﻿ARSENICALS. 9 



(31.39 per cent), arsenious oxid (58.55 per cent), and acetic anhydrid 

 (10.06 per cent). 



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 d is- 

 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 wasned 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 colcr 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 (b) 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 



