1912.] PUBLIC DOCUMENT — No. 31. 199 



Sample d and Cs confirmed the former analyses as to arse- 

 nous oxide, and the molecular ratio of calcium oxide to arsenous 

 oxide was almost theoretical for calcium metarsenite. It would, 

 therefore, appear safe to assume that lime arsenite precipitated 

 from soluble salts of lime and of arsenic is invariably the meta 

 salt. 



Sample C3 was employed in spraying, although in the process 

 of manufacture it had been imperfectly washed, contained a 

 small amount of magnesia and showed a slight oxidation of 

 arsenic. Any arrangement of constituents is of doubtful value ; 

 still, the following may be suggested : — 



Calcium Arsenite employed in Spraying. 

 Manufacturer, ........ 



Water (per cent.), ....... 



Calcium orthoarsenate (Ca3(As04)2 • 3 H2O) (per cent.), 

 Magnesium metarsenite (Mg(As02)2) (per cent.), 

 Calcium metarsenite (Ca(As02)2) (per cent.), . 

 Sodium chloride (NaCl) (per cent.), .... 



Insoluble matter (per cent.), 



Cs 

 67.87 



.18 



.30 



30.31 



1.32 



.01 



99.99 



The above analysis would indicate a purity, on a water-free 

 basis, of 94.34 per cent. 



Calcium metarsenite, prepared according to the directions 

 given, is a smooth white gelatinous mass or jell of very fine, 

 adhesive particles. The power of suspension which has to be 

 determined in lime water to prevent partial solution is ex- 

 tremely high but lessened by drying. Sample C3 gave phenom- 

 enal results, though the actual figures are indicative rather than 

 absolute. A moist paste of arsenite of lime proved unstable, 

 gradually changing to arsenate with the separation of free arse- 

 nic (As). Calcium arsenite is probably the most soluble arsen- 

 ical insecticide in use as shown by the following results : — 



