POISON INSECTICIDES 13 



posed of white arsenic/^ copper oxide, and acetic 

 acid. When pure it consists of 58.65% arsenious 

 oxide, 31.29% copper oxide, 10.06% acetic acid. 

 Not over 3y2% should be sokible. 



Paris green ^^ is a coarse powder and not easily 

 held in suspension; it cannot be used on conifers; 

 cannot be used with fungicides containing am- 

 monia; cannot be combined with lime-sulphur with 

 safety ; does not adhere well to foliage. At least i 

 pound of freshly slaked lime should be mixed with 

 every pound of paris green to take up the soluble 

 arsenic and prevent burning of the foliage or it 

 should be combined with Bordeaux mixture. 



STANDARD FORMULAS 



Paris green 4 oz. Paris green i lb. 



Quick lime i lb. Quick lime. . 2 lbs. 



Water 50 gals. Water 200 gals. 



Stewart recommends i pound of paris green per 

 acre of potatoes whether 50 gallons or 100 gallons 

 of Bordeaux are applied. If the poison is used in 

 water alone then i or 2 pounds of quick lime should 

 be slaked and added. 



Impurities and tests for "^ — Paris green can 

 be tested in three simple ways for impurities: i. 

 Ammonia test. Paris green dissolves wholl)^ in 

 ammonia leaving no residue; 2. Glass slide test. 

 Pure paris green jarred on a slide leaves a bright 

 green streak. If impure the streak is whitish or 

 pale green; 3. Microscopic test. Under the micro- 

 scope the grains of paris green appear like clean 

 round balls. The crystals of the impurities will 

 appear angular, irregular and whitish. 



18 Lodeman — Spraying of Plants, pp. 59-74. 



19 Smith — New Jersey Expt. Stat., Bull. 213. 

 20Woodworth & Colby— Calif. Expt. Stat., Bull. 126. 



