SOME EFFECTS OF SODIUM ARSENITE 15 
This suggests that spraying may fail to kill some plants and also 
that spraying the abovegrouncl portions of plants may not result in 
arsenic being carried to the roots or tubers, thus leaving these por- 
tions safe for animal or human consumption. 
The soil treated with sodium arsenite incident to killing the bar- 
berry showed moderately fast leaching. The arsenic content de- 
creased from 0.676 per cent at the time of application to 0.040 per 
cent after 14 months in well-drained soil under an annual rainfall 
of about 30 inches. 
Various economic plants seeded in this soil containing 0.04 per 
cent of arsenic showed no inhibition of germination, but growth 
was affected. Plants belonging to different families showed vary- 
ing susceptibility. Legumes proved to be the most susceptible and 
rye the most resistant. 
Although precautions were taken to prevent animals from having 
access to the arsenic, accidents occurred in different States where 
barberries were treated. The animals sought arsenic and consumed 
parts of plants and soil to which arsenic had been directly applied. 
This experience demonstrates the necessity of finding a repellent 
that will alter the taste, if it is desired to continue the use of arsenic 
as a weed killer. 
A modified method for determining small quantities of arsenic 
in plant tissue was found useful in these experiments. 
SUMMARY 
A modified volumetric method for the determination of small 
quantities of arsenic in plant tissue was developed and proved to be 
rapid and accurate. 
Sodium arsenite in proper dilution was an effective killing solution 
for most plants. The arsenious acid was the most effective form 
of arsenic tested. 
Arsenic was found in nearly all tissues of treated plants, while the 
controls contained no arsenic. 
Arsenic was most effective in killing plants when applied to the 
roots. Spraying or dipping was not alwaj^s effective. 
The soils used showed rapid leaching of sodium arsenite where 
rainfall was abundant. 
The characteristic brackish sweet taste of arsenic attracted animals, 
and it was found that the use of sodium-arsenite solution in pastures 
without precautions or repellents was not safe. 
