72 PROCEEDINGS OF THE AMERICAN ACADEMY 



II. 



RE-EXAMINATION OF SOME OF THE HALOID COM- 

 POUNDS OF ANTIMONY. 



By Josiah p. Cooke, Jr., 



Erving Professor of Chemistry and Mineralogy in Harvard College. 



Our chief object in this paper is to describe some remarkable crystal- 

 lographic and chemical relations of antimonious iodide, first noticed 

 during the investigation of which an account has just been given ; 

 but we will also take the opportunity to give the results of some obser- 

 vations upon antimonious chloride and antimonious bromide, as well as 

 upon the oxichlorides, oxibromides, and oxi-iodides of antimony, all 

 of which have more or less bearing on the principal subject. 



Antimonious Chloride (SbClg). 



Very perfect and brilliant crystals of antimonious chloride can be 

 made in one of two ways, and both methods yield crystals of the same 

 general form and habit. 



The first method consists in cooling a saturated solution of the 

 chloride in carbonic disulphide. Antimonious chloride is very soluble 

 in this liquid, when near its boiling point ; but the solubility diminishes 

 very rapidly with a falling temperature, and, when the solution is cooled 

 with a freezing mixture, by far the larger part of the substance crystal- 

 lizes out. During our experiments, we frequently noticed, with these 

 solutions of antimonious chloride, the ^ihenomena of supersaturation. 

 A solution saturated at the boiling point of the solvent, and cooled in a 

 clean glass flask, may, if undisturbed, remain liquid for an indefinite 

 time ; but, the moment a bit of the solid substance is dropped in, the 

 crystals form with great rapidity, and the very marked rise of tempera- 

 ture which we have observed under these circumstances indicates that 

 the crystallization is attended with the liberation of an unusually large 

 amount of latent heat. Similar phenomena of supersaturation we 

 noticed with solutions of antimonious bromide, which, although less 

 soluble than the chloride, dissolves very freely in the same solvent ; 



