REPORT OF THE CHEMIST 179 



SESSIONAL PAPER No. 16 



water, in which practically all the arsenic and lead present exist as the insoluble 

 arsenate of lead, and in which the impurities— soluble and insoluble — are present in 

 negligible amounts. The proportion of arsenic to lead will be determined largely by 

 the nature of the chemical used, the percentage of arsenic being higher when lead 

 nitrate is used than when lead acetate is employed as the precipitant. 



We have not as yet any legal standard in Canada for lead arsenate paste, but 

 from the opinion of entomologists and others in the United States who have considered 

 the matter, it seems desirable that, to be accounted genuine, it should contain at 

 least 50 per cent of arsenate of lead, that the arsenic oxide should not be less than 

 12-5 per cent, that the water soluble forms of arsenic should not exceed 1 per cent, 

 calculated as arsenic oxide, and that there should be no admixture with foreign 

 materials to reduce or affect its strength. 



In the table on the following page the analytical data obtained during the past 

 year from the examination of a number of brands of arsenate of lead sold in Canada: 



16— 12i 



