ARSENATE OF LEAD. 



59 



an increase of insoluble lead carbonate. The increase in the 

 percentage of lead acetate that accompanies efflorescence is 

 well illustrated by sample No. 4 of Table No. 1. Pure crys- 

 tallized lead acetate contains 58.81 per cent, of lead oxide; 

 but this sample, which had been exposed to the air in a 

 loosely covered vessel for over six months previous to analy- 

 sis, yielded 66.795 per cent, of lead oxide. The folio wing- 

 table indicates the amounts of available lead oxide contained 

 in different market grades of acetate of lead : 



Table No. 1. 



SAMPLE. 



Percentage of 



Lead Oxide 



(PbO). 



No. 1, crystallized acetate lead, from drug store, . . 59.525 



No. 2, crystallized acetate lead, from drug store, . . 61.548 



No. 3, crystallized acetate lead, from drug store, . . 60.650 



No. 4, crystallized acetate lead (effloresced), . . . 66.795 



No. 5, " chemically pure white acetate lead powder," from 62.500 



wholesale chemist. 



No. 6, "white acetate lead granulated," from wholesale 60.800 



chemist. 



No. 7, " white acetate lead lumps," from wholesale chemist, 60.550 



No. 8, "brown acetate lead," from wholesale chemist, . 62.290 



Samples Nos. 1, 2 and 3 were supposed to be chemically 

 pure. No. 4 has been previously described. No. 5 is some- 

 what more expensive than the other market grades, is in 

 a very finely divided condition and dissolves very readily in 

 water. No. 6 is the grade used last year by the gypsy moth 

 committee for the preparation of arsenate of lead. This 

 salt contains many lumps, which consist of finely divided 

 crystals. These lumps dissolve readily in cold water. No. 

 7 dissolves slowly in cold water, but easily in hot water. 

 No. 8 contains a considerable amount of tarry matters and a 

 small quantity of basic acetate of lead. In handling any of 

 these salts, proper care should be taken to avoid inhaling 

 their dust. Lead is a " cumulative" poison, and when once 

 absorbed is with difficulty eliminated from the system. 



