RICHARDS AND PARKER. — BARIC SULPHATE. 77 



barium salt thau when the pouring takes place in the opposite 

 direction. 



Thir^, that under the usual conditions of careful precipitation in the 

 presence of a small amount of free acid, the error from occlusion is 

 almost balanced by the solubility of baric sulphate in acids and water, 

 which solubility must be considered in careful work. 



Fourth, that the error due to this occlusion may be corrected with 

 great exactness by determining the amount of chlorine held by the pre- 

 cipitate, and subtracting the corresponding amount of baric chloride 

 from the total weight of the precipitate. 



The occlusion of iron and other substances by baric sulphate is 

 being further studied in this Laboratory. 



