DALTON CHEMICAL SCHOLARSHIP. OCTOBER, 1871. I. CONTRIBUTIONS TO OUR KNOWLEDGE OF THE ANTIMONY OXYCHLORIDES. BY WILLIAM CARLETON WILLIAMS. ORIGINAL INVESTIGATION CONDUCTED IN THE LABORATORY OF THE COLLEGE, AS REQUIRED BY THE SCHOLARSHIP REGULATIONS. PHOSPHORUS OXYCHLORIDE, PO Cl, having been prepared by heating together one molecule of phosphorus pentoxide with three of pentachloride, it appeared not unlikely that a similar reaction might occur with antimony, giving rise to the missing oxychloride corresponding to the phosphorus compound above mentioned. The following investigation was undertaken at Dr. Roscoe's request, with the view of elucidating the above reaction, as no oxychlorides derived from the pentachloride have as yet been described. A mixture of one molecule of antimony pentoxide (prepared by heating the pentachloride with water) with three molecules of the pentachloride was heated for some hours in sealed tubes at 140° C. On opening the tube after cooling, it was found to contain, besides unchanged pentachloride and pentoxide, two distinct solid crystalline compounds. When the pentoxide prepared by the action of nitric acid on the metal is heated with the pentachloride in a similar way, no oxychloride is formed. One of these compounds fuses at 85° C. to a clear yellowish liquid, whilst the other, produced only in small quantities, is found in minute yellowish crystals adhering to the top of the tube; and these fuse at a higher temperature. In order to obtain the first of these substances in a pure state, it is sufficient to place the tube upright in a vessel of water at 90°, with the empty end downwards; the fusible oxychloride then melts, and collects as a perfectly clear yellowish liquid; after cooling, the tube is opened, and the small quantity of residual pentachloride having been poured off, the solid mass is dried on a porous plate over solid caustic potash in vacuo. The oxychloride thus obtained is a perfectly white crystalline substance, exceedingly hygroscopic, so that when exposed to the air for a few minutes it becomes a pasty mass which rapidly changes to a liquid. It readily dissolves in an aqueous solution of tartaric acid; whilst it is decomposed by water, and is perfectly insoluble in carbon disulphide. The melting-point of the substance is 85° C., as a mean of wellagreeing determinations made with four different preparations. When heated in a retort until it boils, chlorine gas is evolved, and, whilst pentachloride and trichloride of antimony distil over, a residue of antimony pentoxide remains in the retort. A modification of Rose's well-known method of precipitation, first as insoluble antimoniate of soda, and then as antimony sulphide, was employed for the determination of the antimony. The precipitated sulphide was (1) oxidised to Sb, O4, either by treatment with pure fuming nitric acid, or by heating with from ten to twenty times its weight of pure mercuric oxide; and (2) the sulphide was completely reduced to metallic antimony by heating gently in a current of hydrogen until sulphuretted hydrogen ceased to be evolved. In the estimation of chlorine, it was found that, when silver nitrate is added to a solution of an antimony oxychloride acidified by nitric acid, a small trace of antimony is invariably carried down with the silver chloride. In order to free the precipitate from antimony, the silver chloride is first heated gently in. a current of hydrogen, when the silver is reduced; and on stronger ignition, the whole of the antimony is volatilized as the hydrogen compound. Thus 1.277 grm. of an alloy, containing 2.5 parts of antimony to 97.5 parts of silver, was found to lose on heating in hydrogen 0·0321 grm., corresponding to 97.48 per cent. of silver. The accuracy of each of the above methods was tested by determining the percentage of antimony and chlorine in pure antimony trichloride, the results agreeing closely with each other and with the theoretical composition. The objection to Schaeffer's method of decomposing the oxychloride by boiling with a solution of sodium carbonate is, |