60 THE GYPSY MOTH APPENDIX. 



Nitrate of Lead, Lead Nitrate, Lead Saltpetre. 



Pb(N0 3 ) 2 . 



The comparative cheapness of this salt first suggested its 

 possible value for the preparation of arsenate of lead. Ex- 

 periments made during the summer of 1897 indicate that 

 arsenate of lead prepared from the nitrate also possesses 

 properties quite as important as the lower market price of 

 the latter salt. The grade of this salt most common in the 

 market varies somewhat in its chemical composition. It is 

 prepared by dissolving "lead scale "or litharge (PbO) in 

 hot dilute nitric acid; upon evaporation, the nitrate of lead 

 crystallizes out in transparent octohedral crystals. Lead 

 nitrate has the advantage of containing a high percentage of 

 lead oxide. In the reaction between lead and nitric acid 

 there is a tendency toward the formation of basic salts, and 



\J 



the commercial lead nitrate usually contains a higher per- 

 centage of lead oxide than the chemically pure crystals. 

 Lead nitrate is not affected by exposure to the air, and does 

 not dissolve in water as readily as the acetate. The results 

 obtained from the analyses of three samples of lead nitrate 

 are o-iven in the following table : 



^ O 



Table No. 2. 



SAMPLE. 



Percentage of 



Lead Oxide 



(PbO). 



No. 1, nitrate of lead, from drug store, 

 No. 2, nitrate of lead, from drug store, 

 No. 3, nitrate of lead, from wholesale chemist, 



68.37 

 67.76 



66.37 



Arsenate of Soda, Arseniate of Soda, Di-sodic Arsenate, 

 Hydrodi-sodium Arsenate. 



Na 2 HAs0 4 (H,O) D . 



Aside from the mono-metallic arsenates, the soluble salts 

 of arsenic acid are limited to those of the alkaline metals. 

 Of the latter, the arsenates of potash and ammonium are 



