BENEDICT. — DOUBLE SALTS OP ANTIMONY. 13 



tory results. For this purpose some litharge was heated to constant 

 weifht, thereby expelling all the carbonic acid gas and moisture. The 

 weighed salt from a weighing bottle was mixed with several grams of 

 the ignited lead oxide in a porcelain boat large enough to fit a com- 

 bustion tube of two centimeteis internal diameter. This was placed 

 in a kerosene oven and dry air drawn through it. Upon heating, the 

 water expelled was absorbed in two weighed U tubes containing sul- 

 phuric acid and phosphoric pentoxide respectively. The apparatus 

 for drawing dry air through the combustion tube was devised, and 

 described at length by Professor Cooke in his paper on " A New 

 Method of Determining Gas Densities." * 



This process for determining water is an ideal one, every trace of 

 the antimony haloid being retained, and tlie water passing off freely 

 at a moderate temperature, 250°. The results were surprisingly 

 constant. 



Although these several analyses are not as concordant with theory 

 as one would wish, yet, when the instability of the compound, the 

 necessarily hasty drying of the salt (freeing from mother liquor), and 

 the difficulties of purification, are taken into consideration, the results 

 are not at all beyond a reasonable limit of error. 



In all three cases we could deal with large isolated crystals. There 

 was no case of a complex crystalline precipitate, for all three com- 

 pounds are most perfectly crystalline, and the only sources of contam- 

 ination are occlusions of mother liquor and imperfect drying due to 

 the haste required in transferring the salt to the weighing bottle. All 

 three salts are decomposed by water, and are soluble in tartaric, 

 hydrochloric, and hydrobromic acids. The last two solvents must 

 be somewhat concentrated, as an excess of water decomposes the 

 antimony salt. 



I. SbCls . CaCla . 8 H„0. 



This is a beautifully crystalline salt, individual crystals often occur- 

 ring over one inch in length. They are large, colorless plates, appar- 

 ently belonging to the triclinic system. Their tendency to effloresce 

 and decompose prevented any very satisfactory crystallographic exam- 

 ination, although traces of biaxial structure were observed with a 

 polariscope. The salt loses all the water of crystallization and all 

 the antimonious chloride in a desiccator over sulphuric acid, leaving a 

 residue of nearly anhydrous calcic chloride. 



* These Proceedings, XXIV. 213, and American Chera. Journal, XI. 521. 



