Lead Arsenate 



47 



Analyses of Lead Arsenate 



It will be seen that both preparations are 

 mixtures of the two compounds, the one made 

 from lead nitrate containing much more, in 

 fact is nearly all, of the acidic compound 

 PbHAs04, while the one made in the presence 

 of less acid contains a large proportion of the 

 basic compound. 



Most of the arsenate of lead on the market 

 is in the form of a paste containing 45 to 50 

 per cent water, consequently the actual per 

 cents of arsenic and lead oxids in the ma- 

 terials would be about one-half the figures 

 just given. The dry powder on the market 

 is said to be made by an entirely different 

 process, by suspending lead plates in arsenic 

 acid and causing chemical action by means of 

 an electric current. The lead arsenate that 

 falls off the plates has only to be washt and 

 dried. 



For most uses lead arsenate replaced Paris 

 green as an arsenical poison. Its two advan- 

 tages are its greater insolubility and its ability 

 to stick. The solubility of lead arsenate in 



