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retain their original character, melting and resolidifying at 15°, and showing no signs of forming allotropic modifications. He is still of opinion that the various modifications of sulphuric anhydride are all due to the presence of traces of moisture. He describes further precautions for obtaining absolutely pure anhydride, and considers the best method to be to cohobate carefully purified sulphuric anhydride with phosphoric anhydride in a slight modification of the bent and sealed distilling tube previously described (loc. cit.). After continued cohobation, the sulphuric anhydride will remain liquid down to 15°, even in contact with the phosphoric anhydride. Finally the sulphuric anhydride may be distilled over into the opposite end of the distilling tube, and this then sealed off without the air being able to come in contact with the inside of the tube. Phosphoric anhydride forms a compound P2O,,3SO3, which crystallises out from the excess of sulphuric anhydride. This compound decomposes at the boiling point of sulphuric anhydride.

L. T. T.

Behaviour of Iodine with Realgar and Arsenic Iodosulphide. By R. SCHNEIDER (J. pr. Chem. [2], 34, 505–514).—Arsenious iodosulphide, AsI,,As2S3, is prepared by heating together either a mixture of realgar (1 mol.) and iodine (2 atoms) with the least possible access of air, or a mixture of 3 parts arsenious iodide with 1.6 parts of arsenic trisulphide. It forms an amorphous, vitreous mass with conchoïdal fracture, and is of a dark red or reddish-brown colour. It is not acted on by the air at ordinary temperatures. When heated at 100°, it softens, and boils at a higher temperature without evolution of iodine vapour, but with partial decomposition into arsenious iodide and sulphide. It is insoluble in hot and cold alcohol, ether, carbon bisulphide, and chloroform. Hot water slowly decomposes it with formation of hydriodic acid. Boiling hydrochloric acid slowly decomposes it with evolution of iodine. When boiled with concentrated sulphuric acid, it gives off iodine, sulphur and sulphurous anhydride. Potassium and ammonium hydroxides dissolve arsenious iodosulphide to a colourless liquid, from which dilute acids precipitate arsenious sulphide, whilst the whole of the iodine and part of the arsenic remain in solution. When treated with an ammoniacal solution of silver nitrate, it is decomposed, forming silver iodide, sulphide, and arsenite. This reaction affords a means of determining the composition of the substance.

When realgar is shaken with a solution of iodine in carbon bisulphide, and iodine is added in small quantities until the whole of the realgar is dissolved (1 mol. realgar requires 6 atoms iodine), and the solution then evaporated, arsenious iodide separates, partly in hexagonal plates and partly in rhombohedrons, mixed with long prisms of sulphur. Also, when a mixture of realgar (1 mol.) with iodine (6 atoms) is heated, and the resulting mass is dissolved in carbon bisulphide, arsenious iodide and sulphur are formed.

G. H. M. Arsenic Pentasulphide. By L. W. McCAY (Chem. News, 54, 287). When a solution of an alkaline arsenate strongly acidified with hydrochloric acid and saturated with hydrogen sulphide is

heated in a closed vessel at 100° for one hour, the arsenate is completely converted into pentasulphide. It contains no trisulphide, and if due precautions have been taken to exclude air, no free sulphur. Pure arsenic pentasulphide is lemon-yellow in colour, does not yield any sulphur to carbon bisulphide, and dissolves in ammonia without separation of sulphur. When the ammoniacal solution is agitated with silver nitrate and filtered, a clear filtrate is obtained, from which nitric acid precipitates silver arsenate. The formation of arsenic pentasulphide in this manner confirms Bunsen's results, he having obtained it by the action of hydrogen sulphide on hot solutions of arsenic compounds. D. A. L.

Carbonic Anhydride in the Atmosphere. By R. BLOCHMANN (Annalen, 237, 39-90).—The author gives an account of the various methods which have been used for the estimation of the carbonic anhydride in the atmosphere from the time of Saussure to the present day. It is pointed out that Pettenkofer's method yields too high results; the normal amount of carbonic anhydride in 10,000 volumes of air is 3, not 4 volumes. The author describes a modification of Pettenkofer's method, which permits of the baryta-water being filtered through asbestos and titrated without coming into contact with the air of the atmosphere. A double burette of special construction is required. Drawings of the apparatus are given in the original. W. C. W.

Bimetallic Phosphates. By A. JOLY (Compt. rend., 103, 1129— 1132). The action of disodium hydrogen phosphate on solutions of metallic salts varies with the conditions, and with the nature of the metal. In some cases, with silver nitrate for instance, an amorphous precipitate of the tribasic phosphate is at once produced; in others, a gelatinous monophosphate is at first precipitated, and this gradually passes into a crystalline diphosphate. In the case of the alkaline earths and manganese, the first stage in the reaction is represented by the equation 4Na2HPO + 4M′′Cl2 = M3"(PO.)2 + M′′H‚(PO4)2 + SNaCl.

The monophosphates decompose in presence of water with a rapidity which depends on the nature of the metal and the concentration of the solution (Abstr., 1884, 556).

In some cases, there is an intermediate reaction, the gelatinous monophosphate becoming crystalline. This is the final stage of the reaction if the conditions are such as to prevent the formation of a diphosphate. The diphosphates decompose at 100° into crystalline tribasic phosphates and the free acid, and at the ordinary temperature the reverse change takes place to a greater or less extent. These facts indicate that the intermediate phosphates described by various authors are in reality mixtures. The precipitation of silver phosphate may be regarded as taking place in two stages, the first products being the trisilver phosphate and the monophosphate, the latter immediately decomposing into the tribasic salt and the free acid, which limits the extent of the reaction. The formation of disilver phosphate is impossible under these conditions, since this salt is immediately decomposed by water (this vol., p. 215).

In the case of hypophosphoric acid, the precipitate is at first a gelatinous bibasic phosphate, which rapidly changes into a crystalline monobasic phosphate (Abstr., 1886, 200, 408, 593, 662).

C. H. B.

Silver Phosphates and Arsenates. By A. JOLY (Compt. rend., 103, 1071-1074).-Precipitated and amorphous silver phosphate dissolve in phosphoric acid solution, the solubility increasing with the concentration of the acid and the temperature. If a liquid containing less than 38 parts of phosphoric anhydride to 100 parts of water is saturated with silver phosphate at 80° and allowed to cool, it deposits trisilver phosphate in pale-yellow, rhombic dodecahedrons modified by faces of the icositetrahedron. The mother-liquor deposits no more crystals on standing, but will dissolve a further quantity of amorphous silver phosphate if heated, and thus the same solution of phosphoric acid can be used for the crystallisation of an unlimited quantity of silver phosphate.

If the solution contains 40 parts of phosphoric anhydride to 100 parts of water, it deposits disilver hydrogen phosphate, Ag2HPO1, in colourless crystals derived from a hexagonal prism. They generally form long prisms with rhombohedral terminations. In contact with water or alcohol, they become yellow, and decompose into trisilver phosphate and phosphoric acid, but they are not affected by ether. If the concentration of the phosphoric acid solution differs much from the strength given, the product is a mixture of crystals very difficult to purify.

When the crystals of disilver hydrogen phosphate are heated to 110-150°, they yield silver pyrophosphate, Ag.P2O1, which can also be obtained by heating the syrupy solution of the silver phosphate to the same temperature. Hurtzig and Geuther obtained the same compound by adding ether to the solution which had been heated. The pyrophosphate is not, however, formed in the wet way as these authors supposed, since under the given conditions of concentration, the fused acid salt, and not its solution, is decomposed. The experiment simply shows that disilver hydrogen phosphate yields the pyrophosphate at a lower temperature than that at which phosphoric acid is converted into pyrophosphoric acid.

Silver arsenate is much less soluble than the phosphate in the free acid. If the solution contains less than 70 parts of arsenic anhydride to 100 parts of water, the solution saturated with amorphous silver arsenate at 80° deposits very brilliant, black, opaque crystals of trisilver arsenate, which are unmodified rhombic dodecahedra.

A solution of arsenic acid of the composition HзASO, + H2O, when saturated with silver arsenate, yields white monoclinic crystals of silver dihydrogen arsenate, a compound which is very readily prepared. It is decomposed into trisilver arsenate and arsenic acid by a trace of water, and if heated to 100° yields silver metarsenate in the form of a white powder which absorbs water very slowly. Before losing water, the crystals of the acid salt become red, probably owing to the formation of arsenic acid and disilver hydrogen arsenate, Ag2HASO.. In fact, if a solution from which silver dihydrogen arsenate will crystallise is saturated with silver arsenate at a tempera

ture a little below 100°, it deposits orange-red hexagonal prisms with rhombohedral terminations. Their form agrees with that of disilver hydrogen phosphate, and indicates that they are disilver arsenate, but they could not be purified.

When a syrupy solution of silver arsenate in arsenic acid is heated above 100°, it yields a white granular powder similar in appearance to the compound Ag20,2As2Os, described by Hurtzig and Geuther.

C. H. B.

Solubility of Silver Chromate in Ammonium Nitrate. By R. F. CARPENTER (J. Soc. Chem. Ind., 5, 286).—It is found that on treating freshly precipitated silver chromate with a strong solution of ammonium nitrate, the solution instantly assumes a bright yellow colour in the cold. On warming, the rate of solution rapidly increases up to the boiling point; on cooling, the silver chromate crystallises out in needle-shaped crystals. In a paper by G. Biscaro (Chem. News, 53, 67) "On a Defect in the Volumetric Estimation of Chlorine by Mohr's Process," it was stated that "if nitrates, especially those of the alkalis and alkaline earths, are simultaneously present, the precipitation of the red silver chromate often takes place too late," a circumstance which the author considers to be fully explained by the above experiments. The subjoined table gives the results of some experiments made to determine the relative solubility of silver chromate in the nitrates of potassium, sodium, ammonium, and magnesium in cold and hot strong solutions:

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50 grains of each of the above salts were dissolved in 100 c.c. of water, and the amount of decinormal silver nitrate solution taken to obtain the reaction with potassium chromate is given in the table. In the last three cases, the author has deducted the amount of silver chromate dissolved by the water alone, and has given the amount due to the solvent action of the respective nitrates. From all these, the silver chromate crystallised out again on cooling.

D. B.

Tetracalcium Phosphate and Basic Converter Slag. By E. JENSCH (Ber., 19, 3093-3101).-It has been generally assumed that the phosphoric acid in basic converter slag is present as tetracalcium phosphate. The author has endeavoured to prepare such a phosphate by heating tricalcium phosphate with calcium carbonate to a high temperature. He has failed to obtain a crystalline substance such as is frequently seen in the basic slag, but at the same time the properties of the tricalcium phosphate are so altered as to indicate some chemical change having occurred.

The following analyses of basic slag are quoted:-I. Mean results

for the slag of all German works (Hasenclever). II. Mean of 12 analyses of slag from the steel works at Friedenshütte. III. Mean of four analyses of slag from Witkowitz.

P205. Cao. MgO. FeO. FeO3. Al2O3. MnO. S. SO3. SiO2. I. 17.25 48.29 4.89 9.44 3.78 2:04 3.91 0.49 0.22 7.96 II. 18.93 54-87 4.90 8.83 5.20 3.51 0.51 0.44 6.85 III. 16-86 49.45 1.26 9.88 5.96 2.17 2.93 0.61 0.10 10.08 The author considers that II may be regarded as consisting of—

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With regard to the statement frequently made, that a large proportion of the phosphorus is present in the form of iron phosphide, the author's results show that at most only 1.5 per cent. can be present in this form, and that even this is rendered soluble in the soil.

A. J. G.

The Determination of Water in the Hydrates of Strontium Oxide. By C. SCHEIBLER (Ber., 19, 2865—2868).-A controversial paper, in which the author rejects the deduction drawn by C. Heyer (this vol., p. 108), as evidence of the existence of a dihydrate of strontium oxide. It is also pointed out that Heyer's method for the determination of water in the dihydrate has only a limited value, since it is inapplicable to the monohydrates of the alkaline earths and to the dihydrate of barium oxide. W. P. W.

Action of Carbonic Anhydride on the Dihydrate of Strontium Oxide. By R. FINKENER (Ber., 19, 2958-2963).-The author finds that well moistened strontium hydroxide, kept for some time at 50° in an atmosphere of aqueous vapour having a tension of 16 mm., is converted into the dihydrate of strontium oxide. When exposed to a current of dry carbonic anhydride, the dihydrate is decomposed into the carbonate, but the product dried at 145° is deficient in carbonic anhydride and contains water. In opposition to Heyer's statement that carbonate alone is formed under these conditions, the author regards this fact as evidence that, in addition, a hydrated basic carbonate is also formed. The basic carbonate is a neutral compound which, in an atmosphere of carbonic anhydride, slowly absorbs that gas. It does not lose its water completely at 120°, but must be raised to incipient redness before complete dehydration occurs; no evolution of carbonic anhydride occurs at this temperature, but the product on moistening with water is strongly alkaline. W. P. W.

Estimation of Water in Strontia Dihydrate. By C. HEYER (Ber., 19, 3222-3224).—The author does not believe in the existence of a basic strontium carbonate, and ascribes the analytical results obtained by Finkener (preceding Abstract) to the use of too great an amount of substance (Finkener used over 5 grams), as not more than 0-5 gram should be used to ensure complete decomposition (compare this vol., p. 108). N. H. M.

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