AKSENICALS. 9 
(31.39 per cent), arsenious oxid (58.55 per cent), and acetic anhydrid 
(10.06 percent). 
The manufacture of Paris green, 4 which has become standardized, 
may be briefly described thus: Solutions of soda ash (commercial 
anhydrous sodium carbonate) and arsenious oxid are first heated 
together, forming sodium arsenite. Crystalline copper sulphate is dis- 
solved in warm water in a separate container. The sodium arsenite 
mixture is poured into a mixing tank, the copper sulphate solution is 
added, and the mixture is stirred. Acetic acid is added, and after a 
little stirring the olive-colored mixture becomes green. The Paris 
green is washed with water, after which it is allowed to settle and all 
the water that can be drained off is so removed. This washing should 
be repeated as often as necessary to remove practically all the sodium 
sulphate. The Paris green is then dried. The dried product is passed 
through a " breaker" and finally through a fine sieve or a bolting 
machine. The " tailings" are mixed with the next batch of Paris 
green. The finely divided Paris green is now ready to be placed in 
containers. 
The color of Paris green varies with the details of manufacture and 
the degree of fineness of the product. The composition of Paris green 
on the market ranges from 54 to 57 per cent of total arsenious oxid, 
from 1.5 to 4.5 per cent of water-soluble arsenious oxid, and from 
29 to 30 per cent of copper oxid. 
Haywood (17) stated that the impurities in Paris green include 
small amounts of sand, sodium sulphate, and arsenious oxid, and 
also that the soluble arsenic in Paris green produces scorching of 
foliage. 
Paris green, when of a high grade, breaks down to some extent when 
water is added, but when it has been improperly prepared much more 
soluble arsenic is yielded on treatment with water. Avery and Beans 
(2) found that high-grade Paris green was slowly attacked by water 
and that the rate of decomposition was increased by grinding to a very 
fine powder and suspending in water. They also found that the pres- 
ence of carbon dioxid in the water increased the rate of decomposi- 
tion. There are two sources of the soluble arsenic in Paris green, (a) 
the soluble arsenic originally present in the sample, and (&) the 
arsenic made soluble by water and carbon dioxid after the material 
has been applied. The admixture of lime with Paris green when used 
as a spray lessens its scorching properties. Analysis of a typical 
Paris green (sample 64) is given in Table 4. 
MISCELLANEOUS COMMERCIAL ARSENICALS. 
Analyses of samples of several miscellaneous arsenicals which were 
tested against insects are given in Table 4. 
4 Details of the manufacture of Paris green are given in 45 Ann. Rept. Sec. Mass. State Board Agr. (1897), 
p. 357. 
27476°— 23 Bull. 1147 2 
