Solidification of Liquids by Pressure. By E. H. AMAGAT (Compt. rend., 105, 165–167).—The author has examined a large number of organic and inorganic liquids at temperatures between 0° and 50°, and at pressures up to 3000 atmos., but has not observed any signs of solidification. Carbon tetrachloride, however, behaves differently, and solidifies at a high pressure, melting again when the pressure is released. The solid has a very distinct crystalline structure; solidification takes place under a pressure of 210 atmos. at -19.5°, 620 atmos. at 0°, 900 atmos. at 10°, and 1160 atmos. at 19.5°.

Carbon protochloride, C.Cl, does not solidify under a pressure of 900 atmos. at 0°, but benzene seems to solidify at about 700 atmos. at 22°.

It is probable that every liquid possesses a critical point of solidification analogous to the critical point of gases, that is, a temperature above which no pressure, however great, will convert the liquid into a solid. C. H. B.

Dissociation of some Gases by the Electric Discharge. By J. J. THOMSON (Proc. Roy. Soc., 42, 343-345).—When the vapour of iodine, at a temperature of 200-230°, is subjected in a tube exhausted of air to the action of the sparks from a coil giving a 3-inch spark in air, the pressure as indicated by a sulphuric acid manometer increases at first rapidly, then more slowly, and finally becomes stationary. On stopping the coil, the greater part of this increase is permanent, or at least lasts for some hours. The author attributes it to dissociation of the iodine-vapour. The amount of dissociation has been measured by observing the vapour-density in a special apparatus, sulphuric acid being excluded. The density after sparking then fell to 100, 115, 86, and 84 (H 1) in different experiments. In the last case (temp. 232°), after standing 24 hours, the dissociation still equalled that produced by Meyer at 1570°. The colour of the dissociated vapour is stated to be a little lighter and less uniform than that of the normal vapour. The electric strength was also reduced.

=

=

When bromine-vapour is sparked in a similar way, an increase of pressure also occurs, but disappears rapidly, probably owing to reunion of the separated atoms. Vapour-density determinations also showed that bromine is dissociated by simple heating at a low pressure for a long time. In such determinations, therefore, the vapour should be maintained at constant temperature for some time before observing.

Experiments have also been made with chlorine and nitrogen

tetroxide.

Ch. B.

Osmotic Equilibrium and the Concentration of Solutions by Gravitation. By Gour and G. CHAPERON (Compt. rend., 105, 117-119). An application of the laws of thermodynamics to the question of osmotic equilibrium.

Demonstration of the Coefficient of Expansion of Gas as a Lecture Experiment. By R. SCHIFF (Gazzetta, 17, 190-191).-In this paper, a simple apparatus is described for demonstrating the law

of the expansion of gases as a lecture experiment. In a graduated tube surrounded with a warming jacket is inclosed 273 c.c. of dry gas; the tube is connected with a piece of flexible tubing, bent in the form of a U, and provided with a mercury reservoir. Previous to the experiment the level of the mercury in both limbs is adjusted, the tube heated with steam, and the level readjusted. If the barometric pressure has remained the same, the reading on the tube will give the coefficient of expansion. V. Í. V.

Estimation of Pressure in Closed Tubes. By A. REYCHLER (Ber., 20, 2461-2462).—In this paper, a simple apparatus is described by means of which the pressure in sealed tubes may be roughly astimated. It consists of a glass tube of small diameter, about 40 cm. long, one end of which is sealed off, and 4-5 cm. length from this end is silvered; the tube is then bent in the form of a U, and filled to a certain height with mercury. The whole is enclosed in the tube in which it is proposed to carry on the reaction at an increased pressure, which forces down the mercury in the open limb, thus causing it to rise in the sealed limb and dissolve off the silver. Then from the rise of level of mercury thus determined and the tension of the vapour of mercury at the temperature of the reaction, the pressure within the tube can be directly calculated. V. H. V.

Inorganic Chemistry.

Selenium Alums. By C. FABRE (Compt. rend., 105, 114-115). -The author has prepared the selenium alums of the following bases: Sodium, potassium, cæsium, rubidium, thallium, ammonium, ethylamine, diethylamine, triethylamine, methylamine, dimethylamine, trimethylamine, and propylamine, by mixing solutions of the corresponding selenate and aluminium selenate. The products have the general composition and crystalline form of the alums, and are colourless. The caesium and rubidium selenium alums are much more soluble than the corresponding sulphur-alums, and it is worthy of note that the soluble thallium alum is formed from a selenate which is almost insoluble in water. The organic alums closely resemble the ammonium salt.

By mixing violet chromium selenate with the selenates of potassium, sodium, cæsium, rubidium, thallium, ammonium, ethylamine, and propylamine, the corresponding alums were obtained. They crystallise well, and frequently form very distinct octahedra. They are violet red by transmitted light, and their solutions are violet when cold, but become green at 55—60°. The green solutions will only crystallise when allowed to evaporate spontaneously for several months. Thallium chromium selenium alum is deep violet by transmitted, and almost black by reflected light. C. H. B.

Monoclinic Form and Optical Properties of Prismatic Arsenious Anhydride. By DES CLOIZEAU (Compt. rend., 105, 96— 99). Prismatic arsenious oxide belongs to the monoclinic system. Measurements of the various angles are given. The angle of the prism is 135° 1', and is similar to that of valentinite or prismatic antimonious oxide, 137° 7', but as the other zones of the crystals are not similar the two compounds are not strictly isomorphous. crystals are highly birefractive, the plane of the optical axis being parallel with the plane of symmetry.

The

The fact that thin plates of ordinary arsenious oxide are sometimes feebly birefractive, indicates that the crystals are possibly only pseudo-cubic. C. H. B.

By

Preparation and Properties of Carbon Oxysulphide. P. KLASON (J. pr. Chem. [2], 36, 64-74).—To prepare this substance, Than recommends (Annalen, Supp. 5, 245) the addition of solid potassium thiocyanate to a cold mixture of 5 vols. strong sulphuric acid and 4 vols. water. The author finds that the purest product and best yield is obtained on adding 50 c.c. of a concentrated aqueous solution of potassium or ammonium thiocyanate to a cooled mixture of 290 c.c. (520 grams) of strong sulphuric acid and 400 c.c. water. The whole is heated at 25° in a water-bath. The gas thus prepared contains only about 24 per cent. of carbonic anhydride and 005 per cent. of carbon bisulphide. Hofmann recommends passing the gas through an ethereal solution of triethylphosphine to free it from carbon bisulphide. The author finds that the absorption of this latter is much more rapid and complete if a small quantity of pure triethylphosphine is used instead of a solution, the gas being then passed through pure sulphuric acid to free it from traces of the phosphine. Carbon oxysulphide is only absorbed very slowly by a 33 per cent. aqueous solution of potash. If the gas obtained as above is passed slowly through about 20 cm. of such a solution, the whole of the carbonic anhydride is absorbed with a loss of only about 7 per cent. of the oxysulphide. A 33 per cent. aqueous solution of potash mixed with its own volume of alcohol absorbs carbon oxychloride completely and rapidly, and is the best reagent for use in estimating it.

Pure carbon oxysulphide is odourless and tasteless. Its physiological effects are very similar to those of nitrous oxide. When passed through a saturated solution of baryta, no opalescence is produced for at least half a minute, whilst if any carbonic anhydride is present, the solution becomes milky at once. With lead acetate solution,

the precipitate is a quarter of an hour forming.

L. T. T.

Action of Chlorine on Carbon Bisulphide and of Sulphur on Carbon Tetrachloride. By P. KLASON (Ber., 20, 2376–2383). -Carbon bisulphide is but slightly attacked by chlorine at ordinary temperatures, but in presence of chlorine-carriers, especially of iodine, action takes place readily with the ultimate formation of carbon tetrachloride. The author has carefully studied this reaction and the intermediate products formed, and also the derivatives

obtained by the action of heat, reducing agents, &c., on such compounds. He has isolated the following compounds :-Thiophosgene, CSC12, boiling at 73.5°, and gradually changing to its polymeride; trichloromethylsulphur chloride, CCI, SCI, boiling at 149°; trichloromethyl bisulphide, CC1, S2 CCl,, boiling at 135° in a vacuum; trichloromethyl trisulphide, CCl3 S CC13, crystalline, and boiling at 190° in a vacuum; and chlorothio-carbonylsulphur chloride, CSCI-SCI, boiling at 140°. The compound CCl, S3 CCl, is identical with that described by Rathke as S(CC), SCI)2.

In the action of sulphur on carbon tetrachloride, only carbon bisulphide, sulphur chloride, and sometimes traces of thiophosgene and CC1, SCI were formed. L. T. T.

Manganese Compounds. By B. FRANKE (J. pr. Chem. [2], 36, 166-174). The blue gas formed when air or carbonic anhydride saturated with aqueous vapour at 40-50° is led over the manganese oxysulphate (MnO3)2SO, (this vol., p. 893), is free from ozone, and consists of a new gaseous oxide of manganese, probably manganese tetroxide, MnO4, which condenses to a blue-violet amorphous substance at a lower temperature. The quantity obtained was too small to allow of analysis; the compound itself differs, however, in its properties from the trioxide and heptoxide; it is more volatile than the trioxide, and is less readily acted on by water, with which it combines to form manganic acid with the liberation of oxygen. The tetroxide is decomposed by the action of sulphuric acid and ether.

When warm and moderately strong sulphuric acid is treated with potassium permanganate until the brown solution no longer dissolves the salt, and the mixture is heated, a beautifully crystalline, claretred salt, 2Mn,(SO1) + 5K2SO,, is obtained. This salt dissolves in dilute sulphuric acid with a brown colour, and in concentrated sulphuric acid with a blue-violet colour, decomposes on heating into potassium and manganese sulphates, oxygen and sulphuric anhydride, and when treated with much water yields the hydroxide 3MnO2,2H,O, and manganese sulphate. Small, yellowish, lustrous scales of a manganic manganous oxide, Mn,O,, are obtained, however, if the salt is added to water, the mother-liquor removed as quickly as possible, and the residue washed with water, alcohol, and finally with ether. On treatment with dilute sulphuric acid, the oxide yields manganese sulphate (2 mols.), and the hydroxide 3MnO2H2O (1 mol.); it may therefore be regarded as 3MnO2,2MnO. When heated, it is converted into trimanganic tetroxide, Mn,О.

W. P. W.

Thorium Silicates. By L. TROOST and L. OUVRARD (Compt. rend., 105, 255-258).—When thorium oxide is fused with silica and calcium chloride at a bright red heat, and the crystalline product is treated with water, and then with hydrochloric acid to remove calcium chloride and silicate, a residue of small, rhombic crystals is left, which are insoluble in acids, but are attacked by potassium hydrogen sulphate; sp. gr. at 16° 6.82. They have the composition 2ThO,SiO, or ThO2,SiO2, but are not isomorphous with zircon. The thorium may, however, be present in the form of a dioxide, and this supposition

=

is supported by Krüss and Nilson's recent determination of the vapourdensity of thorium chloride. These numbers were always lower than those required by the formula ThCl, but the authors have repeated the determination by Dumas' method, and have obtained similar though somewhat higher numbers. In this case, the influence of the hydrogen chloride formed by the action of a small quantity of absorbed moisture on the thorium chloride would be less marked, because the greater part of the gas is expelled together with the nitrogen with which the globe is filled. In Victor Meyer's method, on the other hand, a small quantity of substance is taken, and the hydrogen chloride evolved may introduce very considerable errors.

If the thorium oxide, silica, and calcium chloride are fused together at 1100°, and the product treated with water and hydrochloric acid, a residue of crystals and granules is obtained. The latter are attacked by potassium hydrogen sulphate, whilst the former are not affected, and thus they can be separated. The crystals are triclinic, with an angle of extinction of about 31°; sp. gr. at 25° 5.56. They have the composition ThO,SiO2 or ThiO2,2SiO2. This silicate is therefore not analogous to zircon in form or composition, just as thorium metaphosphate is not analogous to silicon metaphosphate (Abstr., 1885, 1113). C. H. B.

Thorium Sodium and Zirconium Sodium Phosphates. By L. TROOST and L. OUVRARD (Compt. rend., 105, 30-34).-Sodium metaphosphate fused at a red heat readily dissolves thorium oxide, amorphous thorium phosphate, and anhydrous thorium chloride, and the product is completely soluble in water after cooling. If, however, the thorium compound is added to saturation, and the fused mixture is allowed to cool slowly and extracted with water, a residue is left, consisting of elongated, triclinic prisms, which act strongly on polarised light, the angle of extinction being about 44° whilst the angle of the axis is 45° and the twinning plane is parallel with the plane of the optical axes. The crystals are insoluble in hydrochloric or nitric acid and in aqua regia, and have the composition Na 0,8Th0,3P,O, (Th = 116.2), or Na,O,4ThO2,3P2O, (Th = 232·4). They are therefore analogous to the compound previously obtained with potassium metaphosphate (Abstr., 1886, 853).

Zirconium oxide, phosphate, and chloride are less readily soluble in sodium metaphosphate, and the product is a crystalline powder composed of feebly birefractive rhombohedra, extinction taking place along the diagonals. It is insoluble in acids and in aqua regia, and has the composition Na,O,4ZrO2,3P2O; sp. gr. at 12° 3·10.

When fused sodium pyrophosphate is mixed with thorium oxide or phosphate, it yields an insoluble powder, consisting of very thin hexagonal, microscopic leaflets. If sodium chloride is added to the mixture, solidification takes place more slowly, and the product is obtained in hexagonal lamelle, mixed with fragments of hexagonal prisms which act on polarised light, and are soluble in nitric acid. They have the composition 5Na2O,4ThO,3P2O, or 5Na2O,2ThO2,3P2O5. If the fused substance is mixed with excess of sodium chloride, thorium oxide is precipitated in minute cubes.

Thorium chloride and sodium pyrophosphate yield birefractive