12 Miscellaneous-Answers to Correspondents. sometimes sulphite and hyposulphite are present, but no sulphide. Premising this, I will now give the reactions of these salts with nitrate of silver under the conditions proposed by M. Lestelle. A solution of sulphite of soda with ammonia, when heated, and ammoniacal nitrate of silver added, gives, at first, no permanent precipitate; but in a few moments a grey precipitate of metallic silver appears. The change is thus represented NaO,SO2+ AgO,NO, NaO,NO¿+SO ̧+Aq. Hyposulphite of soda, when treated as above, gives no permanent precipitate, but in a short time, longer than in the case of sulphite, a brown coloration is visible, which, especially if more silver salt be added, rapidly accumulates until a deep black is produced. The subjoined equation shows this change NaO,S2O2+ AgO,NO,NaO,NO, +SO1+AgS. A mixture of a solution of sulphite and hyposulphite gives at once, under the same circumstances, a coloured precipitate, the greater part of which re-dissolves, but a black residue remains; and by continuing to add nitrate of silver, the whole quickly becomes quite black, and in appearance is not distinguishable from the precipitate produced in a solution containing sulphide only. The precipitate in this case is a mixture of sulphide of silver and metallic silver. A solution containing sulphide of sodium, sulphite, and hyposulphite of soda, gives at once a black precipitate of AgS, but after the decomposition of the whole of the sulphide of sodium, shown by the addition of acetate of lead to a portion of the solution. When more silver salt is added, the production of a dark brown precipitate, quickly becoming black, continues until the other salts are decomposed. It is evident, therefore, that M. Lestelle's process cannot yield accurate results. The method is not, indeed, applicable to the detection of a sulphide in such compounds. The best mode of determining the amount of sulphide in such cases is by means of carbonate of cadmium, as recommended some time ago by Werther in the Jour. fur Prakt. Chem. I am, &c. Gloucester Street, Dublin. J. W. KYNASTON, F.C.S. Analysis of Soap. To the Editor of the CHEMICAL NEWS. SIR,I have delayed addressing you again on the subject of the analysis of soap, in the hope of being able to make further experiments, and so render my remarks more correct; but business engagements, to my regret, prevent me, so I have thought it best to give the result of my experience, even though it be imperfect. In the first place, I would remark that nearly all, if not the whole, of the soap used in the domestic wash-tub con tains rosin. Nor can this addition of rosin to yellow soap be considered an adulteration, as I have noticed you to call it, in your generally good remarks upon new patents. If it is present in undue quantity, then I would call it an adulteration; and, in that case, the consumer would very soon complain of the soap wasting away too fast. On the Estimation of the Fatty Matter.-If the cake of fat, obtained by adding dilute sulphuric acid to a soap containing rosin (known as pale yellow, &c.), be weighed, the exterior surface being previously dried, it will give about 3 per cent. more fat than really is present, owing, I presume, to the rosin retaining a small quantity of water. So that, in estimating the fatty matter in all soap3 containing rosin, it is necessary to heat the fat obtained in order to expel the water before weighing. Whilst expelling the water, it is requisite to stir well to prevent any of the fat being blown away by smart little explosions, which take place so long as water is present, and the absence of which shows that the water is all evaporated, at which point it is CHEMICAL NEWS, better to stop, or some of the fatty matter may be driven off. 66 On the Estimation of the Water.-The water bath is an extremely tedious affair, and the results very unsatisfactory. I consider the method given by Mr. O'Neill, in his Dictionary of Calico-printing," preferable, if the soap be well stirred, of simply weighing out 100 grs., and heating in an evaporating basin, even until the soap begins to brown a little. It is, according to my experience, more correct than the old plan, and has the advantage of being done in a few minutes, and is very useful in affording a near approximation to the real amount of water present. On the Estimation of the Alkali.-This requires very delicate management to get correct results. There is about 6 per cent. of real soda in good hard soap. In estimating it directly by means of test acid, it is difficult to tell the precise moment when sufficient acid has been added. And it is evident that to be half per cent. wrong will make a very important difference. Also the presence of silicate and carbonate of soda, in very many of the cheaper soaps, will diminish very much the value of an estimation of the alkali in the ordinary manner. To me it appears that the real test of the value of a soap is, the amount of fatty matter it contains; the fat costing more than twenty times as much as the alkali. This important and most expensive article to the soap-boiler is the one that can be the most easily estimated, and that with certainty; for soaps containing no rosin (that is, curd soaps), in the manner usually described; and for yellow semi-transparent soaps containing rosin, with the addition of re-melting the cake of fat obtained, and driving off by heat the water held by the rosin. In conclusion, allow me to say, that I have offered no suggestions for the better estimation of the alkali, because I wish for further experience; and, in the meantime, I shall be glad to learn from any of your correspondents on the subject. I am, &c. TECHNOLOGIST. MISCELLANEOUS. Royal Institution-The following lectures will be delivered by Professor Frankland, F.R.S. :-On Tuesday, January 6, at 3 o'clock, on "Air and Water" (juvenile lecture). On Thursday, January 8, at 3 o'clock, on "Air and Water" (juvenile lecture). Royal Polytechnic Institution.-This Institution, still under the able and enterprising management of Mr. Pepper, opened for the holidays, as usual, on boxingnight. It seems somewhat derogatory to the Polytechnic highest and best sense it is a place of real entertainmentto class it among places of entertainment; but in the great amusement being blended with solid instruction. The new experiments introduced by Mr. Pepper in his "Strange Lecture" are of a most striking character; and the spectres in the scene of the "Haunted Man" have wonderfully substantial appearance. They must be seen The of the pantomine being excellently managed, and exceedingly diverting. Mr. Pepper, we think, may calculate on another very prosperous season. THE CHEMICAL NEWS. VOL. VII. No. 162.-January 10, 1863. THE DISCOVERY OF THE METAL THALLIUM. In another part of this Number, we print at length a translation of the report by M. Dumas on M. Lamy's latest observations on thallium. Our readers will hardly expect, interested as we are in this subject, that we should publish this report without comment. It will be seen that M. Dumas claims for M. Lamy the discovery of the metal thallium. M. Le Verrier had already made the same claim for M. Lamy in the journal La France for October 22, 1862; and, in reply to a letter of our own in answer to M. Le Verrier, published in the Cosmos for December 5, 1862, M. Lamy has since advanced the same claim for himself. Now, as M. Lamy states (Cosmos, December 19, 1862, p. 681) that it is "priority of publication which constitutes priority of invention," we are induced to give a short résume of dates in support of our own claim to the discovery-not only of the new element, but of its metallic character. Our readers will remember that it was in the CHEMICAL NEWs for March 30, 1861, we first announced "The Existence of a New Element, PROBABLY of the Sulphur Group." The word probably is here of some importance, as showing the doubts we had at the time of the exact nature of the new body-doubts which were further indicated in the title of our next paper-"Further Remarks on the SUPPOSED new Metalloid," in the CHEMICAL NEWS for May 18, 1861. Subsequent research soon proved to us that thallium was, in fact, a true metal, but the publication of this discovery was deferred. Lamy, in his letter to the Cosmos, has the hardihood to chemically by the jury; no one tested it; and yet M. assert, that Mr. Crookes" contented himself with exhibiting to the public and the international jury of Class II., as thallium, some centigrammes of a black powder which was not thallium." We shall make no remark on this assertion of M. Lamy; but, as some of our readers may be inclined to ask why the metal was not exhibited in the form of a button, we shall be excused for going into some detail. The source from which we extracted the metal, and the compounds exhibited, was sulphur from the Spanish pyrites mentioned in our paper of May 18, 1861. This sulphur contained no more than one or two grains of thallium in a pound. The metal and compounds we exhibited represented in all about twenty grains of the metal, and the difficulty of extracting this quantity from upwards of fifteen pounds weight of sulphur will be fully appreciated by all chemical readers, when we inform them that the whole of the sulphur had first to be dissolved in nitric acid. We may contrast this, in passing, with the source from which M. Lamy derived his metal, as described by M. Dumas,-namely, the residues of a sulphuric acid manufactory, "which contained thallium in tolerably large quantity, and in a form which made it easy to extract." Ignorant, at the time, of any richer source of thallium, and having in previous fusions of the precipitated metal discovered that it was rapidly volatilised and lost by oxidation, as described by M. Dumas, it was hardly likely that we should risk the loss of the whole of our small specimen for the sake of exhibiting it in a button; it was, therefore, placed in the Exhibition in the form of powder as precipitatel. We might refer to our laboratory note-book, which is open to inspection, to prove that we had obtained the metal and fused it in September, 1861; but as a note in a private book does not constitute a publication. we found no claim on this. Nor do we on the fact, that Mr. Williams saw the metal in our laboratory in January, 1862, as mentioned by him in the CHEMICAL NEWS, vol. v., p. 350. But it may be evidence that we were "aware of the metallic nature of thallium, and acquainted with the essential properties of the new body," to state, that early in April, 1862, we had the following labels printed by Silverlock (as can be proved by a reference to the books of that firm) for the metal and the salts at that time we had prepared : M. Lamy's claim for priority of publication, and, consequently, priority of discovery, as advanced by himself, is founded on a communication made to the Société Imperiale des Sciences, de l'Agriculture, et des Arts, of Lille, on May 16, 1862. On May 1, 1862, however, the International Exhibition opened, and there, in a case, deposited some days before, and open to the inspection of the numerous scientific men of all countries who were present on the occasion, was displayed several grains of the new body, with the following label-" Thallium, a New METALLIC Element, discovered by means of Spectrum Analysis." Besides this there was a card, on which was written" Chemical Reactions of Thallium, by which it is distinguished from every other known element. appears to have the character of A HEAVY METAL, forming compounds which are volatile below a red heat. It is reduced from its acid solutions by zinc in the form of a dense black powder, difficultly soluble in hydrochloric THALLIUM (@aλλos)-OXIDE OF THALLIUM-SULPHILE acid, readily soluble in nitric acid." The above, we OF THALLIUM-BASIC CHLORIDE OF THALLIUM-IODIDE contend, was a publication in the widest sense of the OF THALLIUM-SULPHATE OF THALLIUM-CHLORIDE OF word, and in this publication the metallic nature of THALLIUM-NITRATE OF THALLIUM-FERRO-CYANIDE of thallium was distinctly asserted. The metal, it is true, THALLIUM-CYANIDE OF THALLIUM-PHOSPHATE OF THAL was exhibited in powder, just as it was obtained by LIUM-CARBONATE OF THALLIUM-CHROMATE OF THALLIUM precipitation by means of zinc, but was none the less-THALLIUM, SUBLIMed—Oxalate of THALLIUM. the pure metal. It was there for the jury of chemists It is sufficient for us, however, that the metal, labelled to examine if they thought proper. It was not examined and described as a metal, was in the International It 14 Report on a Memoir of M. Lamy relating to Thallium. Exhibition, at its opening, on the 1st of May, 1862, to prove priority of publication to M. Lamy's communication made at Lille, on the 16th of May, 1862. The fact, that the metal was in the Exhibition, rendered it quite unnecessary for us to do what M. Dumas says we should have done after seeing M. Lamy's specimen. Our metal and two products, the peroxide and sulphide, had been in the Exhibition some time, with the descriptive cards we have quoted; and with regard to | M. Dumas' insinuation, that we borrowed from M. Lamy some, if not all, of the materials for the paper read before the Royal Society a few days after we met that gentleman, it may suffice to say, that, as M. Lamy only spoke French, a language we ourselves speak but imperfectly, it was not possible that either of us could have profited much by the interview. We have no wish to detract in the least from the great merit of M. Lamy's researches. We estimate as highly as any one the skill and industry with which he has worked out the compounds of thallium. But it must not be supposed, as M. Lamy seems to suppose, that we ourselves remained idle during the fourteen months which had elapsed since we remarked the green line in the spectrum. With the limited means at our disposal, and amid other pressing occupations, we had, and have since, been continually engaged in investigating the properties and compounds of the new metal; and all we need say to M. Lamy is, that we heartily congratulate him on his successes, and envy him nothing but his opportunities. SCIENTIFIC AND ANALYTICAL Report on a Memoir of M. Lamy relating to Thallium, AT the origin of human societies, the arts of procuring fire at will, of cultivating corn, and of extracting metals, were considered so great benefits that the inventors of these arts were ranked among the gods. At the present day, the metals are so numerous, that the discovery of a new simple body of this class is less astonishing to ordinary men, although the scientific interest attaching to the discovery has not at all diminished. So far from that, in proportion as new metals are pointed out, the characters which appertain to them throw, by comparison, a strong light on the characters, similar or opposite, which are found in the older metals. CHEMICAL NEWS, this report, could not have escaped the observation of either the one or the other. But, in our opinion, it is neither the process by which the new metal was recognised, nor the material which furnished it, that commends it to our notice. Spectrum analysis has completed its proofs, and manufacturing residues have long since been recognised as fruitful mines to explore. But thallium is destined to mark an epoch in the history of chemistry by the astonishing contrasts exhibited between its chemical characters and physical properties. It is no exaggeration to say, that, in regard to the classification generally accepted for the metals, thallium offers an assemblage of contradictory properties which entitles it to the name of a metallic paradox-the ornithorincus of metals. We shall not detain the attention of the Academy on the history of its discovery. No one disputes that Mr. Crookes first saw, on the 30th of March, 1861, the green line characteristic of thallium in certain selenium residues; that he recognised it again in the products of a specimen of sulphur from Lipari, and in those of a pyrites from Spain; and that he described and named thallium as a new simple body. Nor will any one dispute that M. Lamy was the first to isolate thallium, and establish, in the sequel, that it was not a metalloid analogous to selenium and tellurium, as Mr. Crookes, who had never obtained it free and pure, thought; but that it was, in fact, a true metal. M. Lamy announced his discovery to the Société Imperiale of Lille on the 16th of May, 1862, and on the roth of June he submitted to the jury of chemists in London, in the presence of Mr. Crookes, a beautiful ingot of thallium. If the latter gentleman considered that he had any rights to preserve, he should at once, as is usual in such cases, have taken the members of the jury to his laboratory, and exhibited his notes and his products, instead of silently listening to the communication of M. Lamy, and depositing at the Royal Society, eight days afterwards, a note indicating that he had long been aware of the metallic nature of thallium, and was acquainted with the essential properties of the new body. The historical point which engages us-for, in chemistry, the discovery of each new simple body has its legend or its history-is determined by two authentic dates: one of these is the 30th of March, 1861, on which day Mr. Crookes announces the existence of a new body which he believes to be non-metallic, characterised by the brilliant green line; the other is the 16th of May, As soon as the bold and felicitous labours of Bunsen 1862, the day on which M. Lamy makes known the and Kirchhoff had shown, beyond doubt, that, in study-metal as a metal, and who alone possesses it. ing natural products by spectrum analysis, it was possible to discover traces of metals which ordinary analysis was powerless to recognise, rubidium and cæsium were considered by all chemists as only the two first terms of a long series of new elements. Every one understood that the residues of manufactures, in which, by the elimination of known and useful products, were concentrated the inappreciable traces of useless and unknown substances that the matter originally worked sometimes contained, offered a mine worth exploring. It was, therefore, natural enough that Mr. Crookes in England, and M. Lamy in France, should submit to spectrum analysis the products of the combustion of iron pyrites, which for some years have played such an important part in replacing sulphur in the manufacture of sulphuric acid; and it is easy to understand, when one has seen it, that the beautiful green line produced in the spectrum by the new body which forms the subject of Comptes-Rendus, Iv., 865. It was in the sulphuric acid manufactory of our learned confrère, M. Kuhlmann, among the sediment of the leaden chambers fed by Belgian pyrites, that M. Lamy discovered thallium in tolerably large quantity, and in a form which made it easy to extract; for, by a little manipulation, it could be brought to the state of sulphate or chloride, from which combination the metal itself can be easily separated by means of zinc, which takes its place, and precipitates it in crystals, in the same manner as lead. importance which attaches, in cases of this kind, to posiThe Academy will permit us to draw attention to the tive characters, like those given by spectrum analysis. We shall see, as we proceed, that, beyond his certain conviction and natural penetration, a sure guide was necessary to M. Lamy, to prevent him from going astray in the first steps of the study. In fact, if the green line had not been there to prove incessantly that he was not dealing with lead or a plumbiferous alloy, CHEMICAL NEWS, Jan. 10, 1863. Report on a Memoir of M. Lamy relating to Thallium. how many chemical reasons were there for thinking that such was the fact! This metal, which is separated like lead from solutions of its salts by means of zinc, presents the appearance of lead. It has nearly the same colour as lead; is scratched and cut like it. It makes a streak on paper like that which lead produces; it has the same density, and very nearly the same melting point. It possesses the same specific heat. Its solutions are precipitated black by sulphuretted hydrogen, yellow by iodides and chromates, and white by chlorides, just as those of lead are. We do not then hesitate to assert, that, without the aid of spectrum analysis, this curious and important metal must have remained unrecognised; that, even with this help, it was easy to be mistaken; and that M. Lamy has given proofs of great sagacity, when he places, without hesitation, a metal so much resembling lead in its essential properties beside the alkali metals, potassium and sodium, which it resembles so little. Thallium is a perfect metal, endowed in the highest degree with a metallic lustre, as is seen on examining a freshly-cut surface, or on heating a bar strongly in hydrogen, and allowing it to cool in that gas. It is less blue than lead, less white than silver, and, in its colour, more resembles tin or aluminium than any other metal. It softens at 100° C., and, if kept for some time at that temperature, a crystalline structure becomes apparent in the ingot: this is shown by the appearance of a beautiful watering (moiré), produced when the metal is moistened with water, which cleanses the surface like acids. Before the blow-pipe, thallium exhibits some characteristic phenomena. It melts rapidly, and oxidises, giving off odourless fumes, of a whitish colour, but mixed with reddish or violet tones. It continues to give off the fumes a long time after the heating has ceased. When the principal globule has cooled, it is found to be surrounded with small globules of the volatilised metal. In a closed tube, it melts in the flame of a spirit-lamp, oxidises rapidly, giving an oxide which, when hot, calls to mind the appearance of rubies (metallic sulphides), and which, when cold, more resembles litharge: this is a compound of the protoxide of thallium with the silica of the glass. A globule of the metal, heated over a spirit-lamp in a bulb tube open at both ends, and inclined to facilitate the passage of air, soon melts, forming a layer of the ordinary brown fused oxide, but, at the same time, giving off abundant fumes, which condense a short distance from the bulb as a reddish or violet amorphous powder. When a globule of the metal is placed on a cupel heated to redness, and then plunged into oxygen, the metal burns brilliantly, and oxidises, the fused oxide sinking into the cupel. This oxide is either the peroxide of thallium, or a mixture of the proto- and peroxide of thallium. M. Lamy has discovered that thallium forms two oxides: the protoxide, a strongly alkaline base, like soda and potash; and the peroxide, which gives up oxygen when heated with strong acids, and may be converted into a chloride, which, when heated, gives up a part of its chlorine. Chemists, however, will notice, that the protoxide of thallium, which corresponds to potash, so far from having, like potash, a great affinity for water, loses its water readily when heated, or even when cold in a vacuum. There then remains the reddish anhydrons oxide, while the hydrated oxide is yellowish white: the oxide is hydrated or dehydrated with equal facility. It will be further remarked, that the peroxide of thallium, in the experiments of M. Lamy, has given no sign of the formation of oxygenated water. 15 Thallium burns in dry chlorine. It forms three chlorides, one of which corresponds to common salt, another to sesquichloride of iron, while the third is a bichloride corresponding to corrosive sublimate. The protochloride is white, fusible, slightly soluble, and, when prepared in the moist way, is precipitated in large dense flocculi like chloride of silver. Thallium can also form higher chlorides than the bichloride, but their composition is not definite. The proto-iodide and proto-bromide only have been studied; they resemble the corresponding compounds of lead. Cyanide of thallium is soluble; but a crystalline precipitate of this salt is formed when concentrated solutions of cyanide of potassium and of a salt of thallium are mixed. The sulphide of thallium obtained by precipitation is brownish black; it resembles sulphide of lead. In whatever way obtained, it easily oxidises in the air, and is converted into the soluble and colourless sulphate. Thallium is very slowly attacked by hydrochloric acid even when concentrated and boiling. It is, on the contrary, rapidly attacked by nitric and sulphuric acids. The latter, concentrated and hot, dissolves it with a rapidity which contrasts with the slowness with which the same acid attacks lead. In relation to the action of acids, thallium presents a complete opposition of characters to aluminium, the latter being quickly dissolved by hydrochloric acid, which does not attack the former, and resisting nitric acid, which easily dissolves thallium. In the state of protoxide, thallium forms soluble and crystallisable salts with carbonic, nitric, sulphuric, and phosphoric acids. The carbonate is a very characteristic salt. The salts formed by the protoxide of thallium with organic acids, which have been studied by M. Kuhlmann, jun., are the oxalate, binoxalate, tartrate, paratartrate, malate, citrate, formiate, acetate, and some others of less importance. All these salts are soluble, and, according to M. La Prevostaye, some of them are isomorphous with the corresponding salts of potash. Thallium, then, is a new metal well characterised. It is distinguished from all other reputed simple bodies by the beautiful green line it gives in the spectrum, and which corresponds to the line 1442 in the typical spectrum of Kirchhoff. From the examination of the solar spectrum, we may conclude that thallium does not exist in the solar atmosphere. Thallium undoubtedly forms one of the family of alkaline metals, the number of which has been doubled by recent discoveries. At the beginning of this century, only two of these metals were known, potassium and sodium. Forty years ago lithium was added to the number; and within the last three years three others have been discovered, rubidium, cæsium, and thallium, all three by spectrum analysis. From this we may be allowed to hope that the number of these metals, and of metals in general, is destined, by the application of this new method of analysis, to receive a rapid and considerable extension. Among alkaline metals, thallium occupies the opposito extremity of a scale of which lithium forms the first term, and the equivalent weights mark the different degrees. The weights are, in fact, as follows:— Lithium. Potassium Rubidium Cæsium. Thallium 16 On this point it has been remarked, On Tannate of Rosaniline 1. That the equivalent of sodium is exactly the mean of the equivalents of potassium and lithium, 39+7 2 =23; 2. That by adding double the weight of sodium to the weight of potassium, we obtain the weight of rubidium: 46+39 = 85; 3. That by adding twice the weight of sodium to twice the weight of potassium, we get nearly the weight of cæsium: 46+78 124; 4. That by adding double the weight of sodium to four times that of potassium, we obtain nearly the equivalent of thallium: 47+156 = =202. These considerations are of a nature to attract the attention of chemists; and without attributing to them a value that the actual numbers would not justify, they show the interest which attaches to the careful comparison of the equivalents of bodies belonging to the same family. The alkaline metals have this peculiarity, that to bring them under the law of Dulong and Petit-that is to say, to make their atomic heats equal the atomic heats of other metals,-it is necessary to halve their atomic weights. Thallium does not escape this rule. Its equivalent 204; but its specific heat, as determined by M. Regnault (who appends a note on this subject to this report), being equal to o'03355, it is necessary to reduce the atomic weight to 102. In the same way as potash has for its atomic formula K2O, the protoxide of thallium would have for its formula Tl,O.* (CHEMICAL NEWS, Jan. 10, 1863. is, at least, one of the least soluble in water among rosaniline salts. It is produced by adding a solution either of pure tannin or freshly prepared gall-nut to a watery solution of a neutral, or only slightly acid, rosaniline salt, especially if operating on a salt with an energetic mineral acid (sulphate, nitrate, hydrochlorate). When the salt of rosaniline is too acid, the larger part of the excess of acid should be neutralised by an alkaline carbonate. The insolubility of tannate of rosaniline can be utilised for the precipitation of this body, from solutions too weak to be evaporated or saturated with advantage by an alkaline neutral salt, with the view of precipitating the salt of rosaniline by this saturation. The physical properties of tannate of rosaniline vary according to whether it is precipitated by means of weak or concentrated, cold or hot solutions. By precipitating a salt of rosaniline from a hot and sufficiently concentrated watery solution, by a concentrated solution of tannin, tannate of rosaniline is obtained in the form of a pitchy, resinous mass, of a very dark redbrown tint. When the temperature is raised sufficiently high, the precipitate itself can even be entirely melted, in which case, the mother-waters can be decanted; but then they generally have an intense red colour, especially if excess of tannin has been employed in the precipitation. It would thus appear that there are several combinations of tannin with rosaniline, and that bi- and tri-tannate are more soluble than mono-tannate. The salt, melted and then solidified by cooling, sometimes presents, when dried, beautiful golden metallic reflections. The atomic volume of thallium will be equal to 8.5; By using cold and sufficiently diluted solutions, and and if we do not compare it with the volumes of by avoiding a notable excess of tannin, tannate of rosanisodium and potassium, it is because these present extra-line forms either a flaky or pulverulent precipitate, very ordinary anomalies which have not yet received sufficient attention from chemists. In conclusion, we may remark that the series of alkaline metals actually known contains a body which possesses so light an equivalent that it may be placed near to hydrogen-that is to say, lithium; and also a body, thallium, which has so heavy an equivalent that it may be ranked by the side of bismuth, a metal which possesses the highest of equivalents. We see that the discovery of new bodies extends the circle of our knowledge, not only by the facts with which they enrich practical science, but especially on account of the prospects revealed by the study of them, the laws they lead us to ascertain, and that freer and more general aspect under which we are taught to regard the properties of individual substances, their analogies, differences, and classification, and even their nature and essence. For these reasons, and taking into consideration the difficulties overcome by the author, the clearness and importance of his results, we have the honour to propose to the Academy that his memoir form part of the "Recueil des Savants Etrangers." TECHNICAL CHEMISTRY. On Tannate of Rosaniline, by M. E. KOPP. ONE of the most interesting combinations of rosaniline, and one which plays an important part in the application of this beautiful colouring matter, is that which it forms with tannin and gall nut or quercitannic acid. Tannate of rosaniline, if not the most insoluble salt. * M. Dumas persists in using the symb 1" Th," which we have already shown has been adopted for Thorinum. divided, and of a magnificent carmine-red colour, rivalling the carmine of cochineal. It should then be washed, and dried with gentle heat. The mother-waters are often quite colourless. To obtain a precipitate charged as much as possible with rosaniline, it must be shaken with fresh solutions of aniline red, previously sufficiently purified, until these become colourless, or the shade of the precipitate deepens. Tannate of rosaniline, when heated, becomes darker, and assumes a violet tinge; by raising the temperature, it becomes brown, and then decomposes. In alcohol, wood-spirit, and acetic acid, it dissolves with an extremely dark carmine-red colour. Energetic acids change the red tint to orange-yellow, and the material is dissolved. By the addition of water the red tint is restored, but verging a little to violet. The whole often seems to remain in solution, but alter a certain time a new precipitate of tannate of rosaniline, more or less violet-red, is formed; nevertheless, the liquids generally remain red, sometimes intensely so, especially if the tannate has been strongly saturated with rosaniline. Tannate of rosaniline decomposes and loses its colour under the influence of energetic caustic alkalies. The mixture assumes a tarnished and dirty colour after the alteration of the tannin by atmospheric oxygen in presence of the alkali. In moraanting or printing tissues with tannin, whether pure or associated with metallic salts or other organic substances, and then tinting them in a bath of aniline red, it is during the formation of tannate of rosaniline that the printing becomes apparent, and fixation takes place. This salt will serve directly in printing tissues, on account of its solubility in acetic acid. The acetic solution being sufficiently thickened (by gum arabic, traga |