New York AGRICULTURAL EXPERIMENT STATION. 455 
added to Paris green without increasing the ratio of arsenious 
oxide to copper oxide above 1.87. In the samples examined, 
excluding No. 50, the ratio of arsenious oxide to copper oxide 
varies from 1.81 to 2.24 and averages 1.89. In sample No. 33 
the arsenious oxide exceeds 60 per ct. and the copper is less 
than 28 per ct.; hence, the arsenious oxide is present in amounts 
more than twice exceeding the copper oxide. In other words, 
there ig too much arsenious oxide for the copper oxide present 
and the only possible inference is that white arsenic or some 
other arsenic compound has either been added purposely or is 
present as the result of carelessness in manufacture. 
5. Results of microscopic ecamination—In Bulletin No. 126 of 
the California Experiment Station, the microscopic examination 
of Paris green for adulteration, especially that of uncombined 
arsenious oxide (common white arsenic) is highly recommended. 
This test in our hands has been found helpful as an adjunct, but 
cannot take the place of chemical] analysis. We cannot in our 
work see any definite relation between the number of crystals of 
arsenious oxide shown by the microscope and the amount of 
water-soluble arsenious oxide as shown by chemical determina- 
tion. So far as our experience with the samples examined goes, 
microscopic examination cannot be relied upon to distinguish 
with certainty a Paris green containing an injurious amount of 
water-soluble arsenic. 
6. Solubility of Paris green in ammonia.—The solubility of Paris 
green in ammonia is a useful test for detecting the presence of 
insoluble adulterants like barium sulphate, calcium sulphate and 
similar materials. It cannot, however, be regarded as an 
entirely reliable test for detecting the presence of arsenious 
oxide or common white arsenic, the most common impurity of 
Paris green. 
7. General conclusion as to purity of Paris green in market.— 
Our results indicate a satisfactory condition as to the arsenic 
content of Paris green found in the market during 1900, and the 
same can be said as to the amount of water-soluble compounds 
present in the samples examined, excepting only, No. 50. 
