204 



EXFERLMKNT STATION. 



[Jan. 



Neutral Lead Arsenate produced in the Laboratory. 



Sample number, 

 Water 100° C. (per cent.). 

 Arsenic pentoxide (per cent.). 

 Lead oxide (per cent.), . 

 Water occluded (per cent.), 



99.90 



The lead salt invariably contained a small amount of water 

 probably held by occlusion which is not volatilized at 100° C. 



Acid lead arsenate is readily prepared from nitrate of lead 

 and sodium arsenate provided dilute solutions are employed and 

 the sodium salt added carefully in excess (10 per cent.). 



Pb(N03)2 + Na2HAs047 H2O = PbHAs04 + 2 NaNOs + 7 H2O. 



By this method of procedure no difficulty was experienced 

 in producing salts of theoretical composition. The acetate can 

 be used as a source of lead, but is less satisfactory. 



Six samples of lead arsenate were supplied by three manu- 

 facturers for the spraying tests. Manufacturer C was fur- 

 nished full directions as outlined above for making the acid 

 salt. The detailed process for preparing the neutral salt was 

 not deduced until later. 



