Hydrate of Hydrogen Sulphide. By DE FORCRAND and VILLARD (Compt. rend., 106, 849-851).—The vapour-tension of the hydrate of hydrogen sulphide was determined in presence of excess of water and gas. The following table gives the differences between the tensions and 760 mm. at different temperature :—

2.8° 3.4°

3.8°

3.9° 4.5° 4.9° 5.2°

+222 +288 +323 +337 +403 +463 +490.

The low tension at 0° is especially noteworthy; at lower temperatures the presence of ice interferes with the determinations. The tension is, however, always below that of the atmosphere.

C. H. B. Hydrates of Gases. By DE FORCRAND and VILLARD (Compt. rend., 106, 939-941).-According to Wroblewski, the formation of a hydrate of a gas by compression only takes place when the water holds in solution a quantity of gas corresponding with that required to produce the hydrate. It may also be supposed that at the moment of crystallisation the water contains much less gas than the hydrate, but the formation of the latter takes place with absorption of a considerable quantity of gas. The solution of a gas, and the formation of a hydrate, would then be two perfectly distinct phenomena. The second explanation only is admissible in the case of hydrates of chlorine and sulphurous anhydride, since the solutions contain a much lower proportion of these gases than the hydrates.

The apparatus used for determining the vapour-tension of the hydrate of hydrogen sulphide (preceding Abstract) was arranged so that at a pressure of 60 mm. above atmospheric pressure, it contained crystals of the hydrate, together with hydrogen sulphide and a slight excess of water. If the pressure was increased by 100 mm., and the apparatus agitated to promote the formation of more crystals, there was a considerable absorption of gas, and the pressure sank to its former value. A further increase of pressure produced a further quantity of crystals. An increase of pressure of 100 mm. does not greatly increase the solubility of the gas at constant temperature, and yet the production of the hydrate was evident from the separation of fresh crystals. When the hydrate is formed at 0°, 1 c.c. of water absorbs about 100 c.c. of gas, whereas water at +1° dissolves only 4 vols. of the gas under normal pressure. The composition of the hydrate SH2+ 12H2O corresponds with 102 vols. of gas. Similar results were obtained with methyl chloride, and it would seem therefore that the formation of a hydrate of gas is not merely the solidification of a saturated solution, but an independent act of combination. C. H. B.

Method for Obtaining Definite Hydrates. By E. J. MAUMENÉ and C. LIMB (Bull. Soc. Chim., 48, 777).-Crystals of oxalic acid were kept under a glass shade by the side of dried oxalic acid. After six months the crystals were titrated, and found to have a com

position corresponding with the formula C2H2O, + 2H2O. Crystals from the same preparation were kept in a desiccator over sulphuric acid for more than six months, when they had the composition indicated by the formula C2H2O4. It is suggested that instead of drying substances indifferently over lime or sulphuric acid, some special substance should be selected, according to the nature of the compound to be analysed. N. H. M.

Solubility of Sulphates. By A. ÉTARD (Compt. rend., 106, 740-743).—The author's determinations, extending through a wide range of temperature, show that when the solubility of a salt is represented by a curve which expresses the weight of salt in 100 parts of solution, this curve is a right line, the angular coefficient of which varies with each salt. For one and the same salt, the coefficient changes in value at one or more points, the change being usually abrupt, although in some cases the perturbation extends through a short but measurable distance. In the majority of cases, if not in all, the sign of the coefficient changes, and the solubility decreases beyond a certain temperature. This is especially marked in the case of many sulphates, and the following coefficients have been determined by the author.

Ferrous Sulphate.-From -2° to 65°, y = 13·5 + 0·3784t; from 65° to 98° the curve of solubility is parallel with the axis of temperature; from 98° to 156°, y = 37.5 0.6685t. The last equation indicates that the salt should be insoluble at 156°, and this conclusion has been verified experimentally.

Cadmium Sulphate.-From 0 to 68°, y = 357 +0.2160; from 68° to 200°, y = 50·6 — 0·3681t. At 200° the salt dissolves only to the extent of 2 per cent., and at 215° it is insoluble.

Magnesium Sulphate.-From 0° to 123°, y = 205 +0.2276t; from 123° to 190°, y = 48·5 — 0·4403t.

The salt should become
A solution saturated at

insoluble at 233°, but this was not verified. +15° becomes turbid at 178°, and deposits a hydrate in porcelain-like crusts.

Lithium Sulphate.-From -20° to -10.5°, y = 185 +0.8421t; from 105° to 100°, y = 26.5 0.0274t.

-

Rubidium Sulphate.-From 0° to 49°, y = 26·5 + 0·2959t; from 49° to 170°, y = 41·0 + 0·0661t.

Potassium Selenate.-From -20° to 100°, y = 52 + 0·0250t.
Selenious Anhydride.—From -3° to 36°, y = 450 + 07692t.

In several cases the observations are complete, since they extend from the point of congelation of the solution to the temperature at which the salt again becomes insoluble. The point of congelation corresponds with a certain ratio between the salt and the water. As the temperature rises, the change in presence of an excess by the salt is analogous to etherification. A certain quantity of water is set free, and dissolves a further quantity of the salt, and this change continues as the temperature rises, the solubility of the salt increasing by reason of the dehydration of the original system up to the point of maximum solubility. A change analogous to saponification then sets in, and as the temperature rises the salt is gradually

deposited, the water playing an increasing part in the establishment of equilibrium until at a certain temperature the water completely displaces the salt, and the latter becomes insoluble. C. H. B.

Laws of Chemical Equilibrium. By P. DUHEM (Compt. rend., 106, 846—849).—A continuation of the discussion with Le Chatelier. C. H. B.

Raoult's Method for the Determination of Molecular Weight and on Acetoxime. By K. AUWERS and V. MEYer (Ber., 21, 1068-1070). The authors suggest that in Raoult's method glacial acetic acid should always be employed as the solvent, and neither benzene nor water.

Beckmann's determinations of the molecular weight of oximes (this vol., p. 409) are probably wrong, owing to his having used benzene. Experiments made by the authors on acetoxime show that when glacial acetic acid is used, the results obtained agree with the formula C,H,NO.

When it is absolutely necessary to make use of water or benzene, the results are of value only after having first made experiments with a compound of strictly analogous constitution, the molecular weight of which is known.

F. S. K.

Molecular Weight of Oximes. By E. BECKMANN (Ber., 21, 1163-1164).—The conclusions arrived at by the author with reference to the molecular weights of the oximes (this vol., p. 409) were based on the lowering of the freezing point of benzene, which was employed as the solvent for the various oximes examined. When, however, acetic acid is used, results are obtained which, in the case of acetoxime and benzaldoxime, are in agreement with the molecular weights usually adopted. The molecular weights of these oximes as determined by the lowering of the vapour-tension of their ethereal solutions are also those ordinarily assumed. W. P. W.

Apparatus for Fractional Distillation. By E. CLANDON and E. C. MORIN (Bull. Soc. Chim., 48, 804-811).-The apparatus is intended. for the distillation of large amounts of liquids, 100 litres for example. It is made entirely of copper. For description of the apparatus the original paper, in which sketches are given, must be referred to.

N. H. M.

Apparatus for Fractional Distillation. By T. H. NORTON and A. H. OTTEN (Amer. Chem. J., 10, 62—69).-The apparatus is constructed on the principle of Tcherniac's "déverseur" for the separation of froth during distillation (Wurtz Dict., Supp., 597), so that the vapours are not washed through the condensed liquid, but are at once separated. The apparatus is decidedly fragile, and on the whole yields no better results than the fractionating tubes of Linnemann and Hempel. H. B.

Pressure Tubes. By H. N. WARREN (Chem. News, 57, 155).— The author adopts the following plan to make glass tubes resist internal pressure at high temperatures. For temperatures ranging from 200° to 400°, the sealed tube is enclosed in a copper tube, the

intervening space being closely packed with magnesia. For higher temperatures, a wrought-iron external tube is used with sand as the packing material.

D. A. L.

Turbine for Laboratory Purposes. By H. RABE (Ber., 21, 1200 -1201). The author has devised a simple form of turbine which, when connected with the water service of a laboratory, is capable of providing the motive power required for mechanical stirring.

W. P. W.

Lecture Apparatus for making Sulphuric Anhydride. By W. R. HODGKINSON and F. K. LOWNDES (Chem. News, 57, 193).-The apparatus consists of an inverted bell-jar. The smaller opening is fitted with a caoutchouc stopper carrying a wooden rod to which a piece of stout platinum wire is attached supporting some spongy platinum in the centre of the jar. The large opening is firmly closed by a piece of wood, through which two tubes (one for oxygen, the other for sulphurous anhydride) pass and terminate close to the platinum sponge which just previous to use has been heated in a bunsen flame. Sulphuric acid forms rapidly when the two gases_are made to impinge on the hot spongy platinum. D. A. L.

Inorganic Chemistry.

Relative Values of the Atomic Weights of Hydrogen and Oxygen. By J. P. COOKE and T. W. RICHARDS (Amer. Chem J., 10, 81-110; comp. Lord Rayleigh, this vol., p. 643).-The only direct determinations of this ratio that are independent of all other considerations and determinations are those of Dumas and of Erdmann and Marchand, and both these contain possible errors and uncertainties that are so great as to render the results obtained worthless for deciding between the numbers 15.96 and 16:00 as the atomic weight of oxygen.

The principal source of possible error is that the amount of hydrogen is determined by the difference of the weights of water and of oxygen, and the combined errors of these two determinations are then exaggerated because of the comparative smallness of the number that expresses the hydrogen. In the present determination the hydrogen. was actually weighed. The globe used was counterbalanced by a similar one, and its weight could be satisfactorily determined to onetenth of a milligram; it held nearly 5 litres, and was provided with glass stopcocks. After exhausting to 1 mm. it was weighed, filled with hydrogen, and again weighed.

In the first series of experiments, the hydrogen was prepared from almost pure zinc and hydrochloric acid; the dissolved air was removed from the dilute acid by boiling in a stream of hydrogen and preserving it in an atmosphere of hydrogen. The gas was purified by passing through a 5-foot tube of potash solution (necessary

to remove sulphur dioxide), then dried by calcium chloride, sulphuric acid, and phosphorus pentoxide; wherever possible, joints were made by sealing together the glass tubes, all others were protected by a cement composed of equal parts of pitch and gutta-percha. In the second series of experiments, the hydrogen was prepared from hydrochloric acid and a semi-fluid amalgam of zine; the amalgam could be connected externally with a platinum plate immersed in the acid, and by making connection and interposing a varied electrical resistance, or by connecting with a battery, the hydrogen could be obtained at any desired speed. The gas was purified as before. In the third series, the hydrogen was prepared by dissolving sheet aluminium in pure aqueous potash. The long potash washing tube was dispensed with, but the gas dried as before. The globe was then connected with the rest of the apparatus that had previously been filled with nitrogen. The apparatus consisted firstly of heated tubes containing copper to remove oxygen from the air current, copper oxide to remove hydrogen occluded by the copper or organic matter in the air; secondly, drying tubes containing potash, calcium chloride, sulphuric acid, and phosphorus pentoxide; thirdly, the weighed globe containing hydrogen; fourthly, tube containing heated copper oxide; fifthly, the apparatus for collecting the water, namely, an empty tube, strong sulphuric acid, and phosphorus pentoxide; and, lastly, an apparatus for regulating the suction of air through the whole apparatus. The gas current was rapid the whole time; after the first half hour, more than nine-tenths of the hydrogen was burnt, and after the first hour the first tube containing copper was removed, all possibility of an explosion being at an end, and air instead of nitrogen was drawn through the apparatus. By this means the whole apparatus is left in its initial condition, namely, the reduced copper oxide is reoxidised completely, thus avoiding all error due to occlusion of hydrogen, and the condensing tubes are left also full of ordinary air. The actual experiment lasted altogether about eight hours, which time was shown to be amply sufficient. The weight of hydrogen burnt averaged 0-42 gram. The results obtained

or, having regard only to the substances actually weighed, the composition of water is :-Oxygen (Dumas) 88.864 00044, and hydrogen (Cooke and Richards) 11·140 ± 0·0011; total 100 004.

The results recently given by Keiser (Abstr., 1887, 1078) namely, 15.873, 15-897, and 15 826 are not concordant, and are vitiated by varying impurities in the gas used.

H. B.