BENEDICT. — DOUBLE HALOIDS. 223 



Nos. 1 and 5. The water has all been given off, and these are the 

 two best values for the per cent of water. No. 2. The water is not 

 all off yet, as shown by heating another hour, when per cent = 8.62. 

 Nos. 3 and 4 both showed by analysis that chlorine had been evolved. 

 The dried salts from Nos. 1 and 5 were used in the ignitions, and these 

 gave results corresponding to the formula SbCl 3 . 2 KC1. Calculating 

 the percentages for the additional water of crystallization, the following 

 result was obtained : — 



Calculated for 

 SbCl 3 . 2 KC1 . 2 H 2 0. Found. 



Sb 29.16 29.07 



CI 43.07 43.07 



K 19.02 18.53 



H 2 8.75 8.76 



100.00 99.43 



In the ignited residue there was no insoluble portion of Sb 2 3 . 

 The evidence warrants the selection of SbCl 3 . 2 KC1 . 2 H 2 as the 

 formula for this salt. 



The conditions under which these salts form are closely related. 

 So much so that it has been difficult to establish the exact conditions 

 under which each salt may be isolated. At first the work was wholly 

 tentative, using a saturated solution of potassic chloride, and adding 

 crystallized antimonious chloride, filtering off any insoluble portion. 

 In this way were obtained the salts SbCl 3 . SbOCl . 2 KC1, and 

 SbCl 3 . 2 KC1 (hexagonal). But in order more closely to study the 

 relations of each to the others, a series of experiments was carried out 

 in watch glasses. 



To about 5 c. c. of a saturated solutiou of potassic chloride were 

 added 5 grams of crystallized antimonious chloride ; when this had all 

 dissolved, as it will in the cold, more SbCl 3 was added, till the solu- 

 tion was so to speak saturated with SbCl 3 . In all, about 30 grams 

 of SbCl 3 were added. In each of a series of watch glasses was placed 

 1 c. c. of the above solution, and to the several glasses increasing 

 amounts of a saturated solution of potassic chloride were added, — 

 from 1 c. c. in the first to 5 c. c. in the last. In each a white pre- 

 cipitate was formed which redissolved on heating. 



Then the reverse was tried, i. e. 2 c. c. SbCl 3 , 1 c. c. KC1, down to 

 5 c. c. SbCl 3 . 1 c. c. KC1. There was a precipitate in each watch 

 glass, which however dissolved on heating. The watch glasses were 

 placed on the window sill, with moderately cold weather, and ex- 

 amined at intervals. 



