New YorK AGRICULTURAL EXPERIMENT STATION. 399 
use as an insecticide Paris green or other similar materials that 
vield more than 34 per ct. of water-soluble arsenic compounds 
expressed as arsenious oxide, when treated for 24 hours with 
distilled water at the rate of 1000 parts of water for one part of 
Paris green or arsenic-containing materials. 
The water-soluble arsenious oxide varies in the 40 samples 
of Paris green examined from 0.88 to 2.64 per ct., and averages 
1.28, which is far below the limit of harm prescribed for use as 
an insecticide and the limit fixed by law. 
3. Copper in Paris green determined as copper oxide.——The 
amount of copper expressed as the equivalent of copper oxide, 
varies in the 40 samples of Paris green examined from 26.53 
to 31.14 per ct. and averages 29.88 per ct., which is about the 
same as last year. 
4. Amount of arsenious oxide in combination with copper.—The 
law relating to Paris green in this State was amended in 1901, 
so as to correct certain defects existing in the original law with 
reference to the definition of Paris green. The original law 
required that Paris green should contain the equivalent of 50 
per ct. of arsenious oxide. This provision was needlessly low 
and was also open to the very serious objection that it permit- 
ted indefinite adulteration by common white arsenic. This 
defect has been corrected by requiring that Paris green shall 
contain arsenic in combination with copper, equivalent to not less 
than 50 per ct. of arsenious oxide. In ascertainig the amount 
of copper in combination with arsenic, it has been assumed 
that all the copper present was so combined, except when found 
in excess. While this assumption is not strictly accurate, it 
answers the purpose, especially when the precaution is taken 
to examine the Paris green for water-soluble forms of copper- 
compounds. | 
In the 40 samples of Paris green examined the amount of 
arsenious oxide in combination with copper varied from 49.70 
$5772 per ct. and averaged 55.98 per ct., which is about 6 
per ct. higher than the minimum required by law. Only one 
sample fell below the limit and this was only slightly below. 
