214 PROCEEDINGS OP THE AMERICAN ACADEMY. 



given in Clarke's table of specific gravities of double salts in the 

 " Constants of Nature." 



Rammelsberg, * in 1855, gave the crystalline form of a salt, 

 SbCl 3 . 2 KC1, as trimetric, and adds three measurements which he 

 stated as extremely unreliable owing to the striations of the faces. 



A summary of the crystallographic results obtained could be ex- 

 pressed as follows : 



SbCl 3 . 2 KC1 : — monoclinic, cubic, triclinic, trimetric. 

 SbCl 3 . 3 KC1 : — crystallizes in leaves. 



These variations warranted a research of these salts. Four com- 

 pounds were obtained with the following composition : 



SbCl 3 . SbOCl . 2 KC1 [Monoclinic]. 

 SbCl 3 . 2 KC1 [Hexagonal]. 

 SbCl 3 . 2 KC1 [Monoclinic]. 

 SbCl 3 . 2 KC1 . 2 H 2 [Monoclinic]. 



Methods of Analysis. 



On inspection of the above formulas it is evident that there must be 

 a determination of each of the four elements, Antimony, Chlorine, 

 Potassium, and Oxygen, together with one of water of crystallization. 



Antimony determinations were made by dissolving the salt in tartaric 

 acid solution, to which a small amount of hydrochloric acid was added. 

 The antimonious sulphide resulting from the action of a solution of 

 hydrogen sulphide on this solution was carefully washed and dried at 

 220°. The method was described in detail by Professor Cooke in his 

 paper on the Revision of the Atomic Weight of Antimony. | 



The chlorine determination consisted in weighing the silver chloride 

 which had been precipitated from a solution of silver nitrate by a 

 tartaric acid solution of the salt in question. The precipitate collected 

 on a Gooch crucible was dried at 150°. In no case was there noticed 

 any blackening due to presence of tartaric acid, even after heating 

 to 235°. 



Potassium Determination. — Several attempts were made to pre- 

 cipitate the potassium-platinie chloride, but the presence of tartaric 

 acid, necessary for the solution of the salt, caused the formation of 

 the insoluble potassic bitartrate, which interfered materially with 

 the process. 



* Handbuch der Krystallographischen Chemie, p. 215. 

 t These Proceedings, XIII. 1-114. 



