226 PROCEEDINGS OF THE AMERICAN ACADEMY. 



weather. The excessive moisture caused a white scum of oxichloride 

 on every receptacle of the various solutions. 



According to all analogy regarding the constitution of double salts, 

 there would be three possible forms for the double chlorides of anti- 

 mony and potassium ; i. e. SbCl 3 . KC1 ; SbCl 3 . 2 KC1 ; SbCl 3 . 3 KC1. 

 Singularly enough, as yet only the second one is obtained, and that is 

 dimorphous. Solutions were made containing molecular proportions 

 for SbCl 3 . KG and SbCl 3 . 3 KG. Each solution was divided into two 

 parts, one of which was acidulated with hydrochloric acid, and the 

 other not. The only resulting salts were: 



1st solution, i. e. SbG 8 . KG = I. and II. 



2d " " SbG 3 . 3 KG = at first a lot of cubo-octahedrons 



of potassic chloride ; later, II. 



Although so many different forms were mentioned by previous 

 writers, none such have been definitely proven in this research. Re- 

 garding the statement of Poggiale,* that the SbG 3 . 2 KG crystallizes 

 in cubes, it may be mentioned that in the preparation of that salt a 

 number of crystals appeared under the microscope as perfect cubes. 

 But on isolating them and nursing them till they were of sufficient 

 size to admit measurement, they were proven to be the hydrated salt 

 III. (SbG 3 . 2 KG . 2 H 2 0), with the angle not 90° but 80°. It is 

 simply a different habit of the tabular crystal with no octahedral face. 

 It may be possible that he observed the cubes of potassic chloride, 

 which will crystallize from many of these solutions. 



The mention of a triclinic crystal by Fehling * can be accounted 

 for by the peculiar habit of this same salt III. of developing more 

 rapidly on one side than another, giving to the eye a decidedly 

 triclinic appearance. The trimetric form of Rammelsberg f may 

 be explained in two ways. 



First, the salt III. crystallizes often as per diagram, in which the 

 plane of symmetry is through the dotted line, 

 and O represents the octahedral face.t but the 

 lower face is wanting where the crystal rests 

 on the dish. At first sight this was taken for 

 a trimetric crystal, but the angle of AAC is 

 different from that of O A C, and no interference figure is seen with 

 the polarizing microscope. 



Secondly, the salt (SbG 3 . 2 KG, monoclinic) crystallizes in dia- 



* This paper, page 213. f Ibid., page 214. \ Ibid , page 221. 



