation of 10' pro- duced by a medium of 1 inch in depth a depth of 10 inches would produce a deviation of 100'; so that by merely vary- ing the thickness or depth of the medium you may have the p.mition of greatest obscuration situated in any part of the circle and if the thickness happened to be such as that such position coincided with 180' or o' you might suppose that the medium was not possessed of circular polarization at all; the importance therefore of examining different depths or thicknesses will be apparent; and the depth of each medium which produces a deviation of 1809 furnishes a very useful index of their comparative circularly polarizing energy.If the depth be constant,and two circularly polarizing liquids be mixed together or if the fluid or substance be dissolved or mixed in some other fluid possessing no rotating energy the deviation will bear a direct relation to the proportion in which the two are combined. For instance since according to my own experiments 10 inches of a solution of cane-sugar in water containing half its weight of solid sugar produces a de- viation of 1049 on mixing such solution with an equal bulk of water 10 inches of such diluted solution would produce a rotation of only half that amount or SZ' which coincides with experiment ; having therefore once obtained the rotating power of a soliltion of given strength we may according to Biot calculate thence the strength of any other solution when examined in a similar manner; attention however must be paid to the effects of temperature any condensation which may take place on mixture specific gravity &c.; and I have not found the result of experiments quite accord with those of calculation although the difference has been but slight and this is probtlbly due in some degree to the circumstances hereafter mentioned.?'he rules of proportion do not directly apply to the per- centage of sugar by weight contained in solution unless the 35 by transmission through Fluids. specific gravity and bulk be likewise taken into account. For instance the solution referred to was prepared as follows :- 1000 1000 grains ...dry water sugar and its specific gravity was 1*2371; consequently 1 gallon of such solution would weigh 96,597 grains and contain 48298*5 grains sugar. Now since 10 inches of such a solution produced a rotation of 104' on adding an equal bulk that is another gallon of water to the original gallon 10 inches would pro- duce a rotation of 52'; but 1 gallon of water weighs 70,000 grains which added to the weight of the syrup 96,597 grains gives the weight of 2 gallons 166,597 grains supposing no condensation to arise from the mixture; consequently 1 gal- lon of the new solutioh would weigh 83298.5 grains ; and since it contains half the original quantity of sugar or 24149% grains the proportion by weight will be 24149.25 sugar to 59149% water since 241249% + 59149*25 = 83295*5; so that the proportion of sugar by weight to the water is less than one-half which would have been the case were the rotation in direct proportion to the weight of sugar as compared with that of the water in which it is dissolved without reference to the bulk occupied by the mixture.Again if the proportions of the combination be constant but the depth varied the degrees of rotation will as before stated bear a direct proportion to the depth ; thus since 10 inches of a solution of cane-sugar containing one-fourth its weight of solid scgar produces according to my experinients a rotation of so' if the depth be 1 inch it would produce a rotation of .5' and 36 inches would produce a rotation of 1 80° and conse- quently with such a depth there would be n o apparent rotation.Having thus shown that neither the direction in which the analyser is rotated nor the appearances presented at any given point can alone enable us to determine whether the rotation is right or left-handed we proceed to explain that such in- formation can only be obtained by observing the order of suc- cession in which the different tints or shades of obscuration present themselves. Removing the index of the inner moveable circle (Plate 11.) any number of degrees not exceeding goo either to the right or to the left it will be readily observed that the direction in which it has been moved might be ascertained by observing whether on moving the outer circle or analyser the image X became darker or brighter ; the image X becoming darker when the outer circle or analyser is moved in the same di- rection as the other but lighter if moved in an opposite di- rection.This law however it will be also seen is reversed if 36 I)r. Leeson on ihe Cz'rcdar Polarkation of Light the rotation exceeds 90'. This method then affords the means of ascertaining the direction of rotation provided it does not exceed 90'; the rotation being right-handed if when the analyser is turned to the right-had the image which is the subject of observation becomes darker and darker and Zeft- handed if it becomes lighter. 0'. I t matters not whether X or 0 be the siibjeject of observa- tion OF whether X be light and 0 dark when set to o' pro- vided the amount of rotation be estimated from the position iiecessary to restore either ray to precisely the same condition in which it appeared at O' previous& to the introduction of the circularly polarizing medium.When however a double refracting analyser is used I would in all cases reeommend the experiment to be commenced by placing the analyser and polarizer in such a position as that X is at its greatest point of obscurcrtion when the vernier or index points to OP and as represented when the indices of the two moveable circles of Plates II. V. and VI. are both at When a Nicholl's prism or tourmaline is used as an analyser presenting only one image then previous to the introduction of the circularly polarizing medium it must be so placed with respect to the yolarizer as that the index of the vernier points to 0' when the light is most completely polarized or obscured.Uni- formity in the mode of conducting these experiments will greatly promote accurate results. To return however to the means by which the direction of the rotation is to he ascertained. The method already described might be applied in examining solutions of weak rotatingenergy which exhibit little or no colour when examined by polarized light provided it is not confounded with the eflects of mere depolarization the appearances then presented being similar in some respects to those produced by double refracting sub- stances as described in the twenty-first chapter of Brewster's Treatise on Optics When substances of greater energy are examined they exhibit a gradation of colours corresponding to those of the solar spectrum which affords a still more sa- tisfactory mode of determining whether the rotation is right- or left-handed.The direction corresponds to that in which the analyser must be moved in order to obtain the succession of colours as follows viz. red orange yellow green blue indigo violet. If the analyser be moved in only one direction and that right-handed or in the order of the figures in the outer circle of graduation then the rotation will be right- or left- handed according to the succession of the colours in the fol- lowing tables represented in Plates 111. and IV. The gene- ral order of successiori when the annbser is moved in a righi- handed direction is first given viz.X. to to to Violet to Green Yellow Orange Violet to 180' The following table gives a more detailed account of the succession of tints produced and commences it will be ob- served with th'e boundary of the blue and violet which is the darkest ray corresponding to the greatest obscuration of X and is the point at which the degree of rotation should be ob- served. We may derive much assistance in estimating its precise position when a double refracting analyser is em- ployed by examining the appearance of 0 which will then be at its maximum of illumination and of the brightest and piirest yellow tint. When we travel too far into the violet with X 0 will assume a greenish-yellow tint; when too far into the blue the yellow will deepen towards an orange.If n tourmaline or coloured polarizer be employed attention must be had to its effects upon the yellow ray which mag be easily ascertained by observing the appearance of 0 previous to the introduction of the circularly polarizing medium. 1 3 5 O by transmission through Fltk.ls. Yellow Right- handed. X. to to Violet Orange Yellow to Green Violet to . X. Blue violet. Blue. Greenish blue. Green. Light green Bright yellow. Deep yellow. Orange yellow. Orange. Reddidb orange. Crimson. 0. to t o Orange Violet to Green to Yellow. Bright yellow.Deep yellow. ,Orange yellow. Orange. Reddish orange. Pale green. Crimson. Greenish yellow. Violet. Blue violet. Bright yellow. Violet. Blue violet. 37 O3 to 45' to 90' to 0. Yellow to Green to Violet to Orange Yellow. t o Right-handed. 0. Bright yellow. Greenish yellow. Pale green. Bright yellow. 35 50 Deep yllow. 90 Bright yellow. Blue violet. 100 Greenish yellow. Violet. Crimson. Reddish orange. Orange. Greenish blue. Orange yellow. Deep yellow. 80 Blue. Greenish blue. Green. Light green. Pale green. Greenish yellow 178 116 125 140 155 180 The following general conclusions will be easily understood from the Tables as well as by an examination of Plates 111.- Blue violet. 10 Violet. 0 0 25 Crimson. Reddish orange. Light green. Green. Orange. 65 Orange yellow. Greenish blue. Blue. Pale green. Light green. Green. Blue. Blue violet. 38 Dr. Leeson on the Circular PoLarization of Light and IV. and also of Plates V. and VI. where any amount of rotation may be imitated by moving the index of the respective inner moveable circles as before explained in regard to Plate 11. That whether the rotation be right- or Z&-handed the order of succession of colours is the same i n X as it is in 0 the one lagging as it were goo behid the other. If the analyser be revolved so as to obtain what may be termed a descending succession of colours viz.red orange yellow green blue &c. the direction in which it is revolved corresponds to that of rotation. If the analyser be revolved to the right-hand when exa- mining a substance possessed of left-handed rotation the order will be in what may be termed an ascending scale viz. blue,.green yellow orange red. If in examining a substance possessed of right-handed rota- tion the analyser be turned to the left the order will also be in an ascending scale viz. blue green yellow orange red &c That whether the rotation be right or left provided the amount is alike X and 0 will exhibit the same tints at a si- milar number of degrees of rotation marked in the right- or left-handed circles of graduation respectively. Hence at the points of greatest obscuration there is no dif- ference in the appearances exhibited whether the rotation be right- or Zdt-handed.That X assumes the tint of 0 and 0 that of X at an exact interval of 90'. This is particularly apparent in Plate IV. in consequence of the juxtaposition of the colours. That with a double refracting analyser each particular tint occurs four times in the course of a complete revolution of 360° viz. twice in the ordinary and twice in the extraordinary ray. With a tourmalint or a Nicholl's prism the tints will of course occur only twice in a whole revolution. That in R revolution of 180' the tints have passed through all their phases. The tints that have been described and which are repre- sented in the Plates correspond to those of' quartz and are more or less vivid in proportion to the rotating energy.In fluids the blue violet generally assumes more ofa neutral tint and in many instances the crimson is scarcely to be observed. Of course if the fluid be itself possessed of colour it will greatly interfere with the purity of the tints. When using n piece of red glass as recommended by Biot to obtain hortici- geneous light the tints disappear and the obscuration of X which is then more complete will determine the an~ount of ro- tation. The red glass sent by Mons. Soleil with Biot's ap- 39 without it. by transmission trllrough Fluids. paratus is much too dark and occasions so great a loss of light as materially to interfere with the delicacy of our readings.Of course the direction of the rotation should be observed Daylight is preferable to artificial light for these experi- ments; unless as before explained in the case of a coloured polarizer attenlion is paid to the appearance of 0 when arti- ficial light is employed the results will not agree with those obtained by daylight. Having explained the appearances which are to guide our experiments I proceed to a description of the apparatus which I consttucted for the purpose and which is similar in some respects to the arrangement of the Rev. B. Powell de- scribed in the Philosophical Magazine for April 1843. M N 0 P (figs. 1 and 4 p. 40) is a wooden box the lid of which b b not only opens in front but may be also fixed at any height and fastened by a small bolt at a fig 1.This box serves the purpose of a darkened chamber and the ap- paratus may be ‘packed in it when not in use. K K is a moveable perforated shelf which may be also securecl at any height by means of the screw at I fig. I passing through an opening in the back of the box shown at X fig. 4. On this shelf the vessei containing the fluid to be examined is to be placed its centrality being provided for by fitting into another loose shelf turned out to suit it. To the under side of the shelf K a brass plate is screwed fitted with a socket to receive the polarizer G which may be either a tourmaline or a Nicholl’s prism and which may be revolved by means of the collar at- tached to it for that purpose. H is a mirror to reflect the light through the polarizer and liquid towards the analysing double refracting eye-piece A B C D fig.3 and A figs. 1 2 and 4. This eye-piece consists of a lens C placed at its focal distance from a small aperture at D so as to give a well-de- fined image of it when transmitted towards the observer’s eye at A ; R is a double refracting achromatic analyser of Iceland spar or of quartz which is placed within a tube which slides into the tube containing the lens and also fits into the socket of the vernier it being sometimes desirable not to use the lens. A Nicholl’s prism or a tourmaline similarly fitted may occasionally be substituted. This analysing eye-piece fits tightly into a socket adapted to the vernier E of a circle F fig. 2 graduated as in Plates II.V. and VI. The analyser may be adjusted by turning it in its socket and when set to its proper position revolves with the vernier. The graduated circle with its vernier and eye-piece is attached for the con- venience of removnl in packing to n loose shelf L L and is 40 Dr. Leeson OTL the Circatar Potarixaiion of Light always secured in the same position by steadying pins. The upper end of the box has a circular opening of about. 1; inch diameter which serves to centralize and steadv the tube Dass- ing D through it as shown in fig. I . s T V fii. 1 is a tfiree- Fig. 1. Fig. 2. -.- F b Fig. 4. \! Fig. 3. necked glass vessel to contain the liquid to be examined. W is a tube graduated into inches and tenths passing through an air-tight brass stuffing box cemented to the vessel at V.S is an opening fitted with a stopper which is useful in filling emptying and cleansing the vessel. R is a small condensing 41 E by transmission thoti$ Fluids. air syringe adapted to the vessel at I and Q is a brass screw for the purpose of allowing the air to escape when requisite. The method of using the apparatus is as follows:-First secure the shelf' at the proper height to receive the vessel to be subsequently introduced then adjust the mirror to reflect the light of the sky or a lamp upwards towards the analyser at A set the vernier to zero on the graduated circle then place the analysing eye-piece in the vernier so that the ex- traordinary image X is also directed towards zero; next re- volve the polarizer G until X has attained its maximum of obscuration taking care not to disturb the vernier or mirror.The apparatus is thus ready for experiment and the liquid to be examined must next be introduced. I t may either be contained within i glass vessel S T V such as we have already described or in a simple graduated glass tube as shown at Y fig. 4 in which case the brass tube 2 blackened on the inside and fitted on to the lower part of the analyser is occasionally useful and lessens the necessity of closing the door to obtain a darkened chamber. The bottom of either vessel should be very transparent and free from irregularity or specks. These vessels are to be piaced upon the shelves as shown in the drawings and the door of the box closed.The vessel S T V is contrived for the purpose of examining dif- ferent depths of the same liquid without removing the vessel which is necessary when using only a simple tube as shown at Y fig. 4. By condensing air into the vessel by means of the small syringe the liq~iid may be raised to any height in the tube W and it may again be lowered by allowing the air to escape at the screw I. The liquid having been introduced suppose within the vessel S T V and occupying a depth say of 2 inches the image X which was invisible before will then in all probability* become apparent and tinted if not deci- dedly so raise the liquid by means of the syringe until it does and observe the depth; then move the vernier in a right- handed direction until the image X attains its niaximucn of obscuration and read off the aniount of rotation ; continue the inovenient of the vernier until 0 next becomes obscured then again observe X and then again 0.Thus you will ob- tain four readings corresponding to the depth observed each of which should differ from the preceding 90' if your observa- tions have all been correct but it' not a mean must be taken and it will in all cases be better to take a mean of several ob- servations arid again to compare such mean with that ob- tained froni an observation of the height necessary to rotate * Alluding to the accidental circuriistance of the depth corresponding to 180" rotation. Chemo SOC. Mem. VOL. 11. 42 Dr. Leeson on the Circular Polarization of Light the ray 1 soo which is procured as follows :-Having placed the vernier so that X is at its greatest point of obscuration and observed the height at which the liquid stands punip in air to raise the liquid until 0 becomes most obscured and observe the additional height necessary to effect this corre- sponding to a rotation of 90" ; continue the raising of the liquid until X again becomes obscured and again observe the addi- tional height which if the experiment be correctly conducted should be equal to the former and of course the total height will correspond to a rotation of 180".It is unnecessary to say anythinq more about the mode in which the direction of the rotation is to be ascertained this having been already fuIly explained.I shall conclude therefore with a few further ob- servations on sources of error which may tend to mislead or to interfere with the accuracy of observations. When exa- mining different heights care must be taken that the fluid which adheres to the sides of the tubes has time to subside otherwise the apparent amount of rotation will be thereby increased. Great care must be taken that the position of the mirror is not altered after the adjustments are made as with some Nicholl's prisms I have found a very slight change of the incli- nation of the mirror altogether alter the plane of polarization. After the adjustments are made any double refracting me- dium placed upon the shelf will cause the image X to become depolarized and therefore luminous; this must not be con- founded with circular polarization which I suspect has been the case.Many oils and some solutions of grape and potato sugar exhibit this phanomenon. The difference from circular polarization will be readily understood by attending to our former instructions and observing that in these cases there is no alteration of the positioii of the plane of polarization exhi- bited on rotating the aiialyser more especially on increasing the depth of the liquid; 1 would strongly advise any one ex- perimenting on this subject to examine the appearances pre- sented by pieces of unannealed glass crystals mica selenite &c. by placing them upon the shelf K K when the apparatus is adjusted. I should however observe that some specimens of unannealed glass mica and selenite possess circular pola- rization as in quartz and it probably exists to a much greater extent than has been hitherto noticed.Water cooled below 39' is a curious example of the phae- nonienon last alluded to which I discovered about three years since but did not then feel sufficiently satisfied with the mode of observation. I have iiow completely verified the fact wliich may be readily exhibited by means of the apparatus now de- scribed. Since this paper was read I have however obtained 43 by transmission throigl'r Flziids. apparent evidence of rotation amounting to about 15 degrees for a depth of 15 inches but rapidly disappearing as the tem- perature of the water rises. I am about repeating these expe- riments and shall communicate the result in a future paper.When a Biot's apparatus as constructed by Mons. Soleil is used mistakes may arise not only from the confusion of the extraordinary and ordinary images revolving round each other before alluded to but also from the graduation of the circle which is divided to 180' on either side of 0' and no further. Supposing for instance a rotation of 79' to the right since on moving the vernier 11' to the left the obscura- tion of 0 would be observed it might be mistaken for a left- handed rotation of ) 1'. Probably some such error occasioned Subeiran to state that a solution of sugar which showed an original rotation of 71' was altered after boiling as in the following table. Primitive syrup . . . . 71' right-handed.After 20 hours . . . . 0 ... 25 . . . . . . . 11' left-handed. ... 64 . . . . . . . 0 ... '74 . . . . . . . 5' right-handed. Supposing Subeiran mistaken a5 to the direction of the ro- tation (and he tells us nothing of the succession of tints by which it might have been determined) but correct as to the points of obscuration his statements would Iead us to infer creasing as it naturally would do from + 71' to + 95' as the that it was really a right-handed rotation throughout but in- water evaporated. The dimculty of determining the exact reading which requires much practice will readily account for an error of a few degrees and the subjoined tabk (based on the supposition that the original bulk was preserved as it ought to have been by the addition of as much water as was lost by evaporation) will show that in the last four experi- ments 0 was probably mistaken for X.XZ. 0. i80° -______I- 161' o 251' 2700 259' 270' 5) 1375" 71" - __- ___ 900 YeiZow ray depth 100 millimeires = 3-937 inches. 3410 = - 19 3490 = - 11 ... 64 ... Subeiran. X. goo 0 Primitive syrup +7l after 20 hours ... 25 ... -11 ... 74 ... Means ......... I 850 175O 3GOo= . _ _ _ 355O or - 5 169' ]SO0 0 79" 360°= + 5 5)42505)87F5)13250 95' 185' 275O 3650 = + 5 0 26b0 44 9'5 ... 50' ... ... 45 0.. 53*46 ... Dr. Leeson on the Circular Polarization of Fluids. The above table will give a general idea of the mode in which the results are to be taken and tabulated.I find as might be expected that solutions of sugar become decomposed by keeping and by heat but the effect is simply to diminish the amount of rotation and not lo alter the direction. I have already adverted to the care required in observing the precise point of obscuration viz. the extreme boundary between the blue and violet ray and to the assistance to be derived fi*orn observing the complementary tint. It is desirable to preserve one position diiring the observa- tions with the face towards zero and to look steadily in a perpendicular direction as the appreciation of' the tint will vary somewhat if the position of the eye be altered*. I g,e- nerally get an assistant to note the numbers so that the ou- servations may be made with as little looking off as possible.The effect of gazing at all coloured objects must be remem- bered and it would be well to have the whole of the appara- tus blackened or where convenient to make the observations in a darkened chamber. The loss of light occurring from an increased depth or strength of liquid especially if such liquid be coloured must be also considered and 'will frequently prevent the experiments made at different depths from ac- cording as they should do with each other. With constant practice I can obtain a reading to half a degree, beyond which I do not think it is possible in most cases to obtain any certainty ; and of course the method does not furnish an accurate substitute for chemical analysis although it may be useful as a rough mode of appreciating the purity of an oil or the strength of a solution of sugnr.I subjoin a table of the results of some experiments and shall have great pleasure in examining any other samples that may be sent or brought to me at the Laboratory at St. Tho- mas's Hospital. 9 inches. Tabkc of some rotating Liquids. Right-handed. Essential oil of caraway . 200° 0 . . 12 36 Depth 10 inches. 180" rotation. ... ... lemon . . 150' Rectified oil of turpentine . Commoq oil of turpentine . 40' Essential oil of nutmeg. . 33'5' Solution of 1734 grs. cam- ... dill . . . 1 90' phor in 2105 grs. alcohol 52' 34.5 ... * With some analysers the plane of polarization will be entirely changed if the position of the eye be greatly altered.45 Mr. J. T. Cooper 011 Catechuic Acid. Solutions of cane-sugar in cold distilled water 17'307. .. 70' EquaI weights sp. gr. 1'1'371 1 sugar to 2 water 1.1473 1.107 1 sugar to 3 water 36'0 ... 25T ... 90 ... Table of Essential Oils examined and possessing no rota fing energy. 104' Essential oil of anise. 50' Left-handed. Depth 10 inches. 180" rotation. 21.8 inches. Essential oil of cubebs . . 8 3' ... ... lavender . 20° ... ... cloves. ... . ... pimento. ... ... chamomile. ... ... calamus. 26 Dr. Leeson oft ihc Circular Polarization of Light XCI. Observatiom on the Circutar Polarization of Light 133 transmission through Fhids. By H. B. LEESON M.D. A.M. is with considerable diffidence and not without some re-ITgret that 1 present the followitig observations on the cir-cular polarization of light by transmission through fluids.It is with diffidence because the conclusions which are the result of my own experiments differ from those of others de-servedly considered able and acute observers. It is with re-gret because the tendency of the facts which 1 expect to estttblish before you is to lessen in some degree the value of an otherwise beautiful application of optical science to the exigencies of chemical investigation b~ transmission through Fluids. 27 It is equally important to detect that which is erroneous as it is to establish that which is true in science. Truth being my only aim I trust that whilst endeavouring to remove the veil of mystery and obscurity which has hitherto perplexed and thwarted many who in comnion with myself have assayed to follow out the experiments detailed by Biot and others I may not be considered anxious to throw discredit on their la-bours; but candidly detailing the result of my own experi-ments I can only say to them as well as to others :‘Si quid novisti rectius ids candidus itnperti; si non his cltere mecum.” The point in which the results of my own experiments disagree with those of other observers is in regard to the al-leged possession of opposite rotations by certain fluids which have the property of deviating the plane of polarization of a beam of polarized light transmitted through them some of those fluids being said to produce a right-handed rotation, others B left-handed ‘rotation.On examining a great variety of samples of the particular fluids said to possess opposite rotations I found that such fluids deviated the plane of pola-rization in only one direction namely towards the right-hand. The only fluids in which I have hitherto been able to discover a decided Zeff-handed rotation is in the essential oil of lavender arid in that of cubebss. The interesting fact if true that solutions of sugar when obtained from different sources and in different conditions possess in same cases a right-handed and in others a left-handed rotation has not bee11 corroborated by my own observations. When such so-lutions did exhibit any decided rotating influence it was uni-formly right-handed. It is however curious that solutions of cane-sugar differ from those of grape potato and diabetic sugar in this respect; that whilst the former possessed a powerful rotating influence the latter exhibited little or no rotating energy although their solutions were in some cases sufficiently concentrated to furnish crystals after a f’ew days’ repose.It might perhaps be supposed that such result proceeded only from niy own want of information on the subject .or n deficiency of my powers of observation; indeed I long so considered it myself so much so that not satisfied with obser-* The amount of left-handed rotation in oil of ciibebs is much greater than that of oil of lavender. This oil which was colourless and some others contained in the table accompanying this copimunication have been exa-mined since my paper was read the samples having been kindly furnished by Mr.Wwington of Apothecaries’ Hall. Samples of oil of cubebs obtained elsewhere were coloured and possessed much less rotating energy being probably adulterated with oil of peppermint. D 28 Dr. Leeson on the Circttlar Polarization of LighL vations made with apparatus procured in this country I com-missioned a friend to procure for me from Mons. Soleil of Paris an apparatus made according to Biot's own directions. Experinients made with that instrument confirmed the conclu-sioris I before arrived at and I may add that an examination of the apparatus itself has in some degree suggested the pos-sible sources of' error. I do not of course positively assert that the observations of others have been erroneous although strongly inclined to sus-pect they may have been misled.Nothing but an examination of the same sample could indeed establish such conclusion. I have never however been so fortunate as to obtain a solution of sugar possessing a decided left-handed rotation ; and although it is certainly possible that the oil of lemons or oil of turpentine which I have examined may differ from that ex-perimented on by others still I have tried so many samples, warrarited genuine and procured from so many different sources that I can scarcely imagine it possible to procure samples possessed of opposite rotating powers; I may also reniark that although I have observed variations as respected the amount I have never noticed any variation as respected the direction of rotation in any of the samples of the same description of fluid.Misunderstanding may perhaps result from the converse use ofthe terms right- and Zecft-handed rotation by cliffitrent writers, but this cannot affect the essential fact if true that oil of lemons for instance has an opposite rotation to that possessed by oil of turpentine or the still more interesting fact alleged, unfortunately I fear incorrectly that a solution of sugar as existent in the juice of grapes rotates the plane of polarization in an opposite direction to that in which it is rotated by a so-lution of sugar obtained from the cane, The direction to which in common with other writers the term right- handed is subsequently applied cannot be mistaken by those who attend to the instructions hereafter given and I would recommend every one previously to experimenting on ff uid substances to study the opposite appearances presented on analysing polarized light when transmitted through speci-mens of right- and left-handed quartz as usually sold for il-lustrating circular polarization and as exhibited in Plates III., IV.V. and VI. With a view to the more explicit understanding of the mode in which the experiments referred to have been conducted, and to assist those not coiiversant with the subject in repeat-ing them for thernselves I shall very briefly explain what is meant by the deviation or rotation of the rays of polarize by transmission through FZuids. 29 light when transmitted through fluids said to possess circular polarization.Assuming the general principles of the undulatory theory of light and making use of terms which if not absolutely cor-rect are at least convenient I shall first advert to what is meant by rectilinerrr or as I would suggest it should be teymed rectangular polariz a t' ion. When a beam of oi-diiiary light impinges on a polarizing medium it map be considered as dividing itself into two por-tions the waves of which respectively undulate in directions varying from each other YO' i. e. a right angle in other words, they are said to possess opposite planes of undulation and to be rectangularly palarizetl*. This effect may be produced by five different iiiodes viz. refraction reflexion absorption, dispersion and double refraction.A number of pieces of thin glass -f superimposed on each other and inclined at a suitable angle to ii ray of light inci-dent thereon polarizes one portion of the light transmitted through it by refraction whilst the other portion reflected from the surf'ace is also polarized but in an opposite direc-tion. That the two portions into which the light is thus di-vided are oppositely polarized or may be supposed to undulate in opposite directions is estaltlished by the fact that if trans-mitted towards a similar bundle of glass the two rajs would comport themselves differently ; that is they would not both be reflected or both traiisniitted by such second bundle if held in the same direction or plane towartls each respectively. Callirig the one portion of polarized light into which the ori-ginal beam of' orcliunry light R (figs.1 and I p. 30) is divided 0 and the other portion X it will be fuund that the position of the second bundle necessary to reflect X M ~ S L be at right angles to that in which it would reflect 0 and similarly as to refraction or transmission. This second bundle serving to distinguish the two rays is termed the andyser. Figs. 1 and 2 serve to illustrate polarization by refraction and re-flexion. In fig. 1 the bundles of glass are supposed to be all in the same plane or situated parallel to each other whilst in fig 2 the bundles €3 and C are supposed to be situated at right angles to the buiidle A. The beam of light R impinging on the-bundle A is divided into two portions 0 arid X ; and * Consideratinn of the direction in which the waves of light may be supposed to undulate will materiiiily assist the memory in studling the ta-cility of reflexion or transmission of' the respective rags by siirhces opposed to them in different positions.t The very thin glass sold for covering nticrosropic objects is extremely convenient for this purpose 80 Dr. Leeson on the Circular Polarization of Light it will be observed that 0 proceeding in its original course, is transmitted or passes through the second bundle B fig. 1, whilst X is reflected from and does not pass through the bundle C. The converse takes place in fig. 2. Hence it will be observed that in fig. 1 the portion 0 is capable of Fig. 1. 0 X 0 X transmission but not of reflexion whilst the portion X is ca-pable of reflexion only.I n fig. 2 where the bundles B and C me supposed to be placed at right angles to the bundle A, the portion 0 is capable of reflexion only and X of trans-mission. In these figures A forms what is termed the PO-larizer whilst €3 C and D are what are termed analysers, serving to test the condition of 0 and X. A tourmaline effects a similar division of a beam of light impinging on it into two portions oppositely polarized trans-mitting one say 0 in one position whilst X is absorbed re-volving the tourmaline goo X will be transmitted and 0 ab-sorbed. FOP experiments on circular polarization as well as for microscopic purposes the green tourmalines may be re-commended as they can be more easily obtained free from flaws.When of a proper thickness and ground truly parallel, they form excellent analysers to apply to the eye-pieces o by transmission through Fluids. 31 microscopes ; for experirnen ts on circular polarization they form very useful polarizers. The blue yellow and hair-brown tourmalines are perhaps superior when free from flaws, but cannot be so readily obtained perfect. Agates polarize by dispersion but are not suitable for ex-periments on other substances. Iceland spar and quartz polarize light by double refraction. The beam of light transmitted through them is divided into two portions 0 and X polarized in opposite planes but pro-ceeding in paths so closely posited that they may both be the subject of observation at the same time. This is not the case however in what are termed Nicholl’s prisms which are pur-posely so constructed as to allow only one portion to be trans-mitted when held in one direction whilst the other is trans-mitted when the prism is revolved a right nngle.The rhombs of Iceland spar are usually rendered achromatic by cenientirig a piece of glass properly adjusted to them. In order to render quartz available a particular construction is necessary but when well made double refracting analysers of quartz are equally useful for these experiments. It does not matter by what means our polarized beam is first obtained or in what manner the same is analysed or whether one mode be used to polarize the light and another to examine or analyse the same. In all cases the result will be dependent on the relative positions of the polarizer and snalyser and if these are placed in such a direction to each other as that X is not transmitted to the observer’s eye and therefore dark then 0 will be transmitted; but if either the analyser or polnrizer is changed to a position exactly at right angles to its former direction then 0 will be obscured whilst X becomes light.When one portion has obtained its greatest obscuration or is invisible the other will have obtained its maximiim of illutnination whilst they pass gradually from one condition to the other at the intermediate positions * as re-presented in Plates I. and 11. * A most convenient mode of obtaining polarized light which occurred t o me about two years ago and which I have since shown to several friends, consists in placing an ordinary looking-glass on the outside of a common window the bottom of the mirror being placed close to the lower portion of one of the panes of glass whilst the top is inclined from the window tc-wards the sky SO as to reflect the paiie of glass into a horizontal position.Standing then within the apartment and looking tbrougli a toiirmaline or other analysing medium at the light of t h e sky reflected from the mirror through the pane of glass it will be found intensely polarized,and on intro-ducing any substatice such for instance as a fluid contained in a glass tube or a crystal &c. between the analyser and the poiarizer it may be readily examined. The great advantage of this mode of obtaining polar-ized light consists not only in the perfection of the polarization but als 38 Dr..Leeson on t h Cz'rcula?* Polarization of Light On using as an analyser a rhomb of Iceland spar or a prism of quartz constructed as before alluded to the oppositely polarized beams oflight 0 and X may be observed together, and they will become alternately light and dark as the analyser i s revolved according to the law already laid down. This may be understood by revolving the outer circle of Plate IT. whilst the lower moveable circle* remains stationary. The ordinary ray being represented by 0 and what is termed the extra-ordinary ray by X the rhomb or prism should be so ar-ranged or posited in its setting as that 0 be central and therefore apparently stationary whilst X revolves around Of-, as the analyser is itself rotated as represented in the dif-ferent Plates exhibiting the successive changes in the appear-ance of a polarized ray of light transmitted through a small circular aperture and andysed by double refrwtion.This may be also understood by revolving the outer circle of Plate II. as before stated by which it will be seen that each por-tion 0 and X returns to its original condition after a revo-lution of half a circle or 180° and that it passes from the state of greatest obscuration to that of maximum illumina-tion on a rotation of goo or quarter of a revolution. I n all these cases then of what is termed rectangular po-i n the extent ofthe field of view which is a great advantage in examining large specimens such as unannealed glass although not so important in circular polarization.I may here observe that the sky at all times furnishes polarized light, which is more or less intense according to the relative position of the oh-server and the siiti. This circumstance probably influences the chemicsl action of the rays of light and points out the necessity of varying the posi-tion of the camera or the period of exposure in taking Daguerreotypes and other optical investigations according to the tinie of day the state of the sky and the sun's declination. Any person may readily ascertain where the greatest inteiisit~ of polarization exists by using a tourmaline, or other analvsing medium and looking through it a t a piece of selenite, or a piece of'Iceland spar or other crystal cut to exhibit the cross and rings; of course the colours will be most tivid and the black cross most intense where the greatest polarizing force exists.This polarization is most intense where the sky is t)lue and unclouded. The planes of pola-rization appear to vary at a total distance of 900 or of 4.5' measured each way from t h e suli's position. * In Plates II. V. 2nd VI. the lower moveable circle is introduced as a means of imitating the supposed dcviation in the plane of polarization by moving it to the rightbhnnd or to the left i n Plate II. and by moving it t o the left in Plate V. OF to the right in Plate VI. The outer nioveable circle in ail the Plates represents the rotation of the analyser. + This is very important to prevent confusion arising from a Fevolution ofthe two images aroiintl each other whereby the one map be mistaken for the ather.I n Plates II. V. and VI. it is manifest that the exact cen-trality of the ordinary ray could not be preserved as i n using the appa-matiis. itself by transmission through Fluids. 33 larization the maximuni of illurninntion takes place when the analyser is placed with its plane of polarization corresponding to that of the rag to be transmitted whilst such ray attains its greatest obscuration when the analyser is placed at right tirigles to such plane. Now this condition is altered when a medium of a certain thickness s possessing what is termed circular polarization is introduced between the polarizer and analyser; for if the polarizer and analyser be placed so that one ray X is at its greatest obscuration or invisible and the other 0 at its maximum of illumination as represented at 0' in Plate I.and as also shown when the indexes of the moveable circles in Plate 11. are both pointed to O' then on introducing a circularly polarizing medium between the an;ilyser and polarizer the plane of polarization will be re-moved to the right-hand or to the left which may be imitated by moving the index of the inner circle (Plate 11.) in either of those directions whilst the outer circle continues sta-tionary and it will be observed that in consequence of such change in the plane of polarization X will become lighter and 0 darker and that the outer circle which may be sup-posed to represent the analyser must be revolved an equal number of degrees in the same direction as the inner circle in order to restore X and 0 to their primary condition.When the rotation of the analyser proceeds in the direction of the T J U ~ -bers in the outer circle of graduation the rotation is terrned right-handed when in that of the inner circle left-handed. Supposing the rotation produced be 30' to the right ; place the index of the inner moveable circle at 30' on the outer circle of graduation ; then the other moveable circle or am-lyser must be also shifted 30' to tlie right-hand in order to obscure X; proceeding onwards it will be observed that X becomes bright at 120' being a further revolution of 90'; again becomes obscured at ZIO' or a revolution of ISO' and again bright at 240'. On registering? then the degrees at which 0 and X are respectively polarized that is most ob-scured we have the following table :-X 0 X 0 30' 1 zoo 210" 300' the degrees being observed on the outer or right-handed circle of graduation and corresponding to X 0 X 0 3 30' 240" 150' 60' on the inner or left-handed circle of graduation.Had we * A certain thickness is here stated becanse as will be hereafter shown, it is possible in every case to employ a thickness which woi~ld produce no apparent alteration 34 Dr. Leeson ott the Circula~ Polarization of Light moved the analyser or moveable circle in a left handed direc-tion we might have registered our results as follows :-0 X 0 X 60' 150' 240' 380' by which it will be seen that it would be impossible from the appearance presented at any given position or the direction in which the analyser was revolved done considered to say whether the deviation was 30' to the right or 150° to the left; and this woiild of course be equally true of any other amount of deviation.To add to the difficulty the deviation is in direct propor-tion to the thickness and nature of the circularly polarizing medium. If you find for example a deviation of 10' pro-duced by a medium of 1 inch in depth a depth of 10 inches would produce a deviation of 100'; so that by merely vary-ing the thickness or depth of the medium you may have the p.mition of greatest obscuration situated in any part of the circle and if the thickness happened to be such as that such position coincided with 180' or o' you might suppose that the medium was not possessed of circular polarization at all; the importance therefore of examining different depths or thicknesses will be apparent; and the depth of each medium which produces a deviation of 1809 furnishes a very useful index of their comparative circularly polarizing energy.If the depth be constant,and two circularly polarizing liquids be mixed together or if the fluid or substance be dissolved or mixed in some other fluid possessing no rotating energy the deviation will bear a direct relation to the proportion in which the two are combined. For instance since according to my own experiments 10 inches of a solution of cane-sugar in water containing half its weight of solid sugar produces a de-viation of 1049 on mixing such solution with an equal bulk of water 10 inches of such diluted solution would produce a rotation of only half that amount or SZ' which coincides with experiment ; having therefore once obtained the rotating power of a soliltion of given strength we may according to Biot calculate thence the strength of any other solution when examined in a similar manner; attention however must be paid to the effects of temperature any condensation which may take place on mixture specific gravity &c.; and I have not found the result of experiments quite accord with those of calculation although the difference has been but slight and this is probtlbly due in some degree to the circumstances hereafter mentioned.?'he rules of proportion do not directly apply to the per-centage of sugar by weight contained in solution unless th by transmission through Fluids.35 specific gravity and bulk be likewise taken into account. For instance the solution referred to was prepared as follows :-1000 grains dry sugar, 1000 ... water, and its specific gravity was 1*2371; consequently 1 gallon of such solution would weigh 96,597 grains and contain 48298*5 grains sugar. Now since 10 inches of such a solution produced a rotation of 104' on adding an equal bulk that is another gallon of water to the original gallon 10 inches would pro-duce a rotation of 52'; but 1 gallon of water weighs 70,000 grains which added to the weight of the syrup 96,597 grains, gives the weight of 2 gallons 166,597 grains supposing no condensation to arise from the mixture; consequently 1 gal-lon of the new solutioh would weigh 83298.5 grains ; and since it contains half the original quantity of sugar or 24149% grains the proportion by weight will be 24149.25 sugar to 59149% water since 241249% + 59149*25 = 83295*5; so that the proportion of sugar by weight to the water is less than one-half which would have been the case were the rotation in direct proportion to the weight of sugar as compared with that of the water in which it is dissolved without reference to the bulk occupied by the mixture.Again if the proportions of the combination be constant but the depth varied the degrees of rotation will as before stated, bear a direct proportion to the depth ; thus since 10 inches of a solution of cane-sugar containing one-fourth its weight of solid scgar produces according to my experinients a rotation of so' if the depth be 1 inch it would produce a rotation of .5' and 36 inches would produce a rotation of 1 80° and conse-quently with such a depth there would be n o apparent rotation.Having thus shown that neither the direction in which the analyser is rotated nor the appearances presented at any given point can alone enable us to determine whether the rotation is right or left-handed we proceed to explain that such in-formation can only be obtained by observing the order of suc-cession in which the different tints or shades of obscuration present themselves. Removing the index of the inner moveable circle (Plate 11.) any number of degrees not exceeding goo either to the right or to the left it will be readily observed that the direction in which it has been moved might be ascertained by observing whether on moving the outer circle or analyser the image X became darker or brighter ; the image X becoming darker when the outer circle or analyser is moved in the same di-rection as the other but lighter if moved in an opposite di-rection.This law however it will be also seen is reversed i 36 I)r. Leeson on ihe Cz'rcdar Polarkation of Light the rotation exceeds 90'. This method then affords the means of ascertaining the direction of rotation provided it does not exceed 90'; the rotation being right-handed if when the analyser is turned to the right-had the image which is the subject of observation becomes darker and darker and Zeft-handed if it becomes lighter.I t matters not whether X or 0 be the siibjeject of observa-tion OF whether X be light and 0 dark when set to o' pro-vided the amount of rotation be estimated from the position iiecessary to restore either ray to precisely the same condition in which it appeared at O' previous& to the introduction of the circularly polarizing medium. When however a double refracting analyser is used I would in all cases reeommend the experiment to be commenced by placing the analyser and polarizer in such a position as that X is at its greatest point of obscurcrtion when the vernier or index points to OP and as represented when the indices of the two moveable circles of Plates II. V. and VI. are both at 0'. When a Nicholl's prism or tourmaline is used as an analyser presenting only one image then previous to the introduction of the circularly polarizing medium it must be so placed with respect to the yolarizer as that the index of the vernier points to 0' when the light is most completely polarized or obscured.Uni-formity in the mode of conducting these experiments will greatly promote accurate results. To return however to the means by which the direction of the rotation is to he ascertained. The method already described might be applied in examining solutions of weak rotatingenergy which exhibit little or no colour when examined by polarized light provided it is not confounded with the eflects of mere depolarization the appearances then presented being similar in some respects to those produced by double refracting sub-stances as described in the twenty-first chapter of Brewster's Treatise on Optics When substances of greater energy are examined they exhibit a gradation of colours corresponding to those of the solar spectrum which affords a still more sa-tisfactory mode of determining whether the rotation is right-or left-handed.The direction corresponds to that in which the analyser must be moved in order to obtain the succession of colours as follows viz. red orange yellow green blue indigo, violet. If the analyser be moved in only one direction and that right-handed or in the order of the figures in the outer circle of graduation then the rotation will be right- or left-handed according to the succession of the colours in the fol-lowing tables represented in Plates 111.and IV. The gene-ral order of successiori when the annbser is moved in a righi-handed direction is first given viz by transmission through Fltk.ls. 37 X. Violet to Green to Yellow to Orange to Violet 0. Yellow t o Orange to Violet to Green to Yellow. O3 to 45' to 90' to 1 3 5 O to 180' -0 0 10 25 35 50 65 80 90 100 116 125 140 155 178 180 Right- handed. Right-handed. X. 0. Blue violet. Bright yellow. Violet. Greenish yellow. Crimson. Pale green. Reddish orange. Light green. Orange. Green. Orange yellow. Greenish blue. Deep yllow. Blue. Bright yellow. Blue violet. Greenish yellow. Violet. Pale green. Crimson. Light green. Reddish orange. Green.Orange. Greenish blue. Orange yellow. Blue. Deep yellow. Blue violet. Bright yellow. X. Violet to Orange to Yellow to Green to Violet . Blue violet. Blue. Greenish blue. Green. Light green, Pale green. Greenish yellow. Bright yellow. Deep yellow. Orange yellow. Orange. Reddidb orange. Crimson. Violet. Blue violet. 0. Yellow to Green to Violet to Orange t o Yellow. Bright yellow. Deep yellow. ,Orange yellow. Orange. Reddish orange. Crimson. Violet. Blue violet. Blue. Greenish blue. Green. Light green. Pale green. Greenish yellow Bright yellow. The following table gives a more detailed account of the succession of tints produced and commences it will be ob-served with th'e boundary of the blue and violet which is the darkest ray corresponding to the greatest obscuration of X, and is the point at which the degree of rotation should be ob-served.We may derive much assistance in estimating its precise position when a double refracting analyser is em-ployed by examining the appearance of 0 which will then be at its maximum of illumination and of the brightest and piirest yellow tint. When we travel too far into the violet with X 0 will assume a greenish-yellow tint; when too far into the blue the yellow will deepen towards an orange. If n tourmaline or coloured polarizer be employed attention must be had to its effects upon the yellow ray which mag be easily ascertained by observing the appearance of 0 previous to the introduction of the circularly polarizing medium.The following general conclusions will be easily understood from the Tables as well as by an examination of Plates 111 38 Dr. Leeson on the Circular PoLarization of Light and IV. and also of Plates V. and VI. where any amount of rotation may be imitated by moving the index of the respective inner moveable circles as before explained in regard to Plate 11. That whether the rotation be right- or Z&-handed the order of succession of colours is the same i n X as it is in 0, the one lagging as it were goo behid the other. If the analyser be revolved so as to obtain what may be termed a descending succession of colours viz. red orange, yellow green blue &c. the direction in which it is revolved corresponds to that of rotation.If the analyser be revolved to the right-hand when exa-mining a substance possessed of left-handed rotation the order will be in what may be termed an ascending scale viz. blue,.green yellow orange red. If in examining a substance possessed of right-handed rota-tion the analyser be turned to the left the order will also be in an ascending scale viz. blue green yellow orange red &c, That whether the rotation be right or left provided the amount is alike X and 0 will exhibit the same tints at a si-milar number of degrees of rotation marked in the right- or left-handed circles of graduation respectively. Hence at the points of greatest obscuration there is no dif-ference in the appearances exhibited whether the rotation be right- or Zdt-handed.That X assumes the tint of 0 and 0 that of X at an exact interval of 90'. This is particularly apparent in Plate IV., in consequence of the juxtaposition of the colours. That with a double refracting analyser each particular tint occurs four times in the course of a complete revolution of 360° viz. twice in the ordinary and twice in the extraordinary ray. With a tourmalint or a Nicholl's prism the tints will of course occur only twice in a whole revolution. That in R revolution of 180' the tints have passed through all their phases. The tints that have been described and which are repre-sented in the Plates correspond to those of' quartz and are more or less vivid in proportion to the rotating energy. In fluids the blue violet generally assumes more ofa neutral tint, and in many instances the crimson is scarcely to be observed.Of course if the fluid be itself possessed of colour it will greatly interfere with the purity of the tints. When using n piece of red glass as recommended by Biot to obtain hortici-geneous light the tints disappear and the obscuration of X, which is then more complete will determine the an~ount of ro-tation. The red glass sent by Mons. Soleil with Biot's ap by transmission trllrough Fluids. 39 paratus is much too dark and occasions so great a loss of light as materially to interfere with the delicacy of our readings. Of course the direction of the rotation should be observed without it. Daylight is preferable to artificial light for these experi-ments; unless as before explained in the case of a coloured polarizer attenlion is paid to the appearance of 0 when arti-ficial light is employed the results will not agree with those obtained by daylight.Having explained the appearances which are to guide our experiments I proceed to a description of the apparatus which I consttucted for the purpose and which is similar in some respects to the arrangement of the Rev. B. Powell de-scribed in the Philosophical Magazine for April 1843. M N 0 P (figs. 1 and 4 p. 40) is a wooden box the lid of which b b not only opens in front but may be also fixed at any height and fastened by a small bolt at a fig 1. This box serves the purpose of a darkened chamber and the ap-paratus may be ‘packed in it when not in use. K K is a moveable perforated shelf which may be also securecl at any height by means of the screw at I fig.I passing through an opening in the back of the box shown at X fig. 4. On this shelf the vessei containing the fluid to be examined is to be placed its centrality being provided for by fitting into another loose shelf turned out to suit it. To the under side of the shelf K a brass plate is screwed fitted with a socket to receive the polarizer G which may be either a tourmaline or a Nicholl’s prism and which may be revolved by means of the collar at-tached to it for that purpose. H is a mirror to reflect the light through the polarizer and liquid towards the analysing double refracting eye-piece A B C D fig. 3 and A figs. 1 2 and 4. This eye-piece consists of a lens C placed at its focal distance from a small aperture at D so as to give a well-de-fined image of it when transmitted towards the observer’s eye at A ; R is a double refracting achromatic analyser of Iceland spar or of quartz which is placed within a tube which slides into the tube containing the lens and also fits into the socket of the vernier it being sometimes desirable not to use the lens.A Nicholl’s prism or a tourmaline similarly fitted may occasionally be substituted. This analysing eye-piece fits tightly into a socket adapted to the vernier E of a circle F, fig. 2 graduated as in Plates II. V. and VI. The analyser may be adjusted by turning it in its socket and when set to its proper position revolves with the vernier. The graduated circle with its vernier and eye-piece is attached for the con-venience of removnl in packing to n loose shelf L L and i 40 Dr.Leeson OTL the Circatar Potarixaiion of Light always secured in the same position by steadying pins. The upper end of the box has a circular opening of about. 1; inch diameter which serves to centralize and steadv the tube Dass-ing D through it as shown Fig. 1. b in fig. I . s T V fii. 1 is a tfiree-Fig. 2. F -.-Fig. 3. Fig. 4. \! necked glass vessel to contain the liquid to be examined. W is a tube graduated into inches and tenths passing through an air-tight brass stuffing box cemented to the vessel at V. S is an opening fitted with a stopper which is useful in filling, emptying and cleansing the vessel. R is a small condensin by transmission thoti$ Fluids.41 air syringe adapted to the vessel at I and Q is a brass screw, for the purpose of allowing the air to escape when requisite. The method of using the apparatus is as follows:-First, secure the shelf' at the proper height to receive the vessel to be subsequently introduced then adjust the mirror to reflect the light of the sky or a lamp upwards towards the analyser at A set the vernier to zero on the graduated circle then place the analysing eye-piece in the vernier so that the ex-traordinary image X is also directed towards zero; next re-volve the polarizer G until X has attained its maximum of obscuration taking care not to disturb the vernier or mirror. The apparatus is thus ready for experiment and the liquid to be examined must next be introduced.I t may either be contained within i glass vessel S T V such as we have already described or in a simple graduated glass tube as shown at Y fig. 4 in which case the brass tube 2 blackened on the inside and fitted on to the lower part of the analyser, is occasionally useful and lessens the necessity of closing the door to obtain a darkened chamber. The bottom of either vessel should be very transparent and free from irregularity or specks. These vessels are to be piaced upon the shelves as shown in the drawings and the door of the box closed. The vessel S T V is contrived for the purpose of examining dif-ferent depths of the same liquid without removing the vessel, which is necessary when using only a simple tube as shown at Y fig. 4. By condensing air into the vessel by means of the small syringe the liq~iid may be raised to any height in the tube W and it may again be lowered by allowing the air to escape at the screw I.The liquid having been introduced, suppose within the vessel S T V and occupying a depth say of 2 inches the image X which was invisible before will then, in all probability* become apparent and tinted if not deci-dedly so raise the liquid by means of the syringe until it does, and observe the depth; then move the vernier in a right-handed direction until the image X attains its niaximucn of obscuration and read off the aniount of rotation ; continue the inovenient of the vernier until 0 next becomes obscured, then again observe X and then again 0. Thus you will ob-tain four readings corresponding to the depth observed each of which should differ from the preceding 90' if your observa-tions have all been correct but it' not a mean must be taken, and it will in all cases be better to take a mean of several ob-servations arid again to compare such mean with that ob-tained froni an observation of the height necessary to rotate * Alluding to the accidental circuriistance of the depth corresponding to 180" rotation.Chemo SOC. Mem. VOL. 11. 42 Dr. Leeson on the Circular Polarization of Light the ray 1 soo which is procured as follows :-Having placed the vernier so that X is at its greatest point of obscuration, and observed the height at which the liquid stands punip in air to raise the liquid until 0 becomes most obscured and observe the additional height necessary to effect this corre-sponding to a rotation of 90" ; continue the raising of the liquid until X again becomes obscured and again observe the addi-tional height which if the experiment be correctly conducted, should be equal to the former and of course the total height will correspond to a rotation of 180".It is unnecessary to say anythinq more about the mode in which the direction of the rotation is to be ascertained this having been already fuIly explained. I shall conclude therefore with a few further ob-servations on sources of error which may tend to mislead or to interfere with the accuracy of observations. When exa-mining different heights care must be taken that the fluid which adheres to the sides of the tubes has time to subside otherwise the apparent amount of rotation will be thereby increased.Great care must be taken that the position of the mirror is not altered after the adjustments are made as with some Nicholl's prisms I have found a very slight change of the incli-nation of the mirror altogether alter the plane of polarization. After the adjustments are made any double refracting me-dium placed upon the shelf will cause the image X to become depolarized and therefore luminous; this must not be con-founded with circular polarization which I suspect has been the case. Many oils and some solutions of grape and potato sugar exhibit this phanomenon. The difference from circular polarization will be readily understood by attending to our former instructions and observing that in these cases there is no alteration of the positioii of the plane of polarization exhi-bited on rotating the aiialyser more especially on increasing the depth of the liquid; 1 would strongly advise any one ex-perimenting on this subject to examine the appearances pre-sented by pieces of unannealed glass crystals mica selenite, &c.by placing them upon the shelf K K when the apparatus is adjusted. I should however observe that some specimens of unannealed glass mica and selenite possess circular pola-rization as in quartz and it probably exists to a much greater extent than has been hitherto noticed. Water cooled below 39' is a curious example of the phae-nonienon last alluded to which I discovered about three years since but did not then feel sufficiently satisfied with the mode of observation.I have iiow completely verified the fact wliich may be readily exhibited by means of the apparatus now de-scribed. Since this paper was read I have however obtaine by transmission throigl'r Flziids. 43 apparent evidence of rotation amounting to about 15 degrees for a depth of 15 inches but rapidly disappearing as the tem-perature of the water rises. I am about repeating these expe-riments and shall communicate the result in a future paper. When a Biot's apparatus as constructed by Mons. Soleil, is used mistakes may arise not only from the confusion of the extraordinary and ordinary images revolving round each other before alluded to but also from the graduation of the circle which is divided to 180' on either side of 0' and no further.Supposing for instance a rotation of 79' to the right since on moving the vernier 11' to the left the obscura-tion of 0 would be observed it might be mistaken for a left-handed rotation of ) 1'. Probably some such error occasioned Subeiran to state that a solution of sugar which showed an original rotation of 71' was altered after boiling as in the following table. Primitive syrup . . . . 71' right-handed. After 20 hours . . . . 0 ... 25 . . . . . . . 11' left-handed. ... 64 . . . . . . . 0 ... '74 . . . . . . . 5' right-handed. Supposing Subeiran mistaken a5 to the direction of the ro-tation (and he tells us nothing of the succession of tints by which it might have been determined) but correct as to the points of obscuration his statements would Iead us to infer that it was really a right-handed rotation throughout but in-creasing as it naturally would do from + 71' to + 95' as the water evaporated.The dimculty of determining the exact reading which requires much practice will readily account for an error of a few degrees and the subjoined tabk (based on the supposition that the original bulk was preserved as it ought to have been by the addition of as much water as was lost by evaporation) will show that in the last four experi-ments 0 was probably mistaken for X. YeiZow ray depth 100 millimeires = 3-937 inches. Subeiran. X. Primitive syrup +7l 71" ... 25 ... -11 79" ... 64 ... 0 900 after 20 hours o goo ... 74 ... + 5 95' Means ......... I 850 -0. XZ. -______I-161' 251' 169' 259' ]SO0 270' i80° 2700 185' 275O 175O 26b0 5)42505)87F5)13250 __- ___ 3410 = - 19 3GOo= 0 3490 = - 11 360°= 0 3650 = + 5 355O or - 5 5) 1375" ._ _ 44 The above table will give a general idea of the mode in which the results are to be taken and tabulated. I find as might be expected that solutions of sugar become decomposed by keeping and by heat but the effect is simply to diminish the amount of rotation and not lo alter the direction. I have already adverted to the care required in observing the precise point of obscuration viz. the extreme boundary between the blue and violet ray and to the assistance to be derived fi*orn observing the complementary tint. It is desirable to preserve one position diiring the observa-tions with the face towards zero and to look steadily in a perpendicular direction as the appreciation of' the tint will vary somewhat if the position of the eye be altered*.I g,e-nerally get an assistant to note the numbers so that the ou-servations may be made with as little looking off as possible. The effect of gazing at all coloured objects must be remem-bered and it would be well to have the whole of the appara-tus blackened or where convenient to make the observations in a darkened chamber. The loss of light occurring from an increased depth or strength of liquid especially if such liquid be coloured must be also considered and 'will frequently prevent the experiments made at different depths from ac-cording as they should do with each other. With constant practice I can obtain a reading to half a degree, beyond which I do not think it is possible in most cases to obtain any certainty ; and of course the method does not furnish an accurate substitute for chemical analysis although it may be useful as a rough mode of appreciating the purity of an oil or the strength of a solution of sugnr. I subjoin a table of the results of some experiments and shall have great pleasure in examining any other samples that may be sent or brought to me at the Laboratory at St. Tho-mas's Hospital. Tabkc of some rotating Liquids. Right-handed. Depth 10 inches. 180" rotation. Essential oil of caraway . 200° 9 inches. 0 . . ... dill . . . 1 90' 9'5 ... ... ... lemon . . 150' 12 ... Dr. Leeson on the Circular Polarization of Fluids. Rectified oil of turpentine . 50' 36 ... Essential oil of nutmeg. . 33'5' 53*46 ... Solution of 1734 grs. cam-* With some analysers the plane of polarization will be entirely changed Commoq oil of turpentine . 40' 45 0.. phor in 2105 grs. alcohol 52' 34.5 ... if the position of the eye be greatly altered Mr. J. T. Cooper 011 Catechuic Acid. 45 Solutions of cane-sugar in cold distilled water : EquaI weights sp. gr. 1'1'371 104' 17'307. .. 1 sugar to 3 water 1.107 50' 36'0 ... 1 sugar to 2 water 1.1473 70' 25T ... Left-handed. Depth 10 inches. 180" rotation. Essential oil of cubebs . . 8 3' 21.8 inches. ... ... lavender . 20° 90 ... Table of Essential Oils examined and possessing no rota fing energy. Essential oil of anise. ... ... cloves. ... . ... pimento. ... ... chamomile. ... ... calamus

ISSN:0269-3127    

DOI:10.1039/MP8430200026

出版商:RSC    

年代:1843

数据来源: RSC

摘要:

45 Mr. J. T. Cooper 011 Catechuic Acid. December 18 184F. -The President in the Chair. A Specimen of Catechuic Acid was presented by John Thomas Cooper Esq. to the Society’s Museum. Robert Kane Esq. M.D. Amos Swaisland Esq. Thomas Jen- nings Esq. Andrew Muter Eeq. James Millar Esq. and David Waldie Esq. were elected Members ; and Rllessrs. Robert Hunt and John Mercer Jun. as Associates of the Society. The following communications were then read :- COOPER ESq. XCII. Observutions 012 Catechic Acid. By JOHN THOMAS I- 4 SHORT time since I was requested to visit a tannery where the principal tanning ingredient employed was catechu and among other matters my attention was directed to a whitish substance which made its appearance on the ex- ternal surface of the leather when the tanning process was completed and the uniform appearance of this substance over the whole surface is considered by the proprietors as the test of the perfection of their process of tanning which is usually accomplished in about fourteen days.The tanning liquor is prepared by making an imperfect solution of the catechu in warm water or in the liquor that has been previously par- tially exhausted of its tannin by a former operation; the de- pilated hides in their usual state are sewn up so as to form water-tight bags into which the tanning liquid prepared as above is placed so as to completely fill them; they are then placed on floors and turned once or twice a day into every 4 4 6 Mr. J. T. Cooper on Catechuic Acid. possible position to expose the hide as equally as possible to the action and pressure of the tanning liquid and as the pro- cess of tanning advances the appearance of this white matter becomes more and more evident until at length it covers the entire surface of the leather and sometimes acquires consi- derable thickness and solidity.In this state however it is contaminated with many impurities and after repeated trials to obtain it in a state fit for examination I found the follow- ing simple method to answer the purpose 1,had in view very well. The matter as obtained by scraping from the surface of the leather was thrown on a filter of linen cloth and washed with cold water until the water passed through very nearly colourless; by this means a quantity of tannin mucilage ex- tractive matter and a peculiar substance which I have not yet examined were removed; the matter remaining on the filter was then treated with hot water either by washing it on the filter or which is better by removal into a basin and heating it with three times its bulk of water to near the boil- ing point when a brown-coloured solution was obtained and by filtering this while hot in a warm place the substance which has the characters of catechuic acid catechine or tanningenic acid is deposited as it cools but the deposition of the whole I find does not take place until many hours after it has become cold therefore after c? lapse of about twenty-four hours it may be thrown on a filter and washed with cold water in which it is nearly insoluble until the water passes through colour- less or very nearly so and then dried slowly by exposure to a gentle heat; i n this manner the specimen herewith presented to the Society has been prepared arid which if examined will be found to possess the properties described as appertaining to catechine catechuic or tanningenic acids namely a white substance with a light tint of reddish-brown a glistening or micaceous aspect when diffused in water meagre to the feel something like alumina insolubility in cold water and ready solubility to a great extent in hot water; forming a brown solution of greater or less intensity in proportion to the quan- tity dissolved; readily soluble in alcohol and ether and in the weakest alkaline solutions without the assistance of heat tbrming brown compounds; and with the assistance of heat becoming dark brown or almost black owing it is said to the absorption of oxygen from the atmosphere and its con- version into what is called jayonic acid fusible per se into a resinous looking substance hy the cautious application of heat and if heated much beyond its fusing point becorning charred leaving a very bulky charcoal.If it be considered desirable to undertake the organic am- Catechu. 62.8 Tannin . 12-3 Water. 8.2 Extractive or colouring matter. 2- Resinous matter. 8 ' 5 Mucilaginous or gummy matter. 4.4 Insoluble matter. CutcA. Mr. Warington on tile Molecular Structure of Silver. 47 lysis of this substance in all probability the specimen presented may require further purification and by adopting the process recommended by Svanberg namely forming it into a cate- chuate of lead and decomposing this by sulphuretted hydro- gen while warm may in the hands of others be effectual for the purpose but I confess it has not succeeded well with me.- 98.2 12.8 Water. Tannin f 4 ' *ri tannin. 47.7 6*2 altered tannin. 9.2 Extract Eveor colouring matter. 13% Mucilaginous or gummy matter. 6.8 Resinous matter. 9.4 Insoluble matter. - 99.5 Mr. J. T. Cooper 011 Catechuic Acid. 45 December 18 184F. -The President in the Chair. A Specimen of Catechuic Acid was presented by John Thomas Cooper Esq. to the Society’s Museum. Robert Kane Esq. M.D. Amos Swaisland Esq. Thomas Jen-nings Esq.Andrew Muter Eeq. James Millar Esq. and David Waldie Esq. were elected Members ; and Rllessrs. Robert Hunt and John Mercer Jun. as Associates of the Society. The following communications were then read :-XCII. Observutions 012 Catechic Acid. By JOHN THOMAS 4 SHORT time since I was requested to visit a tannery I- where the principal tanning ingredient employed was catechu and among other matters my attention was directed to a whitish substance which made its appearance on the ex-ternal surface of the leather when the tanning process was completed and the uniform appearance of this substance over the whole surface is considered by the proprietors as the test of the perfection of their process of tanning which is usually accomplished in about fourteen days.The tanning liquor is prepared by making an imperfect solution of the catechu in warm water or in the liquor that has been previously par-tially exhausted of its tannin by a former operation; the de-pilated hides in their usual state are sewn up so as to form water-tight bags into which the tanning liquid prepared as above is placed so as to completely fill them; they are then placed on floors and turned once or twice a day into every COOPER ESq 4 4 6 Mr. J. T. Cooper on Catechuic Acid. possible position to expose the hide as equally as possible to the action and pressure of the tanning liquid and as the pro-cess of tanning advances the appearance of this white matter becomes more and more evident until at length it covers the entire surface of the leather and sometimes acquires consi-derable thickness and solidity.In this state however it is contaminated with many impurities and after repeated trials to obtain it in a state fit for examination I found the follow-ing simple method to answer the purpose 1,had in view very well. The matter as obtained by scraping from the surface of the leather was thrown on a filter of linen cloth and washed with cold water until the water passed through very nearly colourless; by this means a quantity of tannin mucilage ex-tractive matter and a peculiar substance which I have not yet examined were removed; the matter remaining on the filter was then treated with hot water either by washing it on the filter or which is better by removal into a basin and heating it with three times its bulk of water to near the boil-ing point when a brown-coloured solution was obtained and by filtering this while hot in a warm place the substance which has the characters of catechuic acid catechine or tanningenic acid is deposited as it cools but the deposition of the whole I find does not take place until many hours after it has become cold therefore after c? lapse of about twenty-four hours it may be thrown on a filter and washed with cold water in which it is nearly insoluble until the water passes through colour-less or very nearly so and then dried slowly by exposure to a gentle heat; i n this manner the specimen herewith presented to the Society has been prepared arid which if examined will be found to possess the properties described as appertaining to catechine catechuic or tanningenic acids namely a white substance with a light tint of reddish-brown a glistening or micaceous aspect when diffused in water meagre to the feel, something like alumina insolubility in cold water and ready solubility to a great extent in hot water; forming a brown solution of greater or less intensity in proportion to the quan-tity dissolved; readily soluble in alcohol and ether and in the weakest alkaline solutions without the assistance of heat, tbrming brown compounds; and with the assistance of heat becoming dark brown or almost black owing it is said to the absorption of oxygen from the atmosphere and its con-version into what is called jayonic acid fusible per se into a resinous looking substance hy the cautious application of heat, and if heated much beyond its fusing point becorning charred, leaving a very bulky charcoal.If it be considered desirable to undertake the organic am Mr. Warington on tile Molecular Structure of Silver. 47 lysis of this substance in all probability the specimen presented may require further purification and by adopting the process recommended by Svanberg namely forming it into a cate-chuate of lead and decomposing this by sulphuretted hydro-gen while warm may in the hands of others be effectual for the purpose but I confess it has not succeeded well with me. 12-3 62.8 8.2 2-8 ' 5 4.4 98.2 12.8 47.7 9.2 13% 6.8 9.4 99.5 --Catechu. Water. Tannin . Extractive or colouring matter. Resinous matter. Mucilaginous or gummy matter. Insoluble matter. CutcA. Water. Tannin f 4 ' *ri tannin. 6*2 altered tannin. Extract Eveor colouring matter. Mucilaginous or gummy matter. Resinous matter. Insoluble matter

ISSN:0269-3127    

DOI:10.1039/MP8430200045

出版商:RSC    

年代:1843

数据来源: RSC

摘要:

Silver. By ROBERT WARINGTON ESP. XCIII. On a curious Change in the Molecular Structure of Mr. Warington on tile Molecular Structure of Silver. 47 TH.E subject of the present brief communicatioii was put into my hands by my friend Mr. Porrett after our last Meeting as bearing on the subject of the memoir which I had the honour of reading before the Society in January 1842% ; a subject I am still prosecuting as my time will permit and the results of which I hope to lay before the Society at an early date. It appears from information furnished me by Mr. Porrett to have been part of a silver funeral vase and was discovered by some labourers about four months since at the depth of seven feet below the surface of the ground while digging for brick-earth between Bow and Stratford.Its height was about ten inches and its greatest diameter about eight inches; it weighed PO ounces and had a smaller vase about the size of a human heart in its interior. When brought to Mr. Ed- wards a watchmaker resident in Shoreditch by whom it was purchased it was without a cover aid the contents had been thrown away with the exception of some black ashes which * See Memoirs vol. i. p. 77. ' 48 Mr. Warington on the Molecular Structure ofSiher. were not preserved. Its thickness was about from 0*015 to 0.0 17 of an inch its surface presented a dull tarnished aspect and was stained in patches with red oxide of iron. I t was extremely rotten and brittle breaking by the application of the slightest force; the surfaces of fracture were uneven and of a hright white metallic lustre.When examined under the microscope by a power magnifying 100 diameters it presented a highly crystalline structure the facets of the crystals being exceedingly bright and approaching the cubic form but none of them could be observed perfectly developed ; they were more analogous to the characters of' grain tin in its broken state :IS met with in commerce. I t appeared also as though there had been a recrFstallization of the metal as the particles looked as if they had been drawn from the central part to the sides of the thin plate leaving cavities or interstices of consirlei-able extent arid depth ; the exterior surface was also coated with B film of about 0.0005 of an inch thick having a grayish-olive coloiir and totally different in its structure from the other parts being striated across its breadth.The specific gravity of the metal in this state was found to be 9937 great care having been taken to remove the air from the internal cavities by means of the air-pump. The metal was next heated to redness in* a crucible and the heat sustained for about ten minutes after which its cha- racters were found to be totally altered ; it had lost its extreme brittleness requiring to be bent ceveral times before a fracture could be effected and then by the aid of the microscope exhibited a close sinall grained tough aspect of a dull white colour and without the previous cavernous appearances ; the superficial film seemed also in places to have partially sepa- rated from the substance of the thin plate of metal during the bending.The specific gravity was a7gRin taken adopting the previous precautions and was found to be 9.95 making an increase of 0.013 or1 the gravity taken before the application of a red heat. I t was next submitted to analysis; 8.5 grains were digested in dilute nitric acid and the soluble parts (A) decanted and the residue well washed. This residue was in small thin grayish-white flakes and by exposure to the light became ra- pidly of cz purple tint indicating the presence of chloride of silver; fearing that this might have arisen from some acci- dental impurity in the materials employed both the nitric ticid and distilled water were carefully tested and proved to be perfectly pure; it was therefore digested in weak solution of ammonia which dissolved the whole with the exception of a small quantity of brown powder which was found to consist 49 of 0.06 gr.of peroxide of iron and a trace of gold. The am- moniacnl solution was precipitated by nitric acid and gave 0.52 gr. of chloride of silver. The solution (A) was next precipitated by solution of chloride of sodiuni arid gave 10.25 grains of chloride of silver equivalent to '7.66 grains of silver ; solution of catistic potash and boiling threw down the oxide of copper and yielded 0.30 gr. oxide of copper = 0.24 gr. of copper. Thus we have- Chloride of silver. . . 0~52 ... . Mr. Arrott O?L a Class of Double Sulphates. Silver . . . . . . '7.66 grains.Oxide of iron . . . . 0*06 ... Copper . . . . . 0-24 ... _- __ Gold . . . . . a trace Loss . 8.48 0.02 -~ 8*50 I t becomes R ciirious question as to the origin of this chlo- ride of silver which was evidently the superficial grayish fillti . observed undrtr the microscope and which partially separated in the act of bending the metal after heating. That it must have been produced by the continued action of cldorides per- haps aided by sulphates present in the brick clay from which the vase was excavated there can be little doubt and the per- oxide of iron also existing in the clay may have assisted this action. The passage of the metal to the brittle state in this and in all other cases will I think be found attributable to some electrical action arising from sudden cooling vibration or concussion chemical acticrn &c.to which the metallic body or alloy may have been exposed. Mr. Warington on tile Molecular Structure of Silver. 47 XCIII. On a curious Change in the Molecular Structure of Silver. By ROBERT WARINGTON ESP. TH.E subject of the present brief communicatioii was put into my hands by my friend Mr. Porrett after our last Meeting as bearing on the subject of the memoir which I had the honour of reading before the Society in January 1842% ; a subject I am still prosecuting as my time will permit and the results of which I hope to lay before the Society at an early date. It appears from information furnished me by Mr. Porrett, to have been part of a silver funeral vase and was discovered by some labourers about four months since at the depth of seven feet below the surface of the ground while digging for brick-earth between Bow and Stratford.Its height was about ten inches and its greatest diameter about eight inches; it weighed PO ounces and had a smaller vase about the size of a human heart in its interior. When brought to Mr. Ed-wards a watchmaker resident in Shoreditch by whom it was purchased it was without a cover aid the contents had been thrown away with the exception of some black ashes which * See Memoirs vol. i. p. 77 48 Mr. Warington on the Molecular Structure ofSiher. were not preserved. Its thickness was about from 0*015 to 0.0 17 of an inch its surface presented a dull tarnished aspect, and was stained in patches with red oxide of iron.I t was extremely rotten and brittle breaking by the application of the slightest force; the surfaces of fracture were uneven and of a hright white metallic lustre. When examined under the microscope by a power magnifying 100 diameters it presented a highly crystalline structure the facets of the crystals being exceedingly bright and approaching the cubic form but none of them could be observed perfectly developed ; they were more analogous to the characters of' grain tin in its broken state :IS met with in commerce. I t appeared also as though there had been a recrFstallization of the metal as the particles looked as if they had been drawn from the central part to the sides of the thin plate leaving cavities or interstices of consirlei-able extent arid depth ; the exterior surface was also coated with B film of about 0.0005 of an inch thick having a grayish-olive coloiir and totally different in its structure from the other parts being striated across its breadth.The specific gravity of the metal in this state was found to be 9937 great care having been taken to remove the air from the internal cavities by means of the air-pump. The metal was next heated to redness in* a crucible and the heat sustained for about ten minutes after which its cha-racters were found to be totally altered ; it had lost its extreme brittleness requiring to be bent ceveral times before a fracture could be effected and then by the aid of the microscope, exhibited a close sinall grained tough aspect of a dull white colour and without the previous cavernous appearances ; the superficial film seemed also in places to have partially sepa-rated from the substance of the thin plate of metal during the ' bending.The specific gravity was a7gRin taken adopting the previous precautions and was found to be 9.95 making an increase of 0.013 or1 the gravity taken before the application of a red heat. I t was next submitted to analysis; 8.5 grains were digested in dilute nitric acid and the soluble parts (A) decanted and the residue well washed. This residue was in small thin grayish-white flakes and by exposure to the light became ra-pidly of cz purple tint indicating the presence of chloride of silver; fearing that this might have arisen from some acci-dental impurity in the materials employed both the nitric ticid and distilled water were carefully tested and proved to be perfectly pure; it was therefore digested in weak solution of ammonia which dissolved the whole with the exception of a small quantity of brown powder which was found to consis Mr.Arrott O?L a Class of Double Sulphates. 49 of 0.06 gr. of peroxide of iron and a trace of gold. The am-moniacnl solution was precipitated by nitric acid and gave 0.52 gr. of chloride of silver. The solution (A) was next precipitated by solution of chloride of sodiuni arid gave 10.25 grains of chloride of silver equivalent to '7.66 grains of silver ; solution of catistic potash and boiling threw down the oxide of copper and yielded 0.30 gr. oxide of copper = 0.24 gr. of copper. Thus we have-Silver . . . . . . '7.66 grains. Chloride of silver. . . 0~52 ... Copper . . . . . 0-24 ... Oxide of iron . . . . 0*06 ... Gold . . . . . a trace . 8.48 Loss . 0.02 8*50 _- __ -~ I t becomes R ciirious question as to the origin of this chlo-ride of silver which was evidently the superficial grayish fillti . observed undrtr the microscope and which partially separated in the act of bending the metal after heating. That it must have been produced by the continued action of cldorides per-haps aided by sulphates present in the brick clay from which the vase was excavated there can be little doubt and the per-oxide of iron also existing in the clay may have assisted this action. The passage of the metal to the brittle state in this and in all other cases will I think be found attributable to some electrical action arising from sudden cooling vibration or concussion chemical acticrn &c. to which the metallic body or alloy may have been exposed

ISSN:0269-3127    

DOI:10.1039/MP8430200047

出版商:RSC    

年代:1843

数据来源: RSC

摘要:

49 GRAHAM Esq. F.li.S. &. ( Was cornmenccd.) M r Arrott O?L a Class of Double Sulphates. January 1 1844.-'l'he President in the Chair. Mr. Warington presented Specimens of Chloride of Antimony a:id of Bichloride of Mercury in Crystals to the Society's Museum. William Lucas Esq. James P. Joule Esq. and Charles J. Hodg- son Esq. were elected Members. The following communications were then read :- On the Iklcat diseqaged irc Combinations. By THOMAS XCIV. On CJ Class of Double Sulphafes corttaining Soda nnd a ikfagnesian Oxide. By A. K. ARROTT Esq. W H E N a mixed solution of sulphate of soda. and any of the magnesian sulphotes is allowed to crystallize by spontaneous evaporation these salts always separate from their 50 r i ... ... 4 HO 4HO 4HO 2 HO Mr.Arrott on a Class of Double Sdphates. solution apart and in their ordinary form no double salt being produced. I find however that if the solution be kept at a temperature exceeding 100’ I?. the temperature at which anhydrous sul- phate of soda begins to be deposited a double salt is formed and this is true of all the magnesian sulphates. The double salts may generally be procured in well-defined crystals ex- cept that of copper which is usually deposited as a crystalline crust. One member of this class of double sulphates namely the sulphate of magnesia and soda was obtained by Dr. Murray in the manufacture of sulphate of magnesia from sea water being produced accidentally during the evaporation of the liquor; but he seems not to have been aware of the circum- stances of its formation.Several soda salts of the same class were also obtained by Mr. Graham by a process which he has described namely by mixing strong solutions of bisulpliate of soda and the mag- nesian sulphate in atcmic proportions; the double salt sepa- rated by crystallization in the course of a few days at the or- tliiiary temperature. The reason why no double salt of soda is formed at low temperatures seems to be the affinity of sul- p h t e of soda for water and the consequent formation of a hydrated sulphate of that base which cannot-enter into such combinations. I h i s interference is however prevented by the use of a high temperature at which as is well known sulphate of soda is deposited from its solution in the anhydrous condition and probably therefore exists dissolved in that state.The method which succeeds best is to dissolve the salts to- gether ill equivalent quantities and to evaporate at n tempe- rature of 130”. In this way I have formed the double salts of soda with magnesia zinc iron copper and manganese. The quantity of water contained in 100 parts of these salts was- Experiment. Theory. Siilphate of niagiiesia and soda 21-68 21.38 19.15 19-69 10.63 ... zinc ... iron ... copper ... . . . manganese 19*’iG 19.86 11.00 11.09 10*89 2 HO which gives 4atonis in the magnesia zinc and iron salts and 2 in those of manganese and copper the per-ceritage of water observed being in all cases rather above the atomic quantity from water mechanically included; double salts being as is Mr.Graham on the Heat disengaged in Combinations. 51 well known remarkable for the quantity of hygrometric water they retain. The salt of magnesia is generally said on the authority of Dr. Murray to contain 6 atonis of water but I have never found it to contain more than 4. These salts are persistent ir air and may be dried at 212' without losing their transparency ; the salts of manganese and magnesia decrepitate strongly when heated. After the loss of their water these salts are all fusible at a low red heat arid undergo that change without decomposition. When the double salt is dissolved in water and the solu- tion allowed to evaporate spontaneously its component salts always crystallize apart the dorible salt heing entirely de- coniposed ; this often happens also with 1 bisulphate of soda.In consequence of this effect of water the solubility at a low temperature ccdd not be observed. When a solntion of the copper salt is boiled a subsalt is precipitated resembling the subsalt of copper and potash formed under similar circumstances. I t is of a pale green colour loses nothing by drying at Z1Z0 but loses weight and becomes much deeper in colour when ignited; it therefore contains water besides an excess of oxide of copper. M r Arrott O?L a Class of Double Sulphates. 49 January 1 1844.-'l'he President in the Chair. Mr. Warington presented Specimens of Chloride of Antimony a:id William Lucas Esq. James P.Joule Esq. and Charles J. Hodg-The following communications were then read :-On the Iklcat diseqaged irc Combinations. By THOMAS GRAHAM Esq. F.li.S. &. ( Was cornmenccd.) XCIV. On CJ Class of Double Sulphafes corttaining Soda nnd a ikfagnesian Oxide. By A. K. ARROTT Esq. W H E N a mixed solution of sulphate of soda. and any of the magnesian sulphotes is allowed to crystallize by spontaneous evaporation these salts always separate from their of Bichloride of Mercury in Crystals to the Society's Museum. son Esq. were elected Members 50 Mr. Arrott on a Class of Double Sdphates. solution apart and in their ordinary form no double salt being produced. I find however that if the solution be kept at a temperature exceeding 100’ I?. the temperature at which anhydrous sul-phate of soda begins to be deposited a double salt is formed, and this is true of all the magnesian sulphates.The double salts may generally be procured in well-defined crystals ex-cept that of copper which is usually deposited as a crystalline crust. One member of this class of double sulphates namely the sulphate of magnesia and soda was obtained by Dr. Murray in the manufacture of sulphate of magnesia from sea water, being produced accidentally during the evaporation of the liquor; but he seems not to have been aware of the circum-stances of its formation. Several soda salts of the same class were also obtained by Mr. Graham by a process which he has described namely, by mixing strong solutions of bisulpliate of soda and the mag-nesian sulphate in atcmic proportions; the double salt sepa-rated by crystallization in the course of a few days at the or-tliiiary temperature.The reason why no double salt of soda is formed at low temperatures seems to be the affinity of sul-p h t e of soda for water and the consequent formation of a hydrated sulphate of that base which cannot-enter into such combinations. I h i s interference is however prevented by the use of a high temperature at which as is well known sulphate of soda is deposited from its solution in the anhydrous condition and probably therefore exists dissolved in that state. The method which succeeds best is to dissolve the salts to-gether ill equivalent quantities and to evaporate at n tempe-rature of 130”. In this way I have formed the double salts of soda with magnesia zinc iron copper and manganese.The quantity of water contained in 100 parts of these salts was-Siilphate of niagiiesia and soda 21-68 21.38 4 HO ... zinc ... 19*’iG 19.15 4HO ... iron ... 19.86 19-69 4HO ... copper ... 11.00 10.63 2 HO . . . manganese 11.09 10*89 2 HO which gives 4atonis in the magnesia zinc and iron salts and 2 in those of manganese and copper the per-ceritage of water observed being in all cases rather above the atomic quantity, from water mechanically included; double salts being as is r i Experiment. Theory Mr. Graham on the Heat disengaged in Combinations. 51 well known remarkable for the quantity of hygrometric water they retain. The salt of magnesia is generally said on the authority of Dr.Murray to contain 6 atonis of water but I have never found it to contain more than 4. These salts are persistent ir air and may be dried at 212' without losing their transparency ; the salts of manganese and magnesia decrepitate strongly when heated. After the loss of their water these salts are all fusible at a low red heat arid undergo that change without decomposition. When the double salt is dissolved in water and the solu-tion allowed to evaporate spontaneously its component salts always crystallize apart the dorible salt heing entirely de-coniposed ; this often happens also with 1 bisulphate of soda. In consequence of this effect of water the solubility at a low temperature ccdd not be observed. When a solntion of the copper salt is boiled a subsalt is precipitated resembling the subsalt of copper and potash formed under similar circumstances. I t is of a pale green colour loses nothing by drying at Z1Z0 but loses weight and becomes much deeper in colour when ignited; it therefore contains water besides an excess of oxide of copper

ISSN:0269-3127    

DOI:10.1039/MP8430200049

出版商:RSC    

年代:1843

数据来源: RSC