14:2 McDonnell and Smith — Lead-Chlor Arsenate. 



cool. However, by first adding arsenic acid to the boiling 

 salt solution, followed by lead acetate just short of a permanent 

 precipitate and allowing the solution to cool, a slightly greater 

 precipitate was obtained. The crystals so produced differed 

 from those obtained from dilute hydrochloric acid solutions in 

 that they were terminated by pyramids of the second order (fig. 



Fig. 1. 



Fig. 1. Lead-chlor arsenate, artificial mimetite ( x 234). 



2). Sodium and potassium chlorides were the only media from 

 which crystals with pyramids and prisms of different order 

 were obtained. . A few attained the dimensions '06 X '04 mm . 



The filtrate from the experiment just described was kept at 

 about 15° C. for 5 weeks, when a mass of sodium chloride con- 

 taining a small amount of lead-chlor arsenate had separated 

 out. The salt was removed by washing with water and the 

 lead-chlor arsenate remaining was examined with the micro- 

 scope. It consisted of small crystals, showing no abrupt transi- 

 tion from lateral to end faces, resembling prolate spheroids. 



