206 



EXPERIMENT STATION. 



[Jan. 



Neutral nnd acid arsenates of lead are qnite insoluble, al- 

 though both salts will undoubtedly yield arsenic slowly to 

 continuous percolation, the acid salt decomposing the more 

 readily. 



Solubilitij. 



Manufacturer, .... 



Water (per cent.), 



Water soluble (Hilgard method): - 



Lead oxide (per cent.), . 



Arsenic pentoxide (per cent.), 



Solids (per cent.), . 



The acid salt C3 was practically insoluble under the condi- 

 tions tested, and nearly free from soluble by-products. 



The legal standard - for commercial lead arsenate in form 

 of paste specifies not more than 50 per cent, of water nor less 

 than 12.50 per cent, of arsenic pentoxide and not more than .75 

 per cent, of arsenic pentoxide soluble in water. Sample C3, 

 acid salt, which was used in experimental work, exceeded stand- 

 ard requirements in all particulars. A careful study of the 

 analytical results, C3, might warrant the following combina- 

 tion : — 



Acid Lead Arsenate employed in Spraying. 



Water, 



Acid lead arsenate (PbHAs04), 

 Lead chloride (PbCh), 

 Lead hydroxide (2 PbO • H2O), 

 Insoluble mailer, . 



Per Cent. 



46.99 



100.11 



Exclusive of water, the purity was approximately 97. 3G per 

 cent. There was a small amount of lead chloride, but the most 

 objectionable feature appeared to be the precipitated lead 

 hydroxide due to careless preparation. 



' Sample rejected. 



2 The insecticide act of 1910, section 7. 



