article is never ideal ; in reality its manufacture is difficult and many 

 chemicals enter into the process. However, from analyses which we 

 have made here and from results obtained elsewhere, most Paris greens 

 contain at least 56 per cent., and there is no reason why they should 

 contain less than 56 per cent, of arsenious oxide, providing - any reason- 

 able degree of care be exercised in the making. 



Total Copper Oxide in Paris Green. Copper aceto-arsenite contains 

 31.29 per cent. CuO, which bears a relation to the total arsenious oxide 

 present of 1 : 1.87. Since it is necessary that arsenious oxide be com- 

 bined with copper in order that it be not in the free state, then, any result 

 of analysis showing a greater factor than 1.87 indicates free arsenic. 

 White arsenic cannot be added as an adulterant without seriously dis- 

 turbing this ratio. 



Physical Conditions. The best grade of Paris green is a powder 

 which will pass through a sieve of not less than 100 meshes to a square 

 inch. A coarse green is one that will settle rapidly from its suspension 

 in water and will require constant agitation during the spraying operation 

 in order that it may be distributed evenly over the foliage. 



Adulterants and their Detection. The more common ones occurring in 

 Paris green are white arsenic, barium carbonate, barium sulphate, gypsum, 

 and road dust. The white arsenic may be added to bring the arsenic 

 content up to the standard, but the presence of any of them is fradulent, 

 and they can only be classed as mere "make weights" which increase the 

 cost of purchase for actual insecticidal value received. As previously 

 stated, white arsenic may be detected under the microscope, when it 

 appears in the shape of white octohedral crystals. The other adulterants 

 mentioned are all insoluble in ammonia, thus any quantity of residue left 

 on dissolving the green in ammonia gives good ground for rejecting a 

 sample on account of adulteration. This test is simple and can be ap- 

 plied by any one. A teaspoonful of the sample is placed in some recep- 

 tacle, preferably glass, and about ten teaspoonsful of strong ammonia 

 added and the whole then thoroughly stirred. The Paris green readily 

 dissolves to form a deep blue solution, whereas the adulterants present 

 are left as solid particles in the bottom of the vessel. As before stated, 

 white arsenic is also quite readily soluble in ammonia, and a complete 

 solution does not show the absence of this material. 



Paris Green in Ontario. 



The consumption of Paris green in this Province amounts to between 

 100 and 120 tons annually. Although the demand is so good, still the 

 product put upon the market is of a very favorable quality. The Inland 

 Revenue Department at Ottawa reports that the samples which they 

 examined in 1902-3 were 95.8 per cent, genuine. The samples analyzed 

 in this department were also of a highly satisfactory standard. 



