110 PROCEEDINGS OF THE AMERICAN ACADEMY 



Analysis of Antimonious Oxichloride (Sb^O^Clg). 

 Phepaeed bt Schaeffer's Process. 



Weight of AgCl 

 Weight taken. obtained. % of Chlorine. 



0.6376 0.2879 11.17 



Theory for Sb,05Cl2 when Sb = 120 11.25 



We have already stated that this same compound is deposited from 

 aqueous solutions of antimonious chloride containing less than a definite 

 proportion of tartaric acid, under conditions which are given at length 

 in our previous paper (page 23, of this volume). The crystals thus 

 obtained differ wholly in general aspect from those we have just de- 

 scribed. While the former were acicular, these are tabular, and, instead 

 of being isolated, generally group themselves in tufts; which, although 

 sometimes a millimetre in diameter, consist of crystals so small and 

 60 closely compacted together, that hitherto we have found it impracti- 

 cable to separate and measure them. As seen under the microscope, 

 the crystals appear distinctly monoclinic ; the tufts presenting termina- 

 tions similar to those of epidote, and the crystals showing the same 

 tendency to growth in the direction of the orthodiagonal which is so 

 characteristic of that mineral species ; while, at the same time, the pack- 

 ing together of the tabular crystals in tufts recalls the phenomenon so 

 familiar on specimens of calamine and prehnite. Assuming that the 

 terminal planes at the ends of the orthodiagonal are the j^lanes of a 

 vertical prism, and the plane of twining the basal plane, then such 

 rough estimates of the axial inclination as we have been able to make 

 with the microscope would indicate that these crystals are much less 

 oblique than the last, and more closely allied in form to the crystals of 

 SbOCl before described. Like these, they frequently present the planes 

 of a klinodome ^011 1, Fig. 7, Plate I., which never appear on the 

 other type of crystals (Fig. 8), and indeed would hardly be compatible 

 with it. By regulating more carefully the amount of tartaric acid in 

 the solution, we hope to obtain hereafter larger crystals of this last 

 variety of Sb^05Cl2. whose exact measurement will settle the question 

 in regard to the relation of the two forms. 



We analyzed with great care the crystals of Sb^OgClg deposited by 

 the tartaric acid solution, in order to obtain additional evidence in 

 regard to the atomic weight of antimony. By the methods already 

 described, both the antimony and the chlorine were determined ; while 

 the oxygen was estimated, as is usual, by loss. The followiog are our 

 results : — 



