8 
about as much Paris green as can be held on a 5-cent piece, transfer 
to a drinking glass and add about six tablespoonfuls of household 
ammonia; stir all the time and continue stirring for about five min- 
utes. If the green is pure a dark blue solution will be formed and no 
residue will remain undissolved. If calcium sulphate is present, how- 
ever, a white residue will remain suspended in the blue liquid, which 
will soon sink to the bottom of the glass in a compact mass. 
Presence of Glauber salts——There is one other substance that com- 
mercial samples of Paris green always contain because of their method 
of manufacture. This is sodium sulphate (Glauber salts). This sub- 
stance will neither harm nor help plants or insects. It should not be 
present in good samples of Paris green except in very small amounts, 
1 to 1.5 per cent, since it only adds weight and causes purchasers to 
pay the market price of standard goods for a weaker article. 
The author has recently examined 47 samples of Paris green col- 
lected by the Division of Entomology, and finds that the total arsen- 
ious acid varies from 56.2 to 62.16 per cent, the copper oxide from 
27.58 to 31.16 per cent, and the acetic acid from 6.5 to 12 per cent. 
Out of these 47 samples 10 had more than 1.5 per cent sodium sul- 
phate, one reaching even to 3.59 per cent. As to free arsenious acid, 
there are two methods for its determination: The first, or sodium 
acetate extraction method, shows more nearly the amount of free 
arsenious acid present in the original green, while the second, or 
water extraction method, shows the amount of free arsenious acid 
originally present in the green, together with some that has been set 
free by the action of water on the green. Although it has not yet 
been proved, the second method more than likely shows more accurately 
the value of Paris green in actual orchard practice. By extracting 
with sodium acetate, one sample contained 8.91 per cent and one sam- 
ple 6.37 per cent. Besides these there were 2 samples containing 
between 3 and 4 per cent, no samples containing between 2 and 3 per 
cent, and the remainder containing less than 2 per cent. By extract- 
ing with water, 19 samples contained above 5 per cent free arsenious 
acid, 16 between 4 and 5 per cent, and the remaining 12 below 4 per 
cent. 
There are two other substances now being sold that are very closely 
allied to Paris green, and consequently will be taken up in this con- 
nection. 
“GREEN ARSENOID.” 
The first of these is ‘Green Arsenoid.” This compound is very 
much like Paris green in its composition and effect on insects. If 
pure, it should be composed of arsenious acid and oxide of copper 
joined to one another in a chemical combination called copper arsenite, 
but unlike Paris green it does not contain any acetic acid. An analysis 
