﻿42 



BULLETIN lUT, U. S. DEPARTMENT OF AGRICULTURE. 



RELATION OF WATER-SOLUBLE ARSENIC TO TOXICITY OF ARSENICALS. 



No perceptible differences in mortality which could be attributed 

 to the usually small differences hi water-soluble arsenic oxid were 

 observed in the 14 commercial acid lead arsenates used in the pre- 

 liminary .tests. Three of these arsenates which have high percent- 

 ages of water-soluble arsenic oxid, however, killed no more insects 

 than the others. 



Table 20. — Relation of water-soluble arsenic to toxicity of arsenicals, 1919. 



Sample 

 No. 



Arsenicals and control. 



Insects tested. 



Number. 



Species. 1 



Water- 

 soluble 

 arsenic, 

 based 

 on total 

 arsenic 



in 

 sample. 



Toxicity 

 after de- 

 ducting 



mor- 

 tality of 

 control. 



Food 

 eaten 

 per 

 insect 

 (esti- 

 mated), 

 based 

 on web- 

 worms 

 and tent 

 cater- 

 pillars. 



Laboratory basic lead arsenate 



Commercial basic lead arsenate 



Laboratory acid lead arsenate 



Pure arsenious oxid 



Pure arsenic oxid 



Commercial zinc arsenite 



Commercial acid lead arsenate (new 

 process) 



Commercial acid lead arsenate 



Commercial calcium arsenate 



do 



do 



do 



do 



do 



Laboratory calcium arsenate 



Laboratory calcium meta-arsenate 



Laboratory monocaleium arsenate 



Laboratory sodium arsenate plus Bor- 

 deaux mixture 



Commercial Paris green 



Commercial magnesium arsenate 



Laboratory barium arsenate 



Laboratory copper barium arsenate 



Laboratory aluminum arsenate 



Control with food 



1,184 

 1,939 

 1,361 

 1,529 

 1,516 

 1,441 



422 

 2,263 

 2,645 

 2,492 

 2,373 

 2,393 

 2,114 

 2,657 

 2,298 

 1,232 

 1,758 



2,674 

 2,059 

 1,651 

 1,706 

 1,814 

 1,482 



sftl... 

 ...do. 

 ...do. 

 ...do. 

 ...do. 

 ...do. 



sfl.... 



sftlg. 

 ...do. 

 ...do. 

 ...do. 

 ...do. 

 ...do. 

 ...do. 

 ...do. 

 ft.... 

 ...do. 



Per cent. 

 1.15 

 1.73 

 .57 

 17.77 

 100. 00 

 1.25 



.69 

 .61 

 .41 

 .88 



1.31 

 .20 

 .52 



5.20 



.88 



.04 



89.26 



...do. 

 flgv- 



...do. 

 fly... 



3.52 

 4.64 



6.27 

 1.91 



Per cent. 

 21.5 

 60.9 

 59.6 

 46.1 

 76.5 

 66.9 



66.9 

 68.9 

 70.0 

 39.9 

 59.2 

 60.1 

 43.1 

 65.9 

 52.5 

 3.6 

 81.2 



61.7 

 65.5 

 50.2 

 43.6 

 48.9 

 39.3 



Units. 

 68.6 

 10.9 

 17.6 

 9.6 

 3.5 

 22.0 



2.8 



2.9 



9.1 



66.0 



30.8 



29.9 



68.1 



18.5 



55.0 



99.9 



2.0 



5.0 

 3.2 

 18.3 

 22.2 

 15.6 

 16.1 

 100.0 



1 s, silkworms; f, webworms (H. cunea); t, tent caterpillars; 1, potato-beetle larvae; g, grasshoppers; and 

 y, webworms (H. tertor). 



Table 20 shows that those arsenicals which are readily water 

 soluble (samples 10 and 46) have extremely high percentages of 

 toxicity, but that some of those which are almost insoluble in water 

 (samples 5, 23, and 39) have percentages of toxicity nearly as high. 

 The toxicity of the insoluble arsenicals does not appear to be based 

 upon the water-soluble arsenic present, but upon the stability of 

 the compound and how readily it can be broken down in the bodies 

 of insects. 



During all of these experiments no special study of the burning 

 effects of the many arsenicals sprayed on foliage was made. The 

 percentage of water-soluble arsenic is generally taken as a criterion 

 for judging the burning effect on foliage. The following spray 

 mixtures badly burned wild-cherry foliage: Sodium and potassium 

 arsenates, sodium arsenate plus Bordeaux mixture, all the samples 

 of arsenious and arsenic oxids used, calcium arsenates (samples 5, 



