No. 4.] GYPSY MOTH — APPENDIX. 



359 



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 following 

 table indicates the amounts of available lead oxide contained 

 in different market grades of acetate of lead : — 



Table No. 1. 



Percentage of 



Lead Oxide 



(PbO). 



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

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

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

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



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



wholesale chemist. 

 No. 6, '• white acetate lead granulated," from wholesale 



chemist 

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



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



59.525 

 61.548 

 60.650 

 66.795 

 62.500 

 60.800 

 60.550 

 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. 



