﻿ARSENICALS. 21 



Table 10. — Arsenic on potato and apple leaves sprayed with lead or calcium arsenates 





Spray used. 



Average 



llllllllier 



Of 

 sample:-. 



Arsenic C As; found. 



Year and locality. 



Per 

 square 

 meter 

 of Leaf 



.-.III l:ice. 



'in di 

 leaves. 



1917. 



POTATO LEAVES. 



7 

 8 

 2 

 2 

 2 

 2 



3 

 3 

 2 

 2 



5 

 5 



2 

 2 



4 

 4 



Milli- 

 grams. 

 5 

 3 

 80 

 56 

 16 

 19 



Parts per 

 million. 



Do 













Do 



Calcium arsenate 



1 270 









Do... 





70 



1918. 





170 



Do 







60 









180 



Do 







270 



1919. 







260 



Do 







210 



1917. 



APPLE LEAVES. 



40 

 9 



510 



Do 





120 



1918. 





130 



Do 







260 











The results of the tests for all three years show an average of 286 

 parts per million of arsenic on the dry leaves receiving the lead 

 arsenate spray and an average of 219 parts per million of arsenic on 

 the dry leaves receiving the calcium arsenate spray. The 1917 and 

 1919 results show that a larger percentage of arsenic of acid lead 

 arsenate adhered to the leaves than of the arsenic of the calcium 

 arsenate. The 1918 results are practically the same for the two 

 arsenates. 



Lime was used with certain of the arsenates in some of the 1918 

 tests (Table 11). Potato vines were sprayed with a commercial 

 calcium arsenate and a commercial acid lead arsenate alone and with 

 the addition of lime to each. Zinc arsenite and calcium meta- 

 arsenate were used without the addition of lime. Two calcium 

 arsenates, one with a molecular ratio of 3 CaO to 1 As 2 5 and the 

 other with one of 4 to 1, were tested, with and without the addition 

 of lime. In these two cases both 2 ounces and 4 ounces of lime per 

 10 gallons of spray were used. The arsenious or arsenic oxid con- 

 tents of the sprays were made the same in all cases, with the exception 

 of calcium meta-arsenate. From the data in Table 11 it is evident 

 that the lime was of no advantage in increasing the amount of arsenic 

 adhering to the leaves. 



