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 is 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 mic7'oscopic examination. — 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 samplers examined goes, 

 microscopic examination cannot be relied upon to distinguish 

 with certainty a Paris green containing an injurious amount of 

 water-soluble arsenic. 



6. SoliiMUti/ 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. 



1. General conclusion as to purity of Paris green m 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. 



