摘要:

J O U R N A L OF THE CHEMICAL SOCIETY. aammittu af H. E. ARMSTRONG Ph.D. F.R.S. W. CROOKES F.R.S. WYNDHAM R. DUNSTAN. F. R. JAPP M.A. Yh.D. F.R.S. A. K. MILLER Ph.D. HUGO MULLER Ph.D. F.R.S. @ubIirarian : S. U. PICKERING M.A. W. RAMSAP Ph.D. F.R.S. W. J. RUSSELL Ph.D. F.R.S. J. MILLAE THOMSON F.R.S.E. T. E. THORPE Ph.D. F.R.S. @,bitax : C. E. GROVES F.R.S. Sdr-6lhitar : A. J. GREENAWAY. VOl. LIII. 1888. TRAKSACTIONS. LONDON: GURNEY & JACKSON 1 PATERNOSTER ROW. 1888 LONDON : ST. MARTIN’S LANE. HARRISON AND SONS PRINTERS IN ORDINARY TO nER MAJESTY C O N T E N T S . PAPERS READ BEFORE THE CHEMICAL SOCIETY. PAGE 1.-Synthetical Formation of Closed Carbon-chains in the Aromatic Series. Part I. On some Derivatives of Hy-drindonaphthene and Tetrahydronaphthalene.By lv. H. 11.-Synthetical Formation of Closed Carbon-chains in the Aromatic Series. Part 11. By F. STANLEY KIPPING Ph.D., D.Sc. . 21 111.-Contribntions from the Laboratory of Gonville and Caius College Cambridge. No. X.-The Interaction of Zinc and Sulphuric Acid. By M. M. PATTISON MUIR M.A. and R. H. ADIE B.A. Scholar of Trinity College Cambridge . 1V.-The Dehydration of Metallic Hydroxides by Heat with special reference to the Polymerisation of the Oxides and t o the Periodic Law. By T. CARKELLEY D.Sc. and Dr. V.-Note on a Modification of Traube’s “ Capillarimeter.” By H. S. ELSWORTHY . . 102 V1.-The Constitution of the Copper-zinc and Copper-tin Alloys. By A. P. LAURIE B.A. B.Sc. . . 104 VI1.-An Extension of Mendel6eff’s Theory of Solution to the Discussion of the Electrical Conductivity of Aqueous Solu-tions.By HOLLAND CROMPTON Student in the Chemical Department of the City and Gnilds of London Central Institution . . 116 V1II.-Note on Electrolytic Conduction and on Evidence of a Change in the Constitution of Water an Addendum t9 the foregoing Paper. By HENRY E. ARMSTWNG F.1t.S. . . 125 By WYNDHAM R. DUNSTAN Professor of Chemistry to the Pharmaceutical Society and T. S. DYMOND . . 134 X.-Contributions from the Laboratory of Gonville and Caius College Cambridge. No. X I -Bismuth Iodide and Bis-muth Fluoride. By B. S. GOTT B.A. Scholar of Gonville PERLIN Jun. Ph.D. . . . . 1 47 JAMES WALKER University College Dundee . . 59 1X.-On the Alleged Existence of a Second Nitroethane.and Caius College and M. M. PATTISON MUIR M.A. ‘ . 13 i v @O NTESTS. PAGl E XI.-Halogen substituted Derivatives of Benzalmalonic Acid. By CHARLES M. STUART M.A. Fellow of St. John's College, Cambridge . . . 140 XI1.-Action of Hydrogen Sulphide on Arsenic Acid. By BOHUSLAV BRbUNER Ph.D. F.C.S. late Berkeley Fellow of Owens College and F. T O M f h K . (Communication from the Chemical Laboratory of the Bohemian University, Prague) . . 145 XII1.-Notes from the Chemical Laboratory of the Yorkshire College. No. I. Reduction of Potassium Diclironiatc by Oxalic Acid. By C. H. BOTHAMLEY Assistant Lecturer on Chemistry in the Yorkshire College. No. 11. Estimation of Chlorates by means of the Zinc-copper Couple. By C. H. BOTHAMLEY and G. R. THOMPSON Senior Brown Scholar .. 159 XIV.-The Alloys of Copper and Antimony and of Copper and Tin. By E. J. BALL Ph.D. Assistant in Metallurgy at the Normal School of Science . . 167 XV.-On Morindon. By T. E. THORPE F.R.S. and WILLIAM J. Smm N.B. (Lond.) . . 171 XV1.-On Manganese Trioxide. By T. E. THORPE F.R.S, and F J. HAMBLY . . 175 XVI1.-Note on Chatard's Method for the Estimation of Small Quantities of Manganese. By T. E. THORPE F.R.S. and F. J. HAXHLP . . 182 XVII1.-Action of Phenylhydrazine on an Unsaturated 7-Dike-tone. 184 X1X.-Contributions from the Research Laboratory of the Owens College. The Synthetical Formation of Closed Carbon-chains. Part 111 (continued). Some Derivatives of Pentamethylene. By H. G. COLNAN B.Sc. arid W. H. PERKIN Junr.Ph.D. . . 185 XX.-The Synthetical Formation of Closed Carbon-chains. Part IV. Some Derivatives of Hexarnethylene. By PAUL XXI.-The Synthetical Formation of Closed Carbon-chains. Part V. Experiments on the Synthesis of Heptamethylene-derivatives. By PAUL C. FREER Ph.D. and W. H. PERKZN, Junr. Ph.D. . . 215 XXI1.-On the Range of Molecular Forces. By A. W. RUCKER, XXII1.-On tbe Supposed Identity of Rutin and Quercitrin. By EDWARD SCHUNCK Ph.D. P.R.S. . . 262 XX1V.-On the Composition of Japanese Bird-lime. By EDWARDIVERS M. D. F.R.S. and MICHITADB KAWAKITA, WE. F.C.S. of the Imperial University Tijky6 Japan 268 By FRANC~S R. JAPP F.R.S. and G. N. HuN'rLY C. FREER Ph.D. and W. H. PERKIN Junr. Ph.D . . 202 M.A. F.R.S. . . 22 CONTENTS. IT PAGE XXV.-Chemical InTestigation of Wackenroder’s Solution, and Explanation of the Formation of its Constituents.By Professor H. DEBUS Ph.D. F.R.S. XXV1.-Note on the Density of Cerium Sulphate Solutions. By B. BRAUNER Ph.D. F.C.S. late Fellow of Owens College . XXVI1.-A Gasornetric Method of Determining Nitrous Acid. By PERCY F FRANKLAND Ph.D. B.Sc. F.P.C. Associate Royal School of Mines . XXVII1.-The Action of some Specific Micro-organisms on Nitric Acid. By PERCY F. FRANKLAND Ph.D. B.Sc. F.I.C., Associate Royal School of Mines . XXIX.-Action of Alcohols on Ethereal Salts in Presence of Small Quantities of Sodic Alkylates. By T. PURDTE Ph.D., B.Sc. Professor of Chemistry in the University of St. Andrews and W. MARSHALL B.Sc. . XXX.-Some Interactions of Nitrogen Chlorophosphide.By WARD COULDRIDGE B.A. . XXX1.-Action of Phosphorus Pentachloride on Salicylalde-hyde. By CHARLES M. STUART M.A. Fellow of St. John’s College Cambridge . XXXI1.-Researches on Chrom-organic Acids. Part 11. Certain Chromoxalates. Red Series. By EMIL A. WKRNER Assis-tant in the Chemical Laboratory Trinity College University of Dublin . XXX1II.-The Action of Isothiocyanates on the Aldehyde-ammonias. By AIJG. E. DIXOX M.D. Assistant Lecturei-in Chemistry Trinity College University of h b l i n . XXX1V.-A New Method of Estimating Nitrites either alone or in presence of Nitrates and Chlorides. By T. CUTHBERT XXXV.-The Action of Acetone on Ammonium Salts of Fatty Acids in presence of Dehydrating Agents. By Dr. S. RUHEMANN and D. J. CARNEGIE .. . XXXV1.-Carboxyl-derivatives of Benzoquinone. By J. U. NEF . XXXVI1.-Researches on the Constitution of Azo- and Diazo-derivatives. 111. Compounds of the Naphthalene &Series. By RAPHAEL MELDOLA F.R.S. and F. J. EAST XXXVII1.-Contributions from the Laboratory of Gonville and Cnius College Cambridge. No. XII. The Action of Finely Divided Metals on Solutions of Ferric Salts and a Rapid Method for the Titration of the Latter. By DOUGLAS J. CARNEGIE B.A. Demonstrator in Chemistry Gonville and Cstius College . . DAY . . 2 78 35 7 364 3 73 391 398 402 404 411 422 424 428 460 46 vi CONTENTS. Annual General Meeting . XXX1X.-The Constitution of certain so-called " Mixed Azo-compounds." By FRANCIS R. JAPP LL.D. F.R.S.and FELIX KLINGEMANN Ph.D. XL.-The Influence of Temperature on the Composition and Solubility of Hydrated Calcium Sulphate and of Calcium Hydroxide. By W. SHEKSTONE and J. TUDOR CUNDALL . XL1.-The Action of Phenylhydrazine on Urea and some of its Derivatives. By SIDNEY SKINNER B.A. and S. RUHEMANN, Ph.D. XLI1.-Some Derivatives of Phenylmethacrylic Acid. By L. EDELRANU Ph.D. XL1II.-On the Magnetic Rotatory Power of some of the Unsaturated Bibasic Acids and their Derivatives ; also of Mesityl Oxide. XLIV. -Oxidation of Oxalic Acid by Potassium Dichromate. By EMIL A. WERNER F.I.C. Assistant in the Chemical Laboratory Trinity College University of Dublin XLV.-The Determination of the Molecular Weights of the Carbohydrates. By HORACE T. BROWN and G. HARRIS MORRIS Ph.D.. XLV1.-The Molecular Weights of Nitrogen Trioxide and Nitric Peroxide. By W. RAMSAY Ph.D. . XLVI1.-The Action of Heat on the Salts of Tetramethyl-ammonium. By A. LAWSON and NORMAN COLLIE Ph.D. F.R.S.E. . XLVII1.-Action of Heat on the Salts of Tetramethylphos-phonium. By NORMAN COLLIE Ph.D. F.R.S.E. . XL1X.-Researches on the Relation between the Molecular Structure of Carbon Compounds and their Absorption-spectra. (Part IX.) On Isomeric Cresols Dihydroxy-benzenes and Hydroxybenzoic Acids. By W. N. HARTLEY, F.R. S. Professor of Chemistry Royal College of Science, Dublin . L.-Proof of the Identity of Natural and Artificial Salicylic L1.-Researches on the Constitution of Azo- and Diazo-deriva-tives. IT. Diazoamido - compounds (continmed).By RAPHAEL MELDOLA F.R.S. and F. W. STREATFEILD F.I.C. . L1I.-The Optical and Chemical Properties of Caoutchouc. By J. H. GLADSTONE Ph.D. F.R.S.,and WALTERHIBBERT F.I.C. LII1.-On an Apparatus for Maintaining a Constant Pressure when Distilling under Reduced Pressnre. By W. K. PERKIN Ph.D. F.R.S. By W. E. PERKIN Ph.D. F.R.S. . . Acid. By W. N. HARTLEY F.R.S. . v . PAGE 474 519 544 550 558 561 602 610. 621 624 636 641 664 664 679 68 CONTENTS. 1'11 PBGE L1V.-Chlorofumaric and Chloromaleic Acids and the blagnetic Rotatory Power of some of their Derivatives. By W. H. PERKIN Ph.D. F.R.S. LV.-On a New Method for the Preparation of Mixed Tertiary Phosphines. By NORMAN COLLIE Ph.D. F.R.S.E. . LVL-The Chemical Actions of some Micro-organisms.By R. WARIWGTON . LVI1.-Some Reactions of the Halogen Acids. By G. H. BAILEY D.Sc. Ph.D. and G. J. FOWLER B.Sc. the Owens College . LVIII .-The Action of Potassium on T et ralkylammonium Iodides. . L1X.-The Vapour-density of Hydrofluoric Acid. By T. E. THORPE F.R.S. and F. J. HAMBLY. (Preliminary Notice.) LX.-Thiophosphoryl Fluoride. By T. E. THORPE F.R.S and J. W. RODGER. (Preliminary Notice.) . LX1.-The Action of Bromine on Potassium Ferricyanide. By EDGAR J. REYNOLDS Student in the Laboratory of the Normal School of Science South Kensington . LXI1.-Some Amines and Amides derived from the Nitrani-lines. By RAPHAEL MELDOLA F.R.S. and E. H. R. SALMON LXII1.-The Rotatory Power of Benzene-derivatives. By J. LEWKOWITSCH P1i.D.. LX1V.-The Solubility of Isomeric Organic Compounds and of Mixtures of Sodium and Potassium Nitrates and the Rela-tion of Solubility to Fusibility. By THOMAS CARNELLEY, D.Sc. and ANDREW THOMSON D.Sc. M.A. University Col-lege Dundee . LXV.-The Action of Chromium Oxychloride on Orthosubsti-tuted Toluenes. By CHARLES M. STUART M.A. Fellow of St. John's College Cambridge and W. J. ELLIOTT Scholar of Christ's College Cambridge . LXVI.-The Molecular Weight of Iodine in its Solutions. By MORRIS LOEB Ph.D. . LXVIL-The Use of Aniline as an Absorbent of Cyanogen in Gas Analysis. By MORRIS LOEB Ph.D. . LXVIII.-On two new Chlorides of Indium and on the Vapour-densities of the Chlorides of Indium Gallium Iron and Chromium. By L. F. NILSON and OTTO PETTERSSON . TlXTX.-On some Derivatives of Anthraquinone.By A. G. PERKIN and W. IT. PERKIN Jun. Ph.D. LXX.-Thc Influence of Silicon on the Properties of Iron and Steel. Part 11. By THONAS TURNER Assoc. R.S.M., F.I.C. Lecturer on Metallurgy Mason College Birming-ham . . . By C. 31. THOMPSON and J. TUDOR CUNDALL . . 695 7 14 727 755 761 765 766 76 7 7 74 781 782 803 805 81 2 814 83 1 84 . V l l l CONTENTS. ??AGE LXX1.-The Isonitrile of Phenylhydrazine. By S. RUHENANN, Ph,D. and W. J. ELLIOTT. . 850 LXXI1.-Researches on Silicon Compounds and their Deriva-tives. Part 111. The Action of Silicon Tetrabromide on Allgl- and Phenyl- thiocarbamides. Part IV. The Action of Ethyl Alcohol on the Compound (H,N,CS),SiBr4. By J. EMERSON REYNOLDS M.D. F.R.S. Professor of Cbemistry, University of Dublin . . 853 LXXII1.-The Heat of Dissolution of Substances in different Liquids and its Bearing on the Explanation of the Heat of Neutralisation and on the Theory of Residual Affinity. By SPENCER UMFREVILLE PICKERING M.A. Professor of Chemistry at Bedford College . . 865 LXX1V.-The Constitution of the Terpenes and of Benzene. By WILLIAM A. TILDEN D.Sc. F.R.S. . 879 LXXV.-Combustion by Means of Chromic Anhydride. By C. El. CROSS and E. J. BEVAN . . 88

ISSN:0368-1645    

DOI:10.1039/CT88853FP001

出版商:RSC    

年代:1888

数据来源: RSC

摘要:

CLOSED CARBOX-CHAINS IN THE AROMATIC SERIES. 21 II.-Spthetical Formation of Closed Carbon-chains in the Aronzatic Series. Part 11. By F. STANLEY KIPPING Ph.D. D.Sc. AMONG the vast number of aromatic hydrocarbons there are many which have been proved to contain two or more benzene nuclei con-densed together that is to say they are compounds in which certain carbon-atoms are common to both rings as for example naphthalene, anthracene and phenanthrene. Other substances are known in which one or more atoms of nitrogen displace one or more atoms of carbon in the closed chain without producing any alteration in the fundamental constitution of the com-pound ; for instance quinoline acridine and pseudoanthroline. Quinoline. Acridine. Pseudoanthroline. Now in examining the formul~ which according to the present theoretical views have been proved both by synthetical and analytical methods to represent the constitution of the compounds mentioned, i t is at once evident that the carbon-atoms which are common to any two rings are situated in the ortho- or 1 .2-position ; up to the present time no compound has been obtained in which two carbon-atoms, occupying the meta- or para-position i n one closed chain enter into the formation of the adjoining one ; although in the present state of our knowledge of the formation of closed chains there is no & priori reason why such compounds should not exist and why for instance, isomeric naphthalenes having the formu1~-I.1 11. 1 could not be formed. In formula I two carbon-atoms in the meta-position would be common t o both rings and in formula I1 this would be the case with two carbon-atoms in the para-position.I t seemed an interesting subject for research to attempt to syntlresis 22 KIPPING SYNTHETICAL FORMATION OF either such hydrocarbons themselves or some derivatives of them in order to obtain experimental evidence as to the possibility of the existence of compounds so constituted. In Part I of this paper (this vol, p. l) W. H. Perkin jun. has described the synthesis of naphthalene from ortho-xylene by a series of reactions which forms an additional proof that condensation of the benzene-rings takes place in the ortho-position ; if isomeric naphtha-lenes or derivatives of such compounds can be produced it seemed probable that they would be obtained in an exactly similar manner when meta- or para-xylene was used in place of the ortho-compound.Acting on the kind suggestion of Perkin I undertook to work out this research and proceeded in the following manner meta-xylene was treated with bromine and the meta-xylylene bromide thus obtained was acted upon in ethereal solution with ethylic chloro-malonate and sodic et hylate when ethylic meta-xylylenedichlorodi-malonate was formed the reaction being expressed by the following equation :-By treating this product with reducing agents the chlorine is dis-placed by hydrogen and ethylic meta-xylylenedimalonat8e formed, thus :-c6H4[ CH,*CC1(COOCzH,)z]z + 2Hz = CsH4[ CH2*CH(COOC,H5),] + 2HC1. On adding sodic ethylate to an ethereal solution of this ethylic salt a disodium-derivative is produced thus :-C6Ha[CH,.CH(COOCzH,)z]2 + 2C2H5.0Na = ~ 6 ~ - [ ~ ~ 2 * ~ ~ a ( ~ ~ ~ ~ 2 ~ > l + 2C2H5*OH.By a,ppropriate treatment vith iodine or bromine it was thought that the sodium would be e'liminated and from this compound a tetrahydrometanaphthalene-derivative obtained according to the fol-lowing equation :--CH,.C (COOC,H,)2 + 2Na1, CH2. CNa (COOCZHJ 2 from which by hydrolysis and removal of two carboxyl-groups tetra-hydroxnetanaphthalenedicarboxylic acid would be obtained CLOSED CARBON-CHAINS I N THE AROMATIC SERIES. 23 A dicarboxylic acid was in fact obtained which was at first thought to be the desired compound ; on careful examination however it was found that it contained no meta-ring but was simply metaphenylene-dipropionic acid--CH,*CH,.COOH /\ It will be seen that this acid differs in composition from the hypo-thetical metanaphthalene-derivative only by two atoms of hydrogen, and that therefore analysis alone would be insufficient to distinguish between them with certainty ; it can be proved beyond doubt how-ever that no closed ring has been formed in the above reactions for when ethylic met.a-xylylenedimalonate is directly hydrolysed without previous treatment with sodic ethylate and iodine (or bromine) the dicarboxylic acid which is ultimately obtained is identical with that which was supposed to be a tetrahydrometanapht#halene-derivative.It is diflicult to explain what takes place when the above-mentioned sodium-derivative is treated with iodine (or bromine) but it would seem that the halogen destroys a portion of the substance with formation of hydriodic (or hydrobromic) acid which then reacts on the remainder reproducing the ethereal salt and the respective halofcl sodium compound.In spite of the failure of these experiments t o produce a meta-closed ring the conclusion was not justified that a para-ring could not be formed since according t o the present theories held regarding the constitution of the numerous compounds containing a pyridine-ring and of the paraquinones a union of two atoms in the para-position either directly or through the interposition of other atoms is assumed. Para-xylene was therefore prepared and submitted to a series of reactions exactly in the same way as in the case of the meta-hydro-carbon ; the sodium compound of ethylic para-xylylenedimalonate was obtained and treated with iodine (or bromine) in the hope of forming a tetrahydroparanaphthalene-derivative.But here again no closed ring could be produced ; when iodine is used the reaction which takes place appears t o be similar to that snggested as the most probable in the case of the meta-cornpound, and the dicarboxylic acid which is the ultimate product is not 24 RIPPING SYNTHETICAL FORMATION OF tetrahydroparanaphthalene-derivative but simply paraphenylenedi-propionic acid-,yCH,*CH,*COOH I I \~-CH,.CH,~COOH This was proved in a manner similar to tbat already described. When bromine is used the reaction is quite different ; substitution takes place and ethylic para-xylylenedibromodimalonate is formed, most probably as expressed by the equation-2C6H4[CH2*CNa(COOC,H,),l + 2Br2 = C6H4[CH2*CBr(COOC,H5>?]2 + ZNaBr + C6H4[ CH,.CNa(COOC2H5),],.From these experiments then the conclusion may be drawn that compounds containing rings condensed together in the meta- or para-position are incapable of existence otherwise they would have been formed by the methods which have been described ; now this may be so for one of two reasons-either on account of the relative positions of the two rings or because of the number of carbon-atoms which would form the reduced ring ; in tetrahydrometanaphthalene as will be seen from the figures already given there would be seven in tetra-hydroparanaphthalene there would be eight carbon-atoms in the larger closed chain.To help to a decision on this point experiments were made with the object of obtaining a derivative of a compound having the formula-which like naphthalene itself would contain six atoms in each ring ; a compound of this character should be obtained by treating meta-xylylene bromide with 2 mols. of sodic ethylate and l mol. of ethylic malonate according to the equation-+ CH2(COOC,H5) + ZC,H,.OKa = ,\CH,Br () CH,Br \/- CH2 + 2C2Hs.0H + ZNaBr, in a manner exactly similar to that in which hpdrindonaphthene CLOSED CARBCN-CHAINS I N TBE AROMATIC SERIES. 25 derivatives were prepared by Perkin (see Part I this vol. p. ’7). But although the experiment was repeated several times under varied conditions no such compound could be obtained ; the reaction was evidently of a very complicated nature and yielded a resinous mass from which no definite product could be isolated.It seems, therefore that the non-formation of R meta- or para-ring in any of these cases is due not entirely to the number G f atoms which would go t’o form the ring but also and perhaps wholly to its relative position. It is a general law in the chemistry of the aromat,ic compounds that no substance can be obtained in which a ring of any sort is joined to the benzene nucleus in other than the ortho-position e.g., the coumarins carbostyrile-derivatives quinoxaline &c. ; the simplest bibasic acid-phthalic-is readily converted into the anhydride, whilst the isomeric meta- and para-anhydrides have not yet been prepared.The two isomeric meta- and para-phenylenedipropionic acids obtained in this research by reactions already described were of considerable theoretical interest owing to the fact that if anhydrides could be obtained from them they would contain a closed ring in the meta- and para-position respectively as shown by the formuh Attempts were therefore made in this direction but without success, and it was thought that perhaps this was owing to the large number of atoms which would have to take part in the formation of the closed ring in the fatty series as is well known many dicarboxylic acids can be converted into anhydrides but whether this is possible or not depends ou the relative positions of the carboxyl-groups that is on how many carbon-atoms go to form the anhydride-ring.To throw some light on this question meta- and para-xylylene cyanides were prepared and from them by hydrolysis the corresponding phenylene-diacetic acids ; it seemed possible that these compounds containing as they do one atom of carbon less in eslch of the side chains would be more capable of forming anhydrides; these would have the € o r m u l 26 KIPPING SYNTHETICAL FORMATION O F No anhydride however could be obtained from either of these acids, and the conclusion drawn from all the experiments briefly described above confirms the general law that no exterior ring in the ineta- or para-position can be formed. CH2Br (1) Meta-xylylene Bromide C6H4 <CK,Br (3). Meta-xylylene bromide was first obtained by Colson (Compt.rend., 99 40) by brominating boiling meta-xylene ; in preparing large quantities of this substance I have found that the following method gives the best results :-50 gmms of pure meta-xyleiie placed in a retort connected with a long reflux condenser are heated in an oil-bath to 125-130" 160 grams of bromine are then added by means oE a dropping funnel inserted into the tubulus of the retort; at first the bromine may be added tolerably quickly but later on when the meta-xylene is partialIy converted and red fumes escape up the condenser, the halogen must be added slowly otherwise loss is incurred. The hydrogen bromide which is eTolved in large quantities during the reaction is absorbed by conducting it into a concentrated solution of caustic soda'. When all the bromine has been added the contents of the retort, which ought to be only slightly coloured are poured out and left 24 hours in a cool place to crystallise ; the mother-liquor is drained off and the crystals after lying for some time on a porous plate are purified by recrystallisation from light petroleum ; meta-xylylene bromide is thus obtained in the pure state as a colourless solid melting a t 77" the melting point given by Colson (Zoc.cit.). From 50 grams of meta-xylene the quantity of pure bromide obtained is not very large the mother-liquor can however be worked up for a less pure product. In consequence of the painful effect of the vapour 011 the eyes it is best when using meta-xylglene to work as much as possible in the open air. Ethyldc Meta-xylyleqisdichlorodinaalonate, CsHa[CHz*CCl( COOC,H,),],.This compound is obtained by t,he action of ethylic chloromalonate and sodic ethylate on meta-xylylene bromide ; 4.4 grams of sodium, dissolved in as small a quantity of alcohol as possible are mixed with about 10 volumes of pure ether and a solution of 37.8 grams of ethylic chloromalonate in 500 C.C. pure ether slowly added ; after well cooling the mixture 25.5 grams of finely -powdered meta-xylylene bromide are thrown in and the whole well shaken. The white pre-cipitate which is a t first formed is the sodium-derivative of ethyli CLOSED CARBON-CHAINS I N THE A4RO?rlATIC SERIES. 27 chloromalonate but as the meta-xylylene bromide dissolves a lively reaction commences and the ether begins to boil the sodium-derivative being decomposed with formation of et hylic meta-xylylene dichlorodimalonate and sodium bromide.The mixture is then heated on a water-bath for a couple of hours great care being taken to shake occasionally otherwise there is considerable danger of the ether boiling over from the bumping which always occurs ; water is subsequently added the ethereal solution washed and separated dried over calcium chloride and the ether distilled off. Ethylic meta-xylylene dichlorodimalonate remains as a thick, yellowish oil which even after long st'anding over sulyhuric acid in a vacuum shows no signs of crystallising ; on analysis the following results were obtained :-I. 0.1615 gram substance gave 01015 gram AgC1. 11. 0.2805 , I 0.1660 , ,, Found. Calculated for -7 C23H2,0&1:.I. 11. C1 14.4 p. c. 15-5 24.6 p. c . The second analysis was made from a different sample the ethereal salt used in (I) having been found to contain a trace of unchanged meta-xylylene bromide. When the calculated quantities of ethylic chloromalonate and nieta-xylylene bromide are carefully weighed the resulting ethylic rneta-xylylene dichlorodimalonate is almost pure and the yield quanti-tative. Eth yZic Meta-xy Zy Zenedimdonufe C6H4[ CH,*CH(COOC,H,),],. When the chlorine-compound described above is dissolved in about 15 volumes of glacial acetic acid and a small quantity of zinc-dust added reduction at once commences the mixture becoming quite warm. The process is best carried out by adding the zinc-dust in very small quantities at a time for about an hour the whole being constantly shaken in a long-necked fiask ; at the end of this time the solution becomes very thick owing to the formation of zinc acetate and reduction proceeds only very slowly ; water is therefore added the mixture warmed on the water-bath and the ethereal salt extracted with ether not only from the solution but also from the undissolved zinc-dust which retains a considerable quantity of the substance; the ethereal solution after washing first with water and then with sodium carbonate solution to get rid of acetic acid is dried over anhydrou 28 KIPPIKG SYNTHETICAL FORMATION OF potassium carbonate and the ether distilled off.The oil which remains still contains a considerable proportion of the unchanged chlorinated derivative the reduction is therefore repeated in exactly the same manner ; it was found however that even after three such treatments a trace of chlorine is still present; the best results are obtained when only small quantities a t a time are operated upon.In order to prepare this substance pure for analysis use is made of the sodium-derivative ; a-hen the calculated quantity of sodium, dissolved in absolute alcohol and mixed with about 10 volumes of ether is added t o a weak ethereal solution of ethylic meta-xylylene dimalonate a white precipitate of the disodium-derivative is formed. This is washed with ether on the filter-pump as quicltly as possible, and then thrown into water or dilute sulphuric acid when it is a t once decomposed yielding ethereal salt and sodium hydrate (or sulphate).The oil which separates is extracted with ether and after drying the ethereal solution with calcium chloride it is treated again, exactly as before with the calculated quantity of sodic ethylate ; the precipitate is washed as above decomposed with dilute sulphuric acid, the solution extracted with ether and the product isolated in the usual manner. Ethylic meta-xylylenedimalonate is thus obtained in the pure state as a t>hick colourless oil which however could not be obtained in the crystalline form ; it is readily soluble in ether alcohol acetic acid, &c. but insoluble in water. The following results were obtained on analysis :-0.1550 gram substance gave 0,3522 gram CO and 0.1016 gram H,O. Calculated for C22H30QY Found.C . . 62.56 per cent. 6197 per cent. H . . . . . . 7.11 , 7-28 ,, 0 . . 30.33 , 30.75 ,, The sodium-derivative of this ethereal salt is a white solid which, however on account of its extremely hygroscopic nature soon decom-poses on exposure to the air. To prepare a sample for analysis a few grams of ethylic meta-xylylenedimalonate are dissolved in a large volume of dry ether and the calculated quantity of sodic ethylate, mixed with about 10 volumes of ether added to the solution. The flask is tightly corked and the mixture after being well shaken is allowed to stand in order that the precipitate may settle; when it has completely subsided i t is washed twice by decantat,ion with pure ether (the air being excluded as much as possible) and after drainin CLOSED CARBON-CHAINS I N THE AROXATIC SERIES.29 off the ether as far as possible quickly transferred to a tared s t,o ppered weighing- bo t tle. After standing in a vacuum over sulphuric acid a sodium determi-nation was made from which the following result was obtained :-0.4055 gram substance gave 0.1215 gram sodic sulphate. Calculated for CzzHzF4NazQ3. Found. Na . . . . . . . . 9.9 per cent. 9.7 per cent. Experiments were now made to obtain a tetrahydrometanaphtha-lene-derivative from the disodium malonate. The following is a description of the methods employed :-The calculated quantity of sodium dissolved in alcohol and mixed with about 10 volumes of ether is added to a weak ethereal solution of ethylic meta-xylylenedimalonate and after allowing the sodium-deriva-tive to separate out which takes but a very few moments a very slight excess of the calculated qiiantity of iodine also dissolved in ether is added and the mixture vigorously shaken.The dark-brown colour of the iodine rapidly disappears and in a few minutes the reaction is completed the slightly brown colour of the solution being due to the small excess of the halogen used; after adding water t o dissolve the sodic iodide and removing the trace of iodine by means of dilute sulphurous acid the colourless ethereal solution is washed with water dried and the ether dislilled off when the ethereal salt of a tetracarboxylic acid remains behind as a thick brown oil. This salt is hydrolysed by boiling it for two hours on the water-bath with a solution of potash in methyl alcohol ; the alcohol is then evaporated and the potassium-compound dissolved in water ; on acidifying this solution with dilute sulphuric acid a small quantity of impurity is pre-cipitated this is filtered off and the filtrate extracted repeatedly with ether.The acid obtained on distilling off the ether is a thick brown oil which as it could not be obtained crystalline was without purify-ing converted into the dicarboxylic acid ; this is effected by heatirig it in a flask in a metal-bath at 180-200" a considerable amount of decomposition taking place with a copious evolution of carbonic anhydride. When no more gas is given off the process is at an end, and on cooling the contents of the flask become solid. To purify the product it is now converted into the ethylic salt ; for t'his purpose it is dissolved in dilute ammonia the excess of the latter removed by standing in a vacuum over sulphuric acid and the solution filtered to get rid of a small quantity of oil which is present; silver nitrat'e is then added to the filtrate and the silver salt thus formed is washed with water ou the filter-pump.After careful drping it is suspeiide 30 KIPPINQ SYNTHETICAL FORJIATION O F in ether treated with an excess of ethyl iodide and boiled on the water-bath with reflux condenser for about two hours whereby the silver salt is completely decomposed. The silver iodide is filtered off and well washed with warm ether the washings added to the filtrate and the ethereal salt obtained by distilling off the ether ; it is however still impure and is therefore submitted to fractional distillation under diminished pressure.A trace of ethyl iodide first comes over the t’hermometer then rapidly rises and the whole distils between 200” and 250” (60 mm. pressure) ; the high boiling portion is again fractioned when almost the whole distils over without decomposition constantly a t 247-250” as a colourless mobile oil. An analysis was now made which however agreed equally well for either of the two formula+-CII,CH(COOC2H,) CH2*C H2 (C 0 0 C,H,) \CH,CH (cooc,~,) “CH2*CH,( COOC,H,j C6H4’ I or CH’ As the acid itself would probably crystallise and conId therefore be more easily obtained in a high degree of purity furtber attempts to purify the ethereal salt were considered unnecessary and it was converted into the acid by boiling with a solution of pure potash in methyl alcohol ; when hydrolysis was complete the solution was evaporated to dryness the potassium salt dissolved in water dilute sulphuric acid added in excess and the organic acid extracted with ether.After isolating the product in the usiial way and recrystal-lising it from boiling water it was obtained in beautiful glistening plates ; an analysis was made which again did not decide whether the ring formation had taken place or not and other means had therefore to be employed to settle this point beyond doubt. Metaphenylenedi-propionic acid was prepared according to the methods described later on and as this substance which must hare the formuIa CsH,(CH2*CH,.COOH)2, is identical with the acid obtained above i t is quite clear that no met,a-ring had been formed by the action of iodine on the sodium-derivative of ethylic meta-xylylenedimnlonate.Another attempt to obtain a tetrahydrometanaphthalene-derivative was therefore made ; in this case bromine was used instead of iodine, and since there was a considerable loss from decomposition on heating the tetracarboxylic acid in the metal-bath another method for eliminat-ing the two carboxyl-groups was adopted. The following is an account of the manner in which the experiment was carried out to a solution of 1.4 grams of sodium dissolved in 15 grams of absolute alcohol and mixed with 50 C.C. of pure ether 12 grams of ethylic meta-xylylene CLOSED CARBON-CICAIKS IN THE AROMATIC SERIES.31 dimalonate in ethereal solution were added and the mixture allowed to stand in a freezing mixture until the sodium compound had com-pletely subsided ; 4.6 grams of bromine were then gradually dropped in the whole being kept well cooled. Each drop of bromine was immediately absorbed the few last oiily causing the solution to assume a slightly yellow colour. The product of this reaction was separated as already described in the experiment with iodine and the ethereal salt hydrolysed by boiling it for two hours with alcoholic potash ; 9 grams of the tetra-carboxylic acid were thus obtained in the form of a brown oil which could not be got to crystallise; it was therefore mixed with about three times its weight of water and heated in a sealed tube first a t l l O o then after opening the capillary to get rid of the carbonic anhydride a t 150° and finally again a t 180" until the evolution of gas entirely ceased.The contents of the tube when cool consisted of two layers; the undermost after standing for some time solidified almost completely, whilst the upper one was filled with colourless crystals. After purifi-cation these crystals were found to be identical with the acid obtained before-viz. metaphenylenedipropionic acid. The solid mass which formed the lower layer was dissolved in boiling water and after filtering allowed to crj-stallise; again the same acid was proved to have been formed and the quantity obtained was from l$-2 grams. About 3 grams of a black resinous mass from which no crystalline product could be isolated remained on the filter ; the mother-liquor from the acid yielded nothing but a further quantity of impure meta-phenylenedipropionic acid which took the form of a slightly yellow oil.The result of these two experiments showed therefore that by acting on the sodium compound of ethyl meta-xylylenedimalonate with bromine 01- iodine no meta-ring is produced and the same compound is ultimately obtained after hydrolysis and elimination of two carb-oxyl-groups whether this reaction is carried out or not ; the possibility that such a ring can exist is thereby rendered improbable. ~ ~ t a - x y ZyZenedimaZonic Acid C6H,[ CH,-CH( COOH)2]2. When the crude ethylic salt of this acid (see p. 27) is boiled with excess of potash in methylic alcohol until no oil is precipitated on addition of water hydrolysis is complete ; this is the case after about two hours.The alcohol is distilled off and the potassium salt which is obtained on evaporation to dryness is dissolved in water; the addition of sulphuric acid in excess produces a slight turbidity the solution i 32 KIPPING SYNTHETICAL FORMATION OF therefore filtered and the product extracted from the filtrate hy shaking out about 10 times with pure ether. When the ehher is distilled off meta-xylylenedimalonic acid remains behind as a thick, slightly brown oil which is readily soluble in water alcohol and ether Unfortunately it could not be obtained in the crystalline form so no analysis of it was made; that its constitution is that represented by the above formula is however proved by its method of formation and by its decompositions also by a comparison with the isomeric para-acid described later on to which it is strictly analogous.iMet apheny Zenedipropio~zic Acid CsH,( C H,* CH,*CO OH) ,. On heating the tetracarboxylic acid just described it is readily convertfed into metaphenylenedipropionic acid with elimination of 2 mols. of carbonic anhydride. This conversion may be effected in two different ways:-First, meta-xylylenedimalonic acid is heated in a small flask in a metal-bath ; as soon as the temperature rises above 100" carbonic anhydride begins to be evolved the evolution becoming more rapid as the temperature rises; after keeping the bath a t about 180" for some time no more carbonic anhydride is given off and the change is com-plete.On cooling the dark-brown oil solidifies to an almost solid cake which is dissolved in hot water boiled with animal charcoal, and the solution filtered ; the new acid crystallises from the filtrate in beautiful colourless plates and is obtained pure by three recrystallisa-tionfi from boiling water. The second method for the preparation of this substance takes up far more time but it is preferable as the yield is far better mek-xylylenedimalonic acid is dissolved in about three times its volume of water and heated in a sealed tube for one hour a t 100-120"; the tube is then allowed to cool and the capillary opened to permit of the escape of the carbonic anhydride ; after re-sealing it is heated again a t 150" for an hour the gas formed allowed to escape and the contents of the tube raised to a temperature of about 180" for Some considerable time.The tetrabasic acid is now completely decomposed, and the liquid which was a t first homogeneous is found after cooling, to have separated into two layers; the bottom one solidifies corn-pletely whilst the top one is filled with leaf-like crystals. To purify the product the whole is collected and the residue after spreading on ;t porous plate to remove traces of oil is dissolvcd in boiling mrater, and the solution filtered. On cooling pure metaphenylenedipropionic acid separates in magnificent lustrous colourless plates. It was drie CLOSED CARBON-CHAINS IN THE AROMATIC SERIES. 33 over sulphuric acid then a t loo" and analysed with the following result :-0.1690 gram substance gave 0.4010 gram CO and 0.0985 gram H,O.Calculated for Cl2H140.1. Found. C 64.86 per cent. 64.71 per cent. H . . . . . . . . 6.31 , 6.47 ,, 0 . . . . . . . . 28-85 , 28.82 ,, Metaphenjlenedipropionic acid when pure melts a t 146-147" ; it is nioderately soluble in hot but almost insoluble in cold water and dissolves easily in ether and alcohol. On precipitating a neutral solution of the ammonium salt with silver nitrate the silver salt falls clown as a white amorphous precipitate; after washing well and drying over sulphuric acid in a vacuum it was analysed with the following result :-0.3318 gram substance gave 0.1638 gram Ag. Calculated for CnH,:Ag@4. Found. Ag 49-54 per cent. 49.37 per cent.This salt is very stable and does not darken when exposed to diffuacd light. In an aqueous neutral solution of the ammonium salt lead acetate gives a white amorphous precipitate copper sulphate a light bluish-green precipitate and zinc sulphate a white crystalline precipitate. Barium chloride gives no reaction. An experiment was made to try and obtain the anhydride of this acid by heating a small quantity for half an hour in a metal-bath a t a temperature of 250". The acid darkened in colonr traces of water were evolved and a slight amount of decomposition took place ; on heating more strongly over the naked flame a brown oil distilled and almost immediately solidified. After washing the product with ether on a porous plate an almost colourless substance was obtained which showed the same melting point as the original acid; no anhydride was therefore formed.ill eth y 1 ic Metapheny lenedipropionate. This ethereal salt is obtained in the usual manner by treating argentic metaphenylenedipropionate with methyl iodide. The pure dry silver salt is mixed with at1 excess of methyl iodide dissolved in 10 volumes of ether a i d the mixture heated on the VOL. LIII. 34 RlPPING SYNTHETICAL FORMATION O F water-bath with reflux condenser for about five hours ; a t the end of this time the silver salt will be entireIy decomposed. To isolate the product the silver iodide is filtered off wnslied with ether and the washings added to the filtrate ; on distilling off tlie ether a thick colourless oil remains behind which in a short time solidifies to a hard cake of crystals ; it is purified by spreading on a porous plate and recrpstdlising from dilute methyl alcohol.Mc4hylic meta-phenylenedipropionate is thus obtained pure in tlie form of colonrless plates and on analysis the following results were obtained :-0.1570 gram substance gave 0,3865 gram CO and 0.1065 gram H,O. Calculated for C14HI,O,. Pound. C 67-2 per cent. 67.14 per cent. H 7.2 , 7.53 7, 0 25.6 , 25-33 ,, This substance is very easily soluble in ether alcohol and benzene, but only sparingly in cold methyl alcohol ; it melts at 51" and when heated in small quantities at a time distils a t a high temperature almost without decomposition. E t lay 1 i c Met ap he 11 y 1 e n e d $3 r opio n at e .This is obtained in a manner exactly similar to that used in the preparation of the methyl salt just described; it is a colourless oil, which boils at 247-250" (60 mm. pressure) without decomposition. The analysis gave the following results :-0,1243 gram substance gave 0.3171 gram CO and 0.0866 gram H,O. Calculated for C 6 ~ ~ 2 2 0 4 * Found. C 69.07 per cent. 69.55 per cent. El 7.91 , 7.74 ,, 0 23.02 , 22.71 ,, Pal-a-zy 7y lene Bromide C6H4 ( C H,Br) 2. This is prepared by brominating para-xylglene in the same way a s described ullder the meta-compound. When the reaction is finished, the product is allowed t o stand for a short time ; it then solidifies and is purified by simply spreading on a porous plate. The yield obtained ranges from 85-90' of the theoretical.The action of the vaponr of this substance on the eyes is extremely painful it is adrisable there-fore to work as much as possible iii the open air CLOSED CARBOY-CHAIXS I N THE RRONATIC SERIES. 35 Ethy 1 ic Para-x y 1 y Ze ned icl~lorod imn Zonat e C5H4 [ CH,C C 1( C 0 0 C2H5) 2 1 2 . 36.8 grams of ethylic chloromaIonate are dissolved in about 500 C.C. of ether the calculated quantity of sodium dissolved in absolute alcohol and mixed with 10 volumes of ether added and then 25 gmrris para-xyljlene bromide thrown in and the mixture vigorously shaken. The sodium-derivative of ethyl chIoromalonate first forms, but on continued shaking the para-xylylene bromide dissqlves and the reaction commences ; no appreciable warming of the mixture how-ever is noticed.After heating on the water-bath with reflnx condenser for about! four hoiirs care being taken on account of the great tendency of the niixture t o bump water is added to dissolve the sodium bromide, and the ethereal solution is then separated ant1 dried. When the ether is distilled off ethyl para-xylylenedichlorodimalonate remains as a thick brownish oil the amount obtained being in accordance with theory. On standing for some houm this oil is converted into a crystalline solid mass ; the adhering mother-liquor is removed by spreading on a porous plate and the product puizified by recrystallisation from alcohol. In this way the ethereal salt is obtained in large colourless six-sided plates ; it melts a t 86-87' is readily soluble in alcohol ether light petroleum acetic acid &c.but is insoluble in water. A chlorine determination gave the following result :-0.3715 gram substance gave 0.2200 gram AgCl. Calculated for W%*CI,O,. Found. (31 . . . . . . 14.4 per cent. 14.6 per cent. Rt lag Zic Para-xy 1 y ZenadirnaZonnte C,H [ CH,*CH ( C 0 0 C,H j 2] 2. To prepare this substance the chlorine-compound just described is reduced with zinc-dust and acetic acid in exactly the same way as the corresponding meta-ethereal salt. About 15 grams are dissolved in 15 C.C. of glacial acetic acid and a small quantity of zinc-dust added ; as the reduction commences the mixture becomes warm After constant shaking for about an hour with frequent addittion of small quantities of zinc-dust wafer is added and the mixture warmed on the water-bath in order to dissolve the zinc acetate ; the whole is then shaken out with ether several times the ethereal solution washed with water and sodium carbonate to get rid of the acetic acid dried over anhydrous potassium carbonate and the ether distilled off.Ethyl para-xylylenedirnalonate remains behind as in the case of the u . 3 6 RIPPING SYNTHETICAL FORJIATIOX OF meta-derivative however a very considerable quantity of the chlorine eompoiind still remains unreduced ; it is necessary therefore to repeat the treatment with zinc-dust and acetic acid and it was found best to work with only small quantities of the substance and submit it to a t least three reductions. It is thus obtained as a slightly yellow oil, which if allowed to remain over sulphuric acid in a vacuum in a few days deposits a quantity of colourless crystals ; these are freed from oil by spreading them on a porous plate and washing with a trace of alcohol, when the substance is obtained quite pure ; after drying in a vacuum, an analysis was made with the following results :-0.2285 gram substance gave 0.5215 gram C02 and 0.1495 gram H20.Calculated for C22HROO,S. Found. C 62.56 per cent. 62.24 per cent. H . . 7.11 , 7-27 ,, 0 . . 30-33 , 30.49 ,, E thylic para-xylylenedimalonate is a fine white crystalline sub-stance which melts at 51" ; it is very readily soluble in ether far less so in alcohol and insoluble in water. This ethereal salt like the corresponding meta-derivative forms a compound with sodium which is obtained as a white precipitate when the calculated quantity of sodic ethylate aiid ethyl para-xylylenedimalonate are mixed together in ethereal solution.The precipitate is washed with pure dry ether, by decantation the same precautions being taken to exclude the air as mere described in the preparation of the meta-compound thrown on to a filter and transferred as quickly as possible to a tared stoppered weighing bottle ; after standing in vacuum over sulphuric acid a sodium estimation was made of which the following was the result :-0.5010 gram substance gave 0.1520 gram Na,SOp. Calculated for C,H,,N 5t208. Found. Nn 9.9 per cent. 9.8 per cent. This sodium-derivative is white and extremely hygroscopic in con-sequence of which it decomposes quickly on exposure to t h e air and immediately on the addition of water or acids the ethereal salt being regenerated.It was thought that if this compound were treated with iodine or bromine a tetrahy dropam-naphthalene-derivative would be formed, as shown by the following equation : CLOSED CARBON-CHAINS 1;N THE AROMATIC SERIES. 37 CH2.CXa (COOC,H,) __ C H2* C ( C 0 0 C2H5) 2 + Bra = (‘1 1 + 2NaBi \L C H2. C (COOC,II,) 2 \L CH2.CNa (COOC,H,), The experiment was carried out thus 12 grams of ethyl para-xylylenedimalonate dissolved in about 50 C.C. of ether were mixed with an ethereal solution of sodic ethylate containing 1.4 grams of sodium and then 5 grams of bromine slowly added. The colour of the bromine disappeared instantly on coming into contact with the sodium-compound the last few drops however causing a yellow coloration.Water was then added to dissolve the sodium bromide, and after separating and drying the ethereal solution the ether WRH distilled OB ; 16 grams of a heavy oil remained which on examina-tion was found to contain bromine. On standing for 24 hours in a cool place ci-jxtals were deposited ; these were partially separated from the mother-liquor by speading on a porous plate and while still on the plate purified by washing with a trace of methyl alcohol in which the oil is readily soluble whilst the crystals are hardly dissolved at all. After crystallising from hot methyl alcohol, 4.5 grams of a fine colourless substance were obtained and oil analysis numbers were found agreeing with the formula-C,H4[CHzCBr(COOCzH,)z]z.I. 0.2370 gram substance gave 0.3990 gram COz and 0.1090 gram H20. 11. 0.29U~ gram substance gave 0.1820 gram bromide of silver. Found. r-A- -7 Calculated. I. 11. H . . . . . . 4.8 , 5.1 -c 45% p. c. 45.9 -Br . . . . . 27.5 , - 26.5 per cent. This substance is therefore ethylic para-xylylenedibromodi-malouate ; it is only sparingly soiuble in cold but readily in hot methyl alcohol from which i t crystallises on cooling in magnificent glittering plates which melt a t 1Oi-108’. In order to prove that it really had the constitution assigned to it above it was treated with zinc-dust and acetic acid when it was reduced to ethyl para-xylylenedi-malonate and far more readily than the corresponding chlorine-compound. On extracting with ether a quantity of a crystalline product was obtained which melted a t 51” and possessed all the properties of ethylic para-xyljlenedimalonate there can therefore be no doubt that this substance is para-xylylenedibromodimalonate 38 RIPPING SYNTHETICAL FOR,lIhTION OF Since bromine acted on the sodium-compound of ethylic para-xylylenediiiialonate in this manner an experinlent was made in exactly the same way using the calculated quantity of iocliiie however, instead of bromine ; the product of the reaction was a thick brown oil which owing to the impurities present could not be got to crystal-lise; on heating a few drops in a test-tube violet vapours were evolved and traces of iodine sublimed.The analysis of the impure substance showed that it contained only from 2 to 2 i per cent.of iodine vhich was present in the combined state so that ethylic para-xylyleaediiododimalonate was either not formed a t all or oiily in very small quantities as this compound would contain 38 per cent. of iodine. The oil was hherefore hydrolysed and converted into the dicarboxylic acid by heating i t i n a sealed tube a t 180" until there was no further evolution of carbonic anhydride ; the product was isolated recrystallised and when pure its melting point was found to bc 223-224" (the melting point of para-phenylenedipropionic acid). In this case also i t is clear that no r i n g formation had taken place. Para-xy Zy Zmedima Zonic Acid C6H* [ C Hz* C H (C 0 OH) J2. When the ethereal salt of this acid which has been already described is boiled for about four hours on a water-bath with excess of potash in methyl alcohol hydrolysis is complete.The solution is theu evaporated to dryness to drive off the alcohol the residual potassium salt is dissolved in water and tho solution after acidifying with snlphuric acid is extracted repeatedly with ether. When the ethereal solution has been dried over calcium chloride and the ether distilled off para-xyljlenedimalonic acid is obtained as a thick syrup which on standing solidifies to a hard cake. This is spread on a porous plate in order to get rid of traces of oil and is then warmed with water and a small quantity of animal charcoal ; the filtered solution when allowed to evaporate over sulphuric acid in a vacuum slowly deposits a finely divided crystalline powder; this is collected and dried first on a porous plate and then in a vacuum over sulphuric acid.0.1982 gram substance gave 0.3905 gram GO and 0.0885 gram HzO. C14H1408. Found. The analysis gave the following results :--Calculated for C 54.2 per cent. 53.7 per cent. H 4.5 , 4.9 7 0 41.3 , 41.4 ,, On heating para-xylylenedimalonic acid melts a t about 195" wit CLOSED CARBON-CHAINS IN THE AROMATIC SERIES. 39 slight> decomposition and evolution of carbonic anhydride ; the whole mass then suddenly becomes solid and on continuing to heat melts again a t 223" (the nieltiug point of para-phenylenedipropionic acid see below). The silver salt was prepared by precipitating a neutral solution of tlie ammonium salt with silver nitrate;.it is a white amorphous substance and on analysis gave the following result :-0.5843 gram substance gave 0.3393 gram silver. Calculated for C14H10h~408- Found. Ag . 58.47 per cent. 58.07 per cent. The neutral solution of the ammonium salt gives with lead acetate, barium chloride and calcium chloride white precipitates of the respective salts. Pwapheizy lenedipropionic Acid C6H ( CH,*CH2*C 0 OH),. Para-xylylenedimalonic acid when heated is easily decomposed yield-ing paraphenylenedipropionic acid and 2 mols. of carbonic anhydride. This decomposition is best effected by h e a h g a solution of the acid in about 3 parts of water at 180" in a sealed tube until the evolution of gas ceases exactly as is described in more detail under the corre-sponding meta-compound.The reaction in this case goes beautifully, and after cooling the tube is found to be filled with hard white nodular masses of almost pure paraphenylenedipropionic acid. To purify the product it is collected and spread on a porous plate to remove traces of oil and is then dissolved in boiling methyl alcohol ; this solution on standing f o r 24 hours deposits the pure acid in curious nodular aggregates which after washing with a little alcohol and drying a t loo" were analysed and the following results obtained :-0.1770 gram substance gave 0.4200 gram CO and 0.1010 gram H20. Calculated for C12H1404. Found. C 64-86 per cent. 64.73 per cent. H . . 6.31 , 6-34! ,, 0 28.83 , 28.93 ,, Paraphenylenedipropionic acid melts at 223-224" ; it is only sparingly soluble in cold methyl or ethyl alcohol and almost insoluble in water.The silver salt is a white apparently amorphous precipitate which does not blacken on exposure to diffused light ; it was obtained in th 40 KlPPING * SYNTHETICAL FORMATION OF usual way by precipitatinq the neutral solution of the ammoniuni s.tlt and after drying a t loo" analysed. 0.4300 gram substance gave on ignition 0.2125 gram silver. Calculated for C12H12dg204. Found. Ag . . . . . . . 49.54 per cent. 49.42 per cent. The following reactions are shown by a neutral solution of tlic ammoiiinm salt :-Copper eulphate gives a faint greenish-white amorphous precipitate sparingly soluble in cold more readily in hot water ; lead acetate throws down the lead salt as a white compound insoluble in water; zinc sulphate and mercuric cliloride also give white precipitates whilst barium chloride and calcium chloride give no precipitate.The following experiment was then made in the hope of obtaioing an anhydride of this acid:-U,3 gram of the pure substance was heated in a test-tube in a metal-bath for half an hour a t 300-320', the acid darkened slightly but no appreciable quantity of water was given off; on raising the temperature considerably and as quickly as possible the whole distilled over in the form of a thick oil which, however a t once solidified on the colder parts of the tube while a very small quantity of carbonaceous matter remained behind. The solid distillate was scraped out of the tube and washed on a porous plate with a small quantity of ether when an almost colourless substance was obtained which melted at 221-224'; it is there-fore clear that no anhydride was formed but that on heating, paraphenylenedipropionic acid (m.p. 223-224") distils uiichanged. Metlt y lic Parapheny lenedipropionate. By boiling the silver salt of the acid suspended in ether with excess of methyl iodide for about four hours on a water-bath methylic paraphenjlenedipropionate is formed. The solution is filtered the residual iodide of silver washed well with warm ether the washings added to the filtrate and the whole distilled when the ethereal salt remains behind as a white crystallirie mass. It was purified by spreading on a porous plate and then recrystnllising from hot methyl alcohol.0.16225 gram substance gave 0.3995 gram C 0 2 and 0.1050 gram H,O. The analysis gave the following results :-Calculated for Cl-IHI*O'i. Found. C . . . . . . . . 67.20 per cent. 67.14 per cent. H . . . . . . i . 2 0 , 7-19 ,) 0 . . 25.60 ) 25-67 ; CLOSED CARBOS-CHAINS IN THE AROMATIC SERIES. 4 1 Methylic paraphenylenedipropionate is only spa]-ingly soluble in cold methyl alcohol and separates out from the hot solution 0x1 cooling in beautiful glittering plates which melt at 115". Paraphenylefiediacr ylic Acid C,H,( CH CH*COOH j2. Ethylic ortho-xylylenedichlorodimalonate is readily decomposed on heating it with alcoholic potash into hydrochloric acid carbonic anhydride and orthophenylenediscrylic acid. It was thought interesting to try a similar reaction with an analogous para-derivative.2 grams of ethylic para-xylylenedibromo-dimnlonate were mixed with a solution of 3 grams of caustic potash in a little alcohol and the mixture boiled on a water-bath for four hours. After addition of water the solution was evaporated to dryness in order to expel the alcohol and the residual potassium salts dissolved in water; on acidifying with dilute sulphuric acid a yellowish flocculent substance probably consisting of impure para-phenylenediacrylic acid was precipitated ; this was not filtered off but the whole extracted with ether the ethereal solution dried and the ether distilled off. The semi-solid mass which remained was mixed with about 10 C.C. of water and heated in a sealed tube for eight hours a t 180° in order to deconipose any tetrabasic acid which might be present.The slightly yellow flocculent snbstance thus obtained was purified by dissolving it in ammonia boiling with animal charcoal and rcprecipitating ; lastly the substance was well washed with water dried a t 100" and analysed when the following results were obtained :-0.2010 gram substance gave 0.4840 gram CO and 0.0892 gram H,O. Calculated for cI,I-rlOo+ Found. C 66.05 per cent. 65.67 per cent. H 4.59 , 4.96 ,, 0 29-36 , 29.37 ,, Paraphenylenediacrylic acid has been already obtained by Loew (Annalen 231 361-384) by the action of sodic acetate and acetic mhydride on terephthalic aldehyde ; the product obtained from ethylic para-xylylenedibromodimalonste is identical with Loew's compound its properties agreeing with those already given by him.JIeta-xylylene Cyanide C6H4( C K2-CN)2. The method used in the preparation of this substance is as follows :-13 grams of meta-xylglene bromide are dissolved in alcoho 42 KIPPINU SYNTHETlCAL FORMATION O F and a slight excess of the calculated quantity of potassium cyanide, in aqueous solution added. No reaction takes place a t first but on warming potassium bromide begins to crystallise out on the sides of the flask the reaction bcing as follows :-C,H,(CH,Br) + 2KCN = CsH4(CH2-CN) + 2KBr. By boiling 011 a water-bath with reflux condenser for a con-siderable time the change is completed the alcohol is then distilled off and the residue treated with water whereby the crude meta-xylylene cyanide is precipitated 8s a brown oil ; after separating it from the aqueous solution by means of a separating funnel it is dried over calcium chloride and fractioned in a vacuum.Thus purified it is obtained as a colourless oil which on cooling almost immediately solidifies to a white crystalline mass ; the analyses gave the following results :-I. 0.2410 gram substance gave 0.6775 gram GO and 0.1120 gram 11. 0.2195 gram substance gave 0.6155 gram CO and 0.1095 gram 111. 0.22425 gram substance ga~7e 34.75 C.C. Nitrogen. Bar. 718 mm. HZO. H,O. T. 17". Found. Calculated for r-h- - -7 ClO&N2. I. 11. 111. C 76-92 p. c. 76.48 76-67 -H . . 5.13 , 5.54 5.16 N . . 17.95 ,, -17.75 p. c. - -Meta-xylylene cyanide is a colonrless crystalline substance melt-ing at 28-29"; i t boils under 300 nim.pressure a t 305-310" a certain amount of decomposition taking place. Ether alcohol and chloroform dissolve it readily ; it is insoluble however in water and light petroleum. n/letaphenyZenediccelic acid G,H,(CH,*COOH),. To obtain this acid the crude oil formed by the action of potassium cyanide on meta-xylylene bromide is without further purification, hydrolysed by boiling it on a water-bath with an excess of alcoholic potash solution whereby it is converted into the potassium salt of rnetaphenylenediacetic acid. Hydrolysis does not take place a t all readily and it is necessary to boil for about six hours before the cessation of the evolution of am-monia shows that the reaction is a t an end. When this is the case, the alcohol is distilled off and the residue dissolved in water; on acidifying with dilute sulphuric acid a small quantity of a brow CLOSED CARBOS-CIIAINS IN THE AROJlhTIC SERIES.43 resinous substance is precipitated and is filtered off; the clear solution is then extracted about 20 times with ether and after drying the ethereal solution over calcium chloride and distiiling off the ether the acid is left in slightly yellowish crystalline crusts. The product is spread on a porous plate and while still on the plate the traces of oil are washed away with a few drops of ether ; after two crystallisations from water it is obtained piire in the form of colourless needles. It was dried a t loo" and analysed with the following results :-0.1697 gram substance gave 0.3830 gram CO and 0.0800 gram H,O.Calculated for ClOHIOO4. Found. C 61.86 per cent. 61.54 per cent. H 5.15 , 5.24 ,, 0 . . 32.99 , 3 - 2 2 ,, Metaphenylenediacetic acid melt,s a t 170" ; it is easily soluble in water alcohol and ether but almost insoluble in light petroleum or chloroform it crystallises from water in beautiful clusters of con-centric needles. The yield obtained by hydrolysing the cyanide with alcoholic potash is almost theoretical. On adding silver nitrate to a neutral aqueous solution of the am-monium salt the silver salt is obtained as a white amorphous pre-cipitate ; after washing well with water and drying first on a porous plate and then at loo" analysis gave the following result :-0.1305 gram substance gave 0,0685 gram Ag.Calculated for G o H*&O,. Found. Ag. 52.8 per cent. 52.5 per cent. I n an aqueous solution of the arnmonium salt lead acetate gives a white amorphous precipitate but with sulphate of zinc a crystalline substance is produced ; barium and calcium chlorides do not give any react ion. No anhydride of the acid was obtained although an experiment was made as follows :-0.2 gram of the pure acid was heated in a metal-bath for 40 minutes a t 300-320" and theu distilled by quickly raising the temperature a small amount of carbonaceous residue was left but almost the whole of the acid passed over as a slightly yellowish oily distillate which condensed on the cooler parts of the tube and immediately solidified; it was purified by washing with a small quantity of ether and a melting point taken, which was found t o be 170-172" ; metaphenylenediacetic acid melt 44 KIPPING SYNTHETICAL FORJIATIOX O F at 170° and i t is therefore clear t,hal no anhydride had been farmed.Para-xylytene Cyanide C,H,(CH2.CN),. 15 grams of para-xglylene bromide are dissolved in alcohol and 8 grams of potassium cyanide dissolved in as little water as possible are added to the solution; no reaction takes place at first but on heating the mixture double decomposition commences a large quantity of a bright-yellow flocculent substance separating ; this is, however not para-xylylene cyanide but a resinous compound formed by some more complicated secondary reaction after boiling on the water-bath with reflux condenser nntil the penetrating odour of the bromide is no longer perceptible the alcohol is distilled off and water added to the residue when the cyanide is precipitated as a dirty-white solid.On shaking with ether it is dissolved while the in-soluble resinous impurities are left ; after drying the ether is evapo-rated and the para-xylylene c-janide is obtained crystallised on the sides of the flask. It may be purified by redissolving i t in ether boiling with a little animal charcoal filtering and allowing the filtrate t o evaporate slowly by this means well-defined crystals are obtained which after recrjstallisation are quite pure. On analysis the following results were obtained :-I. 0.1690 gram substance gave 0.4755 gram CO and 0*0620 gram Bar. 718 mm. H,O. T = 7". 11. 0,12425 gram substance gave 19.7 C.C.Nitrogen. Calculated for r----C,,H$J,. I. 11. Found. - C 76.90 per cent. 76.TS H 5.13 , 5 3 9 -N . . 17.95 , - 18.16 per cent. Para-xylylene cyanide is a colourless substance which crystallises i n long three-sided prisms and melts a t 96" ; in whatever manner the conditions are varied it seems impossible to avoid the formation of a large amount of the yellow resinous substance alIuded to above ; the yield of cyanide is therefore a poor one being only about 50 per cent. of the theoretical. Parap h eny Zenediacetic Acid CsH4 ( C H2* C 0 0 H) ,. When the preceding compound is hydrolysed paraphenylene-cliacetic acid is obtained ; for its preparation 2 grams of the cjanid CLOSED CARBON-CHAINS I N THE AROMATIC SERIES. 4 5 were added to an excess of tbe calculated quantity of potash dissolved in methyl alcohol and boiled on the water-bath with reflux con-denser until no further evolution of ammonia could be observed.After evaporating the alcohol the residue was taken up with water and dilute sulphuric acid until the solution showed a strongly acid reaction ; paraphenylenediacetic acid was thus partially precipitated together with a small quantity of brown impurity; the whole mas shaken out well with ether when the acid dissolved leaving most of the impurities. The ethereal solution was dried and the product obtained as a crystalline crust when the ether was distilled off; the yield was almost theoretical. To purify the acid it was dissolved in alcohol boiled with a little animal charcoal the filtered solution evaporated to dryness on the water-bath and the residue twice re-crystallised from water containing a trace of alcohol.Para-phenylene-diacetic acid is thus obtained in fine colourless needles which are very readily soluble in alcohol far less so in water or ether and melt a t 240-241'. The analysis gave the following results :-0.1730 gram substance gave 0.3920 gram C02 arid 0.08850 gram H,O. Calculated for C,OH,OO,* Found. C 61.86 per cent. 61.80 per cent. H . . 5.15 , 5.46 ,, 0 32-99 , 32.74 ,, The silver salt is precipitated on adding nitrafe of silver to a neutral solution of the ammonium salt as a white amorphous mass ; i t was collected well washed with water and dried first on a porous plate then at loo" and analysed with the following result :-0.2805 gram substance gave 0.1473 gram silver.Calculated for ClOH8Ag20.4. Found. -4g. 52.8 per cent. 52.6 per cent. Paraphenylenediacetic acid is not converted into its anhydride even on heating at 300-320" for half an hour since by quickly raising the temperature a product distils over which after washing with a little ether showed the same melting point as the original acid. NOTE ON THE PREPAR.ATION OF ISOPHTHALIC ACID. Meta-xy Zy ZenediefhyZ E t h e r C6H,(CH,0C2H,),. The preparation of isopht,halic acid by the oxidation of meta-xylene with potassium &chromate a.nd dilute sulphuric acid (Pittig Velguth 46 SYNTHETICAL FORJIATION OF CLOSED CARBOY-CHAISS. Awnden 148 ll) is known to be very tedioiis owing to the extreme stability of this hydrocarbon the greater portion of which remains unchanged 'even after continued boiling for days tozether.The following method was therefore woyked out and found to give excel-lent results mets-xylene is treated with the requisite quantity ( 2 mols.) of bromine a t 125" and the dibromide formed without purification is boiled with alcoholic potash and thus conrerteci into meta-xylrlene diethy1 ether. When this is treated with potassium dichrornate and sulphuric acid a quantitative yieId of isophthalic acid is obtained ; the ether was however first prepared i n the pure state and investigated a little more closely ; for this purpose pure meta-xylylene bromide was boiled for six hours with a solution of alcoholic potash which contained twice the calcuhted quantity of alkali water was then added and the oii which sett,led t o the bottom separated from the aqueous solution dissolved in ether amd allowed to stand over calcium chloride ; after distilling off the ether the product remained as a dark-brown oil which was found still to contain bromine eitker owing to the presence of a trace of nildecomposed nieta-xylylene hromide or of an intermediate compound having the formula C6H,Br*CH2*OC,IC5.It was therefore treated with zinc-dust and acetic acid. and the ether thus freed completely from bromine was isolated in the usual manner and submitted t o fractional distillation, when almost the whole distiiled over between 235" and 255"; this process w a s twice repeated and meta-xylylene diethyl ether obtained in the pure state in the form of a colourless mobile pleasant-smelling oil ; it was analysed with the following results :-0.1392 gram substance gave 0-3805 gram COs and 0.1153 gram H,O.Calculated for C12H1802. Fonnd. C '74.23 per cent. 74.53 per cent. H . . 9.28 , 9.19 7, 0 . . 16-49 , 16.28 ,, This compound boils at 246-247" (712 mm. pressure uncorr.), and does not solidify even when cooled to 0" ; it is isomeric with the ortho-derivative prepared by Leser (Ber. 17 1825) which boils at 247-240" (720 mm. pressure). Of course when this ether is required for the preparation of isophthalic acid it is quite unnecessary to purify it the crude product of the action of alcoholic potash on the xylylene brornide is mixed directly with an excess of potassium dichromate in a large flask and sulphuric acid added ; the reaction is very energetic and great lieat, is evolved so that in working with large quantities i t is advisable to ad2 the acid very slowly or the mixture will be apt to froth over THE ISTERACTION OF ZINC AND SULPHURIC ACID.47 When the oxidation is completed which is the case in a very short time the isophthalic acid seen as a white sandy powder on the bottom of the flask is collected and washed with water ; it is however, very difficult to get rid of the last traces of the green mother-liquor, slid to obtain the product quite pure it is dissolved in sodium car-bonate and the filtered solution acidified with sulphuric acid. After washing the precipitated isophthalic acid and drying it a t loo" an analysis was made with the following result :-0-1477 gram substance gave 0.3128 gram CO and 0.0500 gram H,O. Catciilated for CgHFO.1. Pound. C 57.77 per cent. 57.75 per cent. H . . 3.61 , 3-76 ,, 8 . . . . . . . . 38.62 , 38.49 ,, I n this way an almost theoretical yield of isopht'tialic acid can be obtained from meta-sylene with comparative ease and in a short time, whereas by the old method several days were required to prepare a few grams. This work was carried out in the laboratory of Professor A. v. Raeyer in Munich and before closing I desire to express my gratitude for the kindness which was invariably shown to me and for the interest which he took in this research

ISSN:0368-1645    

DOI:10.1039/CT8885300021

出版商:RSC    

年代:1888

数据来源: RSC

摘要:

THE ISTERACTION OF ZINC AND SULPHURIC ACID. 47 111.-CONTRIBUTIONS FROM THE LABORATORY OF GONVILLE AND CAIUS COLL'EGE CAMBRIDGE. No. X.-The hteraction of Zinc and Rulphuric Acid. By M. M. PATTISON MUIR M.A. and R. H. ADIE B.A. Scholar of Trinity College Cambridge. 1. I N 1830 De la Rive examined the action which occurs between zinc and aqueous solutions of sulphuric acid (Pogg. Ann. 19 221). He employed both commercial and redistilled zinc and measured the times required for t h e production of equal volumes of hydrogen from acids of different concentrations. De la Rive found that the change proceeded much more rapidly with commercial than with redistille 48 MUIR AKD ADIE THE INTERLICTION zinc ; he also found that the most rapid action occurred when coin-mercial zinc interacted with an acid solution containing about 30 per cent.H,SO,. Ue la Rive added known quantities of tin leatl, copper and iron respectively to molten redistilled zinc and found that the rates of action of the products with sulphuric acid solutions were greater than the rate of action of reclistilled zinc. Finally, De la Rive proved that the solution of sulphuric acid which showed maximum electrical conductivity interacted most rapidly with com-mercial zinc and with redistilled zinc to which a few per cent. of iron had been added. De la Rive concluded that the interaction between pure zinc and dilute sulphuric acid is probably a direct chemical change but that with ordinary comniercial zinc the action is chiefly electrochemical. In the seventh series of his Experrimei7tal Researches (pars.863 et seq.) Faraday proved that a plate of amalgamated zinc remained unchanged in sulphuric acid to which 30 parts of water had been added while a similar plate in the same acid put in contact wit11 a plate of platinum lost 5.2 per cent. of its weight. These experiments conducted by De la Rive and Faraday showed that the interaction which occurs between zinc and dilute sulphuric acid is to some extent a t least an electrolytic action. 2. It is well known that hydrogen is not the only gaseous pro-duct of the interaction of dilute sulphuric acid and ordinary zinc. Everyday experience in the laboratory proves that both sulphur dioxide and sulphuretted hydrogen are often produced in the reaction in question. We have made a fairly complete qualitative examination of this interaction and have found it to be one of great complexity.About 10 grams of zinc were used in each experiment and usually about 50 C.C. of the acid. The reactions proceeded in small flasks, each of which was connected by a T-tube with a flask containing a dilute aqueous solution of iodic acid mixed with a very little starch-paste and also with a flask containing a dilute solution of silver nitrate to which excess of amEonia had been added. Exit-tubes from these flasks communicated with a water-pump ; a current of air could thus be sucked through the whole apparatus and traces of gases pro-duced in the interactions could be swept out from the reaction-flask into the testing-flasks. Those experiments wherein the reaction was allowed to proceed for long periods sometimes extending to three weeks were conducted in small flasks which were not connected with testing-flasks ; a t the end of the allotted time a rapid current of well-washed carbon dioxide was swept through the liquids in the flasks and the escaping gas was bubbled through the testiiig solutions.The higher temperatures were maintained by heating the flasks i OF zrsc AND SULPHURIC ACID. 49 baths of zinc chloride for our purposes it was unnecessary to attempt to regulate the temperatures within a few degrees. The specimens of zinc employed were (1) “ redistilled zinc,” (2) “pure rod zinc,” (3) “ pure zinc foil,” (4) “ commercial granulated zinc,” the chief im-purities in which were lead iron arsenic and traces of cadmium, (5) “ platinised zinc fd,” and (6) “ approximately pure zinc,” prepared by us by dissolving ‘‘ pure redistilled zinc ” in pure very dilute sul-phuric acid saturating with sulphuretted hydrogen boiling filtering, electrolysing (after complete removal of H2S) digesting the zinc thus obtained with a slightly warm aqueous solution of recrystallised “ pure zinc sulphatle,” redissolving i n pure dilute sulphuric acid, electrolysing &c.and repeating the series of operations a third time. The snlphuric acid employed was that sold as “ pure redistilled,” diluted with measured quantities of water. What is hereafter called “ approximately pure H,SO ’’ was prepared by redistilling the “ pure redistilled ” acid collecting the middle portion of the distillate, repeating this process then freezing out the H2S04 and pouring off the remaining liquid.The concentrations of the various acids used are represented by formulq but these are to be regarded merely as approximate represen-tations of the ratio of H,S04 to H20 in the liquids. The concentration varied from H,SO4 to H2SO4,100H2O. No attempts were made to measure the quantities of the different products of the reactions. When a blue colour in the iodic acid and starch test-liquid or a brown colour in the silver nitrate test-liquid, appeared only after the current of air o r carbon dioxide had swept through the apparatus for 30 minutes we note the result as “ a trace” of SOz or SH, as the case may be. Production of a deep-blue coloiir o r a brown-black precipiLate immediately the first bubbles of gas came into contact with the testing liquid is noted as ‘‘ abundance ” of SO (or SH,).To save space and frequent repeti-tion we have adopted the following letters for indicating (very roughly it is to be remembered) the results of the experiments :-t. 1. m. a. Trace. A little. Moderate quantity. Abundance. Statements are made in the sequel regarding the appearance of hydrogen when the acid used was concentrated and the changes proceeded very slowly the presence of hydrogen among the products was proved by continualIy passing a rapid current of carbon dioxide through the reaction-flask and allowing the escaping gas to bubble through potash solution into a tube filled with the same solution, and testing the gas which collected in this tube.Statements are also made in the sequel regarding the solid matter VOL. LIII. 50 MUIR AND ADIE THE INTERACTION formed in the reaction-flasks this solid was proved to be free from zinc sulphide by collecting it on glass-wool filters washing with sulphuric acid thoroughly drying on a porous tile and then decom-posing it by fairly concentrated warm sulphuric acid in a flask con-nected with testing-flasks as already described. Direct experiments proved that zinc sulphide is decomposed by moderately dilute warm sulphuric acid with formation of sulphur dioxide sulphuretted hydrogen and sulphur ; the absence of these three substances was taken as evidence that the solid examined was free from zinc sul-phide. Traces of sulphur were detected by warming the solid pro-ducts of the reaction with carbon bisulphide decanting and evaporating Ihe bisulphide.The experiments which were performed in duplicate were always stopped when some zinc remained undissolved. The following formulse approximately represent the concentrations of the acids used ; each acid is distinguished by a letter or number. Concentration of acid. . HzSOI 9H2SO4,HZO 7H,SOI,3H,0 Concentration of acid. . 7HzS04,4H20 7H2S04,6Hz0. Letter AA. A. B. Letter C. D. Number 1. 2. 3. 4. Concen. of } H2S04,H20 H,S04,BH20 HZS04,3Hz0 H z S ~ ~ ~ H Z ~ ; acid and so on the number ?L representing an acid of concentration The following letters indicate roughly the quantity of the gas produced t trace; 7 a little; m moderate; a abundance.The lines - - - indicate the absence of SO, SH, or S; these three bodies are alwa-j+s enumerated in this order; thus t - - means ‘( a trace of sulphur dioxide sulphuretted hydrogen and sulphur absent.” 3. The following tables embody the greater number of our results :-H,SO4,nnH?O OF ZINC AND SULPHURIC ACID. Temperature . . . . . . OD. 1 20". 51 looo. 160'. SOZ SH, S. _ 1 -1 I -1 1 -1 1 -m I ~ L -m tn -I ?n -t l i b - - I -t 1 -2 1 -Concentr. of acid. B B SO? SH? S. t - -1 1 -1 1 -1 1 -- t -111 111 -a n -C D 1 2 Temperature . . . . . . . . . . . I OO. -___ ----4 6 7 8 lloo. 1 160'. I- -9 10 11 12 13 16 25 BO 100 SO, SH, S. a t t 1 I t m I t r)L - -- _ -- f -- - I n -1 a -t a -SO, SH, 8.a I t f a -I t -Pyoducts obtained by using Redistilled Granulated Z i n c and Acids gf zarious concentyations. Concentr. of Acid. A 1 2 3 4 5 7 9 11 12 13 16 -"j 50 SO, SH S. ' SO, SH3 S. 1 1 -t I -t t -802 SH, S. a t t a a Products obtained by using Ylatinised Z i n c F o i l and Acids of carious Temperature . . . . . . . . . . . 0". 20". Concentr. of acid. SO, SH, S. SO, SH, 8. A m - -B C 1 t(?) t(?) -2 4 5 7 9 t 1 -11 t l -13 - 1 -16 t t -3 I _ - -- - - - - -t - - t(?) - -100". 150". SO, BH2 S. SO, SH2, m - -l t t m - - a m - - 1 I l - m t(?) - -- - -t - 25 -50 - - c 100 --Pyoducts obtained by using " Approximately P u r e " Z i n c and Acids Temperature .. . . . . . . 15-18". Concentr. of acid. A B 2 12 110-112'. 1 135'. 1 145". OF ZINO AND SULPHURIU ACID. 53 Temperature . . . . . . . . . . . 110". Products obtained by using Pure Rod Zinc and Acids of various con-centrations. 160". 13. p. of acid. SO, SH, S. a t m a a a a a a Concentr. of acid. A B C D 1 2 3 4 8 12* SO, SH, S. I t -S02 SHS S. loo". j 160". t t -- 1 -B. p. of acid. * Acid of this strength gives only hydrogen at 85". Products obtained by using Pure Zinc T o i l and Acids of various concen-trations. Temperature . . . . . . I 20". Concent,r. of acid. A B 1 2 3 4 5 1 - - I 1 1 m t 1 1 -4. We think it may be safely asserted that hydrogen was produced in all the reactions.Direct proof of the presence of hydrogen was sought for and found in the cases of the acids HzS04,Hz0 at the ordinary temperature 9H2S0,,H20 at looo 7H2S04,ZH20 at loo", and platinised zinc with 7H,S04,2Hz0 at 150-BOO at which temperature sulphur was freely produced. The only solid product of the interaction is zinc sulphate. This was proved for acid of very varying concentrations and at different temperatures ; for 9HZSO4,I-I20 at 180" ?H2SO4,2HzO at loo", and H2S04,3H20 HzS04,4H20 and H2S04,BHz0 at ordinary tem-peratures. 5. The results of our experiments when regarded broadly esta-blish a similarity between the interaction of sulphuric acid with approximately pure zinc and with commercial zinc. But at the sam 54 MUIR AND ADIE THE INTERACTION time there are differences.Thus the results show that as the zinc becomes purer the quantities of sulphur dioxide and sulphuretted' hydrogen particularly the latter produced a t the ordinary temperature (12-18") become markedly less whether the acid be concentrated or dilute ; when the acid is so dilute as H2S04,lO or 12H20 hydrogen is almost the sole gaseous product even a t temperatures up to the boiling point of the acid used. When approximately pure zinc is employed and the temperature is high (160" o r so) dilution of the acid is accom-panied by diminution both of sulphur dioxide and sulphuretted hydrogen; bnt when commercial zinc is used the sulphur dioxide diminishes more than the sulphuretted hydrogen ; when commercial zinc was used however small quantities of sulphuretted hydrogen were indeed obtained with every acid examined even with HzS04,100H20, and a t temperatures varying from the boiling point of the acid to 0".Platinised zinc foil behaves on the whole similarly to commercial zinc ; sulphur dioxide and sulphuretted hydrogen are produced a t very varying temperatures and with almost every acid examined. When the acid is fairly concentrated sulphur dioxide begins to be produced a t a temperature lower than that a t which sulphuretted hydrogen appears both in the case of platinised foil and commercial zinc ; when the acids are dilute the tendency in the case of platinised zinc foil is to produce sulphuretted hydrogen more freely than sulphur dioxide. It is somewhat remarkable that scarcely any sulphur dioxide or sulphuretted hydrogen should be produced when comniercial zinc and acid approximately of the concentration HzSO4,2H20 interact a t lo@" but that at 165" abundance of sulphuretted hydrogen accom-panied by a little sulphur dioxide should be formed and that a t 180" torrents of the former gas nearly free from sulphur dioxide should be evolved.I n connection with this result it is of interest to note that " approximately pure " zinc interacting with acid of the same con-centration as the above (H2S04,2H20) a t 160" produces quantities of both the gases i n question. The conditions under which sulphur appeared are noted in the table on In the experiments with platinised foil sulphur disappeared again a t 210-2220" and SHz increased very much.Sulphur did not appeal- in any other experiment with " approxi-mately pure zinc;" the other acids examined were HzSO1 and Sulphur is produced neither at low temperatures nor with acids less concentrated than HzS04,2H20 ; the formation of sulphur is always accompanied by the evolution of sulphur dioxide and sulphuretted hydrogen but the quantity of the latter gas is sometimes extremely 6. The production of sulphur requires a little examination. p. 55. HZS 04,2H20 OF ZINC AND SULPHURIC ACID. 55 , , , . . . . . . . . . . . . , . Concentration of acid. Kind of zinc. gHySO,,H,O 7H,SO4,2H,O 7H2S04,4H,0 7H,S04,6H,0 H,SO,,2II,O 0 zinc" 9 1 7, Y, " Platinised foil " 7 . . . . . . 9 , 7, > 9 . . . .. '' Approximately pwe zinc " 7H,S04,2H20 7 II,S04,6H20 H,S04,H20 7H2S G4,2H,O 7H,S04,4H,0 7H2S 0,,6H20 H2S0,,2H,0 H,SO4,HzO 7HzS 04,2H30 Temp. 165" 165 165 165 165 165 190 165 100 100 100 175-185 175-180 125 170 130 160^ Bemarks. Very little S ; plenty of SO ; Decided S ; plenty of SO,; Decided S; plenty of SO, Decided S ; much SO ; little Little S ; much SO and merest trace of SH,. merest trace of SH,. and SH,. SH,. SH2. Trace of S ; much SO and SH,. Distinct S ; fair quantities Little 8 ; much SO,; little Little S; much SO,; very Little S; little SO2 and SH-. Trace of S; fair quantity of Much S; very inucli SO,; Much S; much SO2; little of SO and SH,. SH2. little SH,. SO,; little SH,.little SH,. SH,. 7 J , 3 3 , Trace of S ; much SO,; fair quantity of SH,. Sinall quantity of S; quan-tity of SO,; trace of SH,. small. Wben " approximately pure " zinc aiicl sulphuric acid are used there is scarcely any separation of sulphur ; with platinised foil, on the other hand sulphur is formed in large quant,ities. The sulphur can scarcely be a product of the interaction of sulphur dioxide and sulphuretted hydrogen else we should expect to find it gencrally accompanying these gases; nor can i t always be produced by the reducing action of the nascent hydrogen on either the sulphur dioxide or sulphuretted hydrogen because these gases are so frequently found at moderate temperatures unaccompanied by sulphur. It may be that the formation of sulphur is sometimes to be traced to the mutual action of sulphuretted hydrogen and hot concentrated sulphuric acid.This supposition would account for the preponderance of sulphur dioxide over sulphuretted hydrogen when the acid is concentrated, and for the increase in the quantity of the latter gas as the acid becomes more dilute for the sulphuretted hydrogen supposed to be formed when the acid is concentrated would be decomposed b 56 MUIK AND ADIE THE INTERACTION reacting with the hot acid but would escape unchanged when the acid becomes more dilute. The fact that the cessation in the produc-tion of sulphur is accompanied by a marked increase in the quantity of sulphuretted hydrogen in the reaction of platinised foil with con-centrated acids is also in keeping wit,h this supposition.The non-production of sulphur when “ approximately pure ” zinc is used supports the view that some of the snlphur is formed in secondary reactions between the gaseous products or between these and the acid, rather than in the direct interaction of the metal and acid. The sulphur produced was soluble in carbon bisulphide. 7. Increase of the mass of the zinc relatively t o that of the acid does not produce any regular and definite effect on the nature or quantities of the gaseous products of the change. This is shown by the tabu-lated results given on p. 57. 8. The interaction between zinc and sulphuric acid evidently differs considerably from the interaction between copper and sulphuric acid (see Pickering Trans. 1878 112).The latter change proceeds in two definitely marked stages expressible by the equations-(1.) 5cu + 4HaSO4 = Cu,s + 3CnSO4 + 4H,O (2.) CU + 2HZS04 = CUSO~ + SO + 2HzO. Hydrogen is not obtained in the reaction between copper and sulphuric acid nor is sulphuretted hydrogen evolved ; the sulphur dioxide produced is most probably the result of secondary reactions occurring between the acid and the cuprous sulphide formed. In the interaction between zinc and sulphuric acid on the other hand, hydrogen appears to be always produced ; both sulphuretted hydrogen and sulphur dioxide are very frequently formed and the production of these gases cannot be traced t o a secondary reaction between the acid and zinc sulphide formed in the primary change ; the entire interaction is more irregular than that between copper and sulphuric acid.The dependence of the production of large quantities of sulphur dioxide and sulphuretted hydrogen in the interaction between zinc and sulphuric acid on the temperature and the concentration of the acid indicates we think that the formation of these gases is not t o be altogether ascribed t o the reducing action of nascent hydrogen on the acid. This view is confirmed by the fact that variations in the mass of the zinc employed and hence in the quantity of hydrogen produced in a specified time do not exert any marked or regular effect on the nature of the change. The behaviour of commercial zinc with acid of the concentration HzSOa,2Hz0 and of approximately pure zinc with the same acid also confirms this supposition in the case of com-mercial zinc very little sulphur dioxide or sulphuretted hydrogen i ON' ZINC AND SULPHURIC ACID.57 Vtwious Z i n c s w i t h Acids of d i f e r e n t concentrations; 50 C.C. acid used in each case. ~~ Acid. I. Pure rod zinc-7H&304,2Hz0 H2SO4,2H,O 11. Pwre zinc fod-7H,S04,2H,O 7H$404,6H,O H+30,,2H,O H,S04,4H,O 111. Redistilled zinc-H2S04,2H,0 IV. Commercial granzc-H,S04,2H20 lated zinc-V. Platinised zinc foil-H9S04,2H20 Weight of zinc used. Approximate temp. of appearance of so,. 0 144-146 150 150-155 135-140 120-125 105-110 105 -110 125-130 130-135 115-120 140-145 145-150 135-140 140 135-140 150 150 130-135 140-145 140 135 140-145 140-145 7 10 105 SHp 0 135-137 137 145 130-135 90-95 70 -75 70-75 105-110 100 85 130 135 125 120-125 120-1 25 120 130-135 130-135 125-130 135-140 125-130 135-140 125-135 '70-80 85-90 formed at 100" ; at 165" both gases are produced Remarks.Little SH even at 150". 1) , Plentiof both-gases at 155'. SO rapidly at once; SH2 slowly increas-ing. Not much SH till 145". Plenty SH2 at 150". Not muchSO till 130°, and SH till 90". reely; and at 180" the latter gas is evolved in very large quantity; in the case of approximately pure zinc both gases are produced in quantity at 165'. Moreover if the gases in question were altogether secondary products of the reduction of snlphuric acid by the hydrogen evolved in the primary change we should expect to find them formed as freely whe 58 THE INTERACTION OF ZINC AND SULPHURIC ACID.the former zinc is used as when commercial zinc is emplored; but this supposition is not confirmed by experiment. We are inclined to think that the interaction between approximately pure zinc and acid is chiefly a direct chemical interaction and that the products of the reactions with the less pure zincs are largely due to the occurrence of secondary electrolytic changes. With pure or almost pure zinc and dilute acid (say H2S04,12 to 15H20) hydrogen and zinc sulphate are the only products of the reaction; with the same zinc and con-centrated acids (say H2SOI,H20 to H,SOJ the chief gaseous product is sulphur dioxide and sulphuretted hgdrogen is also produced at higher temperatures ; with an acid of intermediate concentration (in our experiments with H2S04,'LH20) both compounds of sulphur are formed in considerable quantities a t fairly high temperatures (160").But the results of our experimeiits make i t certain that whether the zinc be pure or commercial the concentration of the acid used plays a most important part in the chemical change ; hence it is probable that the bodies actually interacting are numerous and that the reactions are much more complex than can well be represented in any series of equations which can a t present be devised. It seems to us that the chemical change which occurs is to be ascribed to the interaction of the zinc with various molecular aggregates of H,SO and H,O, probably also of SO and H20 or of H2S04 SO, and H,O; and that the compositions of these aggregates probably vary with variations in the concentration of the acid used and with variations of tem-pera t ure . The results of experiments on the electrolysis and electrolytic conductivity of sulphuric acidX establish a close resemblance between the electrochemical behaviour of this acid and its chemical behaviour as described in this paper. * Wiedemann Die L e h e volz de?. Elektricitat 2 535; also 3'. Kohlrausch, Ann. Ph,ys. Chem. 26 206 ; also Ostwald Phil. Mag. August 1886 and other places ; also Gladstone and Tribe this Journal Trans. for 1879 177

ISSN:0368-1645    

DOI:10.1039/CT8885300047

出版商:RSC    

年代:1888

数据来源: RSC

摘要:

59 IV.-The Dehydration of Metallic Hydroxides by Heat with special reference to the Polymerisation of the Oxides and to the Periodic Law. By Professor T. CARNELLEY D.Sc. and Dr. JAUES WALKER University College Dundee. OXYGEN being a much more fusible and volatile element than chlorine i t would & priori be supposed that the oxides of the elements would also be more fusible and volatile than the corresponding chlorides. Prof. Louis Henry however in a most interesting paper (Phil. JIag. [S] 20 81 ; Alznales de la Soa. Sci. de Brux. 1879) has drawn special attention to the fact that with but comparatively few exceptions, chiefly those of negative elements the oxides are by far the less fusible and volatile of the two classes of compounds and that unlike their chlorides they are distinguished by their comparative fixity and inf usi-bility.The chlorides and oxides are generally represented by comparable formuls but whereas the formulae usually assigned to the chlorides have been deduced from the determination of their vapour-density , those attributed to t,he oxides depend with very few exceptions solely on analytical determinations and they are therefore merely empirical, and have no claim to a molecular signification. Henry for numerous very cogent reasons concludes that most of the known oxides of the elements and notably the metallic oxides are polymerides n( RO,) of the unknown true oxides RO, corresponding to the chlorides RCI,,. Now the fusibility and volatility of a compound are i n a very great measure directly dependent on the molecular weight and he would hence account for the almost general infusibility and fixity of tbe oxides by their being in most cases polymerides with inolecular weights much higher than those represented by the empirical formuls usually assigned to them.The object of the present investigation was first to ascertain whether some light could be thrown on the above question of the polymerisation of the metallic oxides from the change in composition of the hydroxides on heating at regularly increasing temperatures ; and second to determine the minimum temperature of complete dehydration of the metallic hydroxides with a view of ascertaining whether this temperature was a periodic function of the atomic weight of the positive element. Wurtz in 1863 showed that when a hydroxide is decomposed by heat the chemical action is twofold (1.) Dehydration which may be partial or complete.(2.) Molecular condensation resulting from tw GO CXRNELLEY AND WALKER THE DEHYDRATION or more molecules of the hydroxide entering into combination on the elimination of a part or the whole of the hydrogen of the hydroxide as water. It therefore follows that the compounds thus formed become more and more complex in proportion t o the extent of the dehydra-tion. By heating certain hydrates a t regularly increasing temperatures, and determining the degree of dehydration thus produced it seemed probable that data could be obtained for the construction of curves, which would indicate whether atiy compounds were formed inter-mediate between the normal hydrates and the corresponding oxides, and thus give some information in regard to the general phenomena occurring during the dehydration.The composition of these com-pounds if formed might also afford some clue to the true molecular weights of the oxides. Their existence could be recognised by observing when for a considerable increase of temperature little or no decrease in their weight took place. The hydrates (or precipitated oxides) corresponding to the follow-ing were prepared:-1. Ag20, 2. HgO, 3. Ai3O3 In,O3 T1,O3, 4. SiO, TiO, ZrOz SnO, CeO, Pb02, 5. Sbz03 Bi,O,, 6. Fc203 Co303 Ni,03. Many hydrates such as those of calcium barium magnesium zinc, cadmium &c. absorb large quantities of carbonic anhydride from the air whilst drying and therefore could not be employed.The moist oxides of silver and bismuth take up small quantities of carbonic anhydride. To obtain the hydrates as far as possible in the same state of aggre-gation they were prepared under the same conditions as nearly as the differences in the nature of the substances would allow. Solutions of mercuric chloride and silver nitrate were precipitated in the cold, with a slight excess of caustic soda solution. The cold solutions of aluminium sulphate bismuth nitrate antimony trichloride ferric chloride zirconium sulphate thallic sulphate indium chloride and cerium sulphate were precipitated with ammonia. Anhydrous titanium tetrachloride was added gradually to cold aqueous ammonia. Sodium silicate and sodium stannate were precipit'ated with cold dilute hydro-chloric acid.Cobalt chloride and nickel sulphate were precipitated with caustic potash and the precipitate boiled to get rid of any basic salts. Well washed chlorine gas was then passed through the sus-pended oxides after cooling until the liquid was thoroughly saturated OF IIETALLIC HYDROXIDES I1T IIEXT. 6 1 and smelt strongly of chlorinc even on long standing and repeated agitation. In the same way chlorine was passed through a solu-tion of lead acetate precipitated with sodium carbonate solution. The hydrates (and oxides) obtained as above were washed wit,h cold water first by decantation and afterwards on the filter until the washings were quite neutral and showed no trace of the acid con-tained in tlie salt precipitated or in the precipitant as the cnsc might be.After. being partially air-dried on the filter the hydrates were spread out on glass plates and allowed to dry in the air for at least 10 days before being used ; as the drying proceeded the substances were powdered as finely as possible. Thc silver precipitatc was kept in the dark during the whole course of the investigation. For determining the dehydrating action of heat on the hydroxides obtained as above a small double-walled copper air-bath with ordi-nary Bunscn lamp was employed. It was placed inside a draught-cupboard the flue of which mas stopped so that thc temperature inside the bath could be kept constant within less than a degree for several hours a t a time by occasionally regulating the gas pressure by means of the taps.The hydrates were contained in small porce-lain crucibles which were placed on a glass plate resting on a shelf in the middle of the bath. Hydrates of the same group of elements were always heated a t the same time. The lowest temperature used was about 50" and thismas afterwards increased by about 10" at cach heating. After about two hours' heating at any given temperature, the weight of the hydrates remained sensibly constant consequently the crucibles were allowed to remain in the bath for fully two hours at each temperature and were then removed to desiccators cooled and weighed. An ordinary mercury thermometer was used up to 300° and its readings were not corrected as all that was needed for the purposes of the investigation was that the temperature should increase by com-parat'ively small and tolcra bly regular intervals.Abovc :300° the melting points of different salts were used to mcwure the temperature ; under these circumstances the crucibles were placed on an iron plate resting on pieccs of asbestos on the floor of a muffle furnace with the walls of which it was not in contact. The mouth of the mufTle was closed by an iron platc in which was cut a hole for tlie introduction of a long shallow iron trough containing the salts to be used as indicators. This trough could be slid in and out amongst the crucibles and wlien in the muffle it rested on the iron plate. When tlie muffle had attained the correct temperature the following arrangement was used to keep it constant :-An india-rubber tube from the gas main was cotinected with a Y-tube and to the branches of the y n-crc attached other india-rubber tubes one going to the muffle and the other to th ti2 CARNELLEY AND WALKER THE DEHYDRATION small copper air-bath previously referred to.By means of the pinch-cocks b a d c the flow of gas could be so regulated that when the muffle was a t nearly the desired temperature the Bunsen flame under the air-bath was quite sensitive to a small movement of the pinchcock u, which could then be used to get the correct temperature. When this Lad been attained the thermometer in the air-bath was read off and kept by means of a a t the same temperature during tlie whole heating. It was thus assumed that if the flow of gas was so regulated that the temperature of tlie air-bath remained constant that of the muffle would remain constant also.The indications of the thermometer in the air-bath were checked several times in the course of each heating by means of tlie melting points of the salts heated in the muffle. Tests made with the salts showed that there mas an almost uniform temperature prevailing a t the different parts of the iron plates on n-hich the crucibles rested. The following is a list of the salts eniployed as temperature indicators together with their melting points as determined by one of us in a communication made to the Society some years ago. As the temperature of the muffle woul . h m n Uwm c.\7~,c. .7rr / I /(i vcY DIAGRAM SHOW!NG THE DEHYDRATION GF THE METALLIC HYDRATE BY HEAT.800 700 600 500 ii I? w‘ h 300 200 1W 0 801 70L 606 500 I 6 400 300 h %’ 200 100 0 Lcrs per cent. on A b - & ~ d substance 1 1 I 1 -I 1 I 1 I ! -+ I 4-4 CARNELLY h WALKC 10 20 30 I 20 30 10 li I I A 0 50 TOO 700 900 500 WO 300 200 w o 0 800 700 600 “YZ 900 ?OO zoo 100 OF METALLIC HYDROXIDES BY HEAT. 63 always be a degree or two above that at which the salts melted the round numbers given in the third column have been used instead of fhe melting points as determined. Salt. Melting point. KNO, 339" C. KClO ,. 359 PbI,. 383 TlI 439 PbCl, 408 AgBr 527 Ca(N0,)2 561 NaI . 628 Ag,SO, 654 NaBr 708 NaCl 772 Na,C03 814 Ra(ClO,).? . 414 KIOa 582 Temperature of mufie.say 340' 360 385 415 440 500 530 565 585 630 655 710 775 815 The crucibles and their contents were finally ignited over the blow-pipe. The results obtained are shown in the following series of tables in which Column I gives the temperature Column I I the weight of the substance after heating for at least two hours at that temperature, Column III the difference from the previous weighing calculated* f o r an increase of lo" and Colunin IV the loss per cent. on the substance dried at about 15". The above results are represented graphically in Diagram I in which the ordinates indicate temperature and the abscism the coi*l*e-spondiiig loss per cent. on the air-dried substance. The numbers affixed at certain points to the right-hand side of the curves give the composition of the hydrate at these positions and represent the weight of the attached hydrate corresponding to the weight of the anhydrous oxide shown at a higher point in the curve.Thus in Curve 111 the expression [478 = Si02,H20] indicates that at this point the hydrate had the composition SiOz,H20 the number 478 being the weight in mgrms. of this hydrate which on complete dehydration gave 368 mgrms. of anhydrous SOz. (N.B.-These numbers are hken from column I1 in the foregoing table.) * This calculation was necessary as the actual increase was not always the same, but varied from 10-13" for temperatures below 300" and by greater and less regular intervals above that temperature I. Hydrate of AgaO (air-dried for six months).-.-_____ I. Temp-rsture. -0 15 50 62 74 87 99 111 123 135 14'7 159 171 183 195 207 219 230 242 254 266 279 291 IT. Weight. --mgrms. 625 - 5 625 '0 625 .O 625 '0 625 '0 624 *5 621 *O 617 *0 607.5 582.5 567 -5 558 *O 556.0 555 *o 554 - 5 554 *5 554 *o 553'0 551 *5 550 *5 548.5 542 -5 In. Difference from previous weighing for an increase of lo0. mgrms. -0.1 0 0 0 0 -4 2 -9 3 '3 7 . 9 20.8 12.5 7'9 1.7 0 -8 0 -4 0 0.4 0.8 1 *2 0.8 1 *5 5 *o -IT. Loss per cent. ~ - --0 *08 0 -08 0.08 0.08 0 -16 0 '72 1.36 2 -88 6 -88 9 *27 10 *80 11 -11 11 *2'7 11 -35 11 -35 11 *43 11 -59 11 * 83 11 -99 12.31 13 -27 TI.Hydrate of I. Temperature. ---1"5 50 61 74 86 98 110 121 132 143 153 164 174 185 196 208 218 230 241 253 264 275 11. Weight. --mgrms. 794 793.5 z92.5 492.0 791 790 788 785 '782.0 772.5 '760 744.5 '722 716.5 70.5 697 690 682 673 666-660.5 654. 0 a I. Hydrate of Ag20 (air-dried for six months). ? F r( I. H I+ Temperature. 3io 360 385 41 5 440 500 530 565 585 630 655 700 Blowpipe 11. Weight . --mgrms. 528 -0 528 -0 528 *O 528.5 529 -0 529 529 529 529 529 529 527 527 I XI. Difference from previoufi weighing for an increase of 10". mgrms. -3 -0 0 0 +0*2 +0*2 0 0 0 0 0 0 -0.4 0 IV.Loss per cent. --15.57 15 *57 15 *57 15-49 15.41 15'41 15 *41 15.41 15 -41 15 -41 15.41 15 *83 15.83 11. Hydrate I. Temperature. --2i6 298 34Q 360 385" 41 5 %+ 530 565 585 630 655 710 __ 11. Weight. --mgrms. 651 646.0 6ZO 601 656 501 144 * Colour changed from brown to yellow with white specks. t Specks disappeared and the whole turned bright orange. N.B.-In these and all other cases the colour refers to the substanc 111. Hydrate of SiOz (air-dried for five months). -I. Temperature. -$5 51 63 75 87 99 110 123 135 147 159 171 183 195 207 219 231 243 255 267 279 291 340 11. Weight. mgrms.516'0 459 -5 415 *O 4Q9 -5 406 *O 402 * 5 4oL '0 398.5 397 '0 396 -0 305 s o 395 -0 394.0 392.0 391.5 391 *O 390 *5 390.0 389 *5 389 *O 388.5 388 *O 388 *O 111. Difference from xevious weighing €or an increase of loo. mgrms. 37 -1 4 -6 3.0 3-0 1 -4 1.9 1.2 0 - 8 0.8 0 0 *8 1 *7 0 -4 0 -4 0 -4 0'4 0.4 0.4 0 -4 0 *4! 0 I -15.7 -__ IT. Loss per cent. --10 -95 19 -60 20 *64 21 -12 22 *oo 22 -29 22'77 23 -06 23 -26 23 -46 23.46 23 *65 24 *03 24-13 24 -23 24 -33 24.42 24.52 24.61 24 91 24 *81 24 -81 IQ. Hydrate I. Temperature. --$5 51 63 75 87 99 110 123 135 147 159 171 183 195 207 219 231 243 255 267 279 291 340 Weight.-mgrms. 511 471 452 446 440.5 436 433 430.5 429 427 426.5 426.5 425 425 425.0 425 424 424 423 423 422 422 42 I V . Hydrate I 111. Hydrate of SiO (air-dried for five months). I. Temperature. 3600 385 415 440 500 530 5 65 685 630 655 710 775 815 Blowpipe 11. Weight. Difference from previous weighing for an increase of 10”. mgrms. 385 - 5 382 * 5 381 *O 380 ‘0 380 *O 379 - 5 3’78 -5 376’0 376 -0 374 -0 371 -0 368 -0 368 *O 367 *5 mgrms. -1.2 1 -2 0.5 0 -4 0 0.2 0.3 1 *2 0 0 . 8 0.5 0 . 5 0 - I I I I 25.29 25 *87 26.16 26 * 36 26 *36 26 *46 26.67 27 *15 27 *15 27 -53 28 ‘10 28.69 28 -69 28 -79 3600 385 41 5 440 500 530 565 585 630 655 710 7’75 815 Blowpipe mgrms.420 41’ 417 416 413 412.0 411 408.5 4@ M 403 403 403 40 V. Hydrate of ZrO (air-dried for 10 days). I. Temperature. -1"5 51 63 75 87 99 110 123 135 147 159 171 183 195 207 219 231 255 267 279 291 24,3 11. Weight. -mgrms. 264 *O 230 *O 216-0 211'9 206 * 5 200 -5 197 -5 193 *5 190 '0 187'5 185 -0 183 -5 182 -0 180 - 5 180 -0 179 *5 178 '5 178 -0 177 '0 176 - 0 175 '0 174-5 111. Difference from previous weighing for an increase of 10". mgrms. - 9 - 4 11.7 9.2 3.7 5 '0 2.7 3 - 1 2.9 2 - 1 2 -1 1 -2 1.2 1 *2 0 - 4 0.4 0.8 0.4 0.8 0.8 0.8 -0 - 4 IT.Loss per cent. --12 *89 18 *16 20 -01 21 9 9 24.06 26.19 26 -72 28 .OO 29 *OO 29-88 30.49 31 *06 31 *63 31 *82 32 *01 32 -29 32 -58 32 *95 33 '33 33 -71 33 -90 VI. Hydrate I. Temperature. -I_ 1"5 51 63 76 87 99 110 123 135 147 159 171 183 195 207 219 231 243 256 267 279 291 11. Weight. -mgrms. 721 685 649.5 640 634 628 625 620 616 614 612 610 607.0 604 603.0 601 599 597 595 594 592 59 V. Hydrate of ZrOz (air-dried for 10 days). ented further h I I. Tern perat ure. -345 ,360 385 415" 440 500 530 565 685 An accident pri _sting.11. Weight. -mgrms. 1'12 * 5 172 -0 170.5 160 *5 160 -0 159 '5 159 '0 159 *O 158.5 111. Difference from previous weighing for an increase of 10". mgrms. 0'3 0.6 3-3 0'2 0.1 0.2 0 0 -2 -0.4 IV. Loss per cent. --34 -66 34 *85 35 *42 39 -2 39 *39 39 '58 39.77 39 *'17 39 *96 TI. Hydrate of I. Temperature. 3 i O 360 385f 415 4po 500 530 565 585 630 6555 710 775 815 Blowpipe 11. Weight. --mgrms. 587 586 580 579.5 575 574-573 671 567 562 562 562 561 561 559.5 * Changed from grey to pure white. t Changed from dirty brown to pale yellow. $ Took a greenish tinge VII. Hydrate of CeO (air-dried for 12 days). I. Temperature. --1"5 51 63 75 87 99 110 f23 135 147 159 171 183 195 207 219 231 243 255 267 279 291 340 360 11.Weight. --mgrms. 644 -0 623 * 5 620'0 617 -0 614 -0 609 -0 606 -5 600 .O 594.5 584 * 5 565 *5 554 -0 552 *5 550 -0 648 *O 546.5 545 -0 543 *5 542 * 5 541 * 5 541 *O 540.0 536 -0 536 *O 111. Difference from previous weighing for an increase of loo. mgrms. -5.7 2.9 2.5 2 *5 4.2 2 *3 5 *o 4.6 8 '2 15 -9 9.6 1.2 2 '1 1.7 1.2 1 - 2 1 '2 0.8 0-8 0 '4 0 -8 0.8 0 -IV. Loss per cent. -3 *18 3.73 4 -19 4.66 5 -43 5 *82 6-83 7.69 9 *24 12 -19 13 -98 14 '21 14.60 14.91 15 -14 15.37 15 *60 15 9 6 1.5 -92 16 -00 16 * l 7 16.77 16 *77 VIII.Hydrate I. Temperature. -105 51 63 75 87 99 110 123 135 147 159 171 183 195 207 219 231 243 255 267 279 291 340 360 11. Weight. -mgrms. 706 696.5 695 695 695 694 693.5 693 692 691 690 690 690 689 689.0 688 687 686 685 684.5 684 672 668 66 ________~ ~ VII. Hydrate of CeO (air-dried for 12 dajs). I. Temperature. 3805" 415 440 500 530 665 685 630-f 655 710 775 81 5 Blowpipe 11. Weight. in grm s . 534 -0 533.5 533 *o 533 -0 532 - 5 531.5 531 -5 518.5 513-5 494.5 460 *5 437 *O 433 -5 (?) 111. Difference from previous weighing for an increase of 10". mgrins.-0.8 0.8 0 - 2 0 0 -2 0.3 0 2.9 2 *o 3.4 5.2 6 -8 I IV. Loss per cent,. -17 -08 17.16 17 -24 17.24 17'32 17 -47 17'47 19.49 20 *26 23 -21 28 *49 32.68 (T) 32.14 * Changed from brownish-yellow to bright yellow. t Turned ~1 pinkish (salmon) colour. ~~~ VIII. Hydrate I. Temperature. 3550:: 415 440 500 530 565 9 585 630 (fused) 655 710 775 815 11. Weight. --mgrms. 663.0 653 655 656 656 643-641.5 641.5 641.5 639.0 639.0 639 5 Light specks 6 Became yellow IX. Hydrate of Sb,O (air-dried for five months). I. Temperature. -1"5 5 2 64 76 88 100 112 123 135 147 158 1 'lo 181 193 205 217 229 241 252 264 275 287 11.Weight. -mgrms. 932 - 5 932 -0 931 -5 931 *O 931 -0 931 '0 930.5 930 -0 929.6 929 '5 929 -5 929 - 5 929 *5 929 - 5 928 -5 927.5 927 *O 927.0 927.0 926 5 926 * 5 926.0 111. Difference from previous weighing for an increase of 10". mgrms. -0'1 0 -4 0 - 4 0 0 0 . 4 0 '4 0 *4 0 0 0 0 0 0.8 0.8 0 -4 0 0 0 *4 0 0 .J -IV. Loss per cent. ---0 *05 0.11 0 -16 0 -16 0.16 0 -21 0.27 0.32 0 *32 0 *32 0.32 0 *32 0 -32 0 *43 0.53 0 -59 0.59 0 *59 0 *64 0'64 0 -70 X. Hydrate of I. Temperat me. --1"5 52 64 76 88 100 112 3 23 135 147 158 170 181 193 205 217 229 241 252 264 275 287 11. Weight.--mgrms. 975.0 956-950 948 946 943 942.0 939.5 938.5 936 935 934.0 932 929 926' 923 921 920.5 919 518 917 916. IX. Hydrate of Sb203 (air-dried for five months). An accident p r t I 'I. Temperature. ented further %$8 340 360 385 41 5 44!0 500 530 565 585 630 655 710 775 An accident prt 11. Weight. -mgrms. 926 '0 925 0 925 -0 938 -5 942 -5 943 *5 957.0 958 *O 958 *5 972 -0 976 *5 976 -5 979 *5 975 -0 ented further 1 111. Difference from previous weighing for an increase of 10". mgrms. 0 -0'2 0 +5*4 1 -3 0.4 2 -2 0 *3 0 *14 6 -8 1 '0 0 0.5 -0.1 ating. IV. Loss per cent. 0.70 0 *81 0.81 gain 0 -64 , 1.07 , 1 *18 , 2.63 , 2.73 , 2.78 , 4.23 , 4.74 , 4.74 , 5.04 , 4-98 X.Hydrate of I. Temperature. ___.-2980 340 3 60 385 415" 440-f 500 530 565 585 630 655 710 fused 775 11. Weight. -mgrms. 915.0 910 900 890 868 866 856 855 853.5 851.0 852 852.0 852 852 * From light to deep yellow (brown when hot). t Turned light again XI. Hydrate of Al,O (air-dried for six months). I. Temperature. -1"5 60 62 74 87 99 111 123 135 147 159 171 183 195 207 219 230 242 254 266 279 291 340 360 11. Weight. -mgrms. GOO *o 550 .o 494.0 477.0 4.68 -5 462.5 456.5 452 -5 449'0 446 ' 0 440 -5 436 -5 432 -5 429 *O 425 *O 410 -0 386.0 379.0 375 *5 374 *5 373 -5 370 -5 349 -5 342.5 111.Difference from previous weighing for an increase of 10". mgrms. 46 *7 14 '2 6 . 6 5 -0 5 '0 3 . 3 2 *9 2.5 4.6 3.3 3.3 2.9 3 -3 12,5 21 -8 5.8 2 -9 0.8 0.8 2 *5 4.3 3.5 -- 14 '3 IV. Loss per cent. ---8 -33 17 *66 20.50 21.92 22 *92 23 *92 24.58 25 *16 25 *66 26 -58 27 *15 27-91 28 -50 29.16 31 -66 35 -66 36.83 37 -42 37.75 38 *25 41 -75 42.92 37 -58 XII. Hydrate I. Temperature. -I__ 1"5 50 62 74 87 99 111 123 135 147 159 171 183 195 207 219 230 242 254 266 279 291 340 360 11. Weight. --mgrms. 134 127 125 124 122 121 120 119 117.5 116.5 113 111.5 110 109-108 107 105 103 102.5 100 100 100 98 9 XII.Hydrate I XI. Hydrate of A1,0 (air-dried for six months). I. Temperature. .-3805 415 440 500 530 565 585 k30 655 710 775 81 5 Blowpipe ~~ I. 1 11. Weight. Temperature. -3805 415 440 600 530 565 585 630 655 710 Blowpipe Weight. I_-mgrms. 341 -0 338 *o 336 *O 333 -5 333 -5 332.5 331 *O 329 *O 329.0 327 *O 323 -0 111. I IT, Difference from I previous weighing for an increase of loo. Loss per cent. --- I mgrms. -0.6 1 -0 0.8 0.4 0 0.3 0.7 0 -4 0 0 *4 -43 -17 43 *67 44 * 00 44 -42 44.42 44 -59 44 *83 45 el7 45 *17 45 -50 46 *17 11.mgrms. 98 98.0 97.5 97 97 97-97 97 97 97 07 97 9 XIII. Hydrate of T1,0 (air-dried for 14 days). I. Temperature. 15 50 62 74 99 111 123 135 147 169 171 183 195 207 219 230 242 254 266 279 291 a7 11. Weight. -mgrms. 352 *O 347 -0 346 -5 346 *O 345 -5 345 *o 344 -5 344 .o 343.0 342.5 342 -5 342 -5 342 *5 342 *O 341 *5 341 -5 341 .O 341 *O 341 -0 341 -0 341 -0 341 -0 111. Difference from previous weighing for an increaee of 10". mgrms. --1.4 0.4 0.4 0 *4 0.4 0.4 0.4 0.8 0.4 0 0 0 0 -4 0.4 0 0.5 0 0 0 0 0 IT. Loss per cent. --1 -42 1-56 1 90 1 *84 1.99 2 -13 2 *27 a-56 2 -70 2-70 2-70 2 T O 2 -84 2 -98 2 *98 3 '13 3 *13 3 -13 3 *13 3 *13 3 -13 X1V.Hydrate I. Temperature. --1"5 50 62 74 86 98 110 122 134 146 158 170 182 194 206 218 230 24A 257 269 281 293 11. Weight. -mgrms. 862 777 677 645.5 623 611.5 598 590 584 578 573.5 568 564 562 560 557 555 553.5 553 552 552.0 550. XIII. Hydrate of T1203 (air-dried for 14 days). I. Temperature. -3iO 360 385 41 5 440 500 530 565 585" 630 fused+ 655 710 75'5 815 BI ow pipe 11. Weight. mgrms. 341-0 341 -0 340 -0 338 '0 337 -0 337 -0 337 -0 337 '0 335.5 301 *5 290 .O 268 -5 244 -0 239.5 239 * 5 111. Difference from previous weighing for an increase of 10".mgrms. 0 0 -0.4 0.7 0.4 0 0 0 0 -8 7.6 4.6 3.9 3.8 1 -1 0 IV. Loss per cent. . -3 -13 3.13 3 '42 3 *98 4.27 4.27 4 *27 4 *27 4 -69 14.35 1'7 -61 23 *72 30.68 31 *96 31 *96 XIV. Hydrate I. Temperature. -320 360 385 415 4!40 500 530 565 585 630 655 710 Blowpipe 11. Weight. -mgrms. 650 548 640 540 536.5 534.5 534 534 534 534 534 534.5 534 f Lost its gloss and became dull-black. t To a dirty green liquid XV. Hydrate of Co,O (air-dried for 15 days). I. Temperatnre. -1"5 60 62 74 80 98 110 122 134 146 158 170 182 194 206 218 230 244 257 269 281 293 11. Weight.-mgrms. 397 * 5 397 -5 397 -5 397-5 396 -5 395 *5 393.6 391 *O 389 -5 388 '0 387 *O 386 *O 385 -0 384 .O 382.0 378'0 370'0 360 -0 346 *o 341 *O 340-0 340.0 111. Difference from previous weighing for an increase of 10". mgrms. -0 0 0 0.8 0 *8 1 . 7 2 -1 1 -2 1 -2 0.8 0 -8 0 *8 0 '8 1 -7 3 -3 6.7 7.1 10 *7 4 *2 0 *8 0 IT. Loss per cent. --0 0 0 0 -25 0 *50 1 '01 1 -63 2 -01 2 *38 2 -64 2-89 3-14 3 '40 3.90 4 -91 6-92 9 -43 12-95 14 '22 14.47 14 *47 XV. Hydrate I. Temperature. 3iO 360 385 41 5 500 530 565 585 630 655 710 775 81 5 Blowpipe 11. Weight. --mgrms. 339 339 336.5 336.5 336 336 336 336 336 336 336 336 336 336.OF METALLIC HYDROXIDES BY HEAT. 79 XVI. Hydrate of Ni,Oa (air-dried for 10 days). I. Temperature. I 5 50 62 74 86 98 110 122 134 146 158 170 182 194 206 218 230 2444 Stopped 11. Weight. mgrms, 864 -5 792 -0 715'0 700 -5 689 -0 680 - 5 669 *5 659 *O 648.5 637 -5 623 - 5 601-0 587 -5 579 -0 573.0 570.0 567 -0 564 -5 by an accident 111. Difference from previous weighing for a,n increase of 10". mgrms. 20 *7 64.2 12 -1 9 -6 7 . 1 9.2 8.7 8.7 9 -2 11 -7 18 -7 11 *2 7 . 1 6 -0 2 *5 2 - 5 1.8 -tt this point. IV. Loss per cent. ~--8.38 17 -%9 18 -97 20 -30 21 '28 22 5 5 23 - '77 24 *99 26 -26 27 -88 30 '32 32 -04 33 '02 33 9 2 34.07 34 -41 34 -71 As regards the several curves the following remarks will explain the results indicated :-I.Hydrate of Ag,O.-The precipitate obtained on adding caustic soda to a solution of silver nitrate absorbed a very small quantity of carbonic anhydride on drying. The product after drying in the air for six months appeared to be the normal hydroxide AgOH. On heating this was comparatively stable up to about loo" but on further heating it lost water and a small quantity of oxygen and was converted gradually into AgzO (admixed with a small quantity of metallic silver). At a higher temperature the whole of the oxygen was given off leaving a residue of pure silver. The various phenomena therefore were :-(1.) AgOH comparatively stable up to about".. . (2.) Rapid loss of water and small quantity of 100" oxygen * 100-180" * Watts' Dictionapy 6 302 states that precipitated silver oxide becomes anhydrous on drying at 60-70"; and that i t gives off a certain quantity of oxygen a t 100') but whether Ag,O or Ag is thus formed is not known (comp. Bailey Trans. 1887 416 j and v. der Pfordten Bev. 20 1468) 80 CARNELLEY AND WALKER THE DEHYDRATION (3.) AgaO (containing a small quantity of Ag) (4.) Rapid decomposition of AgzO with reduction (5.) Reduction complete at about,. 11. Hydrcxte of Hg0.-The precipitate obtained on adding caustic soda to a solution of mercuric chloride after drying in the air for five months had the composition Hg(OH),.On heating this remained tolerably stable up to about loo" at which temperature (after heating in all ahout 10 hours) it had lost only about one-half per cent. of its weight whereas complete dehydration to HgO would require a loss of nearly 8 per cent. Above loo" it lost water more and more rapidly, and became completely dehydrated to HgO at about 175". Above this temperature incipient decomposition into mercury and oxygen commenced and continually increased up to about 360" when it became much more rapid and developed into full decomposition at from 415" to 440". The changes in colour which the substance exhibits tohen cold after heating above 360" are noteworthy. After heating from 360" to 385" the colour had changed from brown to yellow specked with white.These specks disappeared on heating from 415" to 440", and the whole became bright orange This last change probably indicated the conversion of the yellow oxide into the more stable allotropic ordinary red oxide of mercury, comparatively stable 180-210" to metallic silvers. . 270-300" 300-340" We have therefore :-(1.) Hg(OH) almost stable up t o about?. . (2.) Rapid dehydration 110-175' (3.) Complete dehydration to HgO about. . (4.) Incipient decomposition into Hg and Ox low to the red modification,$ about 100" 175" 175-360" (5.) Full decomposition sets in whilst the still undecomposed HgO changes from the yel-415-440 111. Hydrate of SiOt.-The precipitated silica obtained on adding hydrochloric acid to a solution of sodium silicate after air-drying for * Pure Ag,O begins to give off oxygen a t 250" ( Wutts' Dictionary 1,792).t According to Watts' Dictionary 3 908 yellow mercuric oxide is anhydrous, whereas Schaffner (Annalem 51 181) states that the yellow precipitate formed by the addition of caustic potash to mercuric salts is the hydrate Hg0,3H20. $ These results obtained by heating in a covered but not air-t<qht crucible are in accord with those of Meyers (Ber. 6 11). who determined the courSe of the decomposition by the tension of the gas evolved. Debray (Compt. rend. 77 123), however has shown that if the mercury and oxygen be heated in a sealed tube maintained throwghout at a uniform temperature the oxygen is almost completely absorbed by the mercury even a t M9 OF BIETALLIC HYDROXIDES BY HEAT.81 five months retained a quantity of water corresponding very nearly t o the formula 3Si02,4H,0. On heating this lost water at an almost uniform rate up to 63" passing through the compositions indicated by SiO,,H?O and 2Si02,H,0 without showing any indication of the formation of d e h i t e hydrates of this or other composition. At about 63" the curve turns upward rather sharply and thence assumes almost a straight line until it reaches the position for anhydrous silica at a temperature somewhat above 81.5" (say 850").* These results show that precipitated silica when heated at succes-sively increasing temperatures forms no hydrates which are stable through a range of temperature of at most 13". The phenomena are in fact such as to indicate that probably numerous successive hydrates are formed as the temperature increases but that all these are so very unstable that a small further rise in temperature causes an additional loss of water.The rapid rise of the curve above 63" would seem to show either that the hydrates formed below were much less stable than those formed above that temperature or more probably that the latter were much more complicated in composition. It was at one time supposed that hydrates of a definite and con-stant composition could be obtained by drying gelatinous silica under various conditions and the following have been stated to exist by different observers :-Dialysed silicic acid. . Si02,2H,0. Dried at ordinary temperature SiO,,H,O. 20-25" 2Si0,,H20. 7 7 60" SSi0,.H20.250-270". . 8SiO,,H,O. , 80-100" 4SiO,,H,O. More recent investigations however have shown that the quantity of water contained in the artificial as well as in the natural amor-phous silica varies within very considerable limits whilst the water can be driven off at such low temperatures that it has been suggested that this water is to some extent at least mechanically admixed and that at any rate t'hese h>*drates must be considered to be very loose compounds of silica and water (Eoscoe and Schorlemmcr's Treatise on Chemistry 1 572). IV. Hydrate of Ti02.-This curve is very similar to that for silica, and similar remarks therefore apply in this case. The chief differ-* By the term '' stable hydrate" as used in this paper is meant a hydrate which undergoes no loss of weight on furt,her heating through an appreciable range of temperature above that a t which it had been formed by the dehydration of a higher hydrate whereas a hydrate which is unstable is one which loses more water O n a slight rise of temperature above that a t which it had been formed.This is entirely confirmed by oiir results. VOL. LIII. 82 UARNELLET AXD WALKER THE DEHYDRATION ence is that the steep upward turn of the curve is not nearly so abrupt as for the hydrates of silica. Titanic acid becomes completely dehydrated a t about 710". A very large number of hydrates of TiO are said to have been obtained f o r a list of which see Watts' Dictionar~y 6 1098. As in the case of the silicic hydrates it is very doubtful whether these are of definite or constant composition (com-pare Rose Aitranlerz 53 267 ; CnzeliiL's Handbook 3 475 ; Roscoe and Schorlemmer's Tyeatise 2 ii 259).The regular and unbroken form of the curve obtained by LW i s certainly against the existence of definite hydrates of any evident degree of stability. V. Hydrate of ZrO,.-With one or two marked exceptions this curve iiidicates that phenomena occur on heating similar to those in the case of silicic and titanic hjdi-ates. The upward turn o€ the curve takes place even more gradually than with titanic acid. The two special characteristics of this curve however are :-(1) For tempera-lures below 385" it shows that though the percentage loss is greater a t any given temperature yet B milch greater quantity of water i s re-taintd per molecule of ZrO than in the case of eihher SiO or TiO,.Thus. whereas silica is dehydrated t o 2SiO,,H,O a t about GO" and titania to 2Ti0,,H20 a t about 70" zirconia is dehydrated t o 2Zr02,Hz0 only a t 389". (2) The most noteworthy difference however is the sudden break in the continuity of the curve between 385" and 415", the sudden inorease in the loss per degree of rise in temperature being much greater than it had been for the previous 280". Unfortunately no observation was made between 385" and 415" but somewhere between these temperatures a very sudden increase in the elimination of water took place; for whereas the hydrate a t 385" had the com-position 2ZrO,,H,O it had a t 415" the composition 24Zr02,H20 and soon after became completely anhydrous.Curiously enough this phenomenon was accompanied by a change in calour from grey to pure white whilst other observers state that this change in colour occurs a t the same time as a vivid incandescence, and a considerable modification in the chemical properties of the zirconia. Owing to the conditions of the experiment we could not tell whether this incandescence took place or not. The peculiar incandescence referred to was first noticed by Sir Humphry Davy, whilst Chevreul observed that' it was preceded by blackening; the latter was ascribed by Hermann to the presence of impurities (com-pare Gmeliti,'s HawdbooL 3 343). Gmelin states (loc. cit.) that zirconia becomes anhydrous considerably below red heat and that the above incandescence only occurs after all the water has been driven off.This must be an error as we found that a t or very near the temperature a t which incandescence takes place the composition was represented by 2ZrOz,H,0 and that even after the incandescenc OF METATJLlC HYDROXIDES BY HEAT. 83 a loss of at least 0.76 per cent. occurred on further heating to 585". The actual loss on complete dehydration rnay possibly have been even slight'ly greater for an accident unfortunately prevented heating to a higher temperature. These results seem to show that the incandeh-cence which occurs a t about 400" is not due as hitherto supposed t o tbe conversion of one form of anhydrous zirconia inbo a denser aiitl more stable modification but to the sudden elimination of water, accompanied probably by a considerable condensation of the zirconia from the comparatively small molecule n(2Zr0,,HzO) to the large molecule n(24Zr02,H20).The form of the curve asppears to indicate that no definite stable hydrate is formed by heating precipihted zirconia and this is coil-firmed by the discordant results obtained by other observers thus :-According to Berzelics the dry hydrate has the composition Zr02,H20 = 12.9 per cent. H20 whereas Davy stated that it contained 20 iwr cent. and Klaproth gave as much as 33 per cent. Hermann fount1 that the hydrate dried a t 17" was represented by Zr0,,2H,O = 23 per cent. VI. Hydrate of SnO,.-This curve is very similar to those for silica aiid titania aiid like them shows that no definite stable hydrates were formed. The oxide became anhydrous a t 630-655".A little above 360" it had the composition indicated by 3SnO2,HZO and was of ;I dirty-brown colour. On a further small rise in temperature it sud-denly changed from brown to pale yellow and simultaneously lost, weight a t a rate nearly three times as great as during the previous loo" after which the rate of loss during the next YO" o r 40" was reduced to less than one-seventh of that which occurred during the change of colour. After changing colour i t had the composition 7Sn0,,2H20. The following stannic hydrates are said to have been obtained by different observers :-(a.) Of ordinuvy 8tannic Ac.; ,H,O. (By action o€ Acids on Solu nnates.) Dried in stream of dry air (Fremy) 381io,,7H~o, Dried a t ordinary temperature in air (Weber) SnO2,2H,O.Dried in a vacuum (Fremy) . . . . . . . . . . . . . . SnO,,H,O. Dried at 140' (Fremy) . . . . . . . . . . . . . . . . . . 3SnO2,2H2O 84 CARNELLET AXD WALKER THE DEIIYURATION ( h . ) Of Metastannic Acid Sn50,,,5Hz0. Nitric Acid.) (By oxidation of Tin with Dried at ordinary temperature (Fremy). . 7 ) Y (2) (Berzelius) 7 9 7 7 (Thornson) . Dried over sulphuric acid (Weber). . Dried in a vacuum or a t 100" (Fremy) Dried a t 130" (Fremy) Dried at 160' , Dried a t 55" (Thornson). . 5Sn02,1 OH,O, Sn02,H20. Sn02,H20. Sn02,H20. 5SnO2,5HzO. 5Sno2,4H20. 5Sn02,3H,0. 2Sn02,H,0. (c.) Intermediate Acids (Jluscwlus) Sa,O4,2H2O and Sn,0s,3H20. VII. Hydrate of Ce02.-This curve is a characteristic one and is distinguished from those of the other metals of the silicon-group, which i t ot'herwise resembles to temperatures of about 600" by the fact that after rising almost perpendicularly from 200" to 600" it bezins at the latter temperature to curve towards the horizontal and this continues even up to S15".The composition a t 600" just before this change occurs is represented by CeOZ,2H2O. This would seem t o be a definite hydrate for the composition had previously remained nearly constant the loss?of water for 12 hours between 383" and 600" not having amounted to more than 0.39 per cent. or for eight hours' heating between 440" and 600" to 0.23per cent. Further the rate of loss which commences at 600" is 20 times as great as the average rate during the previous 220° and moreover at 600" the colour suddenly changes from a light yellow (presumably tjhe colour of the hydrate Ce02,2H20) to salmon colour the latter prevailing until complete dehydration.Finally a t the temperature a t which the com-position became practically constant (385") and therefore presumably that at which the hydrate Ce20,2Hz0 was formed there was a change of colour from brownish-yellow t o bright-yellow. We may therefore conclude that ceric oxide forms a definite hydrate CeO2,2H20 or normal ortho-ueric hydrate H,CeO or Ce(OH)4 which is very nearly stable even up t o COO" at which temperature rapid dehydration begins. We have as regards colour the following :-Hydrates Ce02 (2 + a)H,O. . brownish-yellow. Hydrate Ce02,2H20 bright-yellow. Hydrates CeO, (2 - b ) H20 salmon colour.Anhydrous oxide CeO ditto. Pure cerium dioxide is said to be a white or pale straw-colonred powder but that after an hour's ignition it acquires a reddish ting OF METALLIC HYDROXIDES BY HEAT. 85 (Mosander). Watts states that it is fawn- or salmon-coloured. The hydrate precipitated from ceric salts by alkalis is pale or sulphur-yellow according to Berzelius and Illosander but they do not state what its composition is. A sulphur-yellow hydrate of the formula 2Ce02,3H,0 is formed on heating the acid sulphate with caustic potash or by the action of chlorine on the hydroxide of the sesqui-oxide suspended i n water (Roscoe and Schorlemmer Xreatise 2 i, 428). VIII. Hydrate of Pb@,.-This curve has a form quite different from those for SiO, Sn02 &c. owing to the decomposition which the oxide itself undergoes on heating being ultimately converted into PbO and 0.Precipitated lead dioxide after drying in the air for 10 days had very nearly the composition 3PbO2,H2O. On heating it gradually lost water and became dehydrated to PbO at about 230°, on further heating its weight remained nearly constant up to 280" a t which temperature it suddenly lost oxygen and was converted into Pb203. This was stable up to about 365" when a further loss of oxygen occurred with the formation of Pb30P ; the latter was stable up to 530-565" when it lost more oxygen became yellow and formed PbO ; this last change being complete a t 585". The PbO thus formed subsequently fused between 585" and 630'. We have therefore-Hydrate dried in air = 3PbO,,H,O.Complete dehydration to PbO a t about PbO stable up to about Loss of oxygen with formation of Pb,03 Pb,Os stable between about Loss of oxygen with formation of Pb304 Pb30a stable between about Loss of oxygen with formation of PbO . PbO stable from PbO fused somewhere between . 230" 280 280-290" 290-360 360-4d-5 415-5301 530-580 580 to above 815" 585-63U" Becquerel (Ann. C'him. P l i y s . [ 3 ] 8 405) states that the hydrate, PbO,,H,O is deposited at the positive pole during the electrolysis of lead salts. This is the only previous notice of a hydrate of PbO,. The difficulties which occur in the manufacture of red lead from massicot (PbO) are doubtless due to not employing the most suitable temperature. Mercier (Annalen 160 252) says that the principal point to be attended to next to the access of sufficient air is consta,ncy of the right temperature; for the temperature a t which massicot takes up oxygen and that at which red lead loses it lie very near to each other.He states that the most favourable temperature approaches that of a dull-red heat without however reaching it. The result 86 CARNELLET ASD WALKER THE DEHYDRATION we have given above may possibly be of service in this important nianu f ac ture . IX. Precipitated Sb,O,.-Precipitated antimony trioxide after drying in the air for five months was found to be anhydrous. On Iieat'ing it underwent but a slight loss in weight and appeared to be very nearly stable up to 360° at which temperature i t took up oxygen, forming an oxide approximating to Sb200,z ; this remained comparn-tively constant between 415" and 440" gaining only 0.11 per cent.in weight. Above 440° i t again took up oxygen with the formation apparently of Sb40i. This remained comparatively conshnt up to about 565" ; above 565" i t again took up oxygen with the formation of Sb204 which then remained stable up to 775" which was the highest temperature reached. We have therefore-Sb,,O,o = 5Sb406 = 10Sb,03 stable UP to . . 360" Rapid absorption of oxygen Sbz,032 comparatively stable 415-440 SbZoO, = 5Sb,O7 comparatively stable Rapid absorption of oxygen 565-585 Sb2004 = 5Sb40 = 10Sb204 stable . . . . . . 360-400" Rapid absorption of oxygen somewhere be-tween 440-500 500-565 590 to above 775" Antimony trioxide is usually said to be anhydrous ; Regnault how-ever (Cours de Chimie 3 239) describes the hydrate Sbz03,H20 and Schaffner (A7znale.r~~ 51 168) the hydrate SbzOj,2H20 ; but neither of these was prepared by direct methods.X. Hydrate of Bi203.-The precipitated hydrate after drying in the air for five months had nearly the composition Bi203,3Hz0 ;* t h i s Jlydrate was not stable but on heating lost water gradually up to 340" and then much more rapidly up to 415" a t which temperature i t contained less water than corresponds to the formula Bi,O,,H,O. It became completely dehydrated a t about 600" and afterwards fused somewhere between 655" and 710". There did not appear to be any clecisive indication of a definite hydrate of any evident degree of stability.Mxir states (Chew. SOC. Jour. 1877 i 648-649) that the following hydrates of bismuth trioxide are known :-Bi2O3,3H20 ; Bi2O3,2HZ0 ; Biz03,H20. An inspection of Curve No. X however shows that none of these are stable o r only through a very small range of temperature and * It also contained some carbonic acid so that the results obtained in this case canriot be considered as conclusive OF METALLIC HYDROXIDES BY HEAT. 87 that on heating the highest hydrate passes gradually into the lowest, and finally into the anhydrous oxide. XI. Hydrate of Al,O,.-The precipitated hydrate of alumina after drying in the air for six montths had the composition A1,o3,5HZ0. It attained the cornposition A1,0,,3H2O on heating at 65" after which the rate of loss diminished considerably up to about 150" when it again increased up to 160° and again diminished up to about 200".Between 160" and 200° the composition approximated to A1203,2H20. From 200" to 250" the rate of' loss was again very rapid but became very much less between 250" and 290" when the composition was approximately AI2O3,HzO. Above 290" the rate of loss rapidly in-creased again up to 360" beyond which it slackened and water was gradually but slowly expelled u n t i l complete dehydration was reached a t a temperature of about 850". A t no point did the coniposition remain constant an increase of 10" always caused a further loss of water except at temperatures above 500" when the alumina was very nearly dehydrated. A certain comparutive-but only comparative-stability however was attained a t or about the three following temperatures viz.:-A1203,3H20 comparativeZy stable. . 65-150" A1203 2 H,O , 160-200 A1 2 0 3 H,O 25'3-290 7 9 7 ,, The following hydrates have been previously noticed :-Precipitated at a boiling heat and dried at ordinary temperature (Ramsay). A120,,5H,0. Hydrargillite and gibbsite ; also the arti-ficial hydrate obtained by precipitation and dried (in air ?) (Torrey Berzelius, Bonnsdorff) A1203,3H20. By heating aluminium acetate a t 100" for some days and drying the resulting pre-cipitate at 100" (Crum) By prolonged ebullition of A1,03,3H,0 sus-pended in water (St. Gilles) Native hydrate from Beaux (Bcrthier). Diaspore A1,0,,H20. Precipitated hydrate dried a t 300" (Ram-A1203,H20 does not part with its water AI2O3,2H20.A1,03,2H,0. A1,O3,2HZO (?). say) . A1,03,H20. below 360" (Dufrbnoy). Our results agree very closely with the above and with tliose o 88 CARNELLEY AXD WALKER THE DEHYDRATION Ramsay on the dehydration of alumina (Chem. SOC. Jour. 1877 ii 395). Ramsay's and our own results show either that there me no definite stable hydrates of alumina or what is more probable that a very large number of hydrates exist b u t so unstable that the smallest rise in temperature is sufficient to convert a higher into a lower hydrate. XTI. Hydrate of In203.-The air-dried hydrate had very nearly the composition In203,6H,0. On heating it lost water gradually and at a nearly uniform rate up to 150" when it had the composition Inz03,3H,0.The rate of loss then rapidly increased up to 160", beyond which it proceeded almost uniformly a t the previous rate and the substance passed successively through the compositions In20,,2H20, 21nO3,3H20 and Jn203,H,0 without giving any evidence of the formation of a stable hydrate. Soon after passing through In203,H20, and a t about 280° the rate of loss suddenly diminished the curve taking a sharp curve upward and becoming nearly perpendicular. Complete dehydration however was finally attained only a t 655", the last traces of water being lost very slowly. The two following hydrates are said to have been obtained (Watts' Dict. 6 732) :-Hydrate precipitated a t boiling heat and air-dried 21n,0,,7H20. Dried at 100". . In20y,3H20.But generally speaking the same remarks apply here as in the case of alumina in so far as there is no indication of the formation of any definite stable hydrates. XIII. Hydrate of Tl,O,.-Precipitated and air-dried thallic hydrate had almost exactly the composition T120J,H20. This however was not stable but on heating gradually lost water until complete de-hydration was attained a t about 230". The weight then remained perfectly constant up to 360" between which and 440" a further very slight diminution occurred due apparently to loss of oxygen. Above 440" and up to between 565" and 585" the weight again remained perfectly constant and corresponded exactly to 3Tl2O3,Tlz0. Some-where between 565" and 585" the substance lost its gloss and became dull black.It then rapidly lost weight owing partly to loss of oxygen and partly t o volatiliaation of the T1,O formed. It fused a t 630" to a dirty-green liquid. It continued rapidly to lose weight u p to 815" but above this temperatwe the weight again remained constant and no further loss occurred on heating over the blowpipe ; the total loss then amounted to 31.96 per cent. The final product probably consisted of uridecomposed T120,. It could not be T1,0 as the latter is readily volatile a t the temperature employed. The mos OF METALLIC HYDROXIDES BY HEAT. 89 probable explanation seems to be that at 585" T120 loses oxygen with partial conversion into T120 but above 815' any T1,O so formed again takes up oxygen re-forming non-volatile T1,0,. .We have there-fore-Air-dried at 15" = Tlz03,H20 but unstable on heating.Complete dehydration with formation of T1,03 about 230" Tl,O perfectly stable 230-360" Reduction to 3T1203,Tla0 360-440 3T1203,T1,0 perfectly stable. 440-565 Rapid loss of oxygen and volatilisation of T120 formed the rate of loss gradually diminish-ing after fusion at 630" 585-815 Remaining T1,03 constant from 815" upwards. The following observations have been noted by others :-Precipitated thallic hydrate dried at 100" Ditto dried over sulphuric acid (Birnbaum) . . Ditto dried at 100" (Birnbaum) . Ditto dried at 260" (Crookes) . (Werther) . T1203,Hz0. Tl,03,H,0. T1,03. Tl,O,. Pure anhydrous Tl,Oj melts at 759" (Carnelley) ; TLO gives off oxygen at a red heat with reduction to T1,O (Watts' Dict.5 753) ; T1,O melts at about 30U" and at higher temperatures volatilises and partially oxidises at the same time to T1,03 (ibid. 752). XTV. Hydrate of Fe203.-Precipitated ferric hydrate after drying at about 15" for 18 days contained more water than corresponded to Fe20,,5H,0. On heating it attained the composition Fe@,3H20 at about 55" but with a further rise in temperature water was graducnlly given off until the oxide was completely dehydrated at 500" ; beyond this there was no more alteration in weight. The curve shows that at no point was there any indication of the formation of a definite hydrate stable through a further rise in temperature except that at about 385" a hydrate was formed represented exactly by 10Fe20,,H,0 ; this remained perfectly constant in weight on heating for two hours from 385" to 415" and was possibly stable through a much larger range of temperature.Ramsay (Chem. SOC. J. 187'7 ii 395) has also investigated the de-hydration of ferric hydrate and he also concludes that no definite $table hydrates are formed except perhaps Fe,0,,H20 ; our results, however give no indication of the formation of the latter. The following minerals are well-known natural crystallised bydrates : 90 CARNELLEY AND WALKER THE DEHrDRATION Limonite . Pe2O3,.?H2O. ,7 Fe,0,,2H20. Gothite . Fe203,H20. Limonite . 2Fe20,,3H,0. Turgite . fLPe203,H20. ,) . 3Fe,03,5H20. . The following have been prepared artificially -Precipitated when cold (Wittsteinj . Fe203,3H20. . ,) (Gmelin and Lefort) . Fe,O,,ZH,O.7 , hot (Lefort Schaffner). Fe203,2H20. 7 and dried in at vacuum 2Fe,03,3H,0. , when cold and dried a t 100" (Muck) . Fe203,2H20. Ry freezing ferric hydrate suspended in water 2Pe,03,3H20. Precipitated when cold (Peau St. Gilles) 2Fe,O3,3H,O. Precipitated and dried at 100 (Muck). Pe20aHz0. Prolonged ebullition of hydrate in water (Peau Ferric hydrate dried a t 100". 2Fe2O3,H20. Totally dehydrated by prolonged ebullition in Precipitated and dried at temperatures between 15" and 100" gives hydrates intermediate between Fe2O3,ZH20 and Fe20,,H20 (Muck). St. Gilles) Fe,O,H,O. water t o . . . Fe,Os. XV. Hydrate of CoLO,.-Air-dried precipitated cobaltic oxide had almost exactly the composition 5C0203,8H20. At this it remained perfectly constant on heating for six hours a t temperatures ranging u p to 74".When heated beyond this it gradually lost water and a t 100" had exactly the composition 2Co2O3,;3H2O ; the latter however, was not stable f o r on further heating i t lost more water at a rate which gradually increased up to 260" when the rate of loss rapidly diminished the curve turning sharply upwards and becoming very nearly perpendicular. The product had now exactly the composition 10C020.,,H20 (or Co203 see below) and a t this it remained almost constant (losing but 1 mgrm.) between 280" and 360". At the latter temperature it underwent a further slight loss and became com-pletely dehydrated a t 385" or possibly lost a small quantity of oxygen givinq a product consisting of C O r 0 3 admixed with a little Co301 (see below).We have therefore OF METALLIC HYDROXIDES BY HEAT. 91 Air-dried cobaltic hydrate 5C0203,8H20 stable Gradual loss of water without formation of up to 75" stable hydrate 75-270" 10C0203,H20 (or else pure Co,O,) stable 280-360 385" Complete dehydration or slight loss of oxygen with formation of a small quantity of Co30A Winkelblech states that precipitated hydrate of cobalt after drying over sulphuric acid h:is the composition C 0 ~ 0 ~ 3 H ~ 0 whereas Hew found that under the same conditions it had the composition Co2O3,'2H20. When cautiously heated to 600" or 700" it yields the anhydrous oxide (Watts' Did. 1 1049). Exposed to a low red heat, it loses oxygen with formation of CO~O (Hess Braun; comp. also Eussell Chem.SOC. J. 1863 16 51). XVI. Hydrufe of Ni,Oa.-The completion of the dehydration in this case was prevented by an accident so that no definite conclusions are possible except that so far as the curve runs there was no indication of the formation of any definite stable hydrate. A general consideration of all the curves shows-(1.) That in no instance [except in the case of Ag(OH) Hg(OH),, Ce02,2H20 and perhaps 5C0,O,,8HZO] is there any certain indication of the formation of definite hydrates which are stableX through any but possibly a very small range of temperature. From this we must conclude either that there are no definite hydrates formed on heating the precipitated hydrst es a t gradually increasing temperatures ; or that a very large nnmber of such hydrates are formed under these conditions but that they are so unstable that a very small further rise in temperature is sufficient to convert a higher into a lower hydrate.If the first alternative be correct then the so-called hydrates would be mechanical mixtures of the oxide with water but this is a supposition which is very improbable for it would be diKicult to suppose that mechanically admixed water could Ee retained at the high temperatures frequently required to produce complete dehydra-tion in some cases a full red heat. The second supposition that there are a large number of definite b u t unstable hydrates formed is far more probable. That definite hydrates of Fe2O,,A1,O3 &c. exist is proved by their natural occur-rence in the form of several well-crystallised minerals and by the artificial production of many crystallised hydrates.The forms of the dehydration curves would also one would think be far more regiilar did the dehydration consist in the expulsion of merely mechanically * For definition of " stable hydrate " see p. 81 92 CSRNELLEY AXD WALEER THE DEHYDRATION admixed water whereas their greater or less irregularity in most cases seems to indicate the formation of hydrates at certain tempera-tures which are relatively more stable than hydrates formed a t other temperatures. The unstable character of the hydrates is further shown by the frequently discordant results obtained by different observers and by the apparently slight circumstances which seem in many cases to influence the qunutity of water retained by an oxide.The snmmary of previous work on this subject given above a t the end of the discussion of each curve will serve to illustrate this. I n view then of the following facts-1. That certain well-defined hydrates are known which are stable through a considerable range of temperature though the number of these is smaller than is usually supposed ; 2. That many well-defined and well-crystallised hydrates axe found as minerals and may also be obtained artificially ; 3. That the artificial hydrates produced by heat and of the same composition as these minerals on further heating lose water more or less gradually at or only very slightly above the temperature at which they were formed ; 4. That the temperatures required for complete dehydration are often high ; 5.That the dehydration curves frequently seem to indicate the formation of hydrates which though unstable themselves except through a very small increase of temperature are relatively much more stable than other hydrates of the same oxide :-We conclude that when a precipitated oxide is heated it gradually loses water with the successive formation of a large nuniber of definite hydrates each of which is further decomposed on a small rise in temperature with the formation of a hydrate containing a smaller proportion of water. As the elimination of water proceeds tile molecule becomes larger and more and more complex until ultimately , when the last molecule of water is given off a highly complex molecule of the anhydrous oxide is left its formula being some multiple n(R0,) of the generally received simple formula RO,.The polymeric character of the oxides we have examined seems to accord fully with our results and this taken in connection with the facts and arguments advanced by Henry (Zoc. cit.) seems t o prove, or a t least to give a very high degree of probability to the truth of his theory that the known metallic oxides are polymerides n(llt0,) of the unknown simple oxides RO,. If this be SO then our results also show that in most cases especially those of SiO, TiO, 91,03 &c. the coefficient n of polymerisation must be very large thus f o r the oxides of silicon titanium and tin it would be a t least 10 aid probably much higher so that the molecules of these oxides would b OF METALLIC HYDROXIDES BY HEAT.93 a t least R,oO, ; whilst oxide of zirconium would be at least Zr24048, ferric oxide a t least FezoO,. I n the case of antimonious oxide the results seem to indicate Sb,O, as the smallest value of its molecule. The most infusibIe oxides such as silica titania etannic oxide, alumina &c. are those which the curves would indicate as having t,he highest coefficient of polymerieat,ion and this is what one would expect if the theory of polymerisation be true. DEHYDRATION AND THE PERIODIC LAW. Having now considered the question of the polymerisation of the oxides we next turn t o the second problem which we had in view in commencing this research viz. :-The relation of the phenomena of the dehydration of the oxides to the Periodic Law.I n dealing with this question the difference between affinity in intension and in eztension must be well borne in mind. The affinity of sodium for chlorine in sodium chloride is greater in intension than that of tin for chlorine in stannic chloride in so far as the force of combination between one atom of sodium and one atom of chlorine is greater than between the atom of tin and any one of the atoms of chlorine. On the other hand the affinity of tin for chlorine is greater in extension tha(n that of sodium for chlorine in so far as one atom of tin is capable of combining with four atoms of chlorine whereas one atom of sodium can combine with one atom of chlorine only. I n like manner the affinity of two oxides for water may differ from one another. An oxide may combine with but a small quantity of water but it may retain that with great force whereas another oxide may combine with a greater quantity of water but give up the whole of it with comparative ease.The Afiinity in Iqttension of the Oaides for Water. The affinity of the oxides for water in intension will be indicated by the temperature required to produce complete dehydration. A careful comparison of these temperatures in the case of the different normal oxides shows that they vary periodically with the atomic weight of the positive element as seen in the table on p. 95. I n this table it is found necessary to distinguish between odd and even series. I n order to render this distinction more evident the even series are printed in ordinary type and the odd series in thick type Group VIII is omitted as there are not data to draw any conclusions in regard to it.This table shows 94 CAHNELLEP AKD WALKER THE DEHTDRXTION A. As r e g a r d s o x i d e s b e l o n g i n g to t h e 4ame group-(1.) T h a t in t h e case of o d d members of the same group the tempera-h i - e of complete dehyd~ation awl (thewfore the a$nify of the normu1 oxides .for water) d i m i n i s h e s as the atomic weight of the positice elemeizt incmases. ( 2 ) T h a t in t h e case qf even menzbew of the sanze group the tem-peratuye of covzplete dehydmtion i n c r e a s e s a s t h e atomic weigkt of t b positive element increases. There is no well-marked exception to this rule f o r in the case of ZrO the determination owing to an accident was not completed so that the temperature of complete dehydration might have been highei- than that given.Similar relationships in so far as the meagre data will allow are also brought out on comparing the heats of combination of the normal oxides with water in the formation of the hydrates for example :-Though the temperatures of complete dehydration of calcium, strontium and barium have not been determined the heat of com-lrination of the oxides with water shows that t'hey would follow the above rule thus :-(Compare also Bloxam Chem. Soc. Journ. 13 15 ; and Smith P h i l . Nag. [ 3 ] 9 87.) CaO + H,O = 15500 SrO + H,O = 17700 (There is not a single exception to this rule.) BaO + H,O = 22300 1 ,, JP,05 + H,O = 10700 t thermal units LNo data for Sb,05 and Bi,05.Odd As,O + €LO = 2300 1 ,, MgO + H,O = 3100 ZnO + H,O = '1700 CdO + H,O = 80(?) 1 : thermal units 2: So far as oxides of the first and second groups are concerned it seems as though the temperature of complete dehydration and therefore the ilzteiisive a f h i t y of the oxide for water increases as we pass from the oxide of the element with highest atomic weight in an odd series to the one with the lowest atomic weight and thence again inc~eases as we pass from the element with lowest atomic weight in an even series to the one with the highest atomic weight; f o r iiistance in the second group we have Table showiiig the Minimum Temperatures of Comnp lete Dehydratio~ of t -Series. -1. 2. 3. 4. 6. 6. 7. 8. 9. 10. 11.12. -Group I. R,O. HZO. Li,O = ? Na,O = not a1 red heat. K 2 0 = not at a red heat. CU,O = 360". RbSO = ? Ag,O = about 150'. cs,o = ? --Au,O =below 15'. 3 -Group 11. R,Oz = 2RO. ---Be0 = high temperature. MgO = 630'.* CaO = red heat. ZnO = 885".+ SrO = dullred CdO = 3 8 5 O . X heat.? BaO = fullred heat.? --HgO = about 175". -Group 111. RZO,. ---Bz03 = b. 577". Al,03 = a. 8513'. s20 = ? GazO = ? Yt203 = red In,03 = 655". heat. La,O = ? --T1203 = 230". -Group IV. RQO = 2R0,. ---GO = b. 100". SiO = a. 850'. TiO = 700". GeO = P ZrO = about SnO = about 650' (?)X 655'. CeO = about 850". --PbO. = about Th02 = red 230". heat (?) Group v. R205.-N205 = affinitj for H, less than that of Pz05 d. at 260" into N, 0 and HzO. P,O = not d. by heat. V,O = on evaporation. As20 = a. 206'; red heat. Nb,Oj = not a t 100"; red heat. Sb,O = above 200 but below redness. Di,O = ? -Ta20 = low redness. Bi,O = 150". Those of the above data which were not determined by us are taken from Watts' Dictionary, * Approximat,ely determined by us. .i. Bloxain (Chew. 8oc. Jour., $ An accident prevented the completioii of the experiment. 5 That is, Qmelin's Handbook. (1 Brawler (Phil. .Wry. [S] 11 62) 96 CARNELLEP AND WALKER THE Temp. of complete dehydration. (HgO 175" CdO 385 rodd { ZnO 585 i I M(r0 630 DEHYDRATION Heat; of cornhiitation of RO*H20. ? 80 2700 3100 Group 114 (Be0 high temperature ? I 1 CaO above 630" 15500 'even{ SrO for Ca9 dull 1 7 700 22300 (above the temp.I red heat (BaO full red heat R. As r e g a r d s oxides b e l o n g i n g t o t h e same period o r That there is a regular periodic variation of the temperature of complete dehydration with the atomic weights of the elements is quite evident from the table but the data are not quite decisive as to whether this variat,ion is according to periods or according to series. The data on the whole are more favourable to variation by periods. If this be the case the rule would run thus:-(3.) For oxides of elements belo?zgiiig to the same period the tempera-ture qf complete deiiydratiorz seems to dinzinish from the beginning to about the ntiddle of the period and then to increase again to the erLd of the p e r i o d thus following the same rule as the specific volumes of the elements as represented in Lothar Meyer's curve of the elements and therefore rising and falling with that curve.The only apparent exceptions are MgO Bi,O, and possibly 120, the existence of the last oxide however is doubtful. The very few cases in which the heats of combination of the oxides with water have been determined are in favour of the above form of the rule thus :-Na20 + 1320 = 35600 ; MgO + HzO = 3100 ; AlzO + HzO = ? ; SiOz + H,O = ? ; Pz05 + H20 = 10700; SO + HR,O = 21300. If the variation be acccjrding to series instead of according to periods though this seems less likely the rule would be :-For oxides of elements belonging to the same series the temperature of complete dehydration increases as me pass from the t o t h e same series.* * Elements in the same horizontal line belong to the same series so that there are seven in each series.Periods are of two kinds a short period contains but seven members thus from Li to F and from Na to C1 are two short periods ; a long period on the other hand embraces 17 members (including Group VIII), thus from K to Br and from Rb to I form two long periods €or we have to pass Over 16 elements before we come to one namely Rb in which the properties of K are more or less repeated whereas starting from Li we have to pass over but six elements before we come to Na or a point at which the properties of Li are in some measure repeated DIAGRAM II SHOWING THE NUMBER OF MOLECULES OF WATER RETAINED BY ONE MOLECULE OF AN OXIDE A T DIFFERkNT TEMPERATURES.CARNELLY &WALKER I U M M R OF I16LI6ULm O F WATER RS7UINRD UY W E YOLa8Ul.E OF OXIDE. lWWR OF YOLLOULU OF WhTTSR ROTAINID Itr OW YOLIOULL Of OX1OI O F METALLIC HYDROXIDES BY HEAT. 97 beginning (positive end or Group I> to the middle (Group IV) of each series and then diminishes to the end (negative end or Group VII) of the series. The exceptions to this form of the rule are more numerous and more serious than those to the form of the rule previously given; they are P205 the whole of the oxides of the second series most probably all the alkaline oxides and Zr02. The temperature given for the last is however doubtful for the reasons already stated.The Afinity iw Extension of the Oxides foy Water. Of two oxides belonging to the same group it does not follow that the one which requires the highest temperature for complete dehydra-tion and which has therefore the greatest intensive affinity will also at any other lower temperature combine with the greater quantity of water per molecule of oxide that is will have a greater affinity in extension. The very opposite in fact is the case sometimes though usually the two phenomena r u n parallel with one another as will be shown in the following table (p. 98). From this table it is seen that in the case of the TiO, P206 and SO groups the order of affinity for water in extension is the same as in intensioiz whereas in the SiO and A1203 groups so far as the first two members are concerned the reverse holds good.The last member of each of these groups however viz. PbO and T1203, follows the same order both in intension and in extension. It is note-worthy that the two corresponding triplets SiO, SnO, PbO and A1203 In,O, T1203 of two different groups are exactly analogous in this respect. Change of Colour occzcrriizg in Dehydration. Some of the substances in the course of being heated changed their colour (when cold) during a single heating and when this occurred the loss was always greater than the average before the change. Such a permanent change in colour probably indicated the formation of a definite hydrate or oxide. This change in colour must be care-fully distinguished from the temporary alteration in colour which many substances undergo when heated in which case the change is always towards the red end of the spectrum as first pointed out by Ackroyd (see Phil.Mag. [ 5 ] 2 423 and Chem. News 34 76). Here the original colour is regained on cooling whereas the changes in colour we refer to are permanent in the cold. The following are ihe colour changes we have noted :-VOT,. LIII. Table showing the Temperatzcres at which one illolecule qf the seve?-al Oaides of wumber of Molecules of Wuter. No. of molccules of water retained. I 1. l-Al,O In,O . . . . . . . . . . . T120 242" 245 II1-1 4'0 97 -SiO . SnO,. PbO,. ~-31 175 731 TiO2 Zr O. . cco 63 See -X P 2 0 1 - As,O,. 15 (?) Sb,O I '5 R;.n 215 180 I00 aht,.15 red heat 206 175 -UlJVj . . . . . . . . . . . . -___-.- *so 1 - SeO 1 -- . TOO - OF METALLIC HYDROXIDES BY HEAT. 9 9 CdO. Hg 0. Zr 0,. Sn 02. Ce 0,. Pb 0,. 1 1 1 2 0 3 . Bi203. 300-3POo.-Light-brown to dark-brown. Loss 12 per cent.; previous average loss* 4.5 per cent. Indicates change from Cd(OH) to CdO. Loss 45 per cent;. Indicates change of yellow into red modification of HgO accompanied by rapid decomposition into Hg and 0. 385-415'. Grey to white. Loss 4 per cent. previous average loss 0.6 per cent. Due to conversion of 2ZrOz,H,0 into 24ZrO2,H2O (comp. Gnudin, 3 342). Loss 0.8 per cent., previous average loss 0.26 per cent. Due to conversion of 3Sn02,H20 to 7Sn02,2H20. Loss 2 per cent. previous average loss 0.1 per cent.Due to conversion of Ce02,2H,0 into Ce02,(2 - b)H20 and finally to CeO,. Loss 1.8 per cent. previous average gain 0.01 per cent. Due to conver-sion of Pb30a to PbO. Loss 10 per cent. previous average loss 0.4 per cent. Due to partial conversion of T1,03 t o TLO. Loss 2 per cent., previous average loss 1.3 per cent. Due t,o conversion of Bi203,H20 to Bi203. 415-44O0.-Dirty-yellow to brigb t-orange. 3ti0-385".-Brownish t o pale-yellow. 585-630".-Light-yellow to salmon colour. 530-565'.-Brown to yellow. 585-630".-Brownish-black to green (fused). 385-415".-Light-yellow to deep-yellow. It did not of course follow that for a great loss of weight there was any change in colour. GENERAL COSCLUSIOSS. (1.) Precipitated antimony trioxide is anhydrous.On heating i t underwent the following changes :-Sb203 or Sb2,,0j0 stable up to 360" then rapid absorption of oxygen with formation of Sb20032(?). the latter comparatively stable a t 415-440" ; then further absorption of oxygen with formation of Sb,,O,(?) the latter comparatively stable 500-565" ; third absorption of oxygen with formation of Sb,Os or Sb,,O,, the latter stable from 590" to above 775". (2.) The following definite stable hydrates appear to exist :-(a.) Ag(0H) stable up to about loo" then rapid loss of water with * That is during the like interval of temperature immediately preceding tlw lower limit of the interval in which the colour change was observed. H ! 100 CARNELLEY AND WALKER THE DEHYDRATION formation of Bg20 (containing a little metallic silver) ; the latter stable 180-270" ; then reduction to metallic silver this reduction being complete at 300-340".( b . ) Hg(OH) stable up to about 100"; complete dehydration to HgO a t about 175" when incipient decomposition into Hg and 0 commences followed by full decomposition at about 415" to 440". (c.) Ce02,2H,0 or Ce(OH)I = orthoceric hydrate ; this hydrate was formed on heating precipitated hydrate of cerium dioxide to about 385". It was of a light yellow colour. On heating to over 600" it underwent dehydration to CeO and became salmon-coloured. This is the only definite stable hydrate of the oxides RO of the silicon-titanium-group we obtained. In other respects cerium hydrate on dehydration behaved like the hydrates referred to in § 5.(d.) 5Coz03,SH20. This was the composition of air-dried cobaltic hydrate and was perfectly stable up to 75". (3.) The following data with regard to the action of heat on the hydrate of PbO will possibly be of interest in the manufacture of red lead :-Hydrate dried in air = 3Pb02,H,0 complete dehydration at about 230"; PbO, stable up to about 280" loss of oxygen with formation of Pb103 280-290" ; Pb,OR stable 290-360" loss of oxygen with formation of Pb304 360-415" ; Pb30a stable 415-530", loss of oxygen with formation of PbO a t 530-580" ; PbO stable from 5SO" to above 815" ; PbO fused somewhere between 585" and 630". (4.) Air-dried thallic hydrate = Tl2O3,K20 but unstable on heat-ing complete dehydration t o T120 a t about 230"; T1,03 perfectly stable between 230" and 360" reduction to .3T1,O3,T1,0 a t 360-440" ; 3Ti,O3,T1,0 perfectly stable between 440" and 565"; rapid loss of oxygen and volatilisation of T1,O formed a t 585-815" ; the rate of loss gradually diminishing after fusion a t 630" ; remaining T1,0, constant from 815" upwards.(5.) An examination of all the results shows that with the excep-tions referred to in 9 2 there is no certain indication of the formation of definite hydrates which are stable through any but possibly a very small range of temperature (less than about 13"). From this we must conclude either that there are no definite hydrates formed on heating at gradually increasiiig temperatures or that a very large number of such hydrates are produced under these conditions but are so unstable that a further small rise in temperature is sufficient to convert a higher into a lower hydrate.Of these the second alternative is for reasons given by far the more probable. Our results accord entirely with Henry's theory tthat the known metallic oxides are polymerides n(R0,) of the unknown simple oxides RO,. The results also show that in most cases especially those of It remained stable from about 385" to 600" OF METALLIC HYDROXIDES BY HEAT. 101 SiO, TiO, SnO, A1,0, &c. the coefficient n of polymerisation must be very large as might be expected from the infusible character of these oxides. Minimum values for this coefficient are indicated in some cases. (6.) The retention of water by many oxides at comparatively high temperatures at and above a red heat is noteworthy. This is espe-cially interesting in the case of the hydrate of cerium dioxide, Ce(OH)4 which is stable to as high a temperature as 600". The re-tention of water at such high temperatures illustrates the great im-portance in quantitative analysis of the thorough ignition of the hydrates in order to drive out the last traces of water before weighing. (7.) The minimum temperature of complete dehydration is a periodic function of the atomic weight as follows :-(a.) For FLornzal oxides of odd meinbew of the sume group the mini-mum temperature of complete dehydration diminishes as the atomic weight of the positive element increases. (b.) For even members of the same group it increases as the atomic weight of the positive element increases. (No well-marked exceptions.) (c.) For fiormal oxides of elements belonging to the same period the minimum te?nperatzcre of complete dehydration diminishes f r o m t h e begin-ning to the middle and then increases to the end of the period. The only apparent exceptions are MgO Bi205 and I,O (?). These results also accord with the heats of combination of the normal oxides with water in the formation of hydrates. (8.) Of two oxides belonging to the same group the one which re-quires the highest temperat are for complete dehydration will usually combine at any other lower temperature with a greater quantity of water per molecule of oxide ; this however is not always the case, the pairs SiO,,SnO and Al,O,,In,O being marked exceptions. From this me may conclude that the order of affinity of the oxides for water is usually the same both in intension and in extension though not always. (9.) Changes of colour on dehydration which are permanent on cooling usually indicate the formation of a definite hydrate or that the dehydration is complete or that some other definite chemical change has occurred. (No exception.

ISSN:0368-1645    

DOI:10.1039/CT8885300059

出版商:RSC    

年代:1888

数据来源: RSC

摘要:

102 V.-Note on cc Modification of Traube's '( Capillnrinaeter." By H. S. ELSWORTHY. HAVING a number of native Indian liquors to analyse especially with regard to the amount of fusel oil contained in them I deter-mined to try the capillarimetric method proposed by J. Traube in the Zeit. fiir Spirit Ind. No. 36 of 1886 this being according to the author both the quickest least costly and most accurate method, especially for small proportions of fusel. Not having the apparatus and there being no time to obtain it from Germany I attempted to make one from a broken thermometer having a thin-walled capillary tube and the scale of which was divided pretty accurately into 1-12 mm. that is 88.5" equalled 100 mm. On testing this I found that a 20 per cent. (vol.) solution of pure alcohol rose to a height of 76" and that 0.1 per cent.of fusel oil depressed the height by very nearly 1". It was therefore, possible to read to per cent. as claimed by Traube but it was, as might be expected rather difficult and the scale had to be adjusted to the surface of the liquid with the greatest nicety. On thinking over the matter I concluded that if the tube were laid at an angle approaching the horizontal the height to which the liquid would rise would be correspondingly increased. I therefore made an apparatus as follows a broken milk scale t,hermometer graduated up to 600" F. furnished the required capil-lary tube. The divisions on the scale very nearly corresponded with 1 mm. that is 151" equalled 150 mm. On a stand A about 15 inches long is placed a sloping piece of wood B the lower end of which is raised 2 inches above the stand and slants upwards a t an angle of 10".In the centre of this inclined plane a piece of wood D is made to slide easily between two other strips CC and to this is attached the scale and capillary tube the end of the latter being slightly bent downwards. The slide can be adjusted by a screw E so as t o bring the lower end of the scale in exact contact with the surface of the liquid. On the stand near the lower end of the inclined plane is placed a piece of glass tube G bent to a convenient angle and ground off level this being filled with the spirit to be tested. This tube is fixed moderately firmly between two small cork blocks HH. The scale must be adjusted accurately to the same point each time and this is effected by bringing the lower end of the scale itself or a point attached to it into exact contact with the surface of the liquid.This may be done with the greatest nicety by placing a polishe A MODIFICATION OF TRAUBE’S “ CAPILLARIMETER.” 103 metal or glass reflector I under the bent portion of the glass tube when the exact moment of contact can be easily observed ; without the reflector it is difficult to adjust it properly. The stand should be set exactly level by means of a spirit-level K and an adjusting screw. Yg attacbing an india-rubber tube F to the upper end of the capillary tube it is easy to suck the liquid up the tube or force i 104 LAURIE THE CONSTITUTION OF back and it is also used for cleaning the apparatus with pure spirit, and for sending dry air through afterwards.I find that the most accurate readings can be obtained by drawing the liquid up the tube five or six times and finally to a fixed point some 10" or 20" above the point reached by pure spirit. In Traube's instrument the rise of a pure 20 per cent. vol. spirit is said to be 50 mm. I n the modification here proposed a pure spirit rises 173 mm. and with 1 per cent. of fuse1 oil the meniscus is lowered 25 mm. against 7 mm. in the former apparatus. The instru-ment described is therefore more than three times as sensitive as Traube's. From my experience ait,h this apparatus I find that it is necessary to distil the spirit under examination with soda or potash in order to eliminate the ethers which have a very considerable influence on the capillary rise. One drawback is the amount of dilution required by, say ft proof spirit. If for instance the original liquid was proof and contained 0.1 per cent. of fuse1 oil it would require approximately one and a half times its volume of water and the percentage of fusel oil in the mixture would be correspondingly lowered. It is quite possible that a stronger spirit may answer the purpose, but I have not as yet had time to try it. It seems t o me that the experiments I have already made fully bear out Dr. Traube's recommendation and the use of the capillarimetric method will tend t o greater accuracy in the estimation of fusel oil than has hitherto been possible

ISSN:0368-1645    

DOI:10.1039/CT8885300102

出版商:RSC    

年代:1888

数据来源: RSC

摘要:

104 LAURIE THE CONSTITUTION OF VI.-T%e Constitution of the Copper-Zinc and Copper-Tin Alloys. By A. P. LAuRrE B.A. B.Sc. IF instead of a simple metal a mixture of two metals is introduced into a voltaic cell the E.M.F. of the cell is that of the more positive metal. For instance a mixture of zinc and copper will give the E.M.F. of zinc. Several experiments in a cuprous iodide cell with plates of copper having pieces of zinc soldered into them of about 3$m of the whole area of the plate showed this. On first connecting with the electro-meter the deflection was about half that for zinc (the deflection for copper being of course zero) but it gradually crept up ultimately attaining a value some 4 or 5 hundredths of a volt below the valu THE COPPER-ZINC AND COPPER-TIN ALLOYS.105 for zinc. This gradual increase of E.M.F. waq due to some change i n the electrical condition of the compound plate and is probably to be explained by the gradual polarisation of the copper plate by the local action between i t and the zinc soldered on to it. But in what-ever way these points are explained the results are sufficient t o show that a mixture of two metals gives the E.M.F. of the more positive metal and that this holds good as long as at least 0.2 per cent. of the positive metal is present. If however in place of a mixture of zinc and copper we have an alloy of the two metals which has been formed with a development of heat and which therefore is of the nature of a chemical com-pound the result will probably be different for it is obvious that the dissolution of the zinc will in this case necessitate the decomposition of this zinc-copper compound whereby energy is absorbed and therefore the E.M.F.of the cell will probably be correspondingly lowered. Now there are three possible ways i n which zinc-copper alloys may be constituted. First they may be merely mixtures of zinc and copper; in that case they would give the E.N.F. of zinc in the voltaic cell. Second they may be of the nature of the solution of sulphuric acid in water; in that case a series of such alloys beginning with 100 per cent. of copper and ending with 100 per cent. of zinc would probably show a gradual rise of E.M.F. in the cell from the value for copper to that for zinc. Third one or more of the series of alloys may be a definite atomic compound the rest being solutions of this cornpound or compounds in an excess of zinc or copper; in that case the E.M.F.would probably rise by a jump when a series of alloys were tested a slight excess of zinc over that necessary for the compound causing a great alteration of E.M.F. in the cell. Further this jump would probably occur where the percentages of zinc and copper corresponded with some simple molecular formula. I n practice the difficulty which presents itself is that of obtaining homogeneous alloys. This difficulty can only be overcome by taking great care in their preparation and by preparing very large numbers of them. In this way any error from this cause may be expected to show’ itself. My zinc-copper alloys were prepared as follows -A certain quantity of copper and of zinc were weighed out, amounting together t o about 9 of an oz.and fused in a Fletcher’s furnace under borax ; when fused the alloy was vigorously stirred with an iron rod coated with borax and poured instantly into a little trough cut i n a block of charcoal. The ingot thus formed was cooled 106 LAURlE THE CONSTITUTION OF weighed and then broken across; if it seemed homogeneous in section the upper layer was filed off the ingot marked and laid aside for testing by the electrometer. Some zinc always burned off and the percentage of zinc and copper was calculated from the weight of copper taken and from the weight of the alloy obtained; this of course assumes that there is no loss of copper-in fact it is but very slight and also necessitates clean casting which is easily managed if the flux is sufficiently fluid.The stirring was always kept up till the last instant before emptying the crucible. The alloys corresponded in appearance to the descriptions already published the yellow tough “brass ” being replaced by white brittle alloys when the copper was diminished below 50 per cent. and these again giving place to hard grey alloys when it was below about 15 per cent. On testing a piece of brass wire in the cell it gave no deflection, showing a diminution of E.M.F. = 0.6 volt. It probably contained about 30 per cent. of zinc. One of my alloys containing about 25 per cent. of zinc gave the same result. As 40 per cent. of copper was approached a slight increase of E.M.F.showed itself amounting at 36 per cent. of copper t o about 0.1 volt ; so that from nothing up to 66 per cent. of zinc the E.M.F. had gradually risen about 0.1 volt. It gave a deflection of about 0.5 volt. All the alloys containing less than this amount of copper though varying a good deal continued on this higher level of E.M.F. The results are qiven in detail in Table A (p. 107) and Plate 4 (p. 116). The want of homogeneity of the alloys is brought out by this table but a t {,he same time is not sufficient in any way to conceal the striking shape of the curve of E.M.F. showing its sudden rise. It is to be remembered that although the alloys may have an average composition very close to that given in the table the electrometer will select t,he portions of the alloy containing an excess of zinc.These experiments indicate in the first place a considerable develop-ment of heat in the formation of brass lowering the E.M.F. of the cell about 0.6 volt and further that the greater part of this develop-ment of heat is due to the formation of a compound CuZn (32.8 per cent. Cu). After these experiments were completed I determined to test whether the zinc-copper alloys could be separated by differences in their specific gravity. Por this purpose imitating Matthiessen’s experiment I raised a porous pot about 3 in. high by 8 in. across to a bright red in a Fletcher’s furnace and poured into it an alloy containing a little over 34 per cent. of copper. The furnace being again closed and the The next alloy tested contained about 33 per cent.of copper THE COPPER-ZINC AND COPPER-TIN ALLOYS. 107 TABLE A.-Zinc copper Alloys. Percentage of copper. 100.0 75.0 54.4 50.5 49.3 47.2 46.1 4;3*9 41.7 37.0 36.5 35.9 33.8 S3.2 31.9 319 30.3 29.2 28.0 26.8 26-2 25.7 24-3 23.0 19.1 18.7 16.4 16.2 14.5 14-1 12.4 12.1 3.5 Zinc. E.M.P. in volts. - 0.020 -0.020 -+ 0.040 0.070 0.070 0.075 0-065 0.070 0.080 0.085 0.085 0.160 0.530 0.520 0.540 0.580 0.570 0-600 0.580 0-490 0.460 0.5 70 0.475 0.600 0.580 0-420 0.580 0.580 0.590 0.580 0.590 0.600 0.590 0.600 blast kept on the alloy was kept fused for at least 30 minutes. It was then allowed to cool the porous pot broken and the cylinder of alloy after it had been filed flat on one side was connected with the electrometer and gradually lowered into the cell.If there had been any regular settling out of alloys according to specific gravity one end should have had a higher E.M.F. than the other. If then the end of lowest E.M.F. was first plunged in the liquid its gradual immersion would cause an increase of the deflection on the scale. No such effect was produced however for no matter which end was first plunged in the E.M.F. continued at about 0.1 volt varying slightly. The same alloy fused up with fresh zin 108 LAURIE THE CONSTITUTION OF to reduce the percentage of copper to about 20 per cent. gave a11 along its length an E.N.F. of about 0.5 volt varying slightly. There is therefore no serious want of homogeneity produced by differences of specific gravity All these experiments tend to confirm the trust-worthiness of the results first obtained.As the slow cooling in an upright position seemed to have no injurious effect six alloys were made up of about 2 oz. each and cast in rnouldei~’~ earth in an upright position as sticks about 2 in. long and A portion about 1 in. long mas broken from each of these sticks by knocking off the two ends ; it was then filed flat on one side and plunged into the cell. The results with these six sticks are given in Table B. I t will be noticed that with one exception the deflections increase as the zinc increases with con-siderable regularity. They are evidently more homogeueous than the first set of alloys.in. in diameter. in it My next experiment was as follows. Taking alloy No. ti of the set Table B I ground it to powder and tested its E.11II.F. by packing into a minute glass vessel shaped like a tobacco pipe with a platinum wire down the stem and into the bowl this bowl being plunged beneath the liquid in the cell. It gave an E.3I.F. of about 0.5 volt but as the experiment failed unless the dust was wet and carefully packed no deflection being obtained I next filled the bowl with mercury mixed i n some of the dust and obtained again an E.M.F. of about 0.5 volt. Some of this dust was next treated with dilute sulphuric acid ; hydrogen was given off but after boiling f o r some time with the acid all effervescence ceased or almost ceased, although fresh acid was put on.The acid contained some zinc but no copper. On burnishing the dust it gave the same bright white lustre as before. The dust when introduced into the bowl of the glass pipe both with and without mercury gave the deflection of about 0.08 rolt so that apparently the excess of zinc had been removed by the acid. TABLE B. Percentage of copper. 34.1 31.5 31.0 30.6 30.1 29.9 E.M.F. in volts. 0.160 0.420 0.560 0.480 0.5 30 0.570 These results certainly indicate the existence of a compound, CuZn, the sudden rise of E.M.F. being difficult to interpret in any other way and seemed to me sufficiently encouraging. At the sam TKE COPPER-ZINC AND COPPER-TIN ALLOYS. 109 time the zinc-copper alloys and especially those containing a high percentage of zinc are difficult of preparation and very little is known about their physical properties.It seemed better therefore to select for further experiments some well-known series of alloys in order to check the results of this new method against the conclusions of other experimentalists. For this purpose the tin-copper alloys seemed especially suitable. In the first place Riche (Compt. rend. 55 1862) states that the curve of densities for these alloys has two maxima corresponding respectively with the alloys Cu4Sn and Cu3Sn. The carve of den-sities given in Thurston’s lZeport* on the copper-tin alloys though not showing two maxima rises to a maximum over the region of these two alloys falling off towards copper and towards tin. Riche further states that these two alloys alone are not subject to liquation.Matthiessen (PhiZ. T y a n s . 1860) failed to find any indication of the existence of these compounds on testing the electric conductivity of these alloys but this has been shown by Lodge to be due t o his not having investigated that portion of the curve. Lodge (Phil. Afag., 1879) finds a minimum conductivity at Cu4Sn and a maximum con-ductivity at Cu,Sn. Again the curve for heat conductivity given by Calvert and Johnson (Phil. T r a n s . 1858) shows a minimum at Cu4Sn and maximum at Cu,Sn. Finally the induction balance curve as determined by Roberts-Austen (Phil. X a g . 1879) shows the same maximum and minimum. There is consequently a con-siderable amount of evidence pointing to the existence of the com-pounds Cn3Sn and CulSn in this series of alloys a mass of evidence first I believe collected and pointed out by Roberts-Austen.These alloys therefore seemed to be peculiarly suitable for testing the new method. The compound CuaSn I did not expect t o find but the com-pound Cu3Sn would in all probability be indicated. In the first place, however I thought it best to again test the behaviour of compound plates adopting a different arrangement. A Daniel1 cell was constructed containing a large cylindrical copper plate coated with india-rubber on the back and with a front surface of 500 sq. cm. This plate was placed in n solution of sul-phate of zinc. A glass tube plugged with plaster of Paris and con-taining a copper wire in a solution of sulphate of copper formed the other pole of the cell.This wire was coiinected permanently to the electrometer. A thin strip of zinc of breadth 5 mm. wa,s arranged so that it could be covered to any depth in the solution. Either the zinc plate or the copper plate or both could be connected t o the electrometer by means of mercury cups. The copper plate was first * Report on Copper-Tin Alloys United States Board to test iron steel &c.: Washington 18’79 110 LAURIE THE CONSTITUTION OF connected. It gave n small deflection of about 0.03 volt. The zinc plate was then immersed in the solution to the depth of 5 mm. and then connected by a wire to the copper plate ; immediately the spot of light on the scale began to move and time observations were taken. The results are plotted on Plate 1 (p.116). The deflection for the zinc alone is also marked on the curve. On disconnecting the zinc plate, the spot of light moved steadily down to the old deflection for copper alone an apprecialde time elapsing before the polarisation of the copper plate ceased. The zinc on removal was found to be corroded, a considerable amount of zinc having been consumed in polarising the copper plate. Similar experiments were made with a cell con-taining an acid solution of stannous chloride and a copper wire coated with cuprous chloride for the other pole. In this case also a similai-curve was obtained on connecting a tin plate to the copper plate in the same way. In both cases the surface of the positive metal amounted to about -&5 part of the surface of the copper plate.No experiments were made to test the effect of distributing the tin over the copper surface though I am disposed to think that this would pmbably increase the rate a t which the plate becomes completely polarised. These experimenh seem to me to open out an interesting method of investigating polarisation. By weighing the zinc before and after some light might be thrown on the thickness of the molecular layer necessary to polarise the copper plate but I did not wait to make any such experiments. I f then one of our tin-copper alloys contained only 0.1 per cent. of its surface of tin merely mixed with it we might hope to detect i t on the electrometer. Preparation of the Alloys. The alloys were prepared from the best grain tin and the best copper 99.9 per cent.obtained from Johnson and Matthey’s. A weighed quantity of copper was in each case melted in a plumbago crucible under charcoal hydrogen bubbled through it to be sure of the absence of suboxide remored from the furnace a weighed quantity of tin rapidly added and thoroughly mixed and the alloy poured into an open mould. The casting formed a cylinder about 13 cm. long by 0.8 em. diameter. The aggregate weight of tin and copper was 100 grams. Prof. Roberts-Austen kindly allowed these alloys to be prepared with the assistance of Mr. Groves a t the Royal Mint. They had thus the advantnge of being made by one skilled in the melting and mixing of metals. They had all a fine appearance on fracture. The alloys prepared were as follows : THE COPPER-ZINC AND COPPER-TIN ALLOYS.111 (1.) (2.) (3.) (4.) (5.) (6.) (7.) (8.1 Cu percent 100 95 90 85 80 75 70 68.16 (9.) (10.) (11.) (12.) (13.) (14.) Cupercent . 67 64 61.64 60 40 0 8 and 11 correspond to the two supposed compounds Cu,Sn and Cu4Sn. Subsequently a fresh set of alloys were prepared of the following percentage composition :-(1.) ( 2 . ) (3.) (4.) (5.) (6.) T’inper cent . 37 38 39 40 41 42 I t was thought a,dvisable to analyse certain of those alloys that were shown to be of especial importance in the ultimate results. These analyses agreed pretty closely with their supposed composition. Alloy 11 was found to contain 61.7 of copper. Alloy 12 analysed at both ends was found t o contain 60.4-60.6 Alloy of 39 per cent.in the second series was found to cont:iin per cent. of copper. 61.2 of copper. T h e Cells used. The cells used consisted either of a solution of stannous chloride and a copper wire coated with cuprous chloride or of stannous sulphate and a copper wire within a porous partition containing copper sulphate. Such tin cells have been carefully tested and found t o yield a definite E.M.F. (Phil. Mug. 1886 [5] 21 13). Experiments with the Electrometer. I first determined to test all the alloys in succession in a solution of stannous chloride acidified with hydrochloric acid. The composi-tion of the solution was as follows SnC1 33 grams water 1750 c.c., strong pure hydrochloric acid 17.5 C.C. The cell consisted of a shallow glass dish with a wooden cover drilled full of holes through each of which one of the sticks could be dropped and its E.31.P.tested by the electrometer; in this way all the alloys were tested under exactly similar conditions. The othei- pole of the cell con-sisted of a copper wire coated with cuprous chloride. The results of the first set of obsemations in which the rods were polished with emery paper and then immersed are shown in Curve ( a ) , Plate 2 which gives the mean of this and the next two methods of testing the alloys. The numbers thus given are the mean of two or three independent sets of observations. In the first place the sudde 112 LAURIE THE CONSTITUTION OF rise in E.M.F. on passing Cu,Sn. will be noticed. No corresponding effect is observable on passing Cn4Sn but the alloys give slightly irregular deflections in the cell as shown by the zigzag of the line joining the observations.The irregular numbers are probably clue to ephemeral causes the metals not entering into the action of the cell and consequently coatings of gas &c. producing variable deflec-tions as has been noticed in the case of platinum plates. Certain precautions are necessary in order t o get trustworthy and uniform results in experiments of this kind. I n the first place the cell used should be so designed as to give a definite E.M.F. free from polarisation effects such as the Daniell cuprous chloride or iodine cell. I n the second place the solution in which the alloys are placed should not direct,ly attack the metals in the alloy. I n the third place, the salt used should be a salt of the more positive metal.For instance I have failed to obtain constant results from a cell contain-ing common salt in place of stannous chloride no doubt due to gas, polarisation of the alloy complex secondary actions &c. In the fourth place the alloys must always be carefully cleaned with fresh emery paper before being plunged in the solution. With the elec-trometer internal resistance can be ignored and many arrangements of cells are consequently available. For instance I sometimes place the inner solution in a glass tube drawn out to a fine c;zpill,sry o r sometimes use as my cell a U tube constricted at the bottom and plugged with plastey of Paris. With reference to alloy 12 a t which the rise occurs two points are worthy of notice.First the rise is instantaneous there is no creeping up of E.M.F. as in the case of the compound plates described before. This is probably due to the distribution of the free tin all over the surface of the alloy instead of being located at one point. The next point is that in about 10 or 15 minutes the deflec-tion disappeared. This can easily be accounted for by supposing the free tin t o exist in pockets and not in veins ; these pockets wouId soon be consumed loy the local action and the E.M.F. would Lhen fall. One confirmation of this is the fact that it is only necessary to reburnish the surface with emery to restore the origiiial E.M.F. Some additional facts favouring this view will be mentioned presently. It is of some interest to note the actual surface of free tin to which the deflection is probably due.If we suppose 1 C.C. of the alloy to be immersed in the solution then the whole area of the rod present, leaving o u t the end amounts to about 2.5 sq. cm. I f we suppose the alloy t o contain 1 per cent. of tin evenly distributed over the surface, this gives 0.025 sq. cm. as the actual surface of tin in action. The E.M.F. of the alloys were next tested in a solution of stannous chloride containing no free acid. The results are given in Curve ( a ) THE COPPER-ZIKC ASD COPPER-TIN ALLOTS. 113 Plate 2. The only difference noticed here was the very gradual disappearance of the deflection of 12 the X.M.F. remaining practically the same for an hour. The polished surface of the alloys having thus been tested t8hey were next broken across the centre and the broken ends plunged in the solution.The yesults are given in Curve (a) Plate 2. The next experiment -as to test the effects of amalgamation. Alloy 11 and alloy 12 were both amalgamated. The E.M.F. were respectively 0.008 volt and 0.26 volt. The only difference caused by amalgamation was that the deflection given by alloy 12 was now permanent. This is of interest as confirming the view taken of the condition of the free tin on the surface. The mercury doubtless eats into the a.lloy and dissolving the tin brings it to the surface. It will also tend to check the violence of the local action. It is also curious to note that the alloy 11 is not affected by amalgamation m i l that consequently the compound is seemingly unaffected by solution in mercury.The alloys were next tested in a cell consisting of stannous sulphate in acid solution and copper sulphate round a copper wire, divided by a porous partition. The results are given in Curve ( b ) , Plate 2. It will be noted that a distinct deflection is given by all the alloys. Alloys of the second series were now prepared and tested. The results obtained were the same and have not therefore been plotted. The alloys were all amalgamated. One alloy however behaved differently namely 3. This alloy gave uncertain values sometimes high sometimes low. If the results of the two groups of alloys are compared together we find that-1st series alloy containing 38.3 per cent. tin gives the low deflectioii 0.008 volt. 2nd Beries alloy containing 38.8 per cent.gives an irregular deflection. 1st series alloy containing 39.5 per cent. gives a definite but vanishing deflection 0.26 volt. 2nd series alloy containing 40 per cent. (not analysed) does the same. 2nd series alloy containing 41 per cent. (not analysed) gives a permanent high deflection. 2nd series alloy containing 42 per cent. (not analysed) gives a, permanent deflection. It will be noticed how closely their percentage compositions and their behaviour on the electrometer agree. Having completed these measurements I next searched carefully for CuaSn by two methods. I n the first place I used a cell in which They are the mean of two distinct sets of observations. VOL. LIII. 114 LAURIE THE CONSTITUTION OF copper gave a definite E.M.F.as well as tin so as to get rid of the small irregular deflections noticed in the former cells. For this purpose silver and sulphate of silver were substituted for the copper and sulphate of copper. In this cell copper gave a deflection of 0.482 volt and tin of 0.965 volt consequently a considerahle deflection for copper was combined with a marked difference of E.M.F. between copper and tin. There was no indication here of a CuiSn compound, the E.M.F. not rising in two jumps but only one. The second method was to use a cell in which copper gave a large deflection but in which the difference between copper and tin was small. Here I hoped that in the region between CutSn and Cn,Sn the curve would dip owing to the necessity of decomposing the mixture of the two compounds.No indications of this have been obtained as the following figures Copper 0.56 volt; alloy 5 0.55 volt; alloy 10 0.60 volt; tin, 0.73 volt. These experiments complete the work with the electrometer. I next experimented on the possibility of eating out the free tin from an alloy by placing it in the cuprous chloride cell and short circuiting. If the electrometer results were trustworthy an alloy containing an excess of tin over Cu3Sn would be attacked when used in place of the zinc plate in such a cell until the excess of tin had been removed. The E.M.P. would then fall practically to zero and all action would stop Cu3Sn Pemaining unaffected. For this purpose I selected alloy 13 (60 per cent. tin) and cast it into a thin plate about 1 in.x 2 in. X in. thick. This was placed in acid stannous chloride and connected with a copper plate in a paste of cuprous chloride inside a porous pot. After two or three days all action seemed to stop and the plate under the microscope in place of having a rough but homogeneous surface seemed made of bundles of needle-shaped crystals with cavities between. It had not however, been eaten through only a thin outer layer having been affected. This outer layer on being scraped off and analpsed was found to contain 45 per cent. of tin. These results being indefinite a cell was next constructed in which the finely-powdered alloy could be attacked. Another point attended to was making the cell air-tight, so as to prevent oxidation of the cuprous chloride and its partial solution diffusion and deposition as metallic copper on the alloy.The following diagram (p. 115) shows the cell used. This consists of a wide-mouthed 1 oz. bottle containing acid solution of stannous chloride ; in this solution is plunged a copper cup supported by two copper strips. A weighed quantity of the finely-powdered alloy is placed in this cup and covered with a disc OF linen to keep out possible impurities. The bottle is then corked show :-The cell used was an iodine cell THE COPPER-ZIXC AND COPPER-TIN ALLOYS. 115 by a glass tube covered at the end with parchment paper and con-taining a paste of cuprous chloride and a copper plate the whole being filled up with paraffin ; after pushing in the glass tube paraffin is poured round the neck of the bottle.The powdered sample of alloy taken was found t o contain on analysis 36.4 per cent. of tin. The current fyom the cell was allowed to flow through a little copper voltameter the plates of which were occasionally weighed ; after 36 hours the plates no longer increasing in weight the alloy was removed and analysed ; it still contained 44 per cent. of tin so that this experiment was not very successful. A second supply of alloy was again placed in the cup and the cell connected to the voltameter. The time curve of the Voltameter is given on Plate 3. When the curve had reached the point ( a ) the alloy was removed from the copper cup re-ground in an agate mortar and replaced in the cup ; immediately the current took a fresh start as is shown by the curve. When the curve had reached ( b ) the alloy was again removed, ground. and put back; this time very little additional tin was removed and the alloy was therefore considered fit for analysis. On weighing the residual alloy and calculating the tin lost the alloy apparently contained 38 per cent. of tin. On analysis it was found to contain 41.2 per cent. of tin. Evidently then this residual alloy agrees pretty closely in composition with the compound Cu3Sn. The difficulty evidently is to remove the last traces of free tin inclosed in portions of the alloy the re-grinding enabling this to be more com-I 116 CROMPTON AN EXTf!”ION OF pletely done. On putting alloy 11 in the copper cup for 35 hours, no change or indication of electrio current could be detected. These experiments therefore afford strong evidence that Cu3Sn is a compound of definite formula and considerable heat of formation, thus confirming the evidence obtained by other me5hods. It remains to apply the method to less known alloys with the view of throwing light on their oonatitution

ISSN:0368-1645    

DOI:10.1039/CT8885300104

出版商:RSC    

年代:1888

数据来源: RSC

摘要:

116 CROMPTON AN EXTfiENSION OF VK-An Extension of MendelLefs Theory of Solution to the Discw-sion of the Electrical Conducti?;ity of Aqueous Solutions. By HOLLAND CROMPTON Student in the Chemical Department of the City and Guilds of London Central Institution. AS a consequence of MendelBeffs original treatment of the subject, our conceptions of the constitution of solutions have suddenly acquirctl a degree of precision which is- altogether remarkable when the nature of the problein is considered. Fellows of the Chemical Society have had the privilege to be put in direct possession of the views of the renowned Russian chemist his method of treating the problem being briefly indicated in a paper on “ The Compounds of Ethyl Alcohol with Water” in the October number of the Transactions (1887 p.778). By discussing the dependence of change of relative density on percentage composition Mendelheff arrives at t’he conclusion that three distinct hydrates of alcohol may exist in solution in a disso-ciated condition-~,H60*120Hz CzH60*30Hz and 3C,H60*OH ; and the reliability of his method is established to demonstration by his success in isolating the first and second of these. Discussing the data f o r sulphuric acid in a similar manner (Ostwald and Van’t Xoff’s Zeit. phys. Chem. 1887 273) he concludes that this acid forms the hydrates-H2S 04.OH2 HZS 04.2 0 Hz HZS O4.60H HZS 0 4 . 1 500H2 * the existence of two of which is already reoognised by chemists. It is evident and was pointed out by MendelBeff in the paper in which he first advanced his views of solution (Ber.1886 379) that tha presence of the hydrates thus indicated must influence other physical properties as well as that of density and the problem there-fore is one of determining in what manner and to what extent this * See Dr. Armstrag’s remarks regarding this “ hydrate. Joum. C k . S o c . Jia. 1888-POLARIZATION OF COPPER BY 001 OF ZINC. LAURIE. Flak 1 E. M. F OF ALLOYS (A) IN STANNOUS CHLORIDE. (B) IN STANNOUS SULPHATE. LAUR I E Plate 2 ' 3 A t i R 9 U313 W VllO CURVE SHOWING THE ELECTROMOTIVE FORCES OF THE ZINC*COPPER ALLOYS IN THE CUPROUS IODIDE CELL. LAURIE Plate 4.k Ihrnson % Sons. Lith. S' M~~UDE La*. k MENDELEEFF’S THEORY OF SOLUTION. 11 7 influence may be rendered evident in different cases. At Dr.Arm-strong’s suggestion I have therefore investigated the dependence of change in electrical conductivity on composition in the case of sul-phuric acid and of a number of other typical solutions in the hope of throwing further light on this question. The number of excellent determinations given by F. Kohlrausch (Arm Phys. Chem. 1 8 i 5 , 154 215; 1876 159 233; 1879 6 l) and the extension of the numbers for sulphuric acid from H2S04 t o H,S,O by W. Kohlrausch (ibid. 1882 17 69) rendered t h i s a comparatively easy task. Taking the curves which show the relation between electrical con-ductivity and percentage composition one peculiarity will be noticed as common to nearly all that they rise from zero and after attaining a maximum more or less gradually fall back again to zero.To all appearances the curve between the two zero points is absolutely con-tinuous. The curve for sulphnric acid differs however in a re-markable manner from the rest in having two maxima the one at a point intermediate between the compound H,SO and the first hydrate H,SO,.OH, and the second beyold the point where the hexahydrnte is situated. It was a question of much interest whether by treating the electrical conductivity as a function of the per-centage composition and differentiating in Mendelbeff’s manner this curve could not be broken up so as to give evidence of the definite hydrates before mentioned. This is therefore what has been done the result being shown in the appended curves. It will be seen at once that the result thus far has beeu disappointing inasmuch as the curve obtained by plotting the differential expressing the change of conductivity with percentage composition E against the percentage composition does not give the broken curve expected but one which is to all appearance con-tinuous.The form of this curve excluded the idea which I at first elltertained that the conductivity might be a parabolic non-ccntinuous function of the percentage composition. There was however obviously a possibilit,y that the function might be of the third order and in this case if-dP K = A + Bp + Cp2 + Dp3, we should have-.’?- = EC + GDp, dP2 that is the second differential coefficient would between certain limits, be a rectilinear function of the percentage composition. On taking the second differential coefficient this was found to actually be the case it is indeed evident that the resulting curve consists of a serie 118 CROMPTON AN EXTENSION OF of rectilinear curves showing breaks and what is most important that these breaks occur at points corresponding with the composition of the hydrates discovered by MendelBeff with the addition of one other, namely HzSOa.240Hz.The numbers by means of which the curves for the conductivity and first and second differential coefficients of sulphuric acid have been drawn are given below. The differential coeficients have been I. Sulphuric Acid. P-1 -03 2 -51 5 '02 10.05 15 '33 19.95 24 -89 29 *98 34.87 39 *39 49 *6L 59 *95 66.16 71 -46 75 -00 78-70 82 -06 84.49 86 *lo 87 -52 90 -50 92 .go 95 -20 96 -87 98 -42 99.08 99 -44 100 * 14 100 *21 100 '40 1OC * 63 101.12 101 * 30 102.08 103 *53 105 -61 107 -61 108 '19 108 *70 109 -20 109 - '74 110 *38 K.443 1026 1944 3679 5168 6100 6701 6911 6784 6383 5112 3494 2554 1823 1421 1109 945 914 927 954 1014 1025 948 790 553 337 -4 199 *o 175 185 *6 202'2 222 *2 251 - 8 2 57 270 253 179 86 *8 60 *5 43'2 33 *2 23-6 13 *05 Pa -0.51 1-77 3 *76 7 *55 12.69 17 *64 22 *42 27 *4Q 32.39 37 -13 M. 50 54 9 8 63 -05 68.81 73 *23 76 *85 80.38 83.27 85 -29 86.82 89.01 91.7 94 -05 96 -03 67'14 98 7 5 99 *26 100 *17 100 '30 100 -51 100 -87 101 * 21 101 *69 102 80 104.57 106 -61 107.90 108 *44 108.95 109 -47 110 '06 I 430 393 366 339 282 202 122 - 25.6 - 88.5 -124.3 - 156 '4 - 151 *3 - 138 '1 -112.5 - 84.3 - 48'8 - 12.7 8 18.3 20 -1 4 * 5 - 33.9 - 95-4 - 152 -9 - 387 - 384 41.7 151 '4 87 -4 86.9 60.4 28-7 16-6 - 11.7 - 35.6 - 46.1 - 45.3 - 33.9 - 20 - 17.9 - 16.5 1 *14 2 -76 5 -65 10 *12 15 -16 20.03 24 -91 29 *89 34 -76 40.81 49.64 59 *01 65 -93 71 -02 75 *04 78'61 81 '82 84 -40 86.05 88 -21 90 -3.5 92-87 95 *04 96 -58 97 *94 99 *oo 100 -23 100 -40 100 .69 101.04 101'45 102 - 24 103 -68 105 '59 107 *25 108.17 108 -69 109.21 109 *76 - 29.3 - 13.6 - 7.1 - 11.1 - 16.2 - 16.9 - 16.2 - 13.5 - 13.2 - 4 '8 - 3 *1 0.6 2 '3 3.5 7.8 10.5 12 *5 10 -2 6.7 0.8 - 5'8 - 16.1 - 48.2 - 51.8 -108.1 - 112 - 492 - 2.4 - 73.6 - 93.2 - 25'2 - 25.5 - 13.6 - 5.1 0.6 21 '1 27 '2 4.1 2.MENDELEEFF'S TBEORY OF SOLUTION. 119 calculated by taking the differences between consecutive observations and dividing by the differences of the corresponding percentages ; although thiH does not give true differentials yet where the observa-tions are accurate the errors thus introduced are small and this method has the advantage of employing only the actual observed values so ihat the curves may be said to b e deduced directly from experiment. This most important concurrence mith Mendelkeff 'a result besides helping to confirm the latter proves that the electrical conductivity of sulphuric acid if not wholly due to is very largely influenced by, the formation of definite hydrates in solution ; and that the rectilinear character of the second differential coefficient curve gives us the means of ascertaining what hydrates there arc which exercise this influence.That this is true for other solutions besides that of sul-phuric acid has been likewise ascertained and in each case it has been found that the points where breaks occur on the - carve exactly correspond with those which occur on MendelBeff's curve for the as change of density with percentage composition -. From the form of the second differential coefficient curve it can easily be seen where breaks in the continuity of the conductivity curve may be expected and equations of the €oFm K = A + Bp + Cp' f Dp3 may be constructed for the various continuous portions of the conductivity curve.Thus the conductivity at 18" of a solution H,sO~WZOH~ is expressed by means of the following equations :-d2k d2J2 4P to r l b = 1 1 From m = - 12 I( = - 34396 - 758.97~ - 3.878~' - G.00205p3 . . (1) From m = 1 t o m = 2. K = - 860 + 617.5;~ - 13.88@ + 0*0807p3 . . . . (a) From m = 2 to 97% = 6. K = 5321 + 252-9p - 7.38~' + O*O&+' . . . . . (3) From m = 6 to m = 24. K = - 1456 + 624.58~ - 14.194~' + 0*c/866p3. . . (4) From m = 24 to m = 150. K = 69.3 + 386.22~ - 1.494~' - 0.1418~~ . . . . ( 5 ) where p is the percentage of acid in the solution. These equations are only applicable strictly between the limits stated.The values deduced by their application agree most satisfactorily with the ob-served values iu the case of (3) but in no case does the averag 120 CROJlPTON AN EXTENSIOS OF difference between the calculated and observed values exceed 1 per cent. Reverting to the sulphuric acid curT-e I would call attention to the following points :-The addition to the acid of any quantity of water up to about 2 per cent. does not appear to influence the electrical conductivity in any regular manner the second differential curve changing its direction in totally irregular fashion. But when the acid is of such a strength that it coiitains about 98 per cent. H2S04 the conductivity is iufluenced perfectly regularly by further dilution ixp t o H2SOI.0Hz the second differential curve between these limits being a continuous straight line.It is specially noteworthy that no change takes place in the differential coefficient curve between these points corresponding with the maximum attained by the conduc-tivity curve. The maximum is evidently due to some influence exerted by both the compounds H,S04 and H,SOa.OH on the con-ductivity in such a way that a t this point the sum of the influence of each becomes a maximum. It will be noticed that the second maxi-mum on the conductivity curve is also in no way indicated on the second differential curve but that it lies between the hydrates 'H2SOa.60Hz and HzSOa*240K? and this is to be explained in a similar manner. On passing the last " hydrate " indicated namely, H,SOa* 1500H, the second differential curve assumes again a per-fectly irregular form just as at the commencement and this irregu-larity continues up to the end.This irregularity a t each end of the curve is a poiiit of special interest. If we st4art again from the compound H,SOa and proceed in the opposite direction towards H2Sz07 we find in this case an exact parallel to what formerly happened. Up to a point corresponding with about 102 per cent. HzSOa the second differential coefticient curve is absolutely irregular; it then takes the form of a straight line and proceeds regularly till the composition 2H2SOa SOs is reached where a break occurs and the direction of the curve changes slightly. It still proceeds regularly however until the point HzSz07 is very nearly reached ; and here again it suddenly becomes irregular.The irregularity in fact always occurs and the same is true for every solution besides that of sulphuric acid that has been ex-amined as yet when the pure compound begins to undergo dilution. I t may be taken as representing an initiative stage during which the action of the compounds that are just beginning to be formed has not come fully into play and the conductivity varies with a series of physical actions which here probably take place and does not assume that regularity which it afterwards attains when depend-ing solely on the influence of the hydrates formed. It is on the case of sulpliuric acid as offeririg the greater range C ROMPTON. -700 & 4m NITBXC ACID SULPEURIC ACID.C KOM PTO N. I?QTASSI’,”M HYDROXIDE. ‘ O I i NENDELEEFF’S THEORY OF SOLUTIOY. 121 and the one for which tbe largest number of determinations have been made that we may a t present rest the hypothesis that electrical conductivity of aqueous solutions is due to the formation and owing to the influence of certain definite hydrates. The sulphuric acid curve is in fact typical of all others that have been examined. In the case of nitric acid for instance on taking the second differential coefficient there is evidence of the formation of two compounds, HN0,*150H2 and HN0,-40H2 and the presence of the same com-pounds is indicated by MendelBeff’s curve for change of density. It is unfortunate that the numbers for the electrical conductivity do not extend beyond an acid containing 62 per cent.of HNO.I so that the presence of hydrates richer in iiit>ric acid than the one indicated by HNO3*4OH cannot be ascertained. Phosphoric acid gives a very characteristic curve for the second differential coefficient and breaks corresponding exactly with those which occur on Mendel6eff’s curve occiir for the hydrates H,PO,.iOH, and H3POa-20H2. In this case also the observations do not extend far enough to enable i t to be ascertained whether a hydrate richer in phosphoric acid exists. Potassium and sodium hjdroxides have likewise been examined, b u t the numbers in these cases are altogether insufficient for any-thing like an adequate investigation. It is of interest that in this case the evideiice as far as.it goes tends to prove that potassium and sodium hydroxides form the same hydrates namely one with 6 mols.H,O and one with 10 to 11 mols. Acetic acid a compound with very low conductivity gives distinct evidence of the formation of two hydrates C,H,O,*OH and C2H402*30H2 and a tlhird hydrate is indicated most probably having the constitution C,H,O2*9OH?. The following are the numbers from which the curves in each case have been constructed :-IT. Nitric Acid. 6 - 2 12.4 18 -6 31 *O 3’7.2 43 *4 49 *6 55 *a 62 -0 24 -a 2924 5072 6460 7185 7319 7062 6550 5935 5290 4646 3 -1 9 *3 15.5 21.7 27 -9 34 -1 40 ‘3 48 -5 52 *7 58.9 - 4’71 343 224 117 21 -6 - 39.8 - 82.6 - 99’2 -104 - 104 6 ‘2 12.4 18.6 24.8 31 -0 37 - 2 43 -4 49 -6 55 -8 62 -0 d‘k.dy“’ -__. - 126 - 121 - 107 - 95.4 - 61’4 - 42.8 - 16.6 - 4.8 122 CROMPTON A S ESTESSION OF 4 '92 10 -25 20.05 30.52 36-90 49 -80 67.80 78 -93 87 *07 P-0.3 1 .o 5 10 15 20 25 30 35 40 45 50 55 60 ti5 70 75 80 99.7 K. 288 54.4 1061 1574 1804 1945 1436 962 660 K. 2 *98 5.48 11 '47 14.30 15.18 15.04 14 *24 13'12 11 -72 10 *13 8-49 6'93 5 -52 4 -28 3 -17 3'20 1 '37 0.76 0 -0004 IIT. Phosp7~0w'c Acid. P. 2 -46 7 -58 15 -15 25.31 33 -71 43 a35 58.80 73 -36 83 *00 dk -dP' 58 *5 48 '1 52'7 49.0 36.0 10 -9 - 28 '2 -42.6 -3'7.1 IV. Acetic Atid.0.15 0 *65 3 7.5 12 -5 1'7.5 22 *5 27 -5 32 '5 37'5 42 -5 47 -5 52-5 57 *5 62 -5 67 *5 72 *5 77.5 90 9 *9 3 -5 1.467 0 -5660 0 * 176 -0.028 -0.160 -0.224 - 0.280 -0.318 - 0 '328 - 0 '312 - 0 -288 - 0 '248 - 0 *222 - 0.194 -0 -166 -0 *122 - 0 '038 5 -00 11 *36 20 *23 29-51 38.53 61 *07 66-08 78.18 io. -0 *4 1-82 5.25 10 15 20 25 30 35 40 45 50 55 60 65 70 75 83 -7 -20'3 - 3.6 -15.5 -27'3 -25.3 - 9.8 + 5 . 7 6.1 - 901 - 390 - 204 - 132 - 64 - 56 - 22 - 10 16 30 34 26 28 28 44 8 MENDELEEFF'S THEORY O F SOLUTION. V. Potassium Hydroxide. 123 4.2 8.4 12.6 16.8 21.0 25.2 29.4 33.6 37.8 42.0 1372 2552 3526 4271 4784 5061 5090 4890 3344 4484 --2-1 6-3 10.5 14.7 18-9 23-1 27-3 31-5 35'7 39.9 2.5 5 10 15 20 25 30 35 40 42 E.1019 1845 2927 3244 3062 2543 1892 1409 1088 995 dk d/p -. -326.6 281 232 179 122 66 7 - 48 - 97 - 129 VI. Sodiunr Hydroxide. P. 1-25 3-75 7'5 12.5 17'5 22-5 27.5 36'5 37.6 41 4.2 8.4 12.6 16.8 21.0 25-2 29.4 33.6 37.8 -45.6 - 49 - 53 - 57 - 56 - 59 - 55 - 49 - 32 dk dp' -4Q7-6 330.4 216.4 63.4 - 36.4 -103.8 -130.2 - 96.6 - 64.2 - 46.5 2.5 5.62 10 15 20 25 30 35 39'25 -3o.ao -30'12 -10'60 -19.96 -13'48 - 5.28 - 6.72 - 6'48 - 5-06 The values for the conductivity which have been used in investi-gating the above cases are those given by Kohlrausch for the t,em-perature of 18".It has not been possible owing to the want of full experimental data to ascertain what effect change of temperature would have on the second differential curye. According to Mende-18eff's theory the only effect which a rise or fall of temperature could have on the solution would be to alter the amounts of the products of dissociation but as the compounds formed would be the same for the same concentrations no change would take place in the position of the points where breaks occur on the second differential coefficient curve although the direction of the lines joining those points might be altered. That is the same hydrates would be formed provided the concentrat'ion were kept constant whatever tihe tempera-ture mightl be as long as it were short of that which would produc 124 AN EXTENSION OF MENDELdEFF'S THEORY OF SOLUTIOY.total decomposition in the hydrates. Proof of this is brought forward by Mendel6eff in his paper on the change of density of sulphuric acid (Zon. cit.). This statement as t o the effect of temperature is fully verified by the electrical data in the case of nitric acid the conductivity of which has been determined hp Kohlrausch at O" 18" and 40° and working out the second differential from the numbers given for these tempera-tures the direction of the straight lines representing the various portions of the second differential curve is found to alter perfectly regularly as the temperature rises or falls but the breaks occur a t the same points for all temperatures.This being the case such experimeiits as those of Heim (Ann. Phys. Chem. 27 643) on change of conductivity with change of tempera-ture and of Nicol (Trans. 1887,389) on change of specific viscosity with change of temperature for saturated solutions cannot be accepted as proving that the composition cf sat'urated and non-saturated solutions is necessarily the same since where the concentration of the solution undergoes no change the composition must of necessity remain the same. It is only by investigating the change of the physical pro-perties with the concentration that change of composition a t the saturation point might be shown to take place and as far as can be ascertained from the few experiments quoted by Nicol (Zoc.cit.) on the rel;tt,ion of specific viscosity to concentration such a change at the saturation point does actually take place. Heim's experiments on the other hand niay be taken as affording additional support to Mende-16effs views of the influence of temperature on solutions. Assuming Mendeldeff's theory to be true and that what we really have in a solution of two substances a t any point is a mixture of two dissociable and dissociating compounds formed from these substances in different proportions we may deduce an expression for the electrical conductivity of such a solution in the following rcaiiner :-If K is the conductivity of the solution we may suppose a certain proportion of this to be borne by each constituent of the solution and if p is the percentage of one constituent and pl the percentage of the othei- and a quantity a of the first is combined with a quantity 7 of the second the remainders representing the products of dissociation, we have-K = ( p - a)k + ( p l - b ) h + ( n + b ) h , where 76 k and k are the conductivities of unit amounts of the components present under the conditions of experiment.But it is obvious that the amount a of p which will remain combinsd will be proportional t o the total amount'p of t'he constituent present all other things remaining constant.; and that in like manner the amount b o ARJISTRONU ON ELECTROLYTIC CONDUCTION. 125 pl remaining combined will be proportional to p . equation becomes-Hence the above K = kcp + klCIp1 + (c2p + c3pJk2, where c cl c2 and cj are constants.But now since neither con-stituent when alone and in a pure condition has any conducting power it is clear that the conductivity of any one constituent must in some way be influenced by the presence of the others and I cannot but think that it is not only the simplest but also a fair assumption to make that this influence will be directly porportional to the amounts of the other constituents present. If this is so k becomes equal to 100 - y multiplied by some constant and k becomes equal to 100 - pl multiplied by some other constant ; or since 100 - p l = p , to p multiplied by a constant. The quantity Tc in the same way is proportional to p since the amounts combined czp and c.p, depend on p andp or 100 - p . But k represents the conductivity of a mixture of two compounds and the influence of each of the compounds on the other must here also be considered. This influence, as will easily be seen is likewise porportional to p . Therefore kz as representing the conductivity of the combined amounts becomes proportional to p and as representing the influence of one compound on the other is also proportional to p ; in this way kz becomes proportional to p2. If we now substitute the values for k kl and k , in the above equation and for p write 100 - p we should find that it would eventually simplify down to K = Bp + Cpa + Dp3, B C and D being constants. The conductivity would thus be represented as a function of the third order of the percentage coin-position a relation which as has been shown is rendered extremely probable by the nature of the second differential coefficient

ISSN:0368-1645    

DOI:10.1039/CT8885300116

出版商:RSC    

年代:1888

数据来源: RSC

摘要:

ARJISTRONU ON ELECTROLYTIC CONDUCTION. 125 VIII.-Note on Electrolytic conduction and on Evidence of a Change in the Constitution of W a t e r ; an Addendum to the foregoing Paper. By HENRY E. ARMSTRONG F.R.S. THE determination of the nature of electrolytic conduction is of such supreme importance in any discussion of the nature of chemical change and of the laws which determine it,* and the results contained * Professor Stokes in his Presidential Address to the Royal Society just de-livered uses the striking words " So closely is electricity related to chemica 126 ARNSTRONG ON ELECTROLYTIC CONDUCTION. in Mr. Crompton’s extension of MendelAef’s conception are in my opinion of such a definite and conclusive character that it appears both permissible and desirable to briefly refer in the first instance to current opinions in order that those who are not specially informed on such matters may gain the necessary clue to understand the ques-tions involved.In my address to the Chemical Section a t the British Association meeting a t Aberdeen (Report ISS5) I entered somewhat fully upon the discussion of the subject of chemiraZ action specially directing n ttention to t’he absolute interdependence of electrolytic and chemical action and in order to emphasise the importance of the study of electrolvtic phenomena I quoted the wordq used the previous year by Lord Rayleigh in his Presidential Address to the Association :-“ From the further study of electrolysis we may expect to gain improved views as to the nature of the chemical reactions and of the forces concerned in bringing them about.. . . . . . I cannot help thinking that the next great advance of which we have already some foreshadowing will come on this side. Arid if I might without presumption venture a word of recommendatioii it would be in favour of a more minute study of the simpler chemical phenomena.” My position a t that time is best indicated by the following quota-tions from my address :-“ The questions ‘ What is electrolysis ? What is an electrolyte ?’ are all-importmt to the chemist. . . . . . Helmholtz tells us that electrolytes belong to the class of typical compounds the con-stituents of which are united by ‘ atomic affinities,’ not to the class of ‘molecular aggregates.’ Is this the fact? Before chemists can accept this conclusion many difficulties must be removed which appear to surround the question.. . . . . The current belief among physicists would appear to be that the dissolved electrolyte-the acid or the salt-is almost exclusively primarily decomposed (Wiedemann, Elektricitlit 1883 ii 924) We are commonly told that sulphuric acid is added to water to make it conduct but the chemist desires to know why the solution becomes conducting. It may be that in all cases the ‘ typical compound ’ is the actual electrolyte-i.e. the body decomposed by the electric current-but the action only tukes place when. the t!jpicnl compounds are conjoined nnd .form the molecular agyre-gate for it is an undoubted fact that HC1 and H2SOa dissolve in water forming ‘ hydrates.’ This production of an ‘ electrolyticd scstem ’ from dielectrics is I venture to think the important question for chemists t o consider.I do not believe that we shall be able to action that coitld we only clearly apprehend the nature of electricity it Reems not unlikely that an unexpected flood of light might be shed on chemical combi-nation. ARMSTHOXG ON ELECTROLYTlC CONDUCTION. 127 state the exact conditions under which chemical change will take place until a satisfactory solution has been found. ''F. Kohlrausch (Pogg. Ann. 1876 159 233) has shown that on adding sulphuric acid to water the electric conductivity increases very rapidly until when about 30 per cent. of acid is present a maxi-mum (6914) is attained ; conductivity then diminishes almost as rapidly and a minimum (913) is reached when the concentration corresponds with that of a monohydrate (n[,S04,0H,) ; from this point conductivity increases somewhat (to 1031 at 92.1 per cent.H2SOa), and then again falls and is probably zero for the pure acid ; on adding sulphuric anhydride to the acid conductivity again increases. Solu-tions of other acids and of a number of salts-chiefly deliquescent and very soluble salts-also exhibit maximum conductivity at particular degrees of concentration. In no other case has the existence of two maxima such as are observed in solutions of sulphuric acid been esta-blished ; but probably this is because the experiments either have not been or cannot well be carried out with pure substances or very concentrated solutions. Solutions of less soluble salts increase in con-ductivity as the amount of salt dissolved increases." Kohlrausch has suggested as an explanation of the influence of the ' solvent ' on t,he conductivity of an ' electrolyte,' that in a solu-tion the ions which are being transferred electrolytically come less fre-quently into collision than would be the case in the pure substance. There is therefore less opportunity for the formation of new molecules, and the ions are able to travel farther before entering into combina-tion. " Regarding the question from a chemist's point of view however, I cannot help thinking that this explanation is scarcely satisfactory or sufficient ; and I cannot resist the feeling that the production of electrolytically conducting solutions from dielectrics is in some manner dependent upon the occurrence of chemical change.If the composition of the solutions of maximum conductivity be calculated, it will be seen that they contain but a limited number of water mole-cules ; thus bhe solution of sulphuric acid of maximum conductivity (at 18') contains 30.4 per cent. of acid and therefore has the com-position H,SO 1'2.4 H,O (approximately) ; for nitric acid the ratio is 1 8 ; for acetic acid it is about 1 17. Now it is highly remarkable that the solutions of maximum electric conductivity are also very nearly those in the formation of which nearly the maximum amount of heat is developed ; this will at once be obvious on comparison of the curves given by Thomsen (Thermocheinische Untersuchungen 3 ), and by Kohlrausch.In the chemist's experience the point of maxi-mum heat development is usually near t o the point of maximum chemical change and I think therefore that we are justified in con 12s ARJfSTROKQ ON ELECTROLYTIC COSDUCTION. cluding that even if electrical conductivity be not a maximum a t a particular concentration on account of the presence of a part'iculsr hydrate (belonging to the class of molecular aggregates) in maximum amount a t all events the ' structure' of the system is especially favourable and the ' chemical influence' exerted by the one set o € molecules upon the other is a t a maximum a t the point of maximum conductivity. The fact that the amount of sulphuric acid required to form a solution of maximum conductivity increases with tempera-ture-Temp.0" 10" 20" 30" 40" 50" 60" 70" Per cent . . . 30.2 30.9 31.7 32.5 33.5 34.1 34.5 35.4 and also the fact that the maxima and minims of conductivity tend to become obliterated with rise of temperature (Kohlrausch) are both in accordance with the view that conductivity is in some way depen-dent upon chemical composition as the efTect of rise of temperature would be t o cause the dissociation of hydrates such as 1 have referred to. The increase in conductivity of aqueous solutioiis with rise of temperature would appear to be against the view here put forward ; but it is probable that this may be largely due to diminution in viscosity and increase in the rate of diffusion." Jn March of last year I submitted to the Royal Society a paper '' On Electrolytic Conduction in relation to Molecular Composi-tion," &c.(Proc. Roy. Xoc. 1886 ass) in which I pointed out thst it was perhaps desirable to distinguish between simple eZecfrolytes-such as fused silrer chloride and composife electro Zytes-conducting mixtures of compounds like water hydrogen chloride and sulphuric acid which behave as dielectrics when pure. The difference between simple and composite electrolytes was so great that it was difficult to resist the feeling that the mode in which their electrolysis was effected was different and I ventured to suggest this without how-ever attaching any particular importance to the point and rather with the object of inciting debate ; but I clearly stated my objections to the current dissociation hypothesis of electrolysis and formulated the view that in the case of composite electrolytes bot,h constituents were immediately concerned and that the one the solvent did not merely exercise a screening effect as suggested by Kohlrausch.Considerable discuss on on these points has taken place between Professor Lodge and myself as co-secretaries of the B. A. Elec-trolysis Committee and in a communication to this committee a t the recent Manchester meeting in answer t o his criticisms I stated "t,he chief reasons which cause me to hesitate in accepting the ' atomic dissociation hypothesis ' and which have led me to snggest an alternative ' molecular hjpothesis,' viz. that in the case of composit ARMSTRONG ON ELECTROLYTIC CONDUCTION. 129 electrolytes at all events electrolysis is the outcome of the combined action of the E.M.F.and of some effect which the one set of mole-cules exerts upon the other set while both are under the influence of the E.M.F.” And I added “ I care little at present what the effect is the important question to settle being whether electrolysis is primarily an affair of atoms or of molecules. . . . Ostwald’s remarkable contributions to our knowledge of molecular conductivity appear to me to bear continuous testimony to the existence of such an influence of molecule upon molecule as that I have pictured” (Electrician August 5th and 26th 1887). I venture now to contend that thanks to our illustrious Russian confrdre the “ great advance ” of which Lord Rayleigh spoke is no longer far distant and that it is patent that electrolysis is primarily an affair of molecules ; that electrolysis takes place in consequence of an influence which one set of molecules A exercises upon another set of molecules B.The results which Mr. Crompton has obtained are to my mind conclusive on this point the information afforded by the study of sulphuric acid solutions being alone sufficient ; and they are of special importance as indicating the superiority of electrical values over all others in any discussion of the constitution of complex systems of dissociable compounds.* This was to be expected as on the hypothesis now under discussion the variations in the electrical values would represent variations in the extent to which the one set of molecules affect the other set the electrical values serving in fact t o quantify an injluence; for changes in constitution or structure might well occur which would involve but a slight degradation of energy aiid consequently a slight change in density and many other physical properties and which yet might lead t o a relatively very considerable change in the extent to which the compound could exert an influence on the course of electrolytic or chemical change.In the case of sulphuric acid the evidence is all but complete and it is no exa*ggeration to say that every peculiarityof the acid is faith-fully pictured in the second differential coefficient curve. It is well known that H2S04 readily loses SO3 and that Marignac’s experiments have shown that a stable equilibrium is attained only when the acid has lost a.nhydride to the extent required to form a hydrate H2S04*T1TH20 = 12H2S04.H20.A sudden change in the direction of the curve will be seen to occur at a point where this “ hydrate ’’ is situate ; and if the same interpretation be given of this and of the subsequent inflexions it would appear necessary to admit the exktence of such a hydrate although it is not usually recognised, it being supposed rather that equilibrium is established between * It is to be expected that the discussion especially of optical and magneto-optical data will afford valuable results in the case of non-electrolytes. VOL. LIII. 130 ARIlSTRONG ON ELECTROLYTlC CONDUCTION. €€,SO, H2S04.0H2 &c. when the composition is that ,of Marignac’s hydrate. I shall again refer to this point later on and will only add that MendelBeff’s curve does not show this hydrate.The three hydrates H2SOa*OH2 H2S04*20H2 H2SOa*60H2 are indicated both on the conductivity curve and on Mendel6eff’s density curve and there is also a marked break on both curves approximately a t a point corresponding to a hydrate H2S04*150H20. The conductivity curve however affords an unmistakable indication of a hydrate H,SO4*240H2 which does not occur on the density curve. The discovery of this hydrate is of fundamental importance, owing to the fact that the maximum conductivity of sulphuric acid solutions is manifested between the points where the two hydrates H2SO4*6H2O and H2SO4*24H2O are situate the two sets of molecules which mutually affect each other and induce electrolysis thus become exhibited.Mr. Crompton’s curve shows an inflexion at a point corresponding to the compound 2H2SOa*S03. I am not aware that any such substance is known or that salts of such an acid have been described, but a trichromate of somewhat analogous composition has been obtained and Weber has prepared octosulphates M2SO4*8SO3. On writing to my friend Dr. Messel who is accustomed to observe the behavionr of sulphuric anhydride on the large scale I learnt “that mixtures of the acid and anhydride containing up to 29-30 per cent. of the latter are liquid a t ordinary temperatures but that then crystallisation takes place ; when more than 55 per cent. of anhydride is present liquids are again obtained but solidification takes place when a little more than 70 per cent.of anhydride is present.” Now-2H,S04 * SO, contains 28.9 per cent,. SO,. 2H2S04*3S03 , 55.0 , ,7 2HzSO4.2S03 , 41.6 , 9 9 H,SO4*3SOj , ’71.0 , 9 , There is therefore independent evidence of the existence of the compound indicated on the conductivity curve and there can be little doubt that other similar compounds will be proved to exist when search is made for them. The concurrence of the evidence derived from the mathematical discussion of data deduced by the observation of properties so dif-ferent as density and electric conductivity with what may be termed the chemical evidence afforded by the recognition of a variety of distinct compounds of sulphuric acid with its anhydride or with water is so complete that I feel we need have no hesitation in apply-ing MendelBeff’s method and in accepting the conclusions to whic ARMSTRONG ON ELECTROLYTIC CONDUCTION.131 it logically leads even when these are beyond control by any ordinary chemical method. There is reason to believe that not only water and sulphuric acid: b u t liquids generally consist of complexes of the fundamental mole-cules ; and in any discussion of elect,rolytic conduction it is of primary importance t o recognise that this is probably the case. Mendeleeff is prepared to admit the existence of a hydrate containing 1500H2, but I must confess that I hesitate to do so and I even think that the inflexion in the curve at the point corresponding to this supposed hydrate is evidence of a change in the constitution of water.The occurrence of a similar change in the curve at about the same point in the case of ammonia and acetic acid and at a point somewhat, more distant from its origin in the case of phosphoric acid affords eonfirmation of this view. I t is possible also to put the same inter-pretation upon the sudden inflexion of the curve at the point corre-sponding to Marignac’s hydrate. Any difficulty which might be felt in admitting the existence of hydrates so abnormal in composition as 12H,S04-OH3 and H,S04*150H,0 would then be removed. But it is also conceivable that Marignac’s hydrate has an existence and that it is a hydrate of a polymer of sulphuric acid-not of the funda-mental molecule H,SO4-consisting of a very limited number of complexes of H,S04 molecules associated with a single water mole-cul e .The assumption that sulphuric acid mainly consists of complexes such as may be represented by the formula (H,S04) would serve to explain many features of the conductivity curve near to its origin from the acid thus the low conductivity of concentrated solutions may be attributed to the presence chiefly of (H2S04) molecules and of hydrates derived therefrom; and it may be supposed that as the complexes become more and more resolved into hydrates of the fundamental molecule H,S04 by dilution a greater influence would be exercised by molecule upon molecule. A somewhat similar view to that here indicated has been advanced by Landolt (Optisclzedrehunqsverm~,~e~ p. 59 j in explanation of the influence of “ neutral ” solvents on the rotatory power of opticallr active substances such as t,urpentine.* Rut the chief evidence in favour of such an cxplanation is probably t be found in the influence * Mr.Crompton has discussed among others the values given by Landolt as representing the change in rotatory power on diluting nicotine with water and turpentine with benzene and acetic acid the curves afford the clearest indications of the presence of molecular compounds of the active substance with the solvent., but the determinations are not nearly numerous enough to permit of the discoverj of the cornposition of these compounds. I therefore propose to reinvestigate the behaviour of turpentine. K 132 ARMSTRONQ ON ELECTROLYTIC CONDUCTION. which a small quantity of one metal-for instance lead or bismuth-exercises on another-for example on gold-the most ductile of metals a minute percentage rendering it highly brittle.It is incon-ceivable that the lead can enter into uniform relationship with the gold molecules throughout the mass L e t that it can combine with the whole of them. In the pure gold the molecules are probably throughout uniformly and continuously related and very probably also they are of simple atomic constitution but not truly symmetrical : on the introduction of a small proportion of foreign iricompatibie molecules continuity becomes disturbed ; the atoms become free to re-arrange themselves and in place of the uniform relationship which previously obtained a non-unif orm relationship results in consequence of the formation of complex aggregates which have less power of cohering than the original simpler molecules.It is perhaps an argument in favour of this “ screen ” hypothesis that as already pointed out the marked change in the curve near to the origin from water takes place in the case of phosphoric acid later than in the case of sulphuric it is not improbable that the molecules of the former acid are of greater complexity than those of the latter so that if a certain proportion of foreign molecules be necessary to produce maximum effect a larger absolute proportion of phosphoric acid would be required. Considerations of this character whatever their value in the present instance are certainly of importance in connection with the study of the influence of small quantities of foreign sub-stances on the properties of metals generally and in preventing superheating superfusion &c.It’ the argument advanced in this and the foregoing paper be cor-rect it becomes more than ever necessary to consider the grounds on which the conclusion is based that electrolysis is the outcome of atomic dissociation. It has always appeared to me that Kohlrausch’s curve for sulphuric acid affords the most positive evidence that electrolysis cannot be a simple dissociation phenomenon as in that case it is to be expected that dissociation would take place to a. gradually in-creasing extent until a maximum was reached and not as the curve would indicate that after attaining a maximum it should diminish and then again increase until a much higher maximum is attained.The first differential curve may bs regarded as picturing the manner in which the influence is exercised at various points by the compounds whose existence is indicated on the second differential curve and this curve most clearly indicates that the effect is exerted mainly at two points-the one lying between the acid and the bihydrate and the other between the two hydrates containing 6 and 24OH, the discontinuity of the phenomena at points intermediate between these two principal points is very striking. An explanation of the discon ARMSTRONG ON ELECTROLYTIC CONDUCTION. 133 tinuity has already been given viz. that it is due t.0 the fact that in the one case the polymerised acid in the other the fundamentrat mole-cule is active ; and if it be difficult to understand the changes which occur on passing from acid to water on the dissociation hypothesis if is undoubt,edly still more difficult to understand the sudden rise and subsequent fall in conductivity on passing from sulphuric t o pyro-sulphuric acid and to account for the fact that the latter has a lower conductivity even than the former acid.On my hypothesis however, the fact that H,S,07 is chemically in a certain sense the more stable compound affords a sufficient explanation of the difference in its behnviour and that of sulphuric acid. Any conclusion relating to electrolytic phenomena will doubtless be found to apply equally to allied chemical phenomena so that if it be asserted that too much stress has been laid on the part which atomic dissociation plays in electrolysis the same remark must be made regarding its influence on the course of chemical change.Cer-tainly the more I study the subject experimentally the more the conviction is forced on my mind that an explanation of the majority of chemical changes will ultimately be found in the principle of association and not in that of dissociation. Reference was made in the early part of the paper t o the division of electrolytes into two classes of simple and composite electrolytes. There is no reason to cease making this distinction on the contrary. But it being established as I believe that in the case of solutions electrolysis is the outcome of the influence exerted on each other by molecular aggregates consisting of the same proximate elements but differently constituted there appears no longer to be any necessity to suppose that there is any fundamental difference in the mode in which e1ect)rolysis takes place in solutions and in fused salts Le., simple electrolytes. It is in the highest degree probable that fused salts contain molecules of different orders of complexity and it may fairly be supposed that these would be capable of influencing each other much in the same way that I suppose the different aggregates in aqueous solutions influence each other. With regard t o the nature of the influence thus pictured as exerted between molecule and molecule I do not propose to discuss this now, and would only add Chat my views are entirely based on the assump-tion of the existence of what I have termed “ residual affinity,” and that they necessarily involve the recognition of the potency of this factor. Central Institution, City and Guilds of London I n s t i t u t e

ISSN:0368-1645    

DOI:10.1039/CT8885300125

出版商:RSC    

年代:1888

数据来源: RSC

摘要:

134 IX.-On the Alleged Existence of a Second Nitroethane. By WYNDHAM R. DUNSTAN Professor of Chemistry to the Pharma-ceutical Society and T. S. DYMOND. IN 1873 Victor Meyer (Annalen 171 1-56) found that by the interaction of ethyl iodide and silver nitrite two compounds of the formula C2H,N02 were produced. One of these he recognised as the previously known ethyl nitrite (b. p. 16*5") the other as a new sub-stance (b. p. 113") to which he gave the name of nitroethane. In this interaction much heat is evolved and the temperature soon rises far above the boiling point of ethyl nitrite. In order to complete the change the mixture is heated for some hours with a reflux condenser on a water-bath when the greater part of the ethyl nitrite will escape unless special means are adopted to condense it ; some how-ever remains dissolved in the nitroethane generally with a little ethyl iodide and on fractionating the liquid a mixture of these three substances will distil below 100".According t o Meyer the two isomerides are formed in equal quantities. More recently the interaction of ethyl iodide and dry silver nitrite has been studied under somewhat different conditions by Kissel" (Journ. Russ. Chcm. Xoc. 1882 226-230; and 1884 135-140) ; he adds dry silver nitrite in small quantities at a time to the ethyl iodide cooled to O" until no further action ensues. The mixture is kept cool and shaken during one day great care being taken t o avoid any permanent rise in temperature. Under these conditions accord-ing to Kissel no ethyl nitrite is formed but when the mixture is dis-tilled a considerable quantity of liquid comes over between 29" and :30°.This fraction is redistilled between 28" and 35O washed with water a solution of silver nitrate and a weak sodium carbonate solution; it is then heated with silver nitrate and distilled from dry calcium nitrate. The liquid it is stated now boils constantly a t 29-30" and on combustion yields results agreeing with the formula C2HsN02. This substance is said to resemble in its properties both ethyl nitrite and nitroethane but is characterised by its chemical reactions as a nitro-compound. It yields a crystalline sodium-derivative is violently acted on by hydrochloric acid with the production of a new compound and forms with solution of ferric chloride a blood-red colour with solution of copper sulphate a clear * Kissel's papers hare been consulted in the original and I must take this opportunity to thank my friend Sir Nicholas Elphinstone to whom I am greatly indebted for a translation from the Russian.-W.R. D THE ALLEGED EXISTENCE OF A SECOND NITROETHANE. 135 green and with a solution of silver nitrate a light-yellow turbidity. As regards the nitroethane proper (b. p. 113") of which according to Meyer half the total amount of liquid consists Kissel alleges that a, yield of from 54 to 66 per cent. may be obtained by adopting the process he has described the remainder of the liquid being the new isomeride. Kissel also claims to have obtained a corresponding com-poiind (b. p. 43-44") by the interaction of isopropyl iodide and silver nitrite.Kissel's description of the properties and reactions of the " second nitroethane " at once suggests the idea that it is merely a mixture of ethyl nitrite with nitroethane although it is true that some of the alleged facts are inconsistent with this view. We have lately had occasion to prepare a comparatively large quantity of nitroethane and we thought it worth while to repeat Kissel's experiments. Dry silver nitrite was gradually added to 180 grams of ethyl iodide cooled below 0" until there was no further evolution of heat the mixture was then frequently agitated at a low temperature during one day. No gas escaped. The distillation flask containing the mixture was connected with a condenser and the temperature slowly raised.Between 16" and 17" a gas was evolved which possessed all the properties of ethyl nitrite It burned with a yellowish flame was absorbed by alcohol and a3t once liberated iodine from an acid solution of potassium iodide nitric oxide being set free. The apparatus was now connected with two bulb-condensers and these were joined to two wash-bottles containing alcohol. Between 19" and 40" a small quantity of liquid condensed; it was tested for ethyl nitrite and nitroethane both of which were found ; the nitroethane was detected by first destroying the et,hyl nitrite with excess of an acid solution of ferrous sulphate, and then rendering the liquid alkaline with potash. The nlliaceous odour which we had previously observed (Chem. News 56 132) whenever nitroethane is reduced with ferrous hydroxide was quite distinct and by distilling the liquid into diluted hydrochloric acid, and evaporating the distillate to dryness the hydrochloride of a base was obtained.This was extracted with absolute alcohol and the alcoholic liquid precipitated with ether to remove ammonium chloride, after which the platinochloride was produced in the usual manner and analysed ; it contained 39.2 per cent. of platinum and was thus proved to be ethylamine platinochloride. Between 40" and 80"' a considerable quantity of liquid distilled ; Che greater part was condensed in the first bulb a little however, was found in the second bulb and this boiled at 17-18" con-sisting almost entirely of ethyl nitrite. Above 80" more liquid distilled and was separately collected.The fraction obtained between 40" and 80" was redistilled; at 16-17" ethyl nitrite passed over 136 THE ALLEGED EXISTENCE OF A SECOND NITROETHANE. between 18" and 30" the greater part distilled a third fraction was collected between 30" and loo" and a fourth above 100". From the sub-joined table of results arranged for convenience in the form of a tree, it will be seen that each of these fractions when redist<illed is resolved into liquids boiling at a lower and a higher temperature and by repeatedly fractionating these liquids ethyl nitxite is obtained boiling at 16.5" and nitroethane boiling at 113'. When the fraction was too small t o be redistilled it was tested for ethyl nitrite and for nitro-ethane both of which were invariably found.It was often difficult to ascertain exactly the temperature at which distillation commenced, Table showing the Results of the Fractional Distillation of the Liquid produced by the Interaction at O" of Ethyl Iodide and Xilver Kitrite. * Contained both ethyl nitrite and nitroethane. t Ethyl nitrite. $ Nitroethane BISMUTH IODIDE AND BISMUTH FLUORIDE. 137 and when two figures are given in the table the first is to be regarded as approximate only. We could discover no liquid which boiled con-stantly at 29" and 30"; the fraction obtained at this temperature be-haved both physically and chemically as a solution of ethyl nitrite in nitroethane. The alcohol in the wash-bottles attached to the bulb-condensers was renewed after each distillation and when tested every specimen contained more or less ethyl nitrite which had escaped con-densation. It was also noticed that when the original mixture was distilled some nitric oxide escaped and later distillates contained a little acetic acid. We are justified in concluding from these results that the so-called '' second nitroethane '' is indistinguishable from a mixture or solution of the two known isomerides of the formula C2H,N02

ISSN:0368-1645    

DOI:10.1039/CT8885300134

出版商:RSC    

年代:1888

数据来源: RSC

摘要:

BISMUTH IODIDE AND BISMUTH FLUORIDE. 137 X.-CONTRIBUTIONS FROM THE LABORATORY OF GON-VILLE AND CAIUS COLLEGE CAMBRIDGE. No. XI.-Bismuth Iodide and Bismuth Fluoride. By B. S. GOTT B.A. Scholar of Gonville and Gains College and M. M. PATTISON MUIR M.A. Bismuth Iodide. IT is known that bismuth iodide Bi13 may be prepared either by heating together bismuth and iodine in the ratio Bi 31 or by adding an aqueous solution of potassium iodide to a solution of bismuth nitrate in dilute nitric acid. The directions given by earlier experi-menters for preparing this compound in the wet way are vague. We have recently made some experiments on the preparation of bismuth iodide and also on the comparative stabilities towards water of this compound according as the specimen is prepared in the dry or the wet may.Preparation of Bismuth Iodide in the Wet Way.-Excess of a fairly concentrated aqueous solution of potassium iodide is added to bismuth nitrate dissolved in the smallest possible quantity of dilute nitric acid ; BiI is thus precipitated along with iodine. The precipitate is dis-solved in as small a quantity as possible of concentrated aqueous hydriodic acid and water is added until the greater part but not the whole of the bismuth is precipitated as brown BiI,. The solid matte 1.38 GOTT AND MUIR BISMUTH IODIDE is collected and dried for some time a t loo" whereby most of the free iodiue is volatilised. The residue is then washed once or twice with absolute alcohol and finally dried a t 100". Some Properties of Bism.uth Iodide.-The salt prepared as described above is somewhat soluble in absolute alcohol ; 100 parts by weight of alcohol at 20" dissolve about 3$ parts of the salt.The sp. gr. of BiI prepared in the dry way was found to be 5.64 20" 'LO" ' a t - and the sp. gr. of BiI prepared in the wet way was found 20" to be 5.65 at -. 20" Specimens of the iodide prepared in both ways were treated with water in about the ratio BiI 3000H20 for different times and at different temperatures ; the amount of decomposition to BiOI and HI was determined by measuring the quantity of hydriodic acid produced a t the expiration of fixed times. The results were as follows :-Temperature = 36O-After 30 ininuteu' action . . 3 ) 60 7 7 7 7 * . a * 7 7 150 7 ) > 7 -. > 7 60 7 9 7 7 .' . * , 150 9 ' 7 ) - * Temperature 60-65". After 30 minutes' action . . Temperature = 100'. After 30 minutes' action . . 97 7 ) Y ) * * * )) 160 )) )) BIT prepared in the dry way. 17 * 5 p. c. decoinposed 19.8 7 ) 24 -4 > 7 22 -5 9 ) 26 *4 7 ) 22 -75 7 ) 35 *1 7 7 30 -7 7 7 27 *4 ) Y BIT prepared in the wet way. 17 -7 p. c. decomposed 19 *.2 97 23 *9 7 ) There is therefore no appreciable difference between the rate of decomposition by water of the two specimens of bismuth iodide. Bismuth Fluoride BiF (comp. Pattison Muir Hoffmeister and Robbs, Trans. 1881 39 33). Prejm-ation.-(l.) Moist freshly precipitated Bi,03,xH20 is added little by little to hot hydroflnoric acid in a platinum dish so long as the oxide dissolves fairly easily ; the liquid is evaporated to dryness at loo" and the residue is heated to bright redness in a closed platinum crucible.If the addition of bismuthous oxide to hydro-fluoric acid is continued until some remains undissolved or if the solution of the oxide in the acid is boiled for some time a considerabl AND BISMUTH FLUORIDE. 139 quantity of a double compound of bismuthyl fluoride and hydro-flnoric acid BiOP,BHP is produced :-Bi,Os + 6HF = 2(BiOP,2HF) + H,O. (2.) A fairly concentrated aqueous solution of potassium fluoride is added to bismuth nitrate dissolved in the minimum quantity of dilute nitric acid until the whole of the bismuth is precipitated. The precipitate is washed repeatedly with cold water and is then sus-pended in boiling water which is changed from time to time until no trace of potassium salt is to be found in the washings.This salt, after drying at loo" is pure bismuth fluoride BiF,. Bismuth fluoride is a heavy crystalline compound sp. gr. -5.32. It is unchanged on heating to fusion (about a full red heat). The salt is insoluble in water or alcohol; it does not react with sulphur when the two are heated together ; it is not changed by heat-ing in the mixture of nitrogen oxides produced by warming starch with nitric acid. Bismuth fluoride is the most stable of all bismuth haloid compounds. 20" -20" Preparation of Bismuthyl Fluoride BiOF. Moist freshly precipitated Biz03,xHz0 is added to hot hydrofluoric acid until all acid reaction has disappeared. The solid thus produced is washed with hot water dried at looo find afterwards heated to moderate redness in a closed platinum dish ; or the solid is suspended in boiling water which is changed from time to time until the wash-ings are perfectly neutral to litmus and the residue is then dried at 100". Bismuthyl fluoride is a heavy white crystalline powder; sp. gr. 2oo - - 7.5 whether prepared by removing all HF by long continued SO" washing or by heating. It is not changed by heating to moderate redness but if the temperature is raised to bright redness decom-position occurs. We are now engaged with an examination of the double compounds formed by the union of bismuth haloid salts with the haloid salts of the alkali metals ; the results we hope will throw some light on the questions suggested by the term moZecuZar com-pounds

ISSN:0368-1645    

DOI:10.1039/CT8885300137

出版商:RSC    

年代:1888

数据来源: RSC