CHAPTER XVI. 



COPPER ACETO-ARSENITE (EMERALD GREEN, PARIS GREEN)— COPIER 

 ARSENITE (SCHEELE'S GREEN)— COPPER SILICATE— COPPEJl CAR- 

 BONATE— BOUILLIE BORDELAISE CELESTE— VERDIGRIS COPPER 

 ACETATE— VARIOUS BOUILLIES. 



96. Aceto-Arsenite of Copper, Emerald Green, Paris Green. 

 — Definition. — The aceto-arsenite of copper sold in commerce under 

 the name of [emerald green], "Paris Green,'' " Schveinfurth green," 

 is a double arsenite and acetate of copper. 



Preparation. — By dissolving 4 lb. of white arsenic in 5 gallons of 

 water, and on the other hand, 5 lb. of verdigris in 5 gallons of water, 

 and mixing the two liquids. The mixture is boiled for some time, 

 then a little acetic acid is added. To prepare a bouillie, it sufl&ces to 

 mix 1 lb. of emerald green in a little water, add milk of lime contain- 

 ing 1 per cent of quicklime, and make up the paste to 10 gallons of 

 bouillie. This mixture of cupric hydrate [acetate] and arsenite is much 

 used in America. Commercial emerald green contains 55-34-60*16 

 per cent of arsenic (As^Oy) and 27"7-30-9 per cent of cupric oxide (CuO). 



Properties. — Commercial aceto-arsenite of copper is not com- 

 pletely msoluble in water, and thus possesses an injurious action on 

 the plants treated. This defect disappears if the acetate of copper be 

 converted into hydrate by quicklime, by mixing the emerald green with 

 lime. Aceto-arsenite of copper freshly prepared is a precipitate fine 

 enough to remain suspended in water. That is not so with the 

 emerald green of commerce. If a bouillie be prepared from the latter, 

 as is generally done, the granular precipitate falls to the bottom of the 

 liquid, and it is necessary to use a sprayer fitted with an agitator to 

 distribute the salt regularly on the trees. Trials by Lintner to de- 

 termine whether arsenites mixed with soil were absorbed by plants led 

 to the conclusion that plants only absorb arsenites with great diffi- 

 culty, and only in cases where it is placed in large doses in direct con- 

 tact with their roots. The aerial organs do not dissolve insoluble 

 arsenites deposited on them by spraying. The ash of potato plants, which 

 has been sprayed with a bouillie of arsenite of copper, does not con- 

 tain arsenic. Baily obtained the same results with peach-trees treated 

 with emerald green, and Pletcher on apple-trees similarly treated. 

 Scheie's green being insoluble behaves like arsenite of lime. When 

 the product is pure, that is to say, when it contains no unconverted 

 arsenite of soda, its action on plants in insecticidal doses is, so to speak, 

 nil, and in many cases it may be employed in 0-05 and 0-1 per cent 

 bouillie. On the other hand, the action of Paris green makes itself 

 felt very energetically when it is not mixed with lime. Baily found that 



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