WHATMAN'S QUALITY TELLS. N experiments, the quality of every detail tells. Filter Papers and Extraction Thimbles are important, therefore get the best-get "Genuine Whatman," manufactured by W. & R. Balston, Ltd., Paper Makers in Britain for over 150 years. Genuine Whatman Filter Papers are made in all grades- Genuine Whatman Extraction Thimbles are Fat-Free and Seamless. CHEMICAL NEWS, May 9, 1919 Contribution to the Chemistry of Tellurium Sulphide. THE apparatus is shown in Fig. 1. The five-litre bottles B contained a supersaturated solution of sodium sulphide. Hydrogen sulphide was generated in this bottle by slowly dropping in I: I bydrochloric acid contained in the bottle A by means of a syphon and stopcock. It was purified from hydrochloric acid gas by passing through the sodium sulphide wash bottles D and E. After passing through the drying tower F, which contained calcium chloride, the gas was reduced to o° C. by passing through the coil condenser G, which was completely surrounded by a cooling mixture. After cooling to o° C. it entered the reaction chamber K, which consisted of a 500 cc. separatory funnel 217 crucible also was jacketed and surrounded by a freezing mixture. The advantages of this apparatus deserve mention. The gas was thoroughly cooled to o° C. before entering the reaction chamber by passing through the long coil condenser surrounded by ice and water. The rate of flow was not great, owing to a fine jet between B and D, but was uniform. The reaction chamber was at o° C. by being completely surrounded by the cooling mixture. After extraction, the carbon disulphide and that part of the precipitate that had actually been extracted could be drawn away. There was always a small amount of precipitate which remained in a fine suspension in the water above the carbon disulphide which was not extracted, but this never reached the filter. Moreover, the difficulty of filtering two immiscible liquids was overcome. The filter being jacketed with the freezing mixture insured its temperature to be at o° C., so that at no stage during the operation was the precipitate subjected to any temperature other than o° C. Using this apparatus, a final series of experiments was carried out which served as a check on the results previously given. The details of procedure may be described as follows:-A sample of tellurous acid, acidified with hydrochloric acid representing approximately 0.2500 grm. of tellurium, was placed in this apparatus along with contained in an asbestos-covered iron box with the stem and stopcock protruding through the bottom of the box. The box was completely filled with a cooling mixture for one hour before and during use, thus insuring that all parts of the reaction chamber with which the precipitate might come in contact would be at o° C. Precipitations were carried out in the presence of 100 cc. of carbon disulphide, into which the precipitate was forced as formed by a constant whirling motion of the box during the introduction of hydrogen sulphide gas. After allowing the precipitate to stand in contact with the carbon disulphide the desired length of time, the carbon disulphide and the precipitate which had collected in it were drawn off through the stopcock on a large Gooch filter. The Gooch Abstract of a part of a thesis submitted to the Graduate School of the University of Wisconsin in partial fulfilment of the require ments for the degree of Doctor of Philosophy. From the Journal of the American Chemical Society, xli., No. 3. 100cc. of carbon disulphide. Hydrogen sulphide was passed in for three minutes. During this time the reaction chamber was shaken to transfer the precipitate down into the carbon disulphide as formed. At the end of nine minutes the carbon disulphide and precipitate contained in it were passed rapidly through a suction filter consisting of a Gooch crucible fitted with a small disc of filter paper. One minute was thus allowed for the filtration. The suction of the precipitate was continued for ten minutes to remove the last traces of carbon disulphide. The precipitate thus collected was removed from the paper, placed in a P2O5 desiccator, and evacuated overnight. A sample of the precipitate was then weighed carefully, oxidised with fuming nitric acid in the cold, and the nitric acid removed by careful evaporation at 80° C. The residue was taken up in 10 per cent hydrochloric acid and the exact tellurium content determined. A short table of results follows: 0.2178 0.1814 0'2074 These results appear to be in fair agreement with those yielded by the previous method. Hence, since the weights of tellurium and sulphur found far exceed the weights required for TeS, the only conclusion at which one can arrive is that TeS is not formed primarily by the action of hydrogen sulphide on tetravalent tellurium. This is in direct contrast to the results obtained by Snelling (Fourn. Am. Chem. Soc., 1912, xxxiv., 802). A Study of the Conditions Necessary for the Existence of TeS2.-It will be noted that all data thus far presented have shown that TeS does not exist. Moreover, the weights of tellurium and sulpbur obtained have approximated the weights necessary for the compound TeS2. Furthermore, the colour of the precipitate first produced is invariably a red-brown. At 25° C. the duration of this colour is short, a grey-black colour rapidly developing, accompanied by the coagulation of the precipitate into granules. At o° C. the precipitate retains its red-brown colour for a considerably longer period. In view of these facts and remembering that ten minutes after precipitation carbon disulphide removes a definite amount of sulphur, its seems justifiable to assume that TeS2 is first produced, but the affinity between sulphur and tellurium being very weak, dissociation takes place, and the chemical compound separates partially into its elements. Since the affinity between elements of this character is usually increased at reduced ten-peratures, a preliminary experiment was carried out at about -40°. A bath of acetone was cooled to -40° C. by the addition of solid carbon dioxide. In it was placed a large test-tube containing 50 cc. of carbon disulphide and 20 cc. of tellurium chloride dissolved in concentrated hydrochloric acid. After the contents of the tube had assumed the temperature of the bath, bydrogen sulphide cooled to o° was passed in. The red-brown precipitate produced was forced into the carbon disulphide as completely as possible. After standing at this temperature for one hour, the precipitate still remained a red-brown and the carbon disulphide still remained perfectly colourless, showing no indication of dissolved sulphur. A second tube containing 50 cc. of carbon disulphide was also cooled to -40° C. To it was added some previously prepared tellurium-sulphur precipitate which had been allowed to decompose at room temperature. This carbon disulphide immediately assumed a yellow colour, indicating the presence of dissolved sulphur. Although this experiment was only qualitative it indicated that tellurium and sulphur form a stable compound at this temperature, since it was shown that small amounts of sulphur impart a distinct yellow colour to carbon disulphide. If this be true, it was of interest to determine the highest temperature at which this compound was still stable. For this purpose determinations were carried out at -10°, -15°, and -20°, respectively. In each case the precipitate was gelatinous, thus differing from the precipitates obtained at o°. In each experiment, too, the extraction with carbon disulphide lasted one hour instead of ten minutes, as previously. During this time the precipitate remained a red-brown colour, showed little tendency to coagulate, and was dissociated but slightly at -10° and -15°. At-20° complete stability apparently existed. The following tables show this to be the case. It would appear, therefore, that −20° is approximately the highest temperature at which the two elements, tellurium and sulphur, form a stable union. The Action of Hydrogen Sulphide on Non-aqueous Solutions of certain Tellurium Compounds.-The preceding work has shown that a temperature of -20°, or below, is 0'1406 O'1102 0.1132 0 1701 essential for the existence of a stable compound of tellurium and sulphur in aqueous solution. At higher temperatures the compound undergoes gradual dissociation into its elements. Although such a decomposition can scarcely be regarded as hydrolysis, the influence of the medium upon the formation and stability of this compound is of interest. Three salts of tellurium were found to have a comparatively wide range of solubility in non-aqueous solvents, namely, tellurium tetrachloride, tellurium acid tartrate, and tellurium acid citrate. Of these three, the tetrachloride showed the greatest range of solubility. The method of testing the solubility of these compounds in non-aqueous solvents consisted in adding to about 25 cc. of the solvent approximately 1 grm. of the finely divided tellurium compound. The mixture was thoroughly shaken and allowed to stand for at least one hour, after which any remaining solid was separated by filtration. The solvent was carefully evaporated from the filtrate, the residue taken up in dilute hydrochloric acid, and a test made for tellurium with hydrasine hydrochloride. In some cases hydrogen sulphide was passed in directly, the appearance of a red colour proving to be a good qualitative test for tellurium. Assuming that the solubility might in some cases be attributed to small amounts of moisture present in the solvent, when a liquid was found to dissolve tellurium tetrachloride, the liquid was subjected to careful dehydration by shaking with KOH, P2O5, or to desiccation by standing over these dehydrating agents until free from moisture. The nature of the liquid determines the method employed. A test of the solubility was then repeated in the absolutely anhydrous reagent, thus insuring that water played no part. Tellurium tetrachloride proved to be soluble in benzene, toluene, methyl alcohol, absolute ethyl alcohol, normal butyl alcohol, amyl alcohol, benzylic alcohol, xylol, chloroform, and ethyl acetate. In petroleum ether, kerosene, benzaldehyde, acetone, isopropyl bromide, and carbon tetrachloride it was but sparingly soluble, while in carbon disulphide it was completely insoluble. Tellurium acid tartrate was found to be soluble in methyl alcohol, normal propiolic alcohol, ether, acetone, pyridine, and acetonyl acetone. It was sparingly soluble in acetonitride, aldehyde-cyanhydrin, acetone cyanhydrin, acetoacetic ester, iso-butyric alcohol, ethyl alcohol, iso-propyl alcohol, fusel oil, acetic anhydride, and benzylic alcohol. The solubility of tellurium acid citrate may be expressed as follows:-Soluble in butyl alcohol, ether, absolute ethyl alcohol, ethyl alcohol, ethyl acetate, and amyl acetate, and slightly soluble in aniline, benzaldehyde, and acetone. The combined solubilities of these three tellurium compounds offered a large number of mediums in which tellurium sulphide precipitations could be carried out. These solutions consequently furnished data which would either prove or disprove whether the medium in which the precipitation of tellurium sulphide is brought about is an influencing factor. Hydrogen sulphide was passed into each solution of the tellurium compound in the organic liquid. At room tem CHEMICAL NEWS. Physical Chemistry and its bearing on Chemical Industries. peratures the procedure consisted in precipitating the sulphide, washing it free from hydrogen sulphide with portions of the solvent, dissolving the precipitate in aqua regia, and making qualitative tests for tellurium and sulphur. In many cases, as with acetone, direct addition took place between the hydrogen sulphide and the solvent with the production of extremely obnoxious odours. No further work was carried on in such cases. In a large number of cases, especially where the tellurium compound in solution was the acid tartrate or acid citrate, colloidal solutions were obtained. This was overcome by passing in pure dry hydrogen chloride gas, which usually coagulated the precipitate. When the hydrogen chloride gas reacted with the solvent this procedure could not be used. A red-brown precipitate at the moment of precipitation was always produced, which appeared identical with the one obtained in aqueous solutions. If allowed to stand at room temperature the precipitate rapidly changed to black, indicating dissociation. The precipitate always gave distinct qualitative tests for tellurium and sulphur. Since the deportment of the tellurium sulphide precipitated in these solutions was so similar to its conduct in aqueous solution, hydrogen sulphide gas at o° C. was passed into each of these solutions after they had been cooled to o° C. As it was practically impossible to make quantitative determinations of the amount of sulphur that could be extracted at this temperature in a given time, and since carbon disulphide is miscible with practically all of these solvents, use was made of the rate of change of colour from red to black. It was difficult at first to determine just when this change in colour had taken place, as it is a gradual one, but practice soon showed that the rate of change of colour of the precipitate in these solutions very closely agreed with the rate of change in colour in aqueous solutions. A final part of the work consisted in reducing these solutions to -20° C. and passing in hydrogen sulphide which had also been reduced to a low temperature. The red-brown precipitate then remained unchanged in appearance for one hour, which was considered a sufficient length of time to indicate that no dissociation was taking place and that the precipitate was stable at that temperature. In some cases the solutions froze before this temperature could be obtained, and in others so little of the tellurium compound remained in solution at that temperature that comparatively few solvents could be used. The solution of the tetrachloride in ether was very satisfactory. All of the experiments made in non-aqueous solutions have shown that tetravalent tellurium is precipitated by hydrogen sulphide in these solutions exactly as in aqueous solutions. There is a tendency for the precipitate to separate in the colloidal form, but this may be prevented by the presence of dry hydrogen chloride. If the concentration of the tellurium solution is sufficient this condition is not encountered. The precipitate undergoes dissociation into tellurium and sulphur at the same rate at o° C. as in aqueous solution, while if the temperature is reduced to -20° C. a stable compound TeS2 exists between tellurium and sulphur. Final Conclusions. The results of this investigation have established the following facts regarding the production and stability of a sulphide of tellurium : 1. The introduction of hydrogen sulphide into an aqueous tetravalent tellurium solution at room temperatures or below causes the immediate production of a redbrown precipitate represented by the formula TeS2. The production of this compound is independent of the acid concentration. 2. At temperatures below -20° C. tellurium sulphide is a stable compound. At temperatures above -20° C., due to the weak affinity existing between these elements, dissociation takes place. At temperatures approximating -20° C. this dissociation is slow, while at higher temperatures dissociation takes place more rapidly. The 219 degree of dissociation at any one time or temperature may be determined by the amount of sulphur that can be extracted with carbon disulphide. 3. Dissociation never continues to completion. The dissociated mass extracted with carbon disulphide always retains at least o 95 per cent of sulphur. This sulphur does not exist as a sulphide of tellurium that is decomposed by hydrochloric or hydrobromic acid of any strength, nor does it exist as a variety of sulphur that is insoluble in carbon disulphide. 4. The compound TeS does not exist. 5. The production of the compound TeS2 is independent of the medium in which it is carried out. The stability of this compound is solely a question of temperature. PHYSICAL CHEMISTRY AND ITS BEARING ON THE CHEMICAL AND ALLIED INDUSTRIES.* IT appears from the figures quoted that if the first portion of the change is left out of account practically and it is a fair conclusion that the later portion of the constant values for the velocity coefficient are obtained, change conforms to the law of mass action. The linear is observed only when the amount of enzyme is relatively relationship between the time and the amount of change small compared with the amount of carbohydrate. Certain recent work indicates that with purified malt diastase the abnormal period of the linear relationship is very short indeed. The combination of hydrogen and oxygen at the surface of hot porcelain, and the action of diastase on starch, have been discussed in detail in order to illustrate some of the complications that arise in applying the mass action formulæ in cases of heterogeneous catalysis. Another very serious obstacle in this matter is the extreme diffi ducing the catalyst in any desired condition of activity. culty, one might almost say the impossibility, of reproIn heterogeneous catalysis the scene of action lies in the surface layers of the solid catalyst, and it is well known in connection with technical catalysed reactions that the activity of the surface depends, in a very high degree, on the way in which the catalyst has been prepared and on the treatment it has received. As an illustration of the influence which the previous history of the catalyst may exert on its activity, some observations made by Bone and Wheeler on porcelain surfaces may be quoted. These investigators found that stimulated quite notably its activity in connection with the previous treatment of such a surface with hydrogen combustion of hydrogen and oxygen. Preliminary treatment of the porcelain surface with oxygen appears, on the other hand, to reduce its catalytic activity. These statements are borne out by the figures in Table IX. k, the velocity coefficient, represents, as already explained, the rate at which the hydrogen and oxygen combine to form and the experiments were performed in the order shown. water. The porcelain surface was the same throughout, It is noteworthy that the stimulus imparted to the porcelain surface by preliminary hydrogen treatment survived a prolonged exhaustion of the apparatus, but gradually wore off as successive charges of electrolytic gas were circulated over the surface. The significance of the previous history factor may be emphasised also in relation to one of the most important applications of catalysis on the technical scale, viz., the bydrogenation of oils. The development of this modern Cc.H2 absorbed 4001 300 extensive technical developments, but work by others on the same lines showed that if hot oleic acid, in the liquid condition, is treated with a current of hydrogen in pre sence of a metal catalyst, such as finely-divided nickel, the hydrogen is absorbed and complete conversion into stearic acid is effected. Further, this method is applicable not only to the liquid unsaturated fatty acids, but also to their glycerides; i.e., the liquid fats such as olive, linseed, and fish oils. As a result of this discovery the hardening |