278 XXV.-Chenzical Inves figation of Wackenroder’s Solution and Explanation of the Formation of its Constituents. By Professor H. DEBUS Ph.D. F.R.S. C 0 “YEN T S . PAGE Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 A. Preparation of Wackenroder’s Solution . . . . . . . . . . . . . . . . . . . . . . . . . 281 Composition of . . ,. 282 A New Allotropic Modification of Sulphur . . . . . . . . . . . . . . . . . . . . . 282-286 Potassic Pentathionate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 7 . . . . . 299 Zinc Cupric 300 Potassic Hexathionate . . . . . . . . . . . . . . . . I. . . . . . . . . . . . . . . . . . . . . . 302 (a) Potassic Pentathionate .. . . . . . . . . . . . . . . . . . . . . . . . 311 (6.) Tetrathionate 311 (c.) Trithionate . 313 Action of Acids . . . . . . . . . . ,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316 Spontaneous Decomposition of Wackenroder’s Solution . . . . . . . . . . . . . . 317 Discussion of the Changes of Polythionates in Aqueous Sohitions . . . . . . 319 Explanation of two Properties of Ozone . . . . . . . . . . . . . . . . . . . . . . . . . . 324 , of the Spontaneous Decomposition of Peroxide of Hydrogen 326 Action of Sulphuretted Hydrogen on Polythionates. . . . . . . . . . . . . . . . . 328 Action of Sulphurous Acid on Polytliioriates . . . . . . . . . . . . . . . . . . . 331 Influence of Time on the Formation of Yentathionic Acid .. . . . . . 336 Sulphurous Acid and Potassic Thioeulphate . . . . . . . . . . . . . . . . . . . . . . . . 343 Sulphurous Acid and Chloride of Sulphur . . . . . . . . . . . . . . . . . . . . . 345 Sulphurous Acid and Sulphur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 Explanation of the Formation of the Polythionates . . . . . . . . . . . . 348 C. The Formulae of the Polythionates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351 7 7 7 9 . . . . . . . . B. Decomposition of an Aqueous Solution of-,, ,, Introduction. THE milky liquid produced by the action of sulphuretted hydrogen on an aqueous solut’ion of sulphurous acid contains according to Wackenroder and other chemists besides free sulphur a peculiar acid called pentathionic acid.This acid cannot be separated from its solution by distillation or crystallisation and consequently has not yet been prepared in a pure state. Ludwig could not produce pentathio-nates but in place of these he obtained bodies having the composition of double salts of tetra- and penta-thionic acids. Wackenroder Kessler, and Spring failed like Ludwig in their endeavours t o produce penta-thinnates from Wackenroder’s solution. These unsuccessful experiments together with some positive indi CHEMICAL INVESTIGATION OF WACKENRODER’S SOLUTION. 2 7 9 cations which need not be considered in this place caused Spring to come to the following conclusions :-1. The so-called pentathionic acid is identical with tetrathionic acid.2. The reactions which are described as characteristic of penta-thionic acid are also produced by ammonic tetrathionate. 3. Pentathionic acid is a solution of sulphur in tetrathionic acid, not in atomic proportions but of the same description as the solution of sulphur in carbon disulphide. A salt prepared by Lenoir before the publication of Spring’s researches by adding baric carbonate to a Wackenroder solution has very nearly the composition of baric pentathionate. This salt is, according to Spring a mixture of sulphur and baric tetrathionate I do not think that Lenoir who is known to me as a careful worker, would ana#lyse such a mixture and describe it as a pure compound. But if the substance is not a mixture of baric tetrathionate and snl-phur then it must be baric pentathionate or a mixture of various polythionates of the average composition of a pentathionate.In order to test the correctness of Spring’s views I suggested to Mr. Lewes Assistant in the Laboratory of the Royal Naval College, some experiments on the preparation of salts of pentathionic acid. He carried out these experimentas with much perseverance and skill, and succeeded in preparing nearly pure potassic and baric penta-thionates. Shaw has repeated some of the experiments of Lewes and con-firmed his results. Lewes however could not recrystallise his penta-thionates they decomposed into sulphur and tetrathionates. This decomposition is regarded by Spring as a posit’ive proof that the salts obtained by Lewes are mixtures of tetrathionates and sulphur.Although I did not doubt the interpretation of Lewes a thorough investigation of the subject appeared to me to be desirable from more than one point of view. It was desirable to prepare pure penta-thionates a,nd t o examine some reactions of the polythionates of more than ordinary interest. The compounds usually called acids like sulphuric acid H2S04 are regarded in this papel. as hydrogen salts and the name of acid is reserved for the so-called anhydrides. Therefore the dioxide of sulphur SOo is called sulphurous acid and the compound with water, H2S03 is called hydric sulphite. Hydrogen plays in such compounds the part of a metal. Polythionates are bodies represented by the formulae MoS306 MoSd06 ;?iT2S506. arid M2S606 in which “ M ” stands for hydrogen or a monovalent metal.Wackenroder’s solution is the liquid obtained by the passage of Correct expression also promotes correct thinking. u 280 ISEBUS CHEXICAL INVESTIGATIOS OF sulphuretted hydrogen through an aqueous solution of sulphurous a,cid until the latter is completely decomposed. 1 will before describing my own experiments give a list of the papers which have hitherto been published on pentathionic acid and pentathionates. 1. PIessy “ On some New Acids of Sulpliur produced by the Action of Sulphur Chloride on Sulphurous Acid ” (Compt. rend. 21, 473 ; Ann. Chim. Phys. 20 162 ; Berzelius Jahresbericht 26, 72; 28 24). 2. Th. Thomson “ A New Acid obtained by the Action of Sul-phuretted Hydrogen on Sulphurous Acid ” (Ann. Phil. 12, 4.41).3. Wackenroder “ On Pentathionic Acid ” (Archiv der Pharmacie, 48 272 140 ; Berzslius Jahresbericht 27 36). 4. Lenoir “ On Baric Pentathionate ” (Annalen der Chernie und Pharmacie 62 253 ; Berzelius Jahresbericht 28 21). 5. Ludwig “ On Potassic and Baric Tetrapentathionate ” (A?-chiu der Pharmacie 51 259 ; Berzelius Jahresbeyicht 28 108). 6. Fordos and GAlis “ Action of Sulphur Chlorides on Sulphurous Acid ” (Ann. Chim. Phys. 22 66 ; 28 451 ; Berzelius Jahres-bericht 29 13). 7. Kessler “ On Polythionates ’’ (Poggendorf Ann. 74 249 ; Ber-zelius Jahresbericht 29 15). 8. Sobrero and Selmi ‘i On the Action of Sulphuretted Hydrogen on Sulphurous Acid ” (Ann. Chim. Phys. 28 210 ; Liebig’s Jahresbericht 3 264). 9. Risler-Bennet “ Formation of Pentathionic Acid by the Action of Zinc on Sulphurous Acid ” (Poggendorf Ann.116 470). 10. Chancel et Diacon “ Conversion of Penta- into Tetra-thionic Acid” (Compt. rend. 56 710). 11. Rammelsberg “ Potassic Pentathionate ” (Liebig’s Juliresbericht, 12. W. Spring “Contributions to our Knowledge of the Poly-thionic Acids ” (Berichte der deutschen chemischen Gesellschatit, 6 1108). “ On the Non-existence of Pentathionic Acid ” Liebig’s Annalen 199 97 ; 213 329). 10 136). 13. Sting1 and Morawski (Liebig’s Jahresbericht (1879) 11 10). 14. Takamatsu and Smith “ On Pentathionic Acid ” (Journal of the Chemical Society 37 552 ; 41 162). 15. Lewes V. “ On Pentathionic Acid ” (Journal of the Chemical Society 39 68 ; 41 300). 16. Curtius ‘‘ Experiments with the so-called Pentathionic Acid ” (Jour.prukt. Cheinie [2] 24 225) WACKENRODER'S SOLUTION. 281 17. Shaw " On the Preparation of Pentathionates" (Journal of the Chemical Society 43 351). 18. Smith " Note on Pentathionic Acid " (Journal of the Chemical Society 43 355). 19. Snlzer " On a New Mode of Formation of the so-called Penta-t'hionic Acid (Rerichte der deutschen cheinischen Gesellscltait (1886) 1696). A. COMPOSITION OF WACKENRODER'S SOLUTION. I. Preparation. A slow current of sulphuretted hydrogen is passed for two hours through 480 C.C. of a nearly saturated solution of sulphurous acid a t a few degrees above 0" C. The liquid which must still contain a large excess of sulphurous acid is now kept for 48 hours in a closed bottle a t common temperatures. The operation is then repeated a current of hydric sulphide is again passed for two hours and the liquid allowed to remain a t rest for two days.The treatment in this manner is continued till all the sulphurous acid is decomposed ; about two weeks are necessary for the accom-plishment of this purpose. Certain precautions have to be observed if the end of the operation is to be recognised by the disappearance of the odour of the sulphurous acid. If the current of hydric sul-phide is discontinued as soon as the liquid ceases to smell of sulphu-rous acid and the bott'le is then taken out of the cold water by which it is surrounded and is allowed to stand for a few hours at common temperatures the liquid will again assume an intense odour like sul-phurous acid. The treatment with sixlphuretted hydrogen must then be repeated and is only regarded as complete when after standing for several holm at common temperatures the solution no longer smells like sulphurous acid.The liquid so prepared is of milky appearance and contains a large precipitate of sulphur which is separated by filtration. The filtrate is however not clear and cannot be obtained clear by filtration because it contains in suspension a con-sidcrable quantity of sulphur in very small particles which will pass .through the best Swedish filtering-paper. In a bottle of about an inch in diameter i t appears semi-transparent i n transmitted light of a reddish-brown colour becoming more transparent on warming and more opaque on cooling. Our problem now will be t o determine the composition of this liquid.We shall have to separate the substances contained in the soli-rtion and ascertain their nature and after completing thia t,ask we shall have to explain their formation from the original material N-ater, sulphurous acid and sulphuretted hydrogen 282 DEBUS CHEMICAL INVESTIGATION OF The experiments described in this paper prove that Wackenroder’s solution contains the following substances :-a. Small drops of sulphur in suspension. b. Sulphur in sohition in the colloidal condition similar to silica dissolved in diluted hydric chloride. Sulphur in this condition forms a new hitherto unrecognised allotropic modification. c. Hydric sulphate. d. Traces of hydric trithionate. e. Hydric tetrathionate. f. Hydric pentathionate.g. A polythionate with more sulphur than a pentathionate probably hydric hexathionate. 11. Examination of the Sulphur which separates as a Precipitate during the Passage of Sulphuretted Eydrogen through the Solution oj. Xu lphurous Acid. The greater mass of this sulphur is of a soft gummy nature and forms with water an emulsion in which drops of sulphur can be seen under the microscope. A portion of it is however present in the ordinary modifications in hard brittle particles and mixed with these are observed elastic membranes. The latter were probably formed by adhesion of liquid sulphur to the sides of the vessel and gradual hardening of the layer into a mass like caoutchouc. The emulsion formed by the soft plastic portion with water cannot be rendered clear by filtration.If it is diluted with much water a brown-yellow semi-transparent liqnid is obtained from which a solution of saltpetre throws down a copious precipitate of sulphur. 111. Examiitation of the Jiltered Wackenroder Solution. The milky fluid does not become clear even after standing two or three weeks in a quiet place. A drop observed under the microscope appears homogeneous but after about five minutes a riiig of yellow particles appears round the edge of the drop and grows by degrees towards the centre. This deposit is seen to be composed of minute dyops of sulphur. The quantity so separating is evidently much larger than the amount in suspension consequently a precipitation of dissolved sulphur has taken place. The addition of a little water causes this precipitated sulphur to dissolve.The filtered Wacken-roder solution contains rather large quantities of sulphur in simple .solution as colloidal sulphur in a new allotropic modification which I will distinguish as “ 6 ” sulphur. The solution of &-sulphur resembles the solution of silica in dilute hydric chloride. A drop o WACKENRODER’S SOLUTION. 283 the Wackenroder solution left on a piece of glass evaporates and dissolved sulphur corresponding to the amount of evaporation, separates in the liquid state. A larger portion of the Wackenroder solution was now evaporated under the receiver of an air-pump over pieces of potassic hydroxide. Considerable quantities of sulphur in a viscous semi-fluid condition, separated as the solution became more concentrated.The surface of the evaporating liquid looked as if a layer of oil was floating on it, and at the sides of the basin a yellow shining coating like varnish was observed. The liquid beca,me clear and transparent in layers of 2+ inches in thickness after about 8 of it had evaporated and appeared slightly opalescent like a solution of a,lbumin. In this condition, however it still contains much 8-sulphur in solution because further evaporation addition of hydric chloride sodic chloride baric chloride, saltpetre cupric sulphate and other salts respectively cause the pre-cipitation of considerable quantities of sulphur. The same effect but in less degree is likewise observed when the concentrated solution is kept in a closed bottle in a dark place. The second port’ion was mixed with twice its volume of water and the third with twice its volume of an aqueous solution of sulphurous acid.After standing 21 days a deposit of sulphur in each of the three portions had taken place. The smallest deposit was in the second and the largest in the third. Water retards sulphurous acid accelerates the precipitation of 6-sulphur. A Wackenroder solution was saturated with sulphurous acid and allowed to remain in a closed bottle for a few days. It became perfectly clear both the suspended and the dissolved &,sulphur falling down as a precipitate. Experiments were now made to separate from Wackenroder’s solution which had been so far concentrated as to appear clear and transparent in layers of 2 inches in thickness the dissolved 8-sulphur by means of diffusion and thus to obtain a pure aqueous solution of sulphur.A porous cell like those used in galvanic batteries was immersed for a few days in dilute hydric chloride in order to remove alkalis and other soluble substances and then well washed with water. Wackenroder’s solution was placed in this cell and the latter in a large vessel containing water. The acid of the solution rapidly diffused through the porous clay but the coagulation of the sulphur began and was completed before all the acid had diffused. A second ex-periment made in the same manner as well as a third made with parchment paper failed in the same way. The sulphur which had separated during the evaporation of the About 100 C.C. were divided into three equal portions 284 DEBUS CHEMICAL INVESTIGATION OF filtered Wackenroder solution was collected on a 6lter.The particles united in the course of the night into one semi-transparent lump of the appearance of wax and of a gummy sticky nature. I n another experiment the sulphur separated in a more fluid condition. The filter on which it had been collected was placed upon blotting-paper. Some of the sulphur like oil was absorbed by the paper after the evaporation of the water. A little of this sulphur was mixed with some clear Wackenroder solution and a drop of the mixture placed under the microscope. The sulphur was partly seen in minute trans-parent drops and partly in irregularly formed masses rounded off a t the edges. The remaining sulphur on the filter could not be purified by washing with water.Much of it passed with the water through the filter and farmed an emulsion resembling the original Wacken-roder solution ; only drops of sulphur could be seen in this emulsion under the microscope and after a few hours a sediment of drops separated. A portion of the emulsion was allowed to remain in a bottle a t rest from June to December It was still of the nature of an emulsion a precipitate could be observed but the liquid above this precipitate was not clear. Carbon disulphide benzene ether olive oil chloroform or tannin did not clear the liquid but powder of charcoal baric carbonate alkalis a concentrated solution of hydric chloride hydric nitrate and potassic nitrate caused complete precipitation of the sulphur in sus-pension and solution.Addition of much water caused the emulsion to become almost clear ; at least in layers of an inch in thickness it appeared perfectly clear transparent and slightly yellow. Solution of saltpetre produced in this diluted clear liquid a copious precipitate of sulphur. The drops of sulphur i n suspension in the emulsion appear therefore to be soluble in much water. Another portion of the said emulsion was allowed to evaporate under the exhausted receiver of an air-pump over hydric sulphate. The sulphur remained as a thin elastic membrane resembling caoutchouc. This membrane did not again form an emulsion with water neither did alcohol appear to produce any effect on it but carbon disulphide dissolved a portion and took away its elasticicy.Some suiphur which had separated during the evaporation of Wackenroder’s solution over potassic hydroxide in the exhausted receiver of an air pump and which mas of the same plastic gummy nature as the sulphur described above was placed in some water, in which it dissolved forming a turbid solution. The dissolved portion was reprecipitated by addition of sodic chloride then filtered, and the filtering-paper with the precipitate placed on blotting-paper ; the adherent aqueous solution passed into the paper and the remain-ing sulphur was then mixed with water with which it formed a WACKENRODER’S SOLUTION. 285 emulsion and from this was again precipitated by a solution of common salt. The sediment was again collected on and pressed between layers of bibulous paper and after these operations put in water in which a portion of it dissolved.After two or three filtrations an almost clear opalescent liquid similar to a solution of albumin was obtained. The filtrate became quite clear on warming and more turbid on cooling. Red and blue litmus-papers were not affected by it. A piece of bright silver foil immersed in it turned black by degrees. Sodic chloride hgdric chloride alkalis saltpetre and baric carbonate res-pectively caused the formation of a precipitate of sulphur. The same effect was produced by recently precipitated baric sulphate. Ammonia produced no change. Some of the filtrate evaporated on a watch-glass left a viscous transparent residue. I conclude from these experiments that a great part of the sulphur which separates during the evspora-tion of a Wackenroder solution is soluble in much water or more correctly in water which conhains a little acid or a very little common salt.We are now able to explain why a Wackenrader solution which contains sulphur in minute drops in Suspension and possesses the character of an emulsion will not become clear even if it is allowed t o stand for months in a closed bottle in a quiet place. We prepare emulsions by mixing intimately oil with gum albumin or other colloids and water. The minute drops of oil are prevented by the colloi’d from uniting and separating as a layer on the surface of the water. A colloyd cannot diffuse through a membrane formed of another colloid perhaps because the molecules are too large and sluggish in their motions.In the case of an ordinary emulsion the large sluggish molecules of the collojid place themselves between the drops of oil impede their motion and thus prevent their union. Now the sulphur which is in solution in the Wackenroder liquid acts like a colloid as gum or albnmin in an ordinary emulsion and prevents the union of the minute drops of sulphur which are in suspension in the liquid. The Wackenroder solutiofi loses the character of an emulsion as soon as the dissolved sulphur is removed. Sulphur separates as a precipitate if Wackenroder’s solution is kept for some time or if it is evaporated. But however the separa-tion is effected the precipitated sulphur is far less soluble than it mas before its coagulation. In the beginning of the evaporation when the liquid is less acid the sulphur fieparates in a more liquid and soluble condition whereas later on when the Wackenroder solution becomes more concentrated the precipitated sulphur is harder and more brittJe in fact is made up in a great measure of the ordinwy modifications.Also the temperature of evaporation has an influenc 286 DEBITS CHEMICAL INVESTIGATION OF on the condition of the sulphur. At lower temperatures a larger proportion of liquid soluble sulphur is separated than at higher temperatures. It will be understood from these remarks that the sulphur which separates during evaporation from a Wackenroder solution is a mixture of different modifications. Besides 8-sulphur7 which forms an emulsion and dissolves in much wgter it contains ordinary sulphur, for if it is treated with alcohol &sulphur is dissolved and the remain-ing portion contains small rhombic octahedra.On the other hand, bisulphide of carbon will extract octahedral sulphur and leave the amorphous behind. It appears according to my observations that 8-sulphur if kept very long becomes gradually converted into hard brittle sulphur. However? I have made no special experiments on this point. The properties of soluble collo’idal sulphur suggest the following method for its preparation. A current of sulphuretted hydrogen is passed through not more than 120 C.C. of an aqueous solution of sulphurous acid a t a few degrees above 0” C. until all the sulphurous acid is decomposed. The liquid is then filtered and concentrated over pieces of potassic hydroxide in the exhausted receiver of an sir-pump.The evaporation is stopped as soon as the liquid commences to become clear and the precipitated sulphur is collected on a filt,er. If we take a retrospective view of the properties of the sulphur as it is contained in solution in Wackenroder’s liquid and can be ob-tained from it by partial evaporation we find that it possesses all the properties which Graham* describes as characteristic of the collo’ids. The sulphur dissolved in Wnckenroder’s solution does not diffuse through porous clay or parchment. It is held in solution by very feeble force. Slow and gradual separation takes place when its solutions are kept for some time or complete precipitation if appa-rently inert substances such as sodic chloride charcoal powder or baric sulphate are added.The unstable condition of its molecules, their slow change into other modifications and finally its gummy, sticky condition remind one of the colloids. Sulphur can com-bine with hydric tetrathionate and form hydric pentathionate and although large quantities of both sulphur and hydric tetrathionate are in Wackenroder’s solution they do not combine but seem to be inert towards each other. All this points to the coiiclusion that we have to deal with a new allotropic modification of sulphur. The chemical powers are likewise very feeble. * Chemical and Physical aesearches. Collected by James Young pp. 593-596 WACKENRODER’S SOLUTION 287 Wnckenroder’s solution can be concentrated on a water-bath with-out decomposition until it reaches the sp.gr. 1.32. The &sulphur is all coagulated before it reaches this point of concentration. Further evaporation on the water-bath causes evolution of sulphurous acid and precipitation of sulphur. In a partial vacuum over pieces of potassic hydroxide at common temperatures I have concentrated i t to the sp. gr. 1.46 without decomposition. In this concentrated con-dition it is usually described in the text-books as pentathionic acid, H2S506. A small quantity which had been left for some time under a bell-jar over pieces of potassic hydroxide had evaporated to dryness. The dry residue was amorphous and intermixed with crystals. A few drops of water dissolved the amorphous portion and left beautiful small octahedral crystals of sulphur.The aqueous solution showed the reactions of a pentathionate. From this observation it seems to follow that hydric pentathionate can exist in the solid form. Wackenroder’s solution of the sp. gr. 1.46 is a colourless transparent oily liquid of great refractive power and intensely acid. It destroys the coherence of the fibres of filtering-paper and cau only be filtered when of lower sp. gr. than 1.4. A sample of 1.3 sp. gr. I have kept in a closed bottle in a dark place for three months without apparent change then a slow decom-position set in with evolution of sulphurous acid aiid precipitation of sulphur a decomposition which was not completed in two years. Wackenroder’s solution is apparently for two reasons described in the text-books as hydric pentathionate :-1.Kessler described three rea’ctions of this liquid which hydric tri-and tetra-thionate do not give; and-2. He found that the acid of the solution contained sulphur and oxygen in the ratio of 5 5. Before I repeated the analysis of Wackenroder’s solution I first investigated Kessler’s analytical method. This chemist found that pot’assic tctrathionate and mercuric cyanide decompose at loo” as represented by the following equations :-(See Potassic Pentathionate.) HgCy2 + K2s406 = 2KCy + HgS406 and HgS,O + 2HzO + 2KCy = HgS + S + 2KHSOa + 2HCy. If instead of potassic tetrathionate a Wackenroder solution is taken, the same products of decomposition are obtained only with this difference that in place of potassic hydric sulphate we have hydric sulphate and in the precipitate instead of 1 atom of mercury and 2 of sulphur 1 atom of the metal and 3 of sulphur.From these results the conclusion has been drawn that Wacken-roder’s solution contains an acid similar to tetrathionic acid with 5 atoms of sulphur in 1 molecule 288 DEBUS CHENICAL INVESTIGATION OF Takamatsu and Smith and also Lewes have confirmed the above results of Kessler. It is however desirable to test Kessler's method with a pure pentathionate which hitherto has not been done. Pot'assic pentathionate should be decomposed according to the fol-lowing equation :-I f therefore the amount of sulphate in solution and the quantity of mercury and sulphur in the precipitate be determined from the numbers so obtained the composition of the pentathionate can be cnl culat ed .The preparation of potassic pentathionate will be described in another part of this paper. A sample of very pure salt was employed in the experiments. The mercuric cyanide was bought as pure in the market. Afterwards whilst using it I discovered the presence of mercuric chloride in it. The error caused by this impurity was duly corrected. 0.703 gram crystallised potassic pentathionate was boiled with a solution of mercuric cyanide. 0.773 gram of a black precipitate was produced. 0.677 gram of the latter yielded on treatment with bromine-water 0.118 gram of pure sulphur and on addition of baric chloride to the filtrate from the sulphur 0.311 gram of bnric sulphate. The filtrate from the baric sulphate gave with hydric sulphide 0.547 gram of mercuric sulpliide.The filtrate from tlie precipitate produced with mercuric cyanide at loo" gave with baric chloride 0.917 gram of baric sulphate. According to these numbers we obtain for the composition of the black precipitate caused by mercuric cyanide-Sulphur 0.183 Mercury. 0.538 Chlorine 0.052 0.773 -The difference obtained by the subtraction of the weights of the sulphur and mercury from the weight of the precipitate represents the weight of the chlorine which was present in combination with mercury and sulphur as mercuric sulphochloride. Mercury 0.392 Sulphur. . 0.183 Mercuric chloride 0.198 G.773 -The amount of sulphuric acid corresponding to 0.917 gram of baric sulphate contains the rest of the sulphur and all the oxygen o WBCRENRODER’S SOLUTION.289 the potassic pentathionate. Adding this amount 0.315 gram to the above mercury and sulphur we obtain the weight of the mercuyic pentathionate corresponding to the weight of potassic pentathionate taken = 0.890 gmm. Replacing the mercury 0.592 gram by its equivalent of potassium 0.152 gram we obtain 0.650 gram of potassic pentathionate which would combine with 0.0525 gram of water forming 0.7025 gram of the crystallised salt instead of 0.703 gram the amount actually taken. In 100 parts we have-Calcnlated according to Found. zK2S506 + 3H20. Sulphur. . 44.01 44-32 Potassium 21.65 81.60 Water . 7.48 Oxygen 26.92 26-59 99-99 The calculated composition of the potassic pentathionate has been proved to be correct by other methods which will be described in another part of this paper ; Kessler’s method therefore yields accu-rate results.A sample of Wackenroder’s solution of the sp. gr. 1.46 was diluted with four times its volume of water and the clear slightly yellow liquid used in the following experiments :-I. Determination of Dissolved Xulyhur. 10 C.C. mixed with solution of saltpetre gave 0.005 gram of sul-phur. 11. Determination of Hydric Xdpha fe. 10 C.C. gave with baric chloride 0.243 gram of baric sulphate. 111. DetermiRation of the Xulphur and Oxygen of the Polythionates. 10 C.C. boiled with mercuric cyanide which contained also a little chloride gave 2.875 grams of mercuric sulphochloride and sulphur. The filtrate gave with baric chloride 3.882 grams of baric sulphate.Subtracting the baric sulphate found previously (11) we have f o r the remaining weight 3.639 grams corresponding to 0.499 gram of sulphur and 0.750 gram of oxygen as derived from the polythionates of the Wackenroder solution. 0.868 gram of the mercuric sulpho-chloride and sulphur precipitate treated with bromine-water gave 0.024 gram of sulphur and the Gltrateon addition of baric chloride gave 1.430 gram of bai-ic sulphate. The filtrate from the bnric sulphat 290 DEBUS CHENICAL INVESTIGATION OF yielded with hydric sulpbide 0.694 gram of mercuric sulphicle. 0.997 gram of the mercuric sulphochloride and sulphur precipitate burnt with plumbic chromate and metallic copper iii the front part of the tube gave 0.683 gram mercury but no water or carbonic acid, According to these data 2.875 grams of precipitate composed of mercuric sulphochloride and sulphur contain after the subtraction of the mercuric chloride and the sulphur which existed in Wackenroder’s solution free and was precipitated by saltpetre (I) 0.724 gram o€ sulphur and 1.494 gram of mercury.If the sulphur of this precipi-tate 0.724 gram is added to the sulpliur of the sulphuric acid pro-duced by boiling with mercuric cyanide 0-499 gram we obtain the sulphur of the polythionates = 1.223 gram and if we add to this sulphur the oxygen of the polythionates 0.750 gram present in the sulphate obtained by boiling with mercuric cyanide and the hydrogen equivalent to 1.494 gram of mercury me obtain the composition of the polythionates of Wackenroder’s solution-Sulphur 1.223 Oxygen 0.750 Hydrogen 0.015 -1.988 Or in 100 parts-Sulphur .Oxygen . Hydrogen . And the atomic mtio-H From these experiments, Calculated. Found. H,S,O,. . 61.52 62.01 . 37.72 37-21 . 0.75 0.77 99.99 99-99 s = 2 5-12 it seeins to follow that Wackenroder’s liquid is really a solution of pentathionic acid and aa Kessier Taka-matsu and Smith and Lewes obtained nearly the same numbers, the probability of this conclusion is thereby increased. I f a substance is obtained under different conditions and a t different times of the Same quantitative composition it is probably a pure compound. Nevertheless another interpretation may be given to the analytical results. Wackenroder’s solution may be a mixture of an equal num-ber of molecules of tetrathionic acid and the unknown hexathionic and if it has this composition it would if analysed by Kessler‘ WACKENRODER’S SOLUTION.291 method yield numbers agreeing with the composition of pentathionic acid. In order to ascertain which of these two interpretations is correct I prepared and examined some of the salts which can be formed by the acid or acids of Wackenroder’s solution with metals, Potassic Pentathionate. Kessler attempted the preparation of this salt but obtained only a mixture of tetrathionate and sulphur. Ludwig divided a Wacken-roder solution into two equal parts neutralised one part with potassic carbonate and added the other part. The solution gave on evapora-tion crystals of the composition K4S9012,H20 which Ludwig regarded as a compound of potassic tetrathionate and pentathionate.Rammels-berg measured the crystals of a salt which he called potassic penta-thionnte but as the mode of preparation the properties and the analysis are not described it remains doubtful whether the salt was a penta- or tetra-thionate. The first chemist who prepared nearly pure potassic pentathionate was Lewes. He added by degrees to a portion of Wackenroder’s solution about half the quantity of potassic hydroxide which would be required for its complete neutralisation. Sulphur was precipitated during this operation and the filtrate from the precipitate gave, by spontaneous evaporation crystals of hydrated potassic penta-thionate. The following experiments were made with a Wackenroder liquid of 1.19 sp.gr. of which 5 C.C. required for neutralisation 8.2 C.C. of a solution containing 13.8 per cent. of potassic hydroxide. The solu-tion of potassic hydroxide was added drop by drop with constant stirring to 25 C.C. of Wackenroder’s liquid until the acid was nearly neu tralised. Much sulphur was precipitated and some sulphurous acid produced. The liquid which was still acid was filtered and allowed to evaporate spontaneously. Sulphur separated again whilst the exaporation proceeded and had to be removed two or three times. At last crystals not of potassic pentathionate but of potassic tri-thionate were formed. This negative result seeins to show that the pentathionic acid of the Wackenroder solution has been decomposed during the neutralisation or subsequent evaporation.One drop of a solution of potassic hydroxide causes imwLediateZy 8 precipitate of sulphur in a solution of potassic peritathionate. This salt cannot exist in alkaline solutions. The addition of potassic hydroxide to an acid solution in the ordinary way even by constant stirring will cause for moments in certain parts of the mixing liquids an alkaline reaction and consequent decomposition in case of penta-thionic acid. As the addition of the base proceeds and the amoun 292 DEBUS CIIEMICAL INVESTIGATION OF of free acid becomes smaller transient alkalinity will be more frequent and of longer duration and consequently the more consider-able hhe decomposition. From these considerations it seems to follow that in order to prevent as much as possible the decomposition of the pentathionate the Wackenroder liquid ought to be concentrated the potassic hydroxide very dilute the mixing of the two as rapid as possible and finally not more of the base ought to be added than is required for tho neutralisation of about.half of the acid present. The experiincnts confirm this conclusion. No pentathionate could be obtained by Ludwig’s method a method which was also adopted by Spring. These chemists divided Wackenroder’s solution into two equal parts and neutralised one part completely. This cannot be done without producing transient alkalinity in parts of the mixing liquids and decomposition of the pentathionate. If the other part of Wackenroder’s solution is added and the united liquids Concentrated no crystals of pentathionate are obtained.Lewes could prepare the potassic pentathionate because he added to a given quantity of Wackenroder’s solution only half the amount of potassic hydroxide required for its neutralisation so that the base nearly always met a n excess of acid. Kessler has by means of his analytical method determined the quantity of polythionic acids in Wackenroder’s solution of given sp. gr. The following are his results :-Specific gravity. Percentage of S505. 1.233 32.1 1.32 41.7 1-47 56.0 1.506 59-7 By means of these numbers the quantity of potassic hydroxide to be added to Wackenroder’s solution of given strength can approxi-mately be calculated. 100 C.C. of a liquid of 1.883 sp. gr. would contain according to my estimate 48.6 grams of acid (S,O,) and would require 22.5 grams of potassic hydroxide for neutralisation.A solution of 6 grams of potassic hydroxide in 1OOc.c. of water was sucked into a pipett,e with a very narrow aperture at its lower end and using the pipette as a stirring rod were allowed to run into 50 C.C. of Wackenroder’s solution of 1.283 sp. gr. As the cnd of the stem of the pipette moved through the acid the weak solution of potassic hydroxide ran slowly out and always met a large excess of acid. In this manner very little sulphur was precipitated indicating that very little if any potassic pentathionate had been decomposed. The mixture was now filtered and allowed to concentrate in a partia WAGKENRODER'S SOLUTION. 293 vacuum over pieces of potassic hydroxide.After two days' evapora-tion a crust of prismatic crystals had formed. This crust weighing 4.6 grams was removed and the mother-liquor put back into the vacuum. Two more crops of crystals were obtained the first weighing 6.2 and the second 1.5 grams. As the crystals of these three separations appeayed to be of the same shape they were united and recrystallised. Lewes could not at first recrystallise potassic pentathionate the salt decomposed with separation of sulphur. Fordos and Gklis observed, long ago that the polythionic acids are more stable in presence of other acids. This observation as well as the conditions under which crystals of potassic pentat,hionate are obtained from Wackenroder's solution suggested to Mi-. Lewes a method of recrystallisation which proved very successful.He dissolved the potassic pentathionate in water which was acidulated with a little sulphuric acid and observed that the crystals could be reproduced from this solution. I took 50 grams of water acidulated with 0.66 gram of hydric sulptiate and introduced into this liquid a t 50" the 12.3 grams of crystals obtained as before described. All dissolved except a few milligrams of sulphur which mere separated by filtration. The filtrate was run into a glass dish with a flat bottom and allowed to concentrate by spontaneous evaporation. As the solution became stronger two descriptions of well-developed crystals some of them Q of an inch in diameter separated from the liquid. Six-sided prisms with pyramids only on one end and with the side on which they were resting much developed could easily be distinguished from four-sided rhombic or six-sided star-like plates.The first were found to be potassic tetrathionate and the second pot'assic pentathionate. The latter is also sometimes obtained in short thick prisms with more or less developed pyramids. It is the eiilargementJ of two sides of these prisms parallel to the chief axis and opposite to each other which causes them to appear sometimes like six-sided plates. Both descrip-tions of crystals were placed on blotting-paper and after they were dry the potassic pentathionate could easily be picked out from the mixture ; its weight was 4.2 grams. Both the potassic penta- and tetra- thionate were recrystallised a second time from water acidulated with hydric sulphat'e.50 C.C. of Wackenroder's solution of 1.283 sp. gr. yielded in this way 12.3 grams of a mixture of potassic tetra- and penta-tbionate and this mixture was resolved by two cry stallisations into 2.25 grams of very pure potassic pentathionate and 4.0 grams of potassic tetrakhionate. The yield by this methodof preparation isnot good as a t least half of the pentathionic acid of Wackenroder's solution remains in the original mother-liquor. I was fortunate enough to find a method VOL. LIIL. 294 DEBUS CHEMICAL INVESTIGATION OF generally applicable by means of which every pentathionate which will crystallise can be prepared without loss of pentathionic acid. The principle of the method will be understood from the following descrip-tion.The acids of Wackenroder's solution are strong and not volatile. If mixed with an acetate the hydrogen of the polythionates, H28506,H2Sa& is exchanged for metal producing metallic poly-thionates and hydric acetate. The latter evaporates if the mixture is exposed t o the atmosphere. These operations can be performed without decomposition of the pentathionates. 43 C.C. of Wackenroder's solution of 1.343 sp. gr. contain according to my calculation (see page 292) 24 grams of pentathionic acid (S60,) and would according to the following equation-H,S506 + 2KCaH,0z = R,S506 + 2C2H4O2, require 19% grams of potassic acetate for the forniation of potassic pentathionate and hydric acetate. I took a little less only 16.66 grams of previously fused potassic acetate dissolved it in the smallest quantity of water and acidulated with a few drops of hydric acetate.This solution was now mixed with 43 C.C. of Wackenroder's liquid of sp. gr. 1.343. The mixture measured 85 c.c. and was put on a large plate so as to present a great surface to the atmosphere and then placed in the window of a small draught closet in order to cause a constant current of air to pass over the surface of the mixture. The acetic acid and water evaporated in 24 hours and left a white crystal-line residue which was repeatedly pressed between layers of Swedish filtering-paper. This residue (26 grams) dissolved in 50 C.C. of water acidulated with 1 C.C. of hydric sulphate a t 40" C. leaving only about 0.005 gram of sulphur behind.The sulphur was separated by means of a filter and the filtrate which did not smell of acetic acid left to spontaneous evaporation in a vessel with a flat bottom. The crystal-lisation commenced on the following day and yielded 18.75 grams of very fine crystals of a mixture of potassic tetra- and penta-thionate, instead of only 12 grams as in the previous experiment. Some of the crystals were & of an inch in diameter. 5.75 grams of potassic pentathionate could be picked out of the mixture. The remaining 13 grams as well as the 5.75 grams of pentathionate were each by itself twice recrystallised from water acidulated with a little hydric sulphate. For 1 gram of salt 2.25 grams of water and 0.02 gram of the acid were taken. The crystals obtained were large and well developed so that the peritathionate could easily be separated from the potassic tetra-thionate.In this manner 5 grams of very pure potassic pentathionat \VBCEENRODER’S SOLUTION. 295 and 6.35 grams of pure pottassic tetrathionate mere obtained. The yield is more than twice as great as in the previous experiment. The use of potassic acetate i n place of potassic hydroxide is there-fore highly advantageous because all the acid of Wackenroder’s solution can be converted into the potassium salt and the hydric acetate which is set free tends to prevent the decomposition of the potassic pentathionate. The pentathionates of the heavy metals can only be produced by the addition of the acetates of the metals to Wackenroder’s solution. The mother-liquors of the crystals mentioned above still contained much potassic pentathionate and tetrathionate ; they can easily be recovered by adding for every molecule of sulphuric acid used 2 mols.of potassic acetate and evaporating to dryness at common tempera-tures. The residue of polythionates and sulphate is then treated in the same way as the original crystals. Potassic pentathionate is obtained quite pure by crystallisation from water acidulated with hydric sulphate. But i t is also possible t o crystallise the salt from pure water. 40 grams of water were heated to 50° and then potassic pentathionate in powder was introduced by degrees until the liquid mas nearly saturated. The solution was now passed through a filter into a beaker. The crystallisation commenced almost immediately and proceeded so rapidly that one could see the lighter mother-liquor rise from the newly-formed crystals towards the surface of the solution.About one or two hours after the latter had assumed the temperature of the room the mother-liquor was poured off a crop of very fine prisms, some 5 of an inch in length. The salt remaining in the mother-liquor can be recovered by precipitation with alcohol but not by evapora-tion because it decomposes in to tetrathionate and sulphur. This decomposition occurs even if a concentrated solution is left standing for several hours. The crystals of potassic pentathionate cannot be kept long. In the course of a month or two yellow points are observed in them these points grow and increase in number, until the whole crystal is turned into a yellow pulpy mass consisting chiefly of water potassic tetrathionate and sulphur.The cause of this spontaneous decomposition is the presence of water contained in cracks and fissures of the crystals. In order tlo preserve the salt the crystals must be rubbed to a fine powder and the latter washed with dilute alcohol. In this state I have kept the salt over hydric salphate in an exsiccator for two or three years without the slightest change. Analysis of Potassic Pedathionate. 0.662 gram were oxidised with hydric nitrate and the excess of the latter I-emoTed by evaporatioii A. Crystallised from pure water. x 296 DEBUS CHEMICAL INVESTIGATION OF with hydric chloride. On addition of baric chloride 2.084 grams of baric sulphate were precipitated.0,972 gram of the same salt gave 0.471 gram potassic sulphate. 11. 0.518 gram were treated with bromine-water and the excess of bromine evaporated on the water-bath. 0945 gram of sulphur remained undissolved ; the filtrate from this sulphur gave with bark chloride 1.3565 gram of baric sulphate. The bromine used in this experiment was proved to be purc. 0.931 gram of the substance was evaporated with pure hydric sulphate and heated to redness. The weight of the residue was 0.448 gram. B. Potassic pentathionate prepared by the addition of potassic hydroxide to Wackenroder’s solution and crystallisation from water containing hydric sulphate. 111. 0.701 gram was oxidised with bromine-water and the un-dissolved sulphur washed with dilute ammonia.0.114 gram of sulphur was obtained and 1.405 gram of bark sulphate by pre-cipitation with baric chloride. 1.598 gram of the substance heated to redness left 0.770 gram of potassic sulphate. 2 931 grams burnt with plumbic chromate in a combustion-tube gave 0.2265 gram of water. IV. Potassic pentathionate prepared by Mr. Lewes a<nd analysed by Mr. Cowper. 0.4895 gram gave 0.235 gram of potassic sulphate. 0.5045 gram gave 1.6175 gram of baric sulphate. 0.7205 gram gave 0.057 gram of water. C. Potassic pentathionate obtained by the addition of potassic acetate to Wackenroder’s solution and crystallisation from water con-taining hydric sulphate. V. 0.541 gram oxidised with bromine-water and the solution precipitated with baric chloride gave 1.741 gram of baric sulphate.0.453 gram heated to redness left 0.221 gram of potassic sulphate. Percentage Conyosition. Theory. I. 11. 1x1. IT. V. 2K,S5O,+3H,O. Potassium 2!.70 21.57 21.58 21.54 21.80 21.60 Sulphur . . 43.23 44.61 43.76 44.03 44.20 44.32 - 26.59 Oxygen. . . . 7.72 1-91 - 7.48 Water . . - -59.99 - - - --The atomic ratios are-I. K S = 2 4.85 II. K S = 2 5-04 111. K S = 2 4.94 IV. K S = 2 4.9 WACKENRUDEB'S SOLUTlON. 297 Potassic pentathionate dried over hydric sulphate has consequently, the formula 2K,S506,:3Hz0. Lewes mentions three salts K2S50G KC2S50G,H20 and K2S50s,2H,0. Shaw calculated from his numbers the formula K,S,O,*H,O. The salts prepared by Lewes and Shaw were not recrystallisod but were analysed in the same state in which they separated from the original solution.I believe they were not quite pure. If we consider the hydrogen of the water of crystallisation replaced by potassium in tlie formula 2K,S506,3H,0 we have the composition of 5 mols. of po tassic thiosul p hate. The crystalline forms of potassic pentathionate have been described on p. 293. The salt dissolves in about 2 parts of water with reduction of temperature forming a perfectly clear transparent and neutral solution. The aqueous solution cannot be kept long without change ; after a few days sulphur separates and potassic tetrathionate remains in solution. The presence of a little hydric sulphate prevents this decomposi-tion. The crystals which are obtained by evaporation from an acidu-lated solution are frequently crossed by fissures.The aqueous ~ o l u -tion can be boiled for a short time without apparent change; if, however the boiling is continued for 15 or 20 minutes then the odour of hydric sulphide becomes perceptible. A piece of sheet copper or silver will turn black in the course of a few days in the aqueous solu-tion in consequence of the formation of metallic sulphides. The brown colour of a solution of iodine in potassic iodide is in the course of a day or two decolorised by potassic pentathionate. Potassic per-manganate produces a brown precipitate and hydric sulphate is formed which remains in solution. Platinum black placed in a perfectly neutral solution of potassic pentathionate causes the latter t o become intensely acid and to comport itself with bark chloride like a sul-phate.Sulphur is not precipitated in this reaction. Potassic penta-thionate decomposes at high temperatures as represented by the equation-It is not soluble in alcohol. 2KzS506,3HzO = 2KzS04 f 2SOz + S + 3HZO. The reactions of Wackenroder's solution have hitherto been described as the reactions of pentathionates. But Wackenroder'e solution is a mixture of at least three polythionates. Being in pos-session of some very pure pentathionate I therefore took the oppor-tunity to study its reactions somewhat minutely. Reactions characteristic of Penta t hionat es. I. An ammoniacal solution of silver nitrate causes in a solution of potassic ammonic or baric pentathionates a brown coloration whic 295 DEBUS CHEMICAL ISVESTIGATION OF rapidly becomes darker and by degrees a black precipitate is thrown down from the mixture.This reaction is not produced in a solution of tri- or tetra- thionat'es pot'assic thiosulphate or ammonic sulphite. An ammoniacal solution of silver nitrate also seems to have no effect on them. Consequently a pentathionate even if present in very small quantity can be detected by means of this reaction in a mix-ture containing potassic tri- and tetra-thionates and sodic potassic or ammonic thiosulphates. The solution of zinc in sulphurous acid produces with an ammo-niacal solution of silver nitrate an immediate grey precipitate and the supernatant liquid appears clear and colourless. 11. Potassic hydroxide in solutions of pentathionates immediately produces a separation of sulphur.As tri- and tetra-thionates and thio-sulphates are not changed by this reagent a proportionally small quantity of a pentathionate can be detected in a mixture of the four salts by addition of potassic hydroxide. The latter however is not so sensitive a reagent as the ammoniacal silver solution. 111. Ammonia added to a solution of potassic pentathionate causes, after about one or two minutes a precipitation of sulphur. IV. Sulphuretted hydrogen produces in an ammoniacal solution of a pentathionate an immediate precipitate of sulphur. V. An ammoniacal solution of mercuric cyanide produces with pc tassic pentathionate a black precipitate by degrees at ordinary temperatures at once at 100" C. VI. Ferric chloride plumbic nitrate cupric chloride cupric acetate, cobaltic nitrate zinc sulphate cupric sulphate plumbic acetate hydric chloride and bark chloride cause no change in solutions of potassic pentatbionate.Qeneral Reactions of Polythiovtates and Thiosulphates. I. Mercurous nitrate produces with penta- and tetra-thionates a fine yellow and with trithionates and thiosulphates a black precipitate. 11. Cupric sulphate mixed with solutions of potassic tri- tetra- 01-penta-thionates or an aqueous aolution of sulphurous acid or the solu-tion of zinc in sulphurous acid causes no apparent change at common temperatures. The same reagent does not affect tetra- and penta-thionates at loo", but produces at this higher temperature with trithionates or thio-sulphates a black and with the solution of zinc in sulphurons acid a red precipitate.Cupric snlphate added to a solution of ammonic sulphite produces a yellow precipitate at common temperatures. 111. Hydric chloride does not change solutions of tetra- and penta WACKENRODER'S SOLUTION. 299 thionates but in about ten minutes in such as contain trithionates and in about one minute in those of thiosulphatee it causes a separation of sulphur and sulphurous acid. A mixture of the four salts became turbid in two minutes. IV. Ferric chloride causes transient coloration in the following solutions :-a. Thiosulphates violet changing to yellow. 71. Sulphurous acid in water brown changing to yellow. c. Zinc in aqueous sulphurous acid brown changing to colonrless. The reagent causes a permanent brown colour in aqueous solution of amm onic sul phi t e.V. Baric chloride produces in solutions of sodic or potassic thio-sulphate a white crystalline precipitate which even in boiling water, is only sparingly soluble but it does not change solutions of the poly-thionates at common temperatures or those of tetra- and penta-thio-nates at 100". Thiosulphates and trithionates can be detected in a mixture of the two in the following manner :-Chloride of barium is added to the neutral mixture as long as a precipitate is formed ; the latter is baric thiosulphate and can be proved to be so by means of ferric chloride and hydric chloride respectively. The filtrate from the baric thiosulphate is boiled for about five minutes when if barium trithionate is present the smell of sulphurous acid will appear and a white precipitate will be thrown down insoluble in hydric chloride, and not volatile at a red heat on a piece of platinum-foil.These reactions are not observed with baric dithionate. If free acid should happen to be present in the original mixture it must be neutralised wihh baric carbonate. Zinc Pentat hionat e could not be obta.ined in a pure state. 45 C.C. of Wackenroder's solution of the sp. gr. 1.325 mere mixed with a concentrated solution of 22 grams of zinc acetate Zn(C2H302)2,3H20 and the mixture allowed to evaporate at common temperatures. A crystalline mass and a very little mother-liquor remained after two days' exposure to a current of air in a draught closet. The residue (46 grams) was pressed between layers of blotting-paper and then dissolved in 30 C.C.of water which were acidulated with a little hydric sulphate. No insoluble matter remained behind. The solution left to spont'aneous evaporation deposited nothing but crystals of zinc sulphate. T'he mother-liquor remained liquid in common air but in dry air under a bell-jar over pieces of potassic hydroxide solidified to a white amorphous mass like porcelain which dissolved again in yery little water. The solution gave the reactions of a pentathionate 300 DEBUS CREJIICAL INVESTIGATION OF The solid residue decomposed completely in the course of two months sulphur zinc sulphate and probably sulphurous acid being the products found. C u p ic Pent a thiona t e was obtained in small fine blue crystals by the following method :-20 grams of cupric acetate were dissolved in 250 C.C.of water and the solution mixed with 45 C.C. of Wackenroder’s solution of sp. gr. 1.325 and the mixture left to evaporate on two large plates in a draught closet a t ordinary temperatures. After two days a blue crystalline mass was formed on each plate the residue of one plate was pressed between blotting-paper and then dissolved in water acidulated with hydric sulphate. A few brown flakes remained undissolved. The blue filtrate from these during spontaneous evaporation yielded long fine needles in such abundance that the whole appeayed like jelly, and this when placed on bibulous paper left a blue solid mass which could not be dried over hydric sulphate without decomposition. It turned brown and was after this change of colour only partially soluble in water.The residue on the second plate also changed its colour in the course of two days from blue to brown because a portion of it had undergone a similar decomposition to the needle-shaped crystals mentioned above. The brown mass was pressed between layers of filtering-paper and then extracted with water. A portion dissolved forming a blue solution and a brown solid in appear-ance like cuprous oxide was left. The blue solution which was a1 lowed to evaporate at common temperatures yielded crystals without decomposition. Three crops of crystals were obtained ; the first and second consisted of cupric sulphate the third of fine prismatic crystals cf cupric pentathionate ; 0.460 gram of the latter dried over hydric sulphate and dissolved in bromine-water gave by the usual methods 0.095 gram of cupric oxide 1.350 gram of bslric sulphate and 0.002 gram of sulphur ; 100 parts contain-Theory.Found. CUS,O + 4Hz0. Copper . . . . 16.49 16-11 Sulphur . . 40.74 40.92 Cupric pentathionate is easily soluble in water. Mercurous nitrate produces in the solution a yellow and ammonia a blue precipitate ; the latter is soluble in an excess of the reagent. The blue ammoniacal solution thus obtained reacts with ammonia-silver nitrate like potnssic pentathionate. Potassic hydroxide causes in solution of cupric penta-thionate a blue precipitate which is only partially soluble in hydric chloride Ieaving a residue of sulphur. Similar experiments with WACKENRODER’S SOLUTION. 301 mixture of potassic tetrathionate and cupric sulphate in place of cupric pentathionate gave no brown colouring with the silver solution and no precipitate of sulphur with potassic hydroxide.A brown solid a product of decomposition of one of the salts con-tained in the original mixture of Wackenroder’s solution and cupric acetate has been mentioned on p. 300 ; the mode of forniation and the composition of this substance I have not accurately ascertained. Wackenroder’s solution contains an acid with more sulphur than the pentathionic acid probably hexathionic acid. The atomic ratio of copper to sulphur in the brown product was found t o be = 1 4. From this it would appear probable that it is formed from cupric hcxathionate according t o the equation-CUS,O + 2H2O = 2H2SO4 + CUS,.A more detailed and accurate examination was not carried out because the substance absorbed oxygen from the air. A tube con-taining a portiou which had been dried over hydric sulphate for the purposes of analysis increased 0.035 gram in weight in two weeks. The brown product of decomposition resembled in colour and other properties the precipitate which forms on the addition of the higher sulphides of potassium to a solution of cupric snlphate. The colour is at first a bright red or reddish-brown but during washing on the filter acquires a darker colour no doubt in consequence of oxidation. Examination of the Nother-liquor of Potassic Pmtathionate. According to the experiments described so far Wackeiirod er’s solution-the pent athionic acid of the text-books-is a mixture of at least two acids tetra- and penta-thionic acids.The tetrathionic acid is not a product of decomposition of pentathionic acid because a Wackenroder solution can be evaporated with potassic acetate with precipitation of very little sulphur. We have now to examine the mother-liquors (pp. 293 294) from which pot’assic tetra- and penta-thionate had separated by crystallisation. For this purpose, the filtering-paper which had been used to free the crystals from adhering mother-liquor (p. 294) was extracted with water and the extract mixed with the mother-liquors which had been poured off the crystals (p. 295). The united liquids contained hydric sulphate according to my calculation a quantity capable of decomposing 8 grams of potassic acetate.A concentrated solution of a little less than this quantity of potassic acetate was now added and the entire mixture left to evaporate on plates in a draught closet. Nearly all the water had disappeared in two days and a solid residue with very little mother 302 DEBUS CHEMICAL INVESTIGATION OF liquor was left. This was pressed between layers of blotting-paper, and then dissolved in 30 C.C. of water acidulated with 1 C.C. of hydric sulphate. Only a little sulphur according to my estimate not more than 0.01 gram remained undissolved. The weight of the dissolved portion was 18 grams. The filtrate from the small quantity of sulphur was clear and slightly yellow. In the course of a day however it turned turbid and a few milligrams of sulphur separated.After a second filtration it remained clear. With reagents it acted like a pentathionate with this difference, that ammonia caused a n immediate copious precipitate of sulphur, and a similar precipitate was obtained a t 100" with cupric sul-phate. The solution was put into a glass vessel with a flat bottom, and allowed to concentrate a t ordinary temperatures. During the evaporation solid matter separated and was collected in six portions. The 1st portion consisted of potassic tetra- and penta-thionate crystals. The 2nd appeared as a crust of warty formation in which no crystalline structure could be discovered by means of a lens. The 3rd formed small six-sided plates the 4th was like the 2nd and the 5th and 6th resembled the 3rd portion. The mother-liquor which remained a t last was so small in volume that no further experiments could be made with it.The 2nd and the 4th portions appeared t o be formed of the samo substance and were homogeneous throughout. They were therefore united washed with dilute alcohol and dried over hydric sulphate. This substance appeared to be potassic hexathionate mixed with some potassic hydric sulphate and free sulphur. I could not remove these impurities. If the substance is dissolved in water with a little hydric sulphate and left to evaporate it will although sulphuric acid is present partially decompose with separation of sulphur and pro-duction of pentathionate. I attempted therefore to determine the impurities and calculate the composition of the remainder. The sub-stance is well characterised by its physical and chemical properties.I will on the basis of the following determinations call it potassic hexathionate. I. 0.240 gram was d-issolved in water slightly acidulated with hydric chloride and precipitated with baric chloride. The precipitate contained besides baric sulphate also the free sulphur which was mechanically mixed with the potassic hexathionate. The precipitate was collected on a weighed filter and dried over hydric sulphate. Its weight was Pound to be 0.033 gram. At a red heat the weight diminished t o 0.024 gram. The difference of the two weights 0.009 gram represents the weight of the free sulphur. 11. 0.288 gram oxidised with bromine-water and the products precipitated with baric chloride gave 1.046 gram of baric sulphate WACKENRODER’S SOLUTION.303 and 0.3124 gram gave after heating to redness 0.1385 gram potassic sulphate. 0.330 gram of the substance burnt with potassic chromate gave 0.021 gram water. According to the dat,a given under 11 100 parts of the substance contain-Potassium 19.92 Sulphur 49.89 Oxygen 23.83 Water 6.36 100.00 According to the determinations of I 3.75 per cent. of sulphur are present in the free state and 1.37 per cent. in the form of potassic hydric sulphate. 5.12 per cent. of sulphur have conse-quently to be deducted from 49.89 per cent. as found under 11. If likewise the potassium oxygen and hydrogen of the potassic hydric sulphate are subtracted the following quantities are left :-Potassium 18.25 Sulphur 44.77 Oxygen 21.09 Water 5.98 90.09 Theory.And in 100 parts :-Found. R2S,06 + 1*5H,O. Potassium 20.25 19.84 Sulphur 49.69 48.85 Oxygen 23.40 24.42 Water 6-63 6.87 99-97 99.98 The atomic proportions are-KzS5.,,05.aa + 1.41 HzO. Sulphur and potassium have been found too high and accordingly oxygen somewhat too low. Potassic hexathionate separates from its solution in crusts of warty masses without crystalline structure. More pure than the sample analysed I found some amongst the 5th crop of crystals (p. 302). As this did not contain free sulphur it dissolved in water to a clear solution. The aqueous solutions of this salt decompose with separation of sulphur even when free hydric sulphate is present and are thu 304 DEBUS CHEMICAL INVESTIGATION O F distinguished from those of the pentathionate.Potassic nitrate, which completely precipitates 2-sulphur (sulphur in the collo'idal con-dition in solution) does not change the solution of the hexathionate. Ammonia produces a precipitate of sulphur immediately (difference from pentathionate) and ammonincnl solution of silver nitrate, potassic hydroxide and mercurous nitrate react with hexathionate as with pentathionate. The crystals obtained from the mother-liquors of potassic hexa-thionate (p. 302) were potassic pentathionate rendered impure by potassic sulphate. 0.369 gram gave after ignition 0.183 gram of potassic sulphate. I n 100 parts :-Found. Theory. Potassium 22.23 21.60 The impure substance which has been described as potassic hexa-thionate decomposes so rery easily that I could not hope to prepare it in a perfectly pure state.I have therefore by the following experi-ments attempted to prove the existence of polythionates containing more sulphur than pentathionates and thus increase the probability of the existence of hexnthionates. The Wackenroder's solution used in these experiments was not pre-pared exactly as described on p. 281. Sulphuretted hydrogen was passed into smaller quantities of sulphurous acid than in former preparations. Not more than 120 C.C. were taken for each experi-ment with the result that the decomposition of the sulphurous acid required less time than before. Hydric sulphide was passed for one hour through the sulphurous acid solution and again on the next day for two hours.The reactions were then completed and no more free sulphurous acid could be observed. The resulting solution was now concentrated on the water-bath until i t showed the sp. gr. 1.257 and then filtered from the precipitated sulphur. Reactions of the Concentrated Solution. It produced with potassic hydroxide ammoniacal silver nitrate, rnercuroiis nitrate and cupric sulphate respectively the reactions of potassic pentathionate. Ammonia gave a copious precipitate of sul-phur. No difference in this respect could be observed when the reagent was added in large excess. Samples of Wackenroder's solu-tion prepared as described on p. 281 did not show this behaviour. Analysis of the Concentrated Solution. 10 C.C. of the sp. gr. 1,257 were diluted with 15 C.C.of water WACKENRODER’S SOLUTION. 305 I. 5 C.C. of the diluted liquid were precipitated with bark chloride. Weight of precipitate = 0.121 gram. Free sulphur was not present. 11. 5 C.C. of the diluted liquid when boiled with mercuric cyanide, gave 0.969 gram of a black precipitate consisting of mercury and sulphur which was collected on a previously weighed filter. The filtrate from this precipitate gave with baric chloride 1.692 gram of baric sulphate. 0.907 gram of the mercuric cyanide precipitate dis-solved in bromine-water gave 0.136 gram of sulphur and 1.052 gram of baric sulphate from which data we calculate for the entire precipi-tate of 0.969 gram 0.299 gram of sulphur and by difference 0.670 gram of mercury. 111. 5 C.C. of the diluted liquid boiled with mercuric cyanide gave 0.971 gram of a precipitate consisting of mercuric sulphide and sul-phur.The filtrate mixed with baric chloride yielded 1.682 gram of baric sulphate. IV. 5 C.C. of the dilnted liquid oxidised with bromine-water and precipitated with baric chloride gave 3.686 grams of baric sulphate and 0.018 gram of sulphur. According to determinations I 11 and 111, 5 C.C. of the diluted liquid contain 0.5135 gram of sulphur in com-bination in the form of polythionic acids. According to determina-tions I and IV 5 C.C. contain after deduction of the sulphur present in the form of sulphuric acid 0.507 gram of sulphur. The two numbers 0.513 and 0.507 are sufficiently near to allow the conclusion that the liquid under examination contains besides some sulphuric acid only sulphur compounds of the form H2S,06 (poly-thionic acids).The atomic ratio of the sulphuric acid formed by boiling the diluted liquid with mercuric cyanide to the mercury and sulphur of the precipitate formed in the same operation is-[I and 111 SO Hg S = 2 1 2.78 [I and 1111 So3 Hg S = 2 1 2-79 which means that the average composition of the polythionic acids of the solution is nearly expressed by the formula Sa.s05 or H,S4.,06, a formula which would correspond to 4 mols. of hydric pentathionate and 1 mol. of hydric tetrathionate (see p. 287) viz. a Wack-enroder solution containing 4 mols. of pentathionic acid and 1 mol. tetrathionic acid would give the analjt.ica1 results described. From the above determinations me calculate that 1 C.C.of Wacken-roder’s solution of sp. gr. 1.257 contains 0.389 gram of acid of the average composition s4.7505 and 0.0207 gram sulphuric acid (SO,). 0-389 gram of acid S4.7505 can decompose 0.3285 gram of potassic acetate KC2H,0, and produce 0,5463 gram anhydrous polythionate. 95 C.C. of Wackenroder’s solution of the sp. gr. 1.257 were therefore 306 DEBUS CHEMICAL INVESTIGATION O F mixed with a solution of 30 grams of potassic acetate and left to con-centrate at ordinary temperatures. The crystalline residue remaining after 24 hours’ evaporation weighed after pressing between filtering-paper 45 grams. According to theory 30 grams of potassic acetate can produce 49.8 of anhydrous polythionates of the average composi-tion K2Sb.7506. The mother-liquor of the crystalline residue wbich bad been absorbed by the Swedish filtering-paper was extracted with water and the aqueous extract examined separately.The pressed residue 45 grams was dissolved in 80 C.C. of water containing 1 C.C. hydric sulphate a t 50” a few milligrams of sulphur were separated hy filtration and the clear filtrate left to crystallise a t common t,emperatures in a vessel with a flat bottom. A crop of fine crystals, consisting partly of potassic tetrathionate and pertly of potassic penta-thionate formed in the course of a few days. The two descriptions of crystals were easily separated from each other. 24.5 grams of potassic tetrathionate and 10.5 grams of potassic pentathionate were collected. The degree of purity of the crystals can be judged by the following determinations :-u.Potassic pentathionate. 0.407 gram gave 0.200 gram of potassic sulphate therefore 100 b. Pot assic t e trathionate. 0.544 gram gave 0,308 gram of potassic sulphate ; 100 parts contain, therefore 25.3s parts of potassium instead of 25-82 parts as required by theory. The potassic pentathionate contains 0.42 per cent. of potassium more and the potassic tetrathionate 0.44 per cent. potas-sium less than the theoretical quantities which means that the picked out pentathionate contained 10 per cent. of tetrathionate and the selected tetrathionate 10 per cent. of pentathionate. Several of the smaller crystals of both salts frequently grow together. 95 C.C. of Wackenroder’s solution of 1.257 sp. gr. contain according to analysis 36.96 grams of acids of the average composition If the solution contains for every molecule of tetrathionic acid 3 mols.of pentathionic acid then after addition of 30 grams of potassic acetate it should have produced 41.4 grams of hydrated potassic pentathionate and 11.5 grains of potassic tetrathionate. Instead of these quantities only 4 of the theoretical amount of pentathionate and more than double the theoretical quantity of tetrathionate were actually ob t ai n e d. The assumption that Wackenroder’s solution contains only tetra-thionic and pentathionic acids is therefore incorrect ; it must contain besides these another acid with more sulphur than pentathionic acid. 95 C.C. of Wackenroder’s solution of 1.257 sp. gr. contain according parts contain 22.02 parts of potassium.Theory requires 21.6 parts WACKENRODER’S SOLUTION. 307 to analysis 24.27 grams of sulphur and 12.73 grams of oxygen united to polythionic acids. 10.5 grams potassic pentathionate ( 2K2S,06,3H20) collected as described contain 4.66 grams of sulphur and 2.33 grams of oxygen united as S,O,. 24.5 grams of potassic tetrathionate ( K2Sa06) contain 10.38 grams of sulphur and 6.49 grams of oxygen united as Sa05. Now if we subtract the sulphur and oxygen of the tetrathionic (S40,) and the pentathionic acids (S,O,) contained in the potassium salts from the sulphur and oxygen of the polythionic acids contained in the 95 C.C. of Wackenroder’s solution the remainder will be the sulphur and oxygen of the acids contained as potassic polythionates in the united mother-liquors.24-27 grams S - (4.66 + 10.38)S = 9.24 grams S. 12.73 grams 0 - (2.33 + 6.49)O = 3.91 grams 0. Now 9.24 3.91 = 189 80 = S5+ O, for which we may take-S 6 0 5 . That is t o say the average composition of the potassic polythionates contained in the mother-liquors of the above potassic penta- and tetra-thionates is represented by the formula-K2S606, or corresponds to the composition of a hexathionate. The united mother-liquors and aqueous extracts of the Swedish filtering-paper were mixed with 3 grams of potassic acetate in order to convert the greater portion of hydric sulphate present into potassic sulphate and then placed on a plate in the window of a draught closet. The solid residue which was still moist was pressed between layers of filtering-paper, and in khis condition weighed 11.5 grams.It was now put in 10 C.C. of water which contained $ C.C. of hydric sulphate ; it all dissolved except a trace of sulphur which was separated by means of a filter. The filtrate which however did not appear to be quite clear was allowed to concentrate at common temperatures. After a few days, a crust of warty formations appeared without crystalline structure. This was removed and the mother-liquor a second time gave a crust of warty matter which like the first was dried on blotting-paper. The remaining mother-liquor was now practically exhausted. A few days after their preparation the two separations of warty forma-tions began to decompose with development of sulphurous acid.In order to prevent this decomposition they were placed in water. The first dissolved with the exceptlion of some sulphur the second left a propori,ionately small quantity of a sparingly soluble potassium salt. The evaporation was finished in 24 hours 308 DEBUS CHEJIICAL INVESTIGATION OF The molecules of potassic hexathionate are evidently of a most unstable nature and little hope was left of their complete separation from other matter. The two aqueous solutions mentioned just before were united, filtered and the atomic ratio of potassium sulphur and oxygen of the salt or salts in solution determined according to Kessler’s method. I. Determination of sulphates. 5 C.C. were mixed with baric chloride and 0.33 gram of bark sul-phate obtained. IT. Determination of sulphur oxygen and metal in the polythio-nates .5 C.C. of the filtrate were boiled with a solution of mercuric cyanide. The precipitate consisting of sulphur and mercury weighed 0.333 gram and the filtrate from this precipitate gave with baric chloride 0.831 gram of baric sulphate. After deducting the sulphate found under I a residue of 0.501 gram is left which contained 0.0688 gram of sulphur. 111. Determiriation of the mercury and sulphur in the precipitate mentioned under 11. 0.313 gram of the precipitate were digested with bromine-water until all the mercury was dissolved. 0.028 gram of sulphur was left undissolved arid the filtrate from this sulphur gave with baric chloride 0.635 gram of baric sulphate which contains 0.08i2 gram of sulphur.The filtrate from the baric sulphate gave with hydric sulphide 0.228 gram of mercuric sulphide which contains 0.196 gram mercury. If however the mercuryis taken to be equal to the difference between the weight of substance taken and the sulphur found then its quantity would be = 0.1978 gram. The last number I consider to be more correct than the former and therefore I shall adopt it. From these numbers we obtain for the composition of 0.333 gram of precipitate found in 11 0.122 gram of sulphur and 0.211 gram of mercury. The atomic ratio of the sulphur in the sulphuric acid pro-duced by boiling with mercuric cyanide to the mercury and sulphur of the precipitate formed at the same time is therefore-S of SO Hg S = 2.04 1 3-63. If the sulphuric acid of 0.501 gram of baric sulphate found in I1 is added to the mercury and sulphur of the mercuric cyanide precipitate, we obtain the weight of the mercuric polythionate and if we replace in this the mercury by its equivalent of potassium we have the average composition of the potassic poly thionates of the solution, as expressed by the forniula-~ * S 5 .6 1 0 6 1 ~ WACKENRODER’S SOLUTION. 309 Therefore the solution contains a polythionate with more sulphur than the pentathionate. The following experiment shows that besides sulphates and pol$-thionates no other sulphur compounds are present in the solutions. IV. 5 C.C. treated with bromine-water until all the sulphur was oxidised t o sulphnric acid and precipitated with baric chloride gave 1.i28 gram of baric sulphate.Deducting from this weight the amount of sulphate found in I tliere remains a quantity of baric sulphate which contains 0.192 gram of sulphur. According to I 11 and 111 fhe total sulphur present in 5 C.C. of the liquid as polythionates is = 0.191 gram. Hence it follows that the solution contains only sulphates and polythionates. Reactiom of the Solui5on. Although clear immediately after filtration the liquid soon became turbid and deposited a comparatively small precipitate of sulphur. This precipitate did not further increase even in the course of weeks. But as soon as it was separated by filtratlion the clear liquid in the course of an hour again became turbid and soon foimed a quantity of precipitate about equal to the former. Then the pre-cipitation would stop until the liquid was filtered when it would commence again.I have repeated the filtration five or six times always with the same result. These observations I explain as follows:-The liquid contains easily decomposable potassio hexathionate which decomposes with separation of sulphul- but the latter separates i n a condition in which it can recombine with potassic pentattionate and produce a higher polythionate. In every unit of time a certain portion of sulphur is set free and a certain portion redissolved. The precipitation stops when both actions become equal. Hydric chloride ferric chloride cobalt sulphate and cuprie sulphate caused no change in the liquid. Ammonia gave a copious precipitate con-sisting of yellow flakes of sulphur ; and a large excess of ammonia a white crystalline precipitate soluble in an excess of water.Potassic hydroxide srnmmiacal solution of silver nitrate mer-curous nitrate and hydric snlphide respectively gave the same reae tions as with a pentathionate. The experiments described prove that Wackenroder’s solution con-tains in addition to tetra- and penta,-thionic acid one or more acids of similar constitution b u t richer in sulphur than the two acids named. The acid is probably hexathionic acid. I f during the preparation insu#icie?.zt hydric sulphide has been passed through the sulphurous acid trithionic acid also will be present. The small amount of liydric sulphate which I found in VOL. LJU. 310 DEBUS CHEMICAL INVESTIGATION OF Wackenroder’s solution is most probably the resnlt of the oxidising action of the air on sulphurous acid.Lenoir Ludwig Kessler and others ha,ve attempted the preparation of pentathionates by the complete or partial neutralisation of the acids in Wackenroder’s solution and precipitation of the salts formed by means of alcohol. The results were as might be expected very dis-cordant. For it is ciear that the concentration of Wackenroder’s solution as well as the strength and volume of the alcohol used must have according to the experiments described in this paper an influence on the composition of the precipitate. Kessler obtained potassic tetrathionate and sulphur Ludwig R mixture of baric tetra- and penta-thionates and Lenoir a precipitate nearly of the composition of baric pentathionate. Some experiments of my own show the variations in the composi-tion of the precipitates very cIenrly.Wackenroder’s solution of sp. gr. 1-25 was neutralised with baric carbonate filtered and then precipitated with twice its volume of alcohol. The crystalline preci-pitate was redissolved in a small quantity of water the solution separated by filtration from a little sulphur and then reprecipitated by alcohol. The precipitate obtained in this way had nearly the composition of baric pentathionate but might be a mixture of baric tetra- penta- and hexa-thionates. On addition of more alcohol to the first filtrate from this precipitate, it gave another precipitate in which barium and sulphur were con-tained in the atomic proportion Ba S = 1 4.28. The filtrate from the last precipitate gave with more alcohol a third precipitate of the atomic ratio Ba S = 1 3.8, and if the alcohol which was added in three portions had been added at once the ratio of barium to sulphur in the precipitate would pro-bably have been = 1 4%.It is clear that by such methods pure substances cannot be obtained with certainty. The Wackenroder’s solution has been proved in this paper to contain before its evaporation large quantities of sulphur in a new modification 8-sulphur in solution and besides this tetra- penta-, and probably hexa-thionic acids. We have now to explain the formation of these prodncts from the original materials-sulphuretted hydrogen sulphurous acid and water. This problem is one of the most complicated in chemistry WACKENRODER'S SOLUTION.311 B. ON THE FORMATION OF THE CONSTITUENTS OF WACKENRODER'S SOLUTION. Decomposition of an Aqueous Solution of Potassic Pentathionate. A concentrated solution of this salt was allowed to stand for a few months in a beaker covered with a piece of filtering-paper. From time to time some water was added in order to make good the loss caused by evaporation. Very soon in less than 48 hours after the preparation of the solution sulphur began to separate and slowly continued to do so for several weeks but even after three months the decomposition was not quite complete for potassic penta-thionate could still be detected (see p. 298). AS soon as the separa-tion of sulphur appeared to be practically complete the solution was passed through a filter and allowed to evaporate spontaneously.A fine crop of crystals of potassic tetrathionate was obtained. 1.228 gram dried over hydric sulphate gave after ignition 0.7035 gram of potassic sulphate. 1.0695 gram of the same subst.ance oxidised with bromine-water gave 0.090 gram of sulphur and 2.616 grams of baric sulphate from which data we calculate for LOO parts-Found. Potassium . . 25.68 Sulphur . . . . 42.02 Theory. K2S40,. 25.82 42.38 The decomposition can be represented by the equation-K2S,06 = R2Sa06 + S. The mot,her-liquor contained however small quantities of potassic tri- and penta-thionates and seme potassic and hydric sulphates. The sulphur on the filter could not be washed because it passed through the pores of the filter with the water.The crystals of potassic tetrathionate obtained formed with water a neutral solution which was not changed on addition of potassic hydroxide or of an ammo-niacal solution of silver nitrate. Decomposition of an Aqueous Xohtion of Potassic Tetrathionate. Fine large crystals of the salt were carefully examined. 1.14 gram dried over hydric sulphate left after ignition 0.656 gram of potassic sulphate. 0.6945 gram of the same substance osidised with bromine-water and the solution precipitated with baric chloride gave 2.145 grams of baric sulphate. Hence in 100 parts 312 DEBUS CIIEMICBL INVESTIGATION OF Found. K&&. Potassium 25-79 25.82 Sulphur. . . 42.41 42.38 The aqueous solution of this substance was not changed on addition of ammonia-silver nitrate and potassic hydroxide respectively.Also cupric snlphate produced no reaction with it a t 100". The substance, therefore is pure potassic tetrathiona,r;e. The neutral solution was left standing for 12 days at 18". It was now stroiigly acid but still clear and smelt strongly of sulphurous acid. The appearance of sulphurous acid without separation of sulphur indicated the probable formation of a compound richer in sulphur than the t e t rathionat e. I now prepared another solution of 0.5 gram of potassic tetrathionate in 10 C.C. of water and made with this and with the solution 12 days old the following corriparative experiments :-0.5 gram of this pure salt was dissolved in 10 C.C. of water. Reagents . Litmus . BaC1 + HC1+ H,O . NaHO . NH,HO AgNO + NH4HO.cut304 . Pe2C16 Hg?(N03)2 Kew solution of potassic tetrathionate. neutral no change J Y > J no change at 100" no change yellow precipitate no change Twelve-days old solution of potas-sic tetrathionate. Strongly acid. Copious precipitate. Brown colouring &black precipitate. Precipitation of much sulphur. Black precipitate a t 100". Turbid after a few minutes. Grey precipitate. No change. These reactions prove that an aqueous solution of potassic tetra-thionate a t 18" slowly decomposes into potassic pentathionate and potassic trithionate sulphurous acid and potassic sulphate as repre-sented by the following equations :-Further on it will be shown that potassic trithionate decomposes as follows :-3&s306 = BKZSO + 2SOz + KZSjO,, and the spontaneous decomposition of potassic tetrathionate a t 18" is fully explained.The following experiment will furnish an idea of the rate a t which the decomposition proceeds :-The temperature of my laboratory is from October to May nearl WACEENBODER'S SOLUTIOS. 313 constant 18" so that all these experiments have been performed practically at the same temperature. A solution of 1 gram of potassic tetrathionate in 10 C.C. of water was tested at intervals as described in this table. Time in hours after preparation. 22 76 96 16s 288 Litmus. --neutral 7 7 7 7 slightly acid strongly acid Reagents. Ammonia-silver nitrate. ~~ No change. Feeble reaction of pentathionate. Reaction of pentathionate.Strong reaction of pentathionate. Very strong reaction of pentathio-natc. Ammonia-silver nitrate is the most sensitive reagent for penfathio-nates. The formation of pentathionate could only be detected with sodic hydroxide after the solution had been standing more thau 168 hours. The crystals of potassic tetrathionate kept in a closed bottle smelt of sulphurous acid after some time. Water enclosed in cracks and fissures of the crystals is the cause of this decomposition. The perfectly dry salt can be kept without the slightest change. Decomposition of an Aqueous Solution of Potassic Trithionate. The equation on p. 312 representing the decomposition of this salt in aqueous solutions has t o be proved. The salt used in the following experiments had been prepared by the action of sulphurous acid on potassic thiosulphate and two or three times recrystallised from hot water.1.2855 gram dried over hydric sulphate gave after ignition 0,8275 0.643 gram of the same substance oxidised with bromine-water gave Hence in 100 parts-gram potassic sulphate. 1.662 gram of baric sulphate. Found. K2s306-Potassium. . 28.85 28.88 Sulphur . . 35.49 35.55 A clear neutral solution of 1 gram of this salt in 10 C.C. of water, Boon after its preparation gave no reaction with ammonia-silver nitrat 314 DEBUS CHEMICAL INVESTIGATION OF or potassic hydroxide and therefore did not contain any pentathi nate; after standing 24 hours the solution had acquired an ac reaction without separation of sulphur. The decomposition can be represented by the equation-2K2S,0 = Kc,S,O + K2S04 + SO2.Potassic pentathionate was not detected at this stage of the trans-formation. Six days after the preparation of the solution potassic sulphate and sulphurous acid were found in abundance and com-paratively large quantities of potassic penththionate were detected by means of ammonia-silver nitrate and potassic hydroxide respec-ti vel y . I t follows therefore that an aqueous solution of potassic tri-thionate decomposes at 18" slowly into potassic sulphate sulphurous acid and sulphur but the latter is not set free as it enters into com-bination with potassic trithionate forming tetra- and penta-thionate respectively-SKZSaOij = 2Kc,S04 + 2SOe + K2S506. A solution of one of the three salts pot,assic penta- tetra- or tri-thionate will contain if left to itself f o r some time all three salts.An attempt to separate the salts so formed by crystallisation failed, because the quantity of material (6 grams) I used was not large enough f o r the purpose the crystals being too small and interlaced t o allow of their mechanical separation. The question " Can common sulphur combine with potassic tri-or potassic tetra-thionate as sulphur does statu nascendi ?" suggested the following experiment :-0.940 gram of sulphur which had been crystallised from carbonic disulphide was left in contact with a concentrated solution of potassic t'etrathionate for 24 hours. The sulphur was after the lapse of this time collected on a weighed filter and found to have lost only 1 mgrm.in weight and the solution of the potassic tetrathionate appeared to be quite unaltered ; no trace of pentathionate could be detected in it. From this experiment and from a similar one made by Mr. Lewes with sulphur and hydric tetrathionate rhombic sulphur appears to be insoluble in potassic tetrathionate. Spring asserts however that hydric t'etrathionate dissolves flowers of sulphur if digested with it for a month or two (Annalen 213, 339). He analysed the solutions according to Kessler's method, by boiling with mercuric cyanide and found that the ratio of sulphur in the mercuric sulphide to the sulphur precipitated in the free state increased during the digestion of hydric tetrathionate with sulphur WXCKENRODER’S SOLUTION. 315 Hydric tetrathionate gave with mercuric cyanide (p.287)-[HzSOA] EIgS S = 1.98 1 1.04. And after treatment with flowers oE mlphur-HZSO HgS 55 = - 1 1.85. The change of the ratio 1 1.04 into 1 1.85 proves according to Spring solution of sulphur in the acid. Now there is good reason for assuming that hydric tetrathionate comports itself in an aqueous s o h -tion like the potassium salt viz. it will decompose into hydric tri-thionnte and hydric pentathionate and the former changes into hydric sulphate sulphurous acid and sulphur which in statzc nascendi would recombine with undecomposed hydric tetrathionate and pro-duce pentathionate. But if these reactions occur then the above ratio 1 1.04 can change into 1 1.85 without the solution of an atom of sulphur in hydric tetrathionste.Therefore Spring has not proved the solubility of flowers of sulphur in hydric tetrathionate. Potassic tetrathionate does not only combine with sulphur in stntu nascendi set free by its own spontaneous decomposition but generally with sulphur in statu nascendi forming potassic pentathio-nate. Bromine-water decomposes potassic tetrathionate according to the equation-K2Sa06 + 2H,O + Br2 = 2RBr + 2H,S04 + s,. I f the bromine-water is added cautiously and slowly the sulphur, instead of falling down will combine with another portion of PO-tassic tetrathionate and produce potassic pentathionate. Or if a solu-tion of potassic tetrathionate is mixed with hydric sulphate and hydric sulphide passed in excess the followiug decomposition will take place :-Also in this case the sulphur instead of becoming free will com-bine with undecomposed potassic tetrathionate and produce the penta-thionate.This behaviour of sulphur in statu ?lascendi enables us to prepare potassic pentathionate from tetrathionate. Preparation of Potassic Pentathionate from Potassic I’etrathionate. 72 grams of pure potassic tetrathionate were dissolved in 24@ C.C. of water acidulated with 4 grams of hydric sulphate. A sample of this solution gave with ammonia-silver nitrate and potassic hydroxide respectively no reactions of pentathionate. A slow current of hydric sulphide was passed for one hour through the solu 31 6 DEBUS CHEMICAL INVESTlGATION OF tion and the liquid after this treatment allowed to stand for two days in a closed cylinder.The smell of sulphuretted hydrogeu was gone a t the end of this time without separation of much sul-phur. The quantity of sulphur which had precipitated was in fact not more than would have separated if sulphuretted hydrogen water had been left standing in a closed bottle for two days. The solu-tion now comported itself with ammonia-silver nitrate and potassic hydroxide respectively like one of potassic pentathionate. I n order to extract this salt the small precipitate of sulphur was separated by filtration the clear filtrate allowed to evaporate spontaneously a t common temperatures and the crystals which formed were from time to time removed from the liquid. Seven portions of crystals were collected. The first consisted of pure potassic tetrathionate the second contained in addition a little potassic pentathionate the third a little more of this salt and the last four crops of crystals were very rich in pentathionate.These which weighed 24 grams were united and dissolved in 70 grams of water acidulated with 1 C.C. of hydric sulphate. The solu-tion left to spontaneous evaporation gave first only crystals o f potassic tetrathionate and towards the end of the crystallisation only crystals of potassic pentathionate. The crystals were very fine most of them a quarter of an inch in diameter and could easily be picked out from a crystal or two of tetrathionnte. A little more than 3 grams of pure potassic pentathionate was collected. I. 0.354 gram gave after ignition 0.171 gram of potassic sulphate. IT. 0.59 gram gave 0.2855 gram potassic sulphate.0.3845 gram completely oxidised with bromine-water pave on addition of baric chloride 1.241 gram of baric sulphate. 111. 0.19 gram of another preparation gave 0.092 gram of potassic sulphate. In 100 parts-I. 11. 111. 2K2S,0 + 3H,O. Potassium . . . . 21.64 21.69 21.68 21.60 Sulphur . . . . . . - 4,492 - 44.32 Action of some Acids OVL the Solutions of Potassic Polythionates. Two test-tubes one containing 10 C.C. of a pure concentrfited solution of potassia pentathionate and the other 10 c,c. of a similar solution mixed with & C.C. of hydric sulphate were corked and kept for several days near each other. The solution containing potassic pentathionate only was after eleven days quite turbid from fre WACKENRODER’S SOLUTION.317 snlphur and after three weeks contained a comparatively large precipitate of sulphur. The solution which contained besides potassic pentathionate a little hydric sulphate appeared to be quite unchanged after three months. Into four test-tubes 10 C.C. of different solutions were introduced in the 1st was a 10 per cent. solution of pure potassic pentathionate in the 2nd a similar solution with one drop of strong hydric chloride in the 3rd a similar solution with three drops of hydric chloride and in the 4th a similar solution with some acetic acid. The solution of pure potassic pentathionate commenced to deposit sulphur within three d a p after its preparation the one which contained hydric acetate in addition to the potassium salt remained unchanged for a fortnight, and then entered into slow decomposition with precipitation of sulphur.The sulphur precipitate continued to increase for some weeks. After seven months the solutions were filtered and carefully examined. The same substances potassic pentathionate potassic trithionate, and potassic sulphate were found in both. The tubes which con-tained hydric chloride besides potassic pentathionate showed no signs of decomposition after seven months’ keeping. Therefore com-paratively small quantities of hydric chloride or hydric sulphate prevent the decomposition of potassic pentathionate in an aqueous solution whilst hydric acet,ate exerts a retarding influence only. The spontaneous decomposition of potassic tetrathionate is likewise prevented by the presence of about 2 per cent.of hydric sulphate ; a solution of potassic trithionate acidulated with hydric sulphate decomposes apparently quite as easily as a solution of the pure salt . 6.5 grams of potassic trithionate were dissolved in 30 C.C. of water containing 4 C.C. of hydric sulphnt,e. After 24 hours large quantities of sulphurous acid were observed and in the course of two weeks precipitation of sulphur had taken place. Spontaneous Decomposition of WacZcen?roder’s 80 lution. As this solution is a mixture of the hydrogen salts of the pols-thionic acids its spontaneous decomposition might be expected if no hydric sulphate were present. But as my solutions usually contained about 2 per cent. of this substanoe the question arose whether this amount of sulphate exerts a protecting influence over the polythionates of the solution.A sample of concentrated Waokenroder’s sollition oould be kept foF three months in a dark place without the slightest decomposition. But after this time a slow decomposition set in whioh manifeste 318 DEBUS CHEMICAL IYVESTIOATION OF itself by the development of sulphui~ons acid and the precipitation of sulphur. After two years the liquid appeared like a strong solution of sulphurous acid and contained a proportionately large precipitate of nionoclinic sulphur. The liquid aboTe this sulphur was perfectly clear it was separated by filtration from the sediment and then placed over pieces of potassic hydroxide under a bell-jar. After eight days, all the sulphurous acid had left the solution and combined with the potassic hydroxide.The small quantity of sulphur which had sepa-rated during the evaporation of the sulphurous acid was removed from the liquid by filtration. The qualitative examination of the filtrate revealed the presence of R small amount of hydric trithionate some hydric liexathionate (ammonia gave an immediate precipitate even when used in excess), and much hydric pentathionate. The remainder of the filtrate was evaporated nntil its sp. gr. was 1.284. During evaporation some sulphur separated. The filtrate from this sulphur measured 35 c.c. and was a t first clear but soon became turbid. A concentrated solution of 13.5 grams of potassic acetate was added to it and the mixture placed in a draught closet. The crystalline cake le€t after evaporation of the water and hydric acetate was recrystallised from water acidulated with a little hydric snlphate.Four portions of crystals were separated and collected. a. Crystals like potassic pentathionate. 0.510 gram gave after ignition 0-2496 gram of potassic sulphate. I n 100 parts-Found. Theory. Potassium 21.93 21-60 The solution of these crystals comported itself with potassic hydroxide ammonia-silver nitrate and mercurous nitrate respectively, like a pentathionate. b. Crystals like potassic tetrathionate. 0.613 gram gave 0.347 gram of potassic sulphate. I n 100 parts-Pound. Theory. Potassium. . 25.37 25.82 A solution of these crystals behaved with solution of potassic hydroxide ammonia-silver nitrate mercurous nitrate and cupric sulphate like a tetrathionate.c . Crystals of potassic sulphate. d. , 9 , From these experiments it follows that Wackenroder's solutio WACKER’RODER’S SOLUTION. 319 decomposes spontaneously like the potassium salts of the polTthionic acids and that this decomposition is very slow being incomplete even after two years and is probably retarded but not prevented by the presence of about 2 per cent. of hydric sulphate. Such an amount of sulphate would prevent the decomposition of potassic pentathionate and tetrbthionate. Does the Air promote the Xpontaueous Decomposition of Potassic Tetra-t hionate,? Three tubes were about half filled with a solution of 8 parts of water and 1 part of potassic tetrathionate. Two of the tubes were exhausted by means of the air-pump and then sealed in a blowpipe flame.The third tube was closed by a cork and placed by the side of the two others. The liquids in all these tubes had become acid after 12 days but only those in the exhausted tubes had deposited sulphur. Potassic pentathionate could be detected in all three tubes. Therefore the decomposition of potassic tetruthionate solution had been more rapid in the exhausted tubes. Discussion of the behaviour of the Potassic Polythionates i n Aqueous So 1 ut ion. I t has been shown (pp. 311 and 312) that these salts decompose in aqueous solutions according to the equations-(1.) K,SSOS = KzSa06 + S. (2.) 2Ki,S406 = K2S,06 + K2S306. (3.) K(zs30tj = KK,SO~ + so + s. But the sulphur of this last reaction is not set free but combines with undecomposed potassic trithionate forming potassic tetra-thionate-or pentathionate-KzS306 + s = Ki,S406; KzS306 + &= &,Sa06.The last three equations can be united-5Ki,s306 = & s 5 0 6 + KzS406 + 3&so4 + 3soz . . . . . (3.) The reactions are consequently of a reciprocal nature that is to say, they are reversible and can take place in opposite directions appa-rently with equal facility. This interesting behaviour is no doubt, in great measure dependent on the heat of formation of the pols-thionates 320 DEBUS CHEMICAL INVESTIGATION OF Thomsen (Thermochenzische Untersicchungen 2 264 ; 3 236) calcu lates the following values for the heat of formation of the bodies in question -Hydric dithionate . . . . . . , trithionate .. . . . , tetrathionate . . . . . , pentathionate . . . . Potassic di thionate. . . . . . . . , trithionate , tetrathionat'e . . . . , pentathionate . . . . From these numbers it appears that the hydrogen and potassium salts of the polythionic acids develop by their formation from water and the elements less and less heat as they become richer in sulphur. When potassic trithionate unites with 1 atom of sulphur no less than 8640 cal. are rendered latent and the same quantity of energy seems to be stored up when potassic tetrathionate unites with 1 atom of sulphur forming pentathionate. The compounds with regard to these sulphur atoms are endothermic. A sulphur-atom which detaches itself from a molecule of potassic tetrathionate carries away with it an amount of energy corresponding to about 9000 cal.and this amount is sufficient to enable the atom to reunite with amolecule of trithionate to tetrathionate or with the latter to form pentathionate. The near approach to equality of the differences in the last column suggests tliat the differellt sulphur atoms are really of equal thermo-chemical value. The reactions represented by the equations (l) (2) and ( 3 ) 011 p. 319 occur under the same chemical and physical conditions and take place in the same liquid. From this i t follows of necessity that in it solution containing potassic tri- tetra- and penta-thionate decomposi-tion and re-formation of these salts must be continuously going on, that is to say the sulphur atoms are in uninterrupted migration from salt to salt.The molecules of liquids are regarded as being in a state of con-tinual motion-translatory rolling one over the other and rotating round their centres of gravity (Clausius Abhandlzclzgen 1867 2,237). The colliding molecules must come in this way in variable positions towards each other. Not every relative position of 2 mols. enables them to enter into chemical reaction but of all positions which 2 mols. can assume towards each other there will be one more favourable to chemical action than the others. This relative position of 2 mols. towards each other I will call their " position of reaction. WACKENRODER’S SOLUTION. 321 Whenever 1 mol. of potassic pentathionate meets a molecule of potassic trithionate in the position of reaction 2 mols.of potassic tetrathionate will be the result of their interaction (p. 319) o r if a molecule of potassic pentathionate meets with one of tetrathionate in the position of reaction the transfer of a sulphur-atom from the pentathionate to the tetrathionate will follow. The penta- becomes tetra- and the tetra- penta-thionate. Two molecules of potassic tetrathionate in their position of reaction produce one of trithionate and one of pentathionbte. Like a pendulum which during its fall acquires the necessary uis viva to rise again to a height equal to that of its descent so the sulphur atoms of one polythionate acquire during decomposition the necessary energy to combine with another polythionate. The decomposition represented by the equations mentioned before and the conditions under which they occur require of necessity the migration of one sulphur atom of potassic tetrathionate and of two sulphur atoms of potassic pentathionate between the molecules of the potassic polythionates ; hut they also point out that after some time a certain transient ratio between the quantities of the polythionates will be established.This will occur if in a unit of time as much of each of the salts present is re-formed as is decomposed. If one of the three polythionates penta- tetra- or tri-thionates is dissolved in water the solution will after some time contain all three and their relative quanfities will depend on the conditions just stated. If this state of equilibrium between the formation and decomposi-tion of the polythionates could be maintained then the relative quantities of the different salts would remain unaltered.But this cannot be on account of the decomposition of potassic trithionate into potassic sulphate sulphurous acid and sulphur a chemical change which cannot be rerersed. Ths oxidation of the sulphurous to sulphuric acid which prevents the decomposition of penta- and tetra-thionate exercises also in course of time a disturbing influence. As soon as a certain amount of hydric sulphate has accumulated the spontaneoiis decomposition of potassic penta- and tetra-thionate will cease but that of potassic trithionate will go on. Hence the final state of equilibrium which ought to result after a long time (several months) would be potassic sulphate hydric sulphate sulphur potassic tetrathionate and potassic pentathionate each of them in certain fixed quantity and not undergoing further chemical change.Another important conclusion following from the equations (p. 319) is that in spite of the liquid condition the molecules come comparatively seldom into the position of reaction. Equation (2) is only partially realised after a 10 per cent. solutio 32 2 DERUS CHEMICAL INVESTIGA TION OF of potassic tetrathionate has been kept for 12 days. In this trans-€ormation no external energy has to be introduced the internal forces are sufficient for the purpose and nevertheless it proceeds very slowly probably f o r the reason given. But if the mo:ecules although they are in the liquid state only seldom assume t h e position of reaction towards each other then t h e y cannot be so movable arnongst each other as i3 commonly assumed they must have a tendency dependent on their chemical nature to set themselves in certain positions towni-ds each other and these positions need not be the positions of reaction.A solution of potassic penta-thionate decomposes by degrees into potassic tetrathionate and sulphur. If a molecule of sulphur contains only six atoms of sulphur and if the composition of potassic pentathionate in solution is the same as in the dry state then 3 mols. of hydrated potassic pentathionate must come into the position of reaction in order to decompose according to the equation-3[2Ki,S,0,,3H20J = 6K2Sa06 + s + 9H,O. The slowness of this decomposition indicates that the position of reaction is not often assumed by the molecules of potassic penta-t hionate.If now we consider molecules of potassic tetrathionate placed between the molecules of the pentathionate then the decomposition of the latter ought to be further retarded. The mere presence of tetra-molecules between the penta-molecules would be a mechanical hindrance to the latter to meet in the position of reaction and the tetra-molecules would also have a tendency to combine with sulphur in s t a t u nascendi set free by the decomposition of potassic penta-thionate and with this sulphur again to form potassic pentathionate, thus restoring the original state of things. To test this conclusion the following experiments were made. Four solutions were prepared of the following composition -I.0.6 gram of potassic pentat'hionate in 10 C.C. of water. 11. 0.6 gram of potassic pentathionate and 0.5 gram potassic tetrnthionate in 10 C.C. of water. 111. 0.6 gram of potassic pentathionate and 2-5 grams of potassic tetrathionate in 15 C.C. of water 1 mol. of K2S,06 and 5 mols. R,S,Os. IV. 0.483 gram of potassic pentathionate and 4.09 grams of potassic tetrnthionate in 15 C.C. of water or 1 mol. of K,S,0,,1&E20 + 10 mols. K2S40s. The solutions were perfectly clear and neutral and were placed i WACKENRODER'S SOLUTION. 323 corked tubes in the same test-tube stand. .After the lapse of 10 days, the following changes had taken place :-I and I1 had deposited a small precipitate of snlphur I11 and IV were still clear and like I and 11 neutral.After the lapse of 14 days an increase in the quantity of the sulphur precipitate in I and I1 was noted ; I was still neutral I1 slight'ly acid. Some of the potassic tet'rathionate of I1 had decomposed into sulphur and trithionate and some of the latter into potassic sulphate sulphur, and sulphurous acid. I11 was still clear but slightly acid and produced with baric chloride a little baric sulphate. NO odour of sulphurous acid was percep tihle. IV was slightly turbid smelt of sulphurous acid and gave a copious precipitate with baric chloride. The sulphur of I and I1 was collected on weighed filters. I gave 0.020 gram. I1 only 0.004 ,, That is to say the solution of pure potassic pentathionate had deposited in 14 d q s five times as much sulphur as the solution which contained for every molecule of potassic pentathionate a molecule of potassic tetrathionate or two-fifths of the pentathionate of I and only two twenty-fifths of that salt of I1 were decomposed.Solution I11 was still clear after the lapse of 21 days and free from the smell of sulpliiirous acid but IV now contained much precipitated sulphur and also free sulphurous acid. I n the course of the fourth week sulphur and sulphurous acid also appeared in Solution 111. In another series of experiments with three solutions of which the first contained only potassic pentathionate the second in addition to every molecule of pentathionate a molecule of tetrnthionate and the third 2 mols. of t'etrathionate to 1 of pentathionate similar resnlts were obtained.After the lapse of seven days much sulphur was found in the solution of pure potassic pentathionate considerably less in the solution which contained an equal number of molecules of both salts and none at all in the liquid in which the molecular ratio of penta- to tetra-thionnte was as 1 to 2. These experiments prove that the decomposition of pota ssic penta-thionate into potassic tetrathionate and sulphur is retarded by the presence of potassic tetrathionate and that the degree of retardation is dependent on the quantity of potassic tetrathionate. The retardation was greatest in the above experiments when the solutions contained 1 mol. of potassic pentathionate to 5 mols. of the tetrathionate. The decomposition became accelerated again whe 324 DEBUS CHEMICAL IXVESTIGSTIOX OF 10 mols.of tetrathionate were mixed with 1 mol. of pentathionate, because the chemical change represented by equation (2) (p. 319) tends to increase the quantity of the potassic pentathionate. By means of similar experiments it was proved tlia t the decomposition of potassic tetrathionate expressed by equation (2) (p. 319) is retarded by the presence of potassic pentathionate. The cause of this influencr is easily seen. If we add potassic pentathionate to a solution of potassic tetrathionate which is partially decomposed according to the equation-2K,S,O = K&06 + K2S30,, TTrith formation of potassic trithionnte then t'he sulphur liberated by the spontaneous decomposition of the pentathionate-K,S,O = K&O + s, will combine with the trithionate and reproduce tetrathionate and so prevent the decomposition expressed by the equation-K,S;,O6 = K2SOd + SO + s.Not less intelligible is the fact that for a certain proportion of the two salts potassic tetra- and penta-thionate the rate of change will be a minimum and if one of these two salts is present in greater pro-portion its peculiar decomposition will preponderate a8nd thereby increase the rate of change. It has been shown that hydric sulphate prevents the spontaneous decomposition of potassic penta- and tetra-thionates. A certain pro-portion of the sulphate about 2 per cent. is sufficient for this purpose, :tnd its action consists in preventing the molecules of these polythio-iiates from assuming towards each other the position of reaction.The hydric sulphate has a polarising action on the molecules and, perhaps in a similar way it acts on the molecules of water in electro-lysis. Explimation of two Properties of Ozone. Ozone and potassic pentathionate resemble each other in some respects ; both undergo slow spontaneous decomposition. Acids render them more stable.* Alkalis cause rapid chemical decomposition, oxygen is given off from ozone and sulphur from potassic penta-t,hionate.t Both the oxygen liberated from ozone and the sulphur from the pentathionate were in endothermic combination. * V. Babo Bmelin-Kraut Randbook 1 26 ; Jeremin Jahresbericht by Liebig. t Soret Gmelin-Kraut 1 and 2 27. &c. 1878 197. This paper p. This paper p. 311 WACKENRODER'S SOLUTION. 325 An aqueous solution of potassic pen tathionate decomposes very slowly into potassic tetratbionate and sulphur.Ozone by degrees, at common temperatures returns to the condition of ordinary oxygen,* and both transformations agree in this respect that they are not com-plete after the lapse of six months. The explanation given of the spontaneous decomposition of potassic pentathionate may therefore, with a high degree of probability be applied to the slow chemical change of ozone. Concentrated solutions of potassic pentathionates decompose with greater rapidity than weak ones and oxygen highly charged with ozone loses the latter more quickly than gas which contains a smaller quantity of ozone. Whenever 2 mols. of ozone meet under favourable conditions that is to say when they come into such a position that an oxygen atom of one can combine with an oxygen atom of the other, or in other words when they come in the position of rewtion then 2 mols.of ozone will be transformed into 3 mols. of common oxygen. This will happen more frequently in a gas which contains a larger than in one with a smaller number of ozone molecules. The 2 mols. which participate in this reaction are of comparatively simple structure, so that we may assume that every collision brings them into the position of reaction and causes their conversion into oxygen. Notl two but perhaps six or more molecules of potassic penta-thionate molecules of complex structure must collide in the position of reaction in order to produce a molecule of sulphur and potassic tetrathionate.This will d priori not happen in every collision as in the case of ozone and consequently we arrive at the conclusion that the spontaneous decomposition of potassic pentathionate into sulphur and potassic tetrathionate will be a much slower process than the transformation of ozone into oxygen. The facts are in perfect accord with this conclusion. Ozone if kept. will become richer in oxygen and poorer in ozone, at first rapidly afterwards as the quantity of oxygen becomes larger more and more slowly until a t last a small residue of ozone appears to undergo no further diminution (Berthelot). Brodie (Phil. Tmns. 1872,445) observed that ozonised oxygen when kept lost nearly one-third of its ozone in the first 90 hours. The loss during this interval of time was by no means uniform but dimi-nished rapidly towards the close.It amounted during the first 66 hours to nearly & and during the next 24 hours only to 2% of the original quantity. The oxygen molecules as they increase in numbers and move between the ozone molecules diminish the 'frequency of collision between the latter and the consequent production of oxygen just as f Andrews and Tait Qmelin-Kraut 1 and 2 26 ; Berthel.ot Jahreshericht 1818, 197; Brodie Phil. Z'pans. 1872 445. VOL. LIlI. 32 ii DEBUS CHEMICAL INVESTIGATION O F potassic tetrathionate retards the decomposition of potassic penta-thionate. And applying the explanation of the chemical action between these two salt,s to ozone and oxygen we arrive at the con-clusion that the oxygen molecules during their motion of translation, and consequent collisions with ozone molecules take an atom of oxygen from the latter and thus become ozone molecules and the ozone molecules in consequence of this loss will become oxygen molecules.Expressed in other words in ozonised oxygen the ozone is continually decomposed and re-formed or oxygen atoms migr:bte between oxygen and ozone molecules. I n the same way as has been shown a siilphur atom passes from a molecule of potassic pentathionate to a molecule of potassic tetrathionate the latter becoming peiita- and the former tetra-thionate. The conversion of ozone molecules into oxygen molecules during the keeping of ozonised oxygen as well as the retardation of this pro-cess as a consequence of an increase of the quantity of tbe oxygen of the mixture are I think fully explained by tbe theoretical views described.But also the fact that the amount of ozone i n oxygen cannot be increased beyond a certain limit call be deduced from the same conceptions. The oxygen molecules are split into atoms by electricity and the atoms so set free combine with oxygen molecules to form ozone. The ozone molecules by their collisions again form oxygen molecules. The limit beyond which oxygen cannot be changed to ozone is attained when in a given time as much ozone is repro-duced in one operation as is decomposed in the other. Explanation of the Decomposition of Peroxide of Hydrogen. This substance comports itself in a chemical sense very much like ozoiie and pentathionates.An aqueous solution ol peroxide of hydro-gen contains less of the latter substance a few months after prepara-tion than it did a t first probably in consequence of decomposition, according to the equation-2H202 = 2H2O + 0 2 . This decomposition proceeds more rapidly in concentrated than i n weak solutions and is accelerated by a rise of temperature.* A solution which in one litre contained 3 8 5 grams of active oxygen, in 87 days lost 3.678 grams but was not completely decomposed after two years. Older samples had lost all their peroxide of hydrogen. This behaviour is very like that of a solution of potassic pentathionate, * Berthelot Jahresbericht 1880 p. 136; also according to my own observa-tions R A CKCNRODE R'S SOLUTION. 32 7 and both substances are endothermic compounds.Whenever 2 mols. of peroxide of hydrogen meet in the position of reaction then decompo-sition into water antl oxygen will take place but if they collide i n other positions thcn they will not decompose. From this teiict the properties of perosirle of hydrogen mentioncrl before can be deduced. The spontaneous decomposition will bo retarded when water molecules are placed between the niolecules of peroxide of hydrogen a,nd tlie retardation will increase with the quan-tity of water. d weak solution ole peroxide of hydrogen is more stable than a concentra,ted one. The similarity which exists between the spontaneous decompositions of potassic pentathionate antl peroxide of hydrogen justifies i l i e assumption that peroxide of hydrogen and water comport themselves towards each other like potassic pantatIiiona0e and tetrat hionate.It has been prove(l that an atom of sulphur can separate from penta-thionate and unite with tetratliionate (p. 323). By analogy then we conclude that when R molccule of water am1 a molecule of peroxide of hydrogen during collision asslime the posit;on of reaction the water will become peroxide of hy'irogen and the peroxide of hydrogen water that is to say an atom oE oxygen will migrate from one mole-cule to another. The peroxide of hydro9en in an aqueous solution is therefore in a continunus state of dec~otuposition and formation hoir-ever in such a -way ifhat for each stale of concefltration the arnonnt of decomposition (very small in weak solutions) prevails over the amount of forniaii,m i n the same time.The decomposiiion of peroxide of hydrogen into water and oxygen is retarded by some and acceleraled by other substances. Platinum, silver. oxide and manganic dioxide respectively promote whilst acids preI-ent the decomposition. Platinnm possesses a great attraction for oxygen its powder absorbs more than 200 times its volume of the gas. This attraction is also exerted towards oxygen which is in chemical combination. If now a piece of platinum is placed in peroxide oE hydrogen the molecules of the latter will place themselves in such a position on the surface of the platinum that one oxygen-atom of the peroxide*is turned towards the plat'inum arid a s near to it as possible. The per-oxide is polnrisetl. Hut th i s has the effect also of bringing the oxygen-atoms of different moleciiles of peroxide in such close proximity on the surface of tlie metal t h a t they can combine to form common oxjgen the decomposition of the peroxide into water and oxygeii and development of euergy being t h e consequence.The action of the platinum places the rnolecules of the peroxide in the posL'tiora of reuctioib towards each other. The action of silver oxide and of black oxide of manganese are similar. 2 328 DEBUS CHEMICAL INVESTIGATION OF Similar observations can be made on the aqueous solutions of the oxides of chlorine &c. (Williamson Annalen 54 133). The Action of Hydric Xulphide on Pentathiolzates. 2.95 grams of potassic pentathionate were dissolved in 20 C.C. of water and a very concentrated solution of 8.458 grains of dihydric tartrate added.The precipitated potassic hydric tartrate was after two days’ standing removed by filtration and a slow current of hydric sulphide passed for half an hour through the clear filtrate. The liquid was now put aside in a well-stoppered cylinder for 24 hours. The smell of hydric sulphide had disappeared after the lapse of this time. This treatment with hydric sulphide was repeated several times until all the hydric pentathionate was decomposed. The result of these operations was a copious precipitate of sulphur and a clear colourless liquid. Only a trace of trithionic acid could be discovered in this liquid. Hydric pentathionate and hydric sulphide therefore form water and sulphur :-H,S,06 + 5H2S = GH2O + 10s.The non-production of hydric sulphate is interesting. An aqueous solution of 10.3 grams of potassic pentathionate was treated like hydric pentathionate with hydric sulphide until no further action appeared to take place. A copious precipitate of sulphur had collected which was separated by filtration and the filtrate care-fully examined. Potassic trithionate and potassic thiosulphate were detected and obtained in crystals by evaporation. The reactions are probably represented by the following equa-tions :-K:,SjOs + H2S = K2SZO3 + H,S?O + Sz H2S,03 = SO + H,O + S 2K2S203 + 3SOs = 2K2Sj06 + S, and these united :-3K2S5Os + 3HzS = K-SSZO + 2K,S30 + 3HzO + 10s. Action of Hydric Xulphide on Tetrathionates. A solution of pure hydric tetrathionate prepared by the same method as that by which the corresponding pentathionate had been obtained was treated repeatedly with hydric sulphide till the decom-position appeared to be complete.Less sulphur was precipitated in these operations than in the cor-responding experiments with hydric pentathionate. In the resulting liquid hydric pentathionate alone could be discovered. From this i WACKENRODER’S SOLUTION. 329 appears that hydric tetrathionate decomposes with hydric sulphide iuto water and sulphur,:-H2S406 + 5H2S = 6HzO + YS. Some of the sulphur in statzc nnscendi combines with hydric tetra-thionate to form h ydric pentathionate. If the treatment with hydric sulphide had been continued long enough only water and sulphur would have been obtained. Action of Hydric Xulphide o n Trithionales.Hydric sulphide acts on potassic trithionate only very slowly much more slowly than on pentathionates or tetrathionates. A solution of potassic trithionate saturated with hydric sulphide had to stand three days before all the hydric sulphide was decomposed. The odour of sulphurous acid could then be perceived and a precipitate of sulphnz. had fallen down. The liquid was separated from the sulphur and examined after it had undergone four treatments with hydric sulphide. Potassic thiosulphate potassic sulphate and sulphur were the only products of decomposition found :-Hydric trithionate was prepared from the barium salt and the latter from a Wackenroder’s solution which contained some free sulphurous acid and baric carbonate.The baric pentathionate and tetrathionate were deprived by the baric sulphite respectively of two and of one atom of sulphur and converted into baric trithionate tbe baric snlphite itself becoming bark thiosulphate. Analysis of the baric tritbionate :-0.3915 gram dried over hydric sulphate and oxidised with bromine-water produced 0.259 gram and the filtrate on addition of baric chloride 0.505 gram of baric sulphate. 100 parts of the salt contain according to these numbers 38.88 parts of barium and 26.89 parts of sulphur. The formula 2BaS306 + 3Hz0 requires 38.48 parts of barium and 86.97 parts of sulphur. The atomic ratio is-Ba S = 1 2.94. 5.942 grams of this salt were dissolved in 50 C.C. of water and pre-cipitated with 1.687 gram of hydric sulphate.The filtrate from the baric sulphate measured 75 c.c. and comported itself with reagents like h y dric t ri t h ionat e. Twenty-four hours after preparation the filtrate had acquired the odour of sulphurous acid and a precipitate of sulphur had fallen down. The latter was separated by filtration and the clear liquid placed unde 330 DEBUS CHEMICAL INVESTIGATION O F a bell-jar over pieces of potassic hydroxide. The sulphurous acid volatilised in the course of two days but another precipitate of sulphur was found in the liquid. Put back into a closed bottle the odour of sdphurous acid reappeared in one 01' two clays. These Observations irldicate that hydric trithionate is a t common tempcratures in a slow state of decomposition. After several weeks undecomposed hydric trithionate could still be detected by means of a qualitative examina-ti o 11.'l'wo days after the preparation of the hydric trithionate no hydric pentathionate could be delected in it but after the hpse of 14 days, considerable quantities of it and also of hydric sulphate were observed. 'The equation-H,S,j06 = HZSO + SO2 + s, 1-epresents the slow decomposition of the solution. But the sulphur does not all separate in the free state a portion unites with undecom-posed hydric trithionate forminq hydric pentathionate and probably h ydric tetrathionate. The solution of hydric trithionate behaves in the same manner during evaporation on the water-bath only the decomposition is much more rapid. But even after the solution has been evaporated to + of its original volume and has parted with much sulphur and sulphurous acid undecomposed hydric trithionate can be detected in it.I concluded from these observations that hydric tritliionate would be easily decomposed by hjdric sulphide. Experi-ment proved this conclusion to be erroneous. A solution of hydric t ri thionate was saturated with sulphuret ted hydrogen immediately after its preparation and kept in a closed bottle for three days. No change could be observed the liquid seemed to contain after this lapse of time as much hydric sulphide as i t did immediately after the passage of the gas. Over pieces of potassic hydroxide under a bell-jar it lost, in a few days the sulphuretted hydrogen and a little sulphur was precipitated. The qualitative examination revealed the presence of some hydric sulphate and hydric pentathionate besides the hydric trithionate.Hence it appears that hydric trithionate is not acted upon 5 y hydyic sulphide a t commoii temperatures. Hy dric pentathionate and hydric tetrathionate are easily decom -posed by hydric sulphide ; hydric trithionate a far less stable compound, which slowly evolves sulphurous acid is not acted on. The explana-tion of this anomaly appears to me to be as follows :-Hydric tetra- and penta-thionate produce with hydric sulphide water and sulphur but n o h y d k sulphute. The hydrogen of the ~ J J chic sulphide reacts with the oxygen of these compounds. During A second experiment gave similar results WACKENRODER'S SOLUTION. 331 their spontaneous decomposition in aqueous solutions sulphur is separated but no sulphate is produced.An aqueous solution of hydric trithionate on the other hand is continuously in a slow st'ate of de-composition with formation of hydric sulphate. The arrangement of the atoms in t'he trithionate must be such that the affinity of sulphur for oxygen is easily satisfied. In the case of a solution of hydric tri-thionate saturated with hydric sulphide two influences make them-selves felt. On the one hand the afEnity of the sulphur atoms for the oxygen atoms a,nd on tbe other hand the affinity of the hydrogen of the hydric sulphide for the oxygen of the trithionate. These two attractions are opposed to and counterbalance each other so that a solution of hydric trithionate saturated with hydric sulphide is accord-i n g to experinlent more stable than one of pure hydric trithionate.A different result is obtained where hydric sulphide is passed into a mixture of the three polythionates hydric trithionate hydric tetra-thionafe and hydric pentathionate. The hydric trithionate quickly disappears. Sulphuret ted hydrogen and hydric tetra- or penta-thionate produce water and sulphur. Sulphur in sfatu nascendi combining with hydric trithionate forming respectively tetrathionate and pent at h i on ate . Prom the foregoing observations the conclusion may be drawn that if a current of sulphurelted hydrogen is passed through a Wach-en-roder's solution in which hyclric trithionate hgdric tetrathiona t,e and hydric pentathionate are present) until t h e gas ceases to act on tlie solution water and sulphur will be the f i n d products of decomposition.This conclusion was verified by experiment. The equation-by which t)he text-books represent the chemical action between hydric sulphide and sulphurous acid is correct for the filial products of the reactions. The polythionntes a,re intermediate products be tween the original materials sulphurous acid sulphurelt,ed hydrogen and water on the one hand and sulphvr and waler the fixed products on tbe other. Action of Sulphurous Acid o n Polythiosmtes. Action of XulpIcurods Acid on Hydric Pe7itathinnate. Sulphurous acid parhially converts hydric pentathiovate into hydric trithionaLe. The solution oE hyclric pentra,bhiooate was obhined by the precipitation of poiassic peviil,oh;outtie wihh hydric dartrnte as described on p.328. One volume of ths liquid so prepared was mixe 332 DERUS CHEMICAL INVESTIGATION OF with two volumes of concentrated hydric sulphite. The colourless liquid became intensely yellow in the course of three hours and during the following t,wo days deposited some sulphur. After it had been kept in a closed bottle for three days i t was placed over pieces of potassic hydroxide under a bell-jar and allowed to remain till all the sulphurous acid had volatilised and combined with the base Sulphur was precipitaked whilst the sulphurous acid was escaping and the yellow liquid became colourless. After all the sulphurous acid was gone a qualitative examination of the remaining liquid proved the presence in it of hydric trithionato and hydric pentathionate.The action of sulphurous acid on hydric pentathionate may therefore be explained as follows The sulphurous acid withdraws sulphur from the pentathionate forming a yellow solution. This solution of sulphur in sulphurous acid deposits some of its sulphur in the form of a precipitate when i t is left standing in a closed bottle or during the vo1at;ilisation of the sulphurous acid. The pentathionate from which the sulphur has been taken by the sulphurous acid becomes in con-sequence hydric trithionate. The sulphur unites with the sulphurous acid with a very feeble force the compound behaving like a simple solution of sulphur in sulphurous acid. I will assume that this com-pound which we shall have to consider again is thiosulphuric or hyposulphurous acid S202 :-H?S,O + 2S02 = H?S,O + 2x202.This decomposition is however incomplete even a Zlxrge excess of sulphurous acid does not convert all the pentathionate into trithionate. Probably therefore the reaction is of a reciprocal nature and the hydric trithionate can receive from thiosulphuric acid SzO, sulphur, and re-form hydric pentathionate. Action of Sulphurous Acid or Sulphites on Potassic Pentathionate. 10 grams of potassic pentathionate dissolved in 30 C.C. of hydric sulphite to a yellow liquid. Baric carbonate was now added until all the acid was neutralised. Instead of baric sulphite baric thiosulphate was obtained as an abundant crystalline precipitate. The filtrate from the sparingly soluble baric thiosulphate was freed from barium by careful addition of potassic carbonate and then concentrated for crystallisation.No potassic pentathionate could be detected the reaction with metallic salts like those of potassium or barium therefore is complete. The reactions can be represented by the following equations :-K2S,0 + 2S0 = K2S306 + 2S202 and 2BaC0 + 2S20 = 2BaSZ0 + 2C0,. Crj-stals of pure potassic trithionate were obtained WACKENRODER'S SOLUTION. 333 Action of Dipotassic Sulphite on I'otassic Pentathionate. 4 grams of pure potassic pentathionate dissolved a t 17" in 20 C.C. of water with a reduction of 3" of temperature. The solution was mixed with one of pure dipotassic sulphite K,SOs. A consider-able quantity of sulphurous acid was set free and a small precipitate of sulphur formed.Addition of barium chloride caused the precipita-tion* of a large amount of baric thiosulphate. The proportionally large quantity of the latter and the evolution of much sulphurous acid lead to the conclusion that dipotassic sulphite is decomposed by water into potassic hydroxide and sulphurous acid and that the potassic hydroxide decomposes the potassic pentathionate according to the equation-2K2S506 + 6KH0 = 5K,X2O3 + 3H20. Action of Xulphurous Acid on Hydric Tetrathionate. The hydric tetrathionate was prepared by double decomposition of potassic tetrathionate and hydric tartrate. One volume was mixed with two volumes of a concentrated solution of sulphurous acid. The mixture was still colourless three hours after preparation and turned yellow in the course of the three following days but without sepura-tion of sulphur.Placed over pieces of potassic hydroxide under a bell-jar for the removal of the sulphurous acid the yellow colour dis-appeared with the sulphurous acid but without the precipit'ation of sulphur (p. 332). The examination of the liquid after the sulphurous acid was gone proved the presence of much hydric trithionate and hydric pentathionate. The sulphurous acid had acted on the tetra-thionate in the same way that it does on the pentathionate it had taken away sulphur from the h-ydric tetrathionate and thus convertecl the latter into hydric trithionate. But the thiosulphuric acid &02, instead of precipitating sulphur during standing or during evapora-tion of the sulphurous acid gave up half its sulphur to hydric tri-thionnte or undecomposed hydric tetrathionate thus causing the formation of hydric pentathionate.The reciprocal nature of the reaction mentioned a,s an explanation on p. 332 is thus confirmed. Action of Sulphairous Acid on Wuclzenroder's Solution. A sample of this solution which did not contain sulphuretted hydrogen or sulphurous acid was used for the following experiments, without concentration on the water-bath. The 8-sulphur in solution as well as the sulphur in suspension were precipitated. To a small portion Borne cupric sulphate was added 334 DEBUS CHEMICAL INVESTIGATION OF The filtrate of this precipitate remained clear a t lOO" hence hydric trithionate was not present. From another portion the collo'idal sulphur was precipitated by a solution of saltpetre and the filtrate from the sulphur tested with an ammonia-silver nit'rate solution.Much hydric pentathionate was discovered. Tetrathionste and hexathionate were also present. Some of this Wackenroder solution was mixed with twice its volume of a concentrated solution of sulphurous acid. The mixture was then divided into two portions one portion was placed over pieces of potassic hydroxide under a bell-jar the other portion tested with cupric sulphate. A considerable dark-brown precipitate was obtained indicating much hydric trithionate. Sulphurous acid solution or the Wackenroder solution each heated with cupric sulphate to loo" re-mained unchanged. The portion of the mixture of sulphurous acid and Wackenroder solut8ion which had been placed over pieces of potassic hydroxide, was likewise tested with cupric sulphate after the volatilisation of the sulphurous acid.No precipitate was obtained at loo" conse-quently no hydric trithianate o r hydric tliiosulphate was present. The sulphur which had been wit>hdrawn from hydric tetrathionate or hydric pentathionate by the sulphurous acid had again united with the hydric trithionate during the voldilisation of the sulphurous acid thus re-forming hydric tetrathionate and hydric pentathionate. Another portion of a mixture of Wackenroder solution and liydric sulphite was allowed to stand 24 hours in a closed bottle before it was placed under a bell-jar over pieces of potassic hydroxide. After the volatilisation of the sulphurous acid considerable quantities of hydric trithionate were discovered by means of cupric sulphate.Another larger portion of Wackenroder's solution was saturated with sulphurous acid gas and then lel't to stand five days in a closed bottle. The liquid was perfectly clear and yellow at the end of this time the collo'idal sulphur having precipitated. It contained, however much sulphur in the form of thiosulphuric acid S,O (p. 332). I will mention here a few more observations on khe properties of this combination of sulphur and sulphurous acid. If left to stand for a long time sulphur will continually but slowly separate from it. The yellow colour becomes paler in consequence. But it appears to require many months before all the sulphur will pre-cipit,ate in this manner.Hydric chloride hydric sulphate potassic nitrate sodic chloi idc respectively do so with decoloration of the solution. The same effect follows the volatilisation of the sulphurous acid either spontaneously 8 t common temperatures or by boiling. I have not been able to separate this The addition of water causes no precipitation oE sulphur WACKENRODER'S SOLUTION. 335 compound from the solution it seems to exist only in presence of free sulphurous acid. Neutralisation with bark carbonate throws down baric thiosulphate as a precipitate leaving baric trithionate in solution. A precipitate so obtained was almost entirely soluble in boiling water, and the solution gave crystals of baric thiosulphate on evaporation. 0.664 gram of the crystals dried over hydric sulphate and oxidised with bromine-water gave 0.596 gram baric sulphate and the filtrate with baric chloride 0.584 gram of the same salt.Hence in 100 parts :-Theory. Found. 3BaS20 + 2H,O. Barium 52.72 52.49 Sulphur 24.40 24.52 For this reason I regard the yellow solution of sulphur in sulphurous The filtrate of the bark thiosulphate gave a crystalline precipitate acid as thiosulphuric acid SzO,. with alcohol. I. 0.739 gram of this precipitate left after ignition 0.482 pan1 bark sulphate. 11. 0.573 gram gave 0.376 gram baric sulphnte. 111. 0-283 gram oxidised with bromine-water gave 0.185 gram baric snlphate and the filtrate on addition of baric chloride again 0.360 gram of the same salt. Hence in 100 parts :-Found. r- 7 Theorv.I. 11. 111. 2BaS,O +" 3H20. Barium . . 38.28 38.59 38.28 38.48 Sulphur - - 26.45 2696 If Wackenroder's solution contains besides its usual constituents hydric pentathionate hydric tetrathionate and hydric hexathionnte, a sufficient quantity of sulphurous acid then only baric thiosulphate and baric trithionate are obtained after neutralisation with baric carbonate. This behavionr probably explains the results obtained by Cnrtius. These observations and experiments explain perfectly the action of. sulphurous acid on a Wackenroder solution. Immediately after the mixture has been prepared some of the hydric pentathionate and hydric tetrathionate are reduced by the sulphurous acid to trithionate, the sulphurous acid itself forming thiosulphuric acid SzOz with sulphur.If now a t once or very soon after the preparation of the mixture volatilisation of the sulphurous acid takes place then half the sulphur of the thiosulphuric acid SzOz will reunite with the trithio 336 DEBUS CHEMICAL INVESTIGATION O F nate forming hydric tetrathionate and hydric pentathionate and the original state of things is re-established. B u t if the mixture is allowed to stand for some time one or more days before the volatilisation of the sulphurous acid then a portion of the sulphur of the thiosulphuric acid S202 will precipitate in one of the ordinary modifications. If after such precipitation volntilisation of the sulphurous acid occurs then the sulphur resulting from the decomposition of the remaining thiosulphuric acid S202 is not sufficient to convert all the hydric trithionatc into tetrathionate or pentathionate.After the evaporation of the sulphurous acid the solution then contains hydric trithionate as is shown by the following experiment. A portion of the Wackenroder's solution charged with sulphurous acid as men-tioned on p. 334 was deprived of its sulphurous acid after five days' standing. The qualitative examination revealed much hydric trithionate and on account of the reciprocal nature of the reactions also hydric tetra-thionate and hydric pentathionate. The yellow colour of another portion of the solution had almost disappeared a year afterwards, that is to say nearly but not all the thiosulphuric acid S202 was decomposed. After removal of the sulphurous acid by evaporation, hydric trithionate hydric tetrathionate hydric pentathionate and hydric hexathionate were found in the remaining liquid.In$icence of Time on the Formation of Hydric Pentuthionate. To a saturated solution of sulphnretted hydrogen a solution of sulphurous acid was gradually added drop by drop until the odoni. of hydric sulphide had disappeared. Every drop of sulphurous acid caused a precipitate of sulphur. The action therefore appears to be instantaneous and the mixhre ought not to contain either of the substances. A tube was now quite filled with the mixture and the liquid poured from it into a larger vessel and shaken with air. The latter acquired the smell of sulphurous acid and paper moistened with lead acetate turned brown when immersed in the air conse-quently small quantities of hydric sulphide and sulphurous acid can exist for some time in a liquid prepared as described without mutual decomposition revealing their presence by their usual odour.The experiment was now repeated in reversed order. A slow current of sulpharetted hydrogen was passed for 20 minutes through a saturated solution of sulphurous acid at 0". After the lapse of 10 minutes, some of the liquid was shaken in a large vessel with air ; the latter took up sulphurous acid gas but not hydric sulphide. The liquid, however turned a paper moistened with lead acetate brown. The latter reaction could not be obtained after 12 hours WACKENRODER’S SOLUTION. 337 The same results were obtained after the liquid bad been treated a second time for 20 minutes with sulphuretted hydrogen.After a third treatment with sulphuretted hydrogen the sulphurous acid appeared to be decomposed. The liquid no longer smelt of sulphurous acid, but had a feeble odour of hydric sulphide. Also when the liquid was shaken with air it did not acquire the smell of sulphurous acid. The feeble odour of hydric sulphide disappeared however after three hours’ standing and a strong smell of sulphurous acid could now be perceived. Some of the liquid now shaken with air transferred to the latter both sulphurous acid and sulphuretted hydrogen the former recog-iiisable by its smell and t<he latter by its action on paper moistened with lead acetate. Even eight days after these experiments traces of sulphuretted hydrogen and sulphurous acid could be detected in the liquid.Similar observations were made repeatedly. The experiments described show that although concentrated soln-tions of sulphurous acid and sulphuretted hydrogen react immediately, small quantities of these two substances can exist side by side in a Wackenroder solution for some time without decomposing each other. An aqueous solution of sclphurous acid heated on a water-bath very soon loses all its acid. A similar solution mixed with sulphur powder requires a very much longer time for the volatilisation of the sul-phurous acid. Between sulphur and sulphurous acid a considerable attraction exists which manifests itself under the circumstances described. The Wackenroder solution holds much colloiidal sulphur in suspension and solution and this by its attraction for the sul-phurous acid may be the cause of the phenomena described.Perbaps also thiosulphuric acid S202 (p. 332) may be present in a Wacken-roder’s solution and by its slow decomposition into sulphur and sulphurous acid cause the reappearance of sulphurous acid some hours after the preparation of the Wackenroder’s solution appears to be finished. The yellow compound of sulphur and sulphurous acid, which I have called thiosulphuric acid plays an important part in the formation of hydric pentathionate. A slow current of sulpliuretted hydrogen was passed through 500 C.C. of a nearly saturated eolution of sulphurous acid at o”, 50 C.C. were taken out after the current had passed 25 minutes and placed in a closed bottle and another 50 C.C.were placed over pieces of potassic hydroxide under a bell-jar. Through the remaining 400 C.C. of the liquid a slow current of sulphuretted hydrogen was again passed for 65 minutes and then 50 C.C. were removed to a closed bottle, and another 50 C.C. put over potassic hydroxide 335 DEBUS CHEMICAL INVESTJGATION OF The same operation was repeated three times. I bad conse-quently five portions of liquid of which No. 1 ha,d been treated with sulphuretted hydrogen 25 minutes ; No. 2 50 minutes; No. 3, 85 minutes ; No. 4 120 minuies ; No. 5 180 minutes. The last portion No. 5 did not smell of sulphurous acid immedi-ately after prepaxation but did so two days later. It was then treated for several minutes wif,h sulphureLted hydrogen and after this did not again acquire the srnpll of snlphurous acid.Each of the 0 t h ~ four portions contained much free sulphuroixs acid. Each portion coiisisted of two parts one kept by itself in a bottle, the other over pieces of potassic hydroxide under it bell-jar. The parts over potassic hydroxide had in the course of two or three days lost their free sulphurous acid. They were now examined for the con-stituents OF Wackenroder’s solution. The srilphur in suspension and in solutiou was precipitated by addition of a solution of potassic nitrate and the clmr filtrate of the precipitate tested wilh the reagents mentioned on pp. 297 and 298. No. 1 contained only a very s m a l l quantity of hydric psntathionate and hydric trithiunats. No. 2 contained more of bolh substances than No.1 No. 3 more than No. 9 a,nd No. 4 more than No. 3. No. 5 was richer in penlathionate and poorer in trithionate than No. 4. Examination of the Poytions whi;h had been kept for a few Days in closed E0ttlt.s. These exhibited remarka hle d i Kerences from those which had been placed over potassic hydvoxide immediately after prepai-ation. The last named still possessed the cbfi racter of an emulsion contaiuing much sulphur in snspension and solution. The porlioas which had been kept a few days in closed vessels were with the exception of Xo. 5 clear and of yellow coZo~ii* and no longer belt1 s r ~ ? p h u r in sus-pension nor did they s’uow the slightest opalescence (p. 283). Nos. 1, 2 3 and 4 still containcd con:iclerable quantities oE sulphurvus acid, and sulphur in combination with it as S202.These differences were caused by the sulphurous acid which as will be remembered precipi I ates the suspended and dissolved collojidal sulphur in the course of a few days. After haviiig stood for five days in closed bottles {,he five portions were placed over pieces of potassic hydrwyide under a bell-jay. In proportion as the sulphurous acid volali1ist.d and was absorbed by the potassic hydroxide the solui ions lost their yellow colour arid deposited sulphnr. Arter the Iirpse of 48 hours tbey were colourless and free from sulphurous acid as shown by the test with starch coloured blue by iodine. The odourless a8nd colourless liquid WACKENIZODE R'S SOLUTION. 339 were now separated from the precjpitaCed sulphur by filtration.The examination of the filtrates showed that Nos. 1 2 3 and 4 contained much more hydric pentathionate and trithionate than the correspond-ing portions which had been placed over potassic hydroxide imme-diaiely after preparation. No. 1 of the latt,er set gave wit)h potassic hydroxide or ammonia-silver nitrate only very feeble indications of the presence of hydric pentathiouate. No. 1 of the set which had been kept five days in closed bottles comported itself with the reageuts like a concentrated solution of hydric pentathionate and similar observations were made with regard to the quantities of hydric trithionate in the two sets OE liqiiids. The examination of Nos. 2 3 and 4 gave the same results. No. 5 again contained much less bydric trithionate than Xo.4 but appeared to be richer in penta-thionate . Consequently if a solution of sulphurous avid is partially decom-posed by sulphurefted hydrogen arid then the residual sulphurous acid immedial,ely removed by evaporation a comparatively sniall yield of hydric penta)thiona,te and hydric trithionate is obtained. If however the solution is allowed to siand a few days before the volatdisation of Lhe undecomposed sulphurous acid then compara-tively large quantities of the two polgthionic acids mentioned are formed. The yellow solu-tion of sulphur in sulphurous acid or more probably combination of the two which I have called thiosulphuric acid Sz02 because it Eorms thjosulphates when neutralised wij h bases and decomposes into sulphur and sulphurous acid when the lather can evaporate, seems t o be the source of the hydric pentsthionate.The thiosulphuric acid is only stable in presence of a very large excess of sulphurous acid. If the excess of sulphurous acid be not very large then condensa-tion of t h e thiosulphuric acid into pentathionic acid will take place by degrees :-and How is this unexpected result to be explained ? 5S2O2 = 2S505, 2s50 + 23320 = 2H',S,O,. This condensation dependent on the quantity of sulphurous acid present requires days for its accomplishment and does not occnr at all if the sulphurous acid is in very large excess. Therefore we conclude that i f hydric sulphide be passed through a solution of sulphurous acid uninterruptedly till all t h e acid is decom-posed but liLtle hydric pentathionate will be found in the resnlting mixture.The followiug experiments were made with the view of testing this conclusion. In order to shorten the time of the experi 340 DEBUS CHEMICAL INTrESTIGATION OF ments quantities of 180 C.C. of sulphurous acid only were operated upon at a time instead of 480 or 500 C.C. as on former occasions. A slow current of sulphuretted hydrogen was passed through 120 C.C. of a saturated solution of sulphurous acid a t a few degrees above 0". The decomposition was complete in three and three-quarter hours. Four operations of this description yielded 480 C.C. of Wacken-roder's solution which were evaporated on a water-bath until the residual liquid was of the sp. gr. 1.267. The filtrate from the coagulated sulphur measured 41 C.C.It was diluted to 52 C.C. and was then of the sp. gr. 1.24. Reactions of this Filtrate.-It gave a bright yellow precipitate with mercurous nitrate (absence of hydric trithionate). Potassic hydr-oxide and ammonia-silver nitrate respectively reacted as with penta-thiunates but with feeble intensity. Analysis of the Filtrate. I. 5 C.C. gave with baric chloride 0.281 gram of baric sulphate. 11. 5 C.C. were boiled for a few minutes with mercuric cyanide aud digested at 100" for two hours. The precipitate of mercuric sulphide and sulphur weighed 2.431 grams and the filtrate from this precipitate gave with baric chloride 4.321 grams of baric sulphate. 0.324 gram of the precipitate by mercuric cyanide treated with bromine water gave 0.0425 gram of sulphur and 0.375 gram of baric sulphate which together contain 0.094 gram of sulphur.The filtrate of the 0.375 gram of baric sulphate gave with hydric sulphide 0.266 gram of mercuric sul-phide containing 0.229 gram of mercury. 0.094 gram of sulphur + 0.229 gram of mercury = 0.323 consequently a loss of 0.001. This loss will probably be in tlhe weight of the mercury ; therefore, we take the mercury to be 0.230 gram. Hence 2.451 grams of the precipitate caused by mercuric cyanide contain 0.711 gram of sulphur and 1.740 grams of mercury. 0-524 gram of the precipitat,e of mercuric sulphide and snlphnr was oxidised with aqua regia and gave on precipitation with baric chloride 1-08 gram of bark sulphate containing 0.1483 gram of sulphur. The difference between the weight of the sulphur and the precipi-tate taken is equal to 0.3357 gram of mercury.According to this second experiment 2.451 grams of the mercuric cyanide precipitate contain 0.694 gram of sulphur and 1.757 grams of mercury. The mean of both experiments is 0.702 gram of sulphur and 1.748 grams of mercury WACKENRODER’S SOLUTION. 341 From these numbers we calculate-SO Hg S = 1.984 1 2.51, and for the composition of the hydric polythionates of the Wacken-roder solution analysed-for which we adopt-and for the mean composition of the acids, H2S4.4905.95, H2S4.506, s4.50,. Preparatiom of the Potassium Salts. The remaining 37 C.C. of the analysed solution mere mixed with a concentrated solution of 12 grams of potassic acetate and the mixture placed on a plate i n the window of a draught closet.The dry residue, obtained after 24 hours weighed after pressing between layers of filter-ing paper 22 grams. It was moistened with some water and pressed again between paper whereby i t sustained a loss of 6 grams. The remaining 16 grams were now dissolved in 30 C.C. of water acidulated with 15 drops of hydric sulphate and separated by filtra-tion from a few milligrams of sulphur. A few hoitrs after filtration, the clear liquid deposited a trace of sulphur and in the course of some days gave t w o crystallisations of po tassic tetrathionate. These weighed 6 grams. Reactions of these Crystals. They formed with water a clear colourless neutral solution which on addition of potassic hydroxide and ammonia-silver nitrate respectively remained unchanged but gave a bright yellow precipi-tate with mercurous nitrate.Determinatio 12 of Potass ifc m. 0.831 gram gave 0-478 gram of potassic sulphate. Hence in 100 parts-Calculated. Found. K2S40,. Potassium . . . . 25.7 25.8 The salt t,herefore is potassic tetrathiona ke. A third crystallisation also consisted of nothing but crystals of tetrathionate. The fourth and last crystallisation contained a few crystals of potassic pentathionate which were picked out from the accompanying potassic tetrathionate. VOL. LIII. 2 342 DEEUS CHEMICAL INVESTIGATION OF The entire weight of the latter amounted to 9 grams and of the penta-salt to 1% grams. Consequently the yield of hydric penta-thionate is much smaller when hydric sulphide is passed uninter-ruptedly through a solution of sulphurous acid till tjhe latter is com-pletely decomposed than when the operation is conducted as described on page 281 with interruptions of from 36 to 48 hours when nearly equal weights of the two potassium salts were obtained.These results confirm the theory mentioned on page 339. Weak solutions of sulphurous acid appear to produce propor-tionately larger quantities of the polythionic acids than more concen-trated solutions. Experiment 1.-A elow current of sulphuretted hydrogen was passed for two hours throiigh 480 C.C. of a concentrated solution of sulphur-ous acid and the liquid was allowed to stand for two days. The operation with sulphuretted hydrogen was then repeated for two hours and the solution allowed to stand for 48 hours.The treatment with sulphuretted hydrogen was continued in this manner until all the sulphurous acid was decomposed which was the caseafter two weeks. Expe&nent 11.-Only 120 C.C. of sulphurous acid was taken in the following preparation. The experiment was made in the same manner as the first but required on account of the smaller quantity of acid much less time for its performance. On the first day hydric sulphide was passed for one hour and on the second for an hour and a half the decomposition of the sulphurous acid was then complete. Experiment I11 was made like Expt. I1 with 120 C.C. of sulphurous acid. I n Expts. I and I1 the acid was of the same strength in Expt. I11 an acid of half this strength was taken.Experime?Lt IV was performed like Expt. 11 with this difference, that the sulphuretted hydrogen was passed uninterruptedly until all the sulphurous acid was decomposed. The results calculated for the same quantity of sulphurous acid are as follows:-Expt. I . 480 C.C. of sulphurous acid gave G5 C.C. of Wackenroder Expt. 11. 480 C.C. of sulphurous acid gave 55 C.C. of Wackenroder Expt. 111. 960 C.C. of siilphurous acid gave 55 C.C. of Wackenroder Expt. IT. 480 C.C. of sulphurous acid gave 41 C.C. of Wackenroder Experiments I and I1 show that occasional interruptions of solution of sp. gr. 1.265. solution of sp. gr. 1.246. solution of sp. gr. 1.268 solution of sp. gr. 1.267 WACKENRODER’S SOLUTION. 313 from one to two days’ duration in the passage of the sulphuretted hydrogen and longer treatment with this gas yield the largest quantity of acid.Expts. I1 and 111 indicate that it is of advantage to use a weak solution of sulphurous acid. Expt. IV shows that if sulphuretted hydrogen be passed through a solution of sulphurous acid uninterruptedly until it is completely decomposed absolutely and relatively the smallest quantity of acid will be produced. The increase in the quantity of the hydric pentathionate which takes place when a solution of sulphurous acid which is only partially decomposed by sulphuretted hydrogen is kept a few days appears to be due to a condensation of thiosulphuric acid S202 according to the equa-tion-5s202 + 2HzO = 2E2S50,. As the quantity of hydric tetrathionate seems to remain unchanged, and not to be dependent on this condition it is probably formed by the direct union of the reacting bodies-3502 + HzS = H,S,Os.If this theory be correct then pentathionates ought to be formed generally by the action of sulphurous acid on sulphur in stutu nascendi. The results of the following experiments support this conclusion. Action of Sulphurous Acid on Potnssic Thiosulphate. Five grams of potassic thiosulphate 2K2S20,,3H20 were dissolved in 100 C.C. of a concentrated solution of sulphurous acid. The intensely yellow solution could be kept without separation of sulphur or any other apparent change. Hydric chloride caused decolorisation and precipitation of liquid sulphur which in the course of a few days became solid and opaque. A portion mixed with two or three volumes of alcohol gave a crystad-line precipitate which was soluble in water with the exception of some globules of sulphur.The a8queous solution produced on addition of baric chloride R crystalline precipitate which was only partially soluble in boiling water. The dissolved portion was baric thiosulphate the insoluble baric sulphate and sulphite. Other substances were not observed. From these experiments i t appears that potassic thiosulphate is decom-posed by sulphurous acid into potassic sulphite and thiosulphuric acid which remains unchanged in the large excess of sulphurous acid present (p. 339). I n another experiment 5 grams of potassic thiosnlphate were dis-solved in only 5 c . ~ . of sulphurous acid. The yellow solution deco-2 A 344 DEBUS CHEMICAL INVESTIGATIQN OF lorised in the course of three days the smell of sulphurous acid disappeared and sulphur was precipitated.A few C.C. of sulphurous acid were again added when the same effects fojlowed the mixture turned yellow and smelt of sulphurous acid but lost both colour and odour with precipitation of sulphur in the course of a day or two. The addition of small quantities of sulphurous acid was continued until it ceased to produce coloration and its odour permanent. Alto-gether 18 C.C. of sulphurous acid were used and 0.153 gram of sulphur was precipitated. Sulphurous acid added in small quantities to potassic thiosulphate therefore does not act like a large excess. Absolute alcohol added to the decomposed solution of potassic thio-sulphate precipitated potassic trithionate and in the filtrate from the latter ?)otassic penfathionate was discovered by means of ammonia-silver nitrate.According to the text-books potassic thiosulphate and sulphurous acid produce potassic trithionate and sulphur as repre-sented by the equation-2KZS203 + 3S0 = 2K2S.306 + S, which would require the precipitation of 0.368 gram of sulphur from 5 grams of potassic thiosulphate. Experiment gave only 0.153 gram, not half t'he calculated quantity. The missing siilphur is in the form of potussic tetrcrthionate and yentathionate in the solution. The sulphurous acid decomposes a por-tion of the potassic thiosulphate into potassic sulphite and thiosulphuric acid which by condensation is transformed into pentatliionic acid.The latter and the potassium salts produce potassic pentathionate and sulphurous acid or thiosnlphuric acid which when very liltle sulphurous acid is present will partially decompose into sulphur and s ulphnrous acid. Potassic sulphite and potassic pentathionate form potassic thiosul-phate and potassic trithionate. The final products of the action of sulphurous acid on potassic thiosulphate are potasssic trithionate as chief product potassic tetra-thionate and pentathionate and sulphur. The reactions may be 1-epresented by the equation-6K2S,03 + 9x0 = K2S5O + K2Sa0 + 4K,S,O,. I n reality less potassic pentathionate and Cetrathionate and more potassic trithionate are produced on account of the precipitation of sulphur in quantities varying in different experiments.In confirmation of the explanations given here of the action of sulphurous acid on potassic thiosulphate I found that potassic penta-thionate and sulphurous acid produce similar results viz. potassic tetrathionate trithionate and sulphur. A third experiment gav WACKENRODER'S SOLUTION. 345 results similar to the second. A fourth experiment was made with a view of separating the potassic tet'rathionate and pentathionate from the trithionate and obtaining each salt in a pure form. 55 grams of potassic thiosulphate were treated with sulphurous acid until the whole quantity was converted into polythionates. Alcohol precipitated potassic trithionate the filtrate on standing deposited crystals of pure potassic tetrathionate but gave by spon-taneous evaporat,ion crystals of all three salts interlaced in such a way that they could not be separated mechanically ; an aqueous solution of the mixed salts however comported it,self with the reagents like one of a pentathionate.The precipitate of sulphur amounted to 4.86 per cent. Chloride of Sulphur and Xu.$hurous Acid. The view expressed on page 343 on the formation of pentathionates is also confirmed by the experiments of Plessy (p. SSO) and Fordos and GBlis (p. 280). The salts prepared by these chemists were how-ever not pure and their analytical methods unsatisfactory. I haw therefore repeated their experiments. Sulphurous chloride SZCl2 and water decompose into hydric thio-sulphate sulphur and hydric chloride-2S,CI + 3H,O = H,Sz03 + 4HC1 + s,.The hydric thiosulphate HzSz03 however soon splits up into water, sulphur and sulphurous acid. Gmelin (G?ne.h-f<ruzbt 1 Abth. 11, 401) quotes a statement of Carius according to which sulphurous chloride and water produce hydric chloride sulphurous acid and sulphuretted hydrogen -S,Cl + 2H,O = 2HC1 + SO + EzS. The sulphuretted hydrogen and the sulphurous acid would form the constituents of Wackenroder's solution. This view of Carius ( A n n a h 107 333 et seq.) of the decomposition of sulphurous chloride by water is entirely hypotheticaz not supported by experi-ments and has been advanced by him as an argument in favour of his view of the chemical constitution of the chlorides of sulphur. Sulphurous chloride dissolves in an aqueous solution of sulphurous acid without precipitation of sulphur but the smallest quautity of sulphuretted hydrogen produces even with a very large excebs of sulphurous acid an ilnmed iute precipitate of sulphur.The formation of hydric sulphide required by the equation of Carins does not therefore occur. Accordingly I adopt the first explanation of t'ho clecornposition of sulphurous chloride by water 346 DEBUS CHEXICAL INVESTIGATION O F 30 grams of sulphurous chloride were introduced by degrees into 480 C.C. of a concentrated aqueous solution .of sulphurous acid. The chloride of sulphur after repeated shaking dissolved witlzozlt precipitation of sulphur but with an increase of temperature from 18" to about 50". A very small precipitate of sulphur separated after the lapse of two or three days.The mixture was kept for a week and then concentrated on the water-bath until all the sulphurous acid was gone. To remove the larger portion of hydric chloride lead carbonate was now added and the filtrate from the lead chloride freed from lead in solution by the careful addition of hydric sulphate. The filtrate of the lead sulphate was concentrated to the sp. gr. 1.285. At this state of concentration it, measinred 26.5 C.C. A qualitative examination of the liquid revealed the presence of hydric pentathionate and a trace of trit,liionste. A strong solution of potassic acetate was added and the mixture allowed to evaporate in a current of ordinary air. A crystalline cake which formed in the course of the two following days was freed from adhering mother-liquor by pressure between folds of filtering-paper ; 11.5 grams of solid matter so obtained dissolved in 15 C.C.of water and 0.3 C.C. of hydric sulphate and left only a few milligrams of siilphur as residue. The filtered solution on spontaneous evaporation yielded 7.2 grams of crystals too small f o r mechanical separation. They were therefore redissolved in another similar quantity of acidulated water and the solution left to concentrate a t ordinary temperatures. This time a crop of fine large crystals of potassic pentathionate and tetrathionate were obtained. Both descriptions of crystals could easily be sepa-rated. Analysis of the Pe&athionic Crystals. 0.52 gram dried over hydric sulphate.left after ignition 0,252 gram of potassic sulphate.I n 100 parts Found. Theory. Potassium 21.72 21.60 The substance gave the reactions of a pure pentathionate. Analysis of Potassic Tetrathionate. 0.6934 gram dried over hydric sulphate gave after ignition 0.396 gram of potassic sulphate. In 100 parts Found. Theory. Potassium. . 25-61 25.82 The reactions likewise agreed with those of a tetrathionate WACKESRODER'S SOLUTION. 347 The polythionic acids have been formed in this experiment by the action of sulphurous acid on one of the products of decomposition of hulphurous chloride and water viz. hydric thiosulphate and I believe whenever nascent sulphur and sulphurous acid meet under favourable conditions polythionic acids will be formed. If so then hydric pentathionate ought to result from the decomposition of hydric thiosulphate H2S303 in water.25 grams of baric thiosulpha0e were digested with 9.1 grams of hydric sulphate diluted with five times its weight of water. The filtrate froni the baric sulphate after concentration on the water-bath, gave a liquid which comported itself with potassic hydroxide am-monia-silver nitrate and mercurous nitrate respectively like a solu-tion of hydric pentathionate. But a considerable portion of the hydric thiosulphate had decomposed into water sulphur and snl-phurous acid. Will ordinary sulphur produce polythionic acids with sulphurous acid ? A quantity of flowers of sulphur was washed for a long time first with cold afterwards with boiling water until the wash-water did not change blue litmus paper. Some of the washed sulphur was placed on blue litmus paper and left on it for some time.The colour did not change. 10 grams of the washed and dried flowers of sulphur were sealed with 36 C.C. of concentrated sulphurous acid in a glass tube and a second tube charged with the same volume of acid mith-out sulphur. The two tubes remained for five days at common temperatures, and were then heated for several hours on a water-bath to 60-80". This treatment did not appear to have effected any change in either of the tubes. Both were now opened their contents transferred to evaporating dishes and warmed on water-baths until all the sul-phurous acid had volat,ilised. I observed on this occasion that the acid escaped from the dish containing sulphur a t a much slower rate than it did from the other.Both liquids were finally concentrated to one-fifth of their original volume. Examination of the Liquid left by the Pure Sulphurous Acid. The blue colour of litmus paper was changed to red ; baric chloride gave a white precipifat e insoluble in hydric chloride and mercurous nitrate a white prec Gitate of mercurous sulphate. Addition of ammonia-silver nitrate produced no change and cupric sulphate gave no reaction a t 100". But silver nitrate caused a very slight floccu-lent precipitate of a very pale brownish colour. Hence hydric sul-phate is present and polythionic acids are absent 348 DEBUS CHEMICAL INVESTIGATION OF Examination of the Liquid left by Sulphurous Acid and Sulphur. Baric chloride indicated the presence of hydric sulphate and mer-curous nitrate gave a precipitate of mercurous sulphate which was coloured slightly yellow.Ammonia-silver nitrate produced a very sZight brownish coloration and a few brown gelatinous flakes made their appearance after some time. Silver nitrate caused a very small brown precipitate. From these reactions it seems to follow that sulphurous acid and flowers of sulphur form under the conditions described an infiiiitesimal quantity of hydric pentathionate. This result is however of a very doubtful nat'ure. Only one reaction the one with the silver solution, can be advanced in its favour and as the number of substances which reduce silver solutions is very great no certain conclusion can be drawn from the experiment. Commercial flowers of sulphur is a very impure substance.It contains sulphates of various descrip-tions hydric calcic aluminic and iron sulphates were found in the wash-water. The latter gave with silver nitrate a precipitate which gradually became black. Some of the wash-water was first concen-trated on the water-bath and then evaporated to dryness on a piece of platinum foil. It left a considerable residue which a t a higher temperature evolved hydric sulphate and a t a red heat assumed :L transient black colour as if an organic substance were present. On the whole the experiment with flowers of sulphur and sulphurous acid is of a negative nature and we are only ceytain that nasceut sulphur with water and sulphurous acid produces polythionic acids. Explanation of the Formaiion of the Comtituents of Wackenroder's Solution.We are now able to explain the formation of the constituents of Wackenroder's solution from the original materials sulphuretted hydrogen sulphurous acid and water. Hydric sulphide and sul-phurous acid in the presence of water react immediately with sepu-ration of sulphur (p. 336). J t appears t'hat hydric pen tathionate is not the direct product of' this react'ion (p. 338) a t all events the greater part of it is slowly formed when a solution of sulphurous acid only partially decomposed by sulphui etted hydrogen is kept for some days (p. 339). A current of sulphuretted hydrogen passed through 120 C.C. of sulphurous acid without interruption until all the acid is decomposed causes the formation of a small quantity of hydric pentathionate (p.342). If the current of hydric sulphide is stopped after the decomposition of about half of the sulphurous acid arid the liquid is now allowed t o reinain a t rest for two days aiic WACKENRODER’S SOLUTION. 349 Potassic tetrathionate. after the lapse of this time sulphuretted hydrogen is again passed until the operation is completed a larger quantity of hydric penta-thionate is produced. But the best yield of hydric pentathionate is obtained when the passage of the hydric sulphide is interrupted five or six times each time for from 36 to 48 hours during the course of the entire opera-tion (p. 281). The following table contains an outline of the experimental re-sults :-Pot assic pentathionate. Time required for the complete decompoei-tion of sulphurous acid by aulphurett ed hydrogen.6 6 6 I. 3 to 4 hours for 120 C.C. in one opera-tion 11. Sulphuretted hydrogen passed twice, each time 18 hours on separate daye. Q,uantity 120 C . C . 111. Sulphuyetted hydrogen passed 8 times, each time 2 hours on separate days. Quantity 480 C.C. 1 2 6 Ratio of the weights of the salts obtained. The quant.ity of tetrathionate appears to be proportionally t.he same in all experiments and quite independent of the time of preparation. From this I conclude that hydric tetrathionate is a direct prodiict of the reaction of sulphuretted hydrogen on sulphurous acid and is formed by combination as represented by the equation-3S0 + H,S = H,S,O,. If hjdric sulphide and sulphurous acid respectively had no action on hydric tetrathionate then the latter would be the sole product O F the reaction.But as both decompose the tetrathionate an unusual complexity of reactions is the result. As long a s the sulphurous acid is in great excess as in the begin-ning of the operation most of the sulphuretted hydrogen reacts with the sulphurous acid and we may at this stage disregard the reaction between the tetrathionate and snlphicle. The two substances hydric: sulphide and sulphurous acid meeting in squeons solution in the proportioris of the above equation and in their positions of reaction, combine and form hydric tetrathionate. But the hydric tetrathionate molecules and free sulphurous acid produce hydric trithionate arid thiosulphuric acid S20 (pp. 333 and 3%).This reaction liowever i 350 DEBUS CHEXICXL INVESTIGATION O F very slow and of a reciprocal nature. I n conseqnence it is only partial, and as thiosulphuric acid can transfer sulphur to hydric tetrathionate, and so cause the formation of hydric pentathionate the solution will now contain-Free sulphurous acid, Thiosulphuric acid, Hydric trithionate, Bydric tetrathionate. and Hydric pentathionate. If now sulphuretted hydrogen were passed in until all sulphurous acid had disappeared and if no other reactions took place then hydric tri- tetra- and penta-thionates would be the products. And for every molecule of hydric pentathionate a molecule of hydric trithionate would be present. This result is modified by the reaction we have so far disregarded viz.by the decomposition of the hydric tetrathionate by sulphuretted hydrogen into water and sulphur ; one part of t.he sulphur so set free combines in statu n a s c e d i with hydric trithionate to form hydric tetrathionate and with tetrathionate to form penta-thionate and with the latter t o form hexathionate. The quantitative relations are such that a t the moment when all the sulphurous acid has disappeared all the hydric trithionate has also been reconverted into tetrathionate. Another part of the sulphur produced by the action of hydric sulphide on hy dric tetrathionate remains in solution as colloidal sulphur-6-sulphur-and the remaining quantity falls down as a precipitate or remains in suspension. If then the three reactions-the formation of hydric tetrathionate and its decomposition by sulphuretted hydrogen and sulphurous acid, respectively-are taken into consideration we should have as final products of the action of sulphuretted hydrogen on an aqueous solution of sulphurous acid sulphur as a precipitate sulphur in suspension sulphur in solution and hydric tetra- penta- and hexa-thionates.This is the condition of the Wackenroder solution the preparation of which has been described on p. 340. Hydric tetrathionate is the chief product. But if the passage of the sulphuretted hydrogen through the solution of sulphurous acid is conducted with interruptions of several hours’ duration then the condensation of thiosulphuric acid into pentathionic acid with formation of hydric pentathionate (p. 281) takes place and the quantity of the pentathionate becomes in consequence five or six times greater than before.And i f sulphuretted hydrogen is passed through n Wackenroder solution after all the sulphurous acid has disappeared and until it ceases to act on the polythioni WACKENRODER'S SOLUTION. 351 acids present water and sulphur will be the final products of decom-position. The polythionic acids acre then intermediate products of t8he reaction of sulphuretted hydrogen with an aqueous solution of sulphurous acid, and the equation-SO2 + 2H2S = Ss + 2H20, given by the text-books is correct for the final products. C. On the Formulce of the Polytkionates. We will now attempt to represent the constitution of the polythio-nates by rational formulae derived from the chemical facts described in this and the papers of other authors.In some of the best of our text-books,* the formula-s3(so2oH)2, is given for hydric pentathionate and it is stated that baric penta-thionate is formed from baric thiosulphate and sulphuric chloride according to the equation-2 [SO { :>Ba] + SCI = BaS,O + BaCl,. These formulze we will trace to their original sources. Bloomstrand (Chenzie der Jetzzeit 158) appears to have been the first chemist who represented hydric pentathionate by the formula S3(S020H), and Mendel6eff (Ber. 3 870) after him adopted the same expression. The latter believes that several unknown compounds of sulphur and hydrogen can exist HzS3 H2S4 H2S5 all derived from sulphuretted hydrogen by replacing an atom of hydrogen by the residue HS.If now in the compounds of sulphur and hydrogen H2S H2S2 and HzS3, the two hydrogen-atoms are replaced by the radical of hydric sulphate, SO,,H the formulze of hydric tri- tetra- and penta-thionate are obtained , OH.S02*OH - S<S02*OH + 2H,0. { 4- O€€-SO,*OH - SO,*OH Hydric trithjonate. So2'oH + 2H20. OH-SO,.OH - ''{ 'J 4- OH*SO,.OH - S2<S0,*OH Hydric tetrathionate. * Kolbe H A Short Text-Book of Chemistry translated by Prof. Humpidge. Richter Lehrbzcch 1881 p. 222; Roscoe and Schorlemmer London 1884 p. 171. 1 p 354 352 DEBUS CHEJIICAL IXVESTIGATIOK OF Hydric pentathionate. MendelAeff shows that the hydrogen salts of the polythionic acids agree in several respects with the sulphonic acids and that his formuh indicate how to prepare the former in a rational manner As a a example he mentions that sulphurous cliloride and dipotassic sulphite ought to give potassic tetrathionate :-Mendeleeff has not as far as I know made this experiment or tested his theoretical conceptions in other ways.This work has beeii carried out by W. Spring ( B e r . 6 1108) who did not realise the last equation but obtained instead of potassic tetrathionate trithio-nate and some potassic thiosulphate. Sulphuric chloride and dipo-tassic sulphite gave likewise potassic trithionate and also potassic chloride. The equation-SCl2 + 2KS03K = 2KC1 + S(S03K),, is given in explanation of the reaction. But Spring did not use sulphuric chloride and dipotassic sulphite only he also had water present. And if the water is taken into con-sideration then a very different explanation may be given of his results.Sulphuric chloride SCI2 and water produce sulphurous acid hydric chloride and sulphur. Hydric chloride decomposes dipotassic sulphite into potassic chloride water and sulphurous acid. If the reacting substances are taken in quantities as required by the equa-tion half the dipotassic sulphi te remains undecornposed. Dipotassic: sulphite and sulphur form potassic thiosulphate. The latter and sulphurous acid produce as is well known potassic trithionate and as has been shown in this paper some potassic tetra-thionnte and pentathionate. Consequently the results of Spring’s experiments can be explained by well-known facts and as they can be explained in more than one way it follows that his experiments cannot throw any light on the coiistitution of the polythionates, and the same remarks may be made with regard to the experiment with baric thiosulphate.Spring mixed this salt with some water and then added sulphurous chloride S,Cl2. After precipitation of the dissolved barium by an excess of hydric siilphstte and the excess of hydric snlphate by baryta- water h WACKENRODER’S SOLUTION. 353 obtained a liquid which gave “ all the reactions of pentathionic acid.” Therefore the formula of this acid is-The experiment teaches nothing about the constitution of penta-thionic acid. Sulphurous chloride and water alone without the assistance of baric thiosulphate will furnish a liquid exhibiting the reactions of hydric pentathionate or baric thiosulphate and dilute hydric sulphate without sulphurous chloride will do the same.SO H The formula S,< so:a is therefore a purely hypothetical concep-tion and it is to be regretted that on the evidence described it has been admitted in books intended f o r beginners. The metallic salts of sulphurous acid are according to Strecker’s reaction (Annalen 148 90-119) constituted as follows :-Ag*S 0,. O*Ag, viz. one atom of metal silver in this case is directly combined with sulphur. Bunte’s (Ber. 7 (1874) 646) experiments confirm Odling’s (Chem. Xoc. J. 22 255) formula for the thiosulphates. Sodic ethylic thiosulphate and hydric chloride produce mercaptan sodic chloride, and hydric sulphate-C,H,-S.S02-OKa + H,O + HC1 = C,H,SH + NaCl + H2SOa, hence the ethyl of the thiosulphate is in direct combination with sulphur.The behaviour of the thiosulphate with mercuric chloride wyrees with this conclusion. The salts of potassium have a similar constitution hence-Dipotassic sulphi te K*SO,*OK, Potassic thiosulphate K.S*SO,OK. Dipotassic sulphite combines directly with sulphur t,o produce the thiosulphate. This sulphur therefore joins the group KSO of clipotassic sulphite. On the other hand some thiosulphates for example the calcium salt easily lose sulphur and become sulphite. Hence this second atom of sulphur of thiosulphates is held by a feeble force only. Potassic thiosulphate and iodine produce potassic tetrathionate and patassic iodide. Three formulae are probable for the tetrathionate : 354 DEBUS CHEMICAL INVESTIGATION OF Potassic tetrathionate can lose one atom of sulphur and become tri-thionate ; hence we have one of the three following f o r m u h for the last-named salt :-KS O,*O K*S 0,O KO.SO,S I VI.I ' SO *OK IV. s<s*;.oK; V. KS - S 0,- 0 Now potassic trithionate can combine with sulphur in statu nascendi as dipotassic sulphite does. The power to take up sulphurbelongs in the case of the last-named salt to the atomic group KSO (p. 353) and we shall be justified in attributing in the case of the trithionate the same property t o the same cause viz. t o assume in the trithionate the presence of the group KSO,. This assumption is also supported by the fact that potassic trithionate is a derivative of potassic hydric sulphite and sulphur.Hence the formula 1V must be eliminated because it .does not con-tain the atomic group KSO, and there remain the formulE V and V I for the trithionate. Our choice is guided by the following considerations :-Two of the sulphur-atoms of the potassic pentathionate occupy positions in the molecule essentially different from those of the other three. These two atoms of sulphur can successively or together be removed, and the residue of the molecule can exist by itself or can reunite with sulphur and reproduce pentathionate. The trithionate behaves with regard t o sulphur like an element. Bnt if an atom of sulphur is removed from potassic trithionate then the residue K2S,06 decomposes at the same time into potassic sulphate and sulphurous acid and from these materials the original salts (K,S,Os K2S5O6) cannot be obtained by direct combination.Froni this it follows that one of the three sulphur atoms of potassic tri-thionate holds the proximate constituents of the salt in chemical combination viz. the existence of the salt as a polythionate is de-pendent on this sulphur-atom. This condition is satisfied by for-mula. VI but not by formula V. We support this conclusion by the following experiments and considerations :-If potassic pentathionate had the constitution-S,(SO,.OK), WACKENRODER’S SOLUTION. 355 bromine-water would decompose the salt according to the equation-S,SO,.OK + Br2 + 2H20 = S3 + 2KBr + 2H2S04. I. 1.4089 grams of potassic pentathionate were dissolved in water, and mixed by degrees with bromine water containing 0.684 gram or 1 mol.of bromine. Every drop of bromine-water caused turbidity, which disappeared again on stirring the mixture with a glass rod. But i t remained thick after a certain quantity of bromine had been added. A precipitate of sulphur fell down. This was of a soft, plastic nature and was collected on a weighed filter. Its weight was found to be = 0.075 gram but on account of its soft nature it could not be powdered in a mortar and could not be entirely freed from potassium salts by washing. Heated on platinum foil i t left some residue. The filtrate from the sulphur precipitate contained much potassic pentathionate and hydric or potassic sulphate. It was slightly opalescent and on standing deposited a thin membrane of sulphur on the side of the beaker.Probably some of the sulphur separated by bromine had combined with undecomposed pentathionate to form hexa-thionate and the spontaneous decomposition of the latter caused the deposition of the sulphur membrane. Sodic chloride caused no pre-cipitate in the filtrate. 11. 0.561 gram potassic pentathionate was mixed in aqueous solu-tion by degrees with 0.497 gram of bromine (2 mols.). The sulphur precipitate weighed after washing with diluted ammonia and drying over hydric sulphate 0.0635 gram. The filtrate contained besides undecomposed thionate sulphates. 111. 1.0965 grams of potassic pentathionate were mixed in aqueous solution with 1,948 gram of bromine (4 mols.). The precipitated sulphur was a t first soft but soon became hard and brittle.It was powdered in an agate mortar washed with dilute ammonia and dried over hydric sulphate. The .filtrate was n o longer acted o n by bromine-watay. All potassic pentathionate had been decomposed. Baric chloride added to the filtrate gave a precipitate of baric sul-phate weighing 2.034 grams. Hence 1.0965 gram of potassic penta-thionate gave with bromine-water 0.206 gram of sulphur as a precipi-tate and 0.279 gram in the form of baric sulphate. Its weight was 0.806 gram. In 100 parts-Found. Theory. Sulphur . . . . . . 44.31 44.32 Therefore 4 mols. of bromine had precipitated from 1 mol. of potassic pentathionate 2.13 atoms of sulphur and oxidised to sulphuric acid 2.87 atoms 3 5 6 CHEMICAL INVESTIGATION OF WXCKENRODER'S SOLUTION. 1 mol of I. One rnol. of potassic pentathionate } + { bro;ine 1 gave 0.6 atom of sulpliur. KzS506 . . . . . . . . 11. Ditto + 2 mols. , 1.27 7 , 111. Ditto f 4 mols. , 2.13 7 7 The sulphur in I and 11 on account of its physical properties, coiild not be obtained quite pure by washing ; hence it has been found too high. From these experiments I conclude that the decomposition of potassic pentathionate by bromine-water takes place according t o the equation-2&S506,3H20 + 8Br2 + 9H20 = 4KBr + 4 s + GH,SO + 12HBr, and that if less bromine be taken than is required by this equation a proportionate quantity of pentathionate remains undecomposed. Two atoms of the sulphur of a molecule of potassic pentathionate, K2S506 are precipitated as such and three are oxidised to sulphuric acid. The conclusion is that the tlhree oxidisable atoms of sulphur are alreacly in the molecule of pentathionate in combination with oxygen, :ind are so in the trithionate resulting from the decomposition of the p3ntathionate. As the formula V does not fulfil these condi-tions we must eliminate it and we have then only one foi*rnula VI, left for potassic trithionate and this formula agrees with the proper-ties of the salt. We find then the following formulae for the potassic polythionates :-K- S O,-O KO-SO,*S 1 Potassic trithionate. KS.SO2.O I Potassic tetrathionate. KO.SO2.S K Sz.S 0,O KO.SO,*S KS,*SO,*O KO*SO,*S I Potassic pentathionate. I Potassic hexathionate. According t o these formulae potassic trithionate contains the group K*S02 in which the potassium is in direct combination with the sulphur. Potassic sulphide K,S can combine with two three or more atoms of sulphur and this propertcy of potassic sulphide is not. lost i ON THE DENSITY OF CERIUN SULPHATE SOLUTIONS. 357 the combination K-SO,. The hydrogen salt of tetrathionic acid contains according to this theory the radicals HO and HS and that of pentathionic acid the radicals HO and HS, and hydric hexathio-nate HO and HS,. The hydrogen of these radicals is replaceable by metals. HS also occurs' in persulphide of hydrogen and like this compound potassic pentathionate is immediately decomposed by alkalis and rendered more sta3blc by acids. Water also causes both snbstances to decompose in the same manner. Moist persulphide of hydrogen produces sulphuretted hydrogen and sulphur a solution of potassic pentathionate potassic tetrathionate and sulphur. Groups of the same constitution as HS and KS confer similar properties on the compounds in which they occur. Royal Naval College Greenwich, December 1887