Spraying Kotes. 269 



copper, and the lime compound with arsenic is insoluble in ammonia 

 water. Although this material is a good insecticide, it is not Paris 

 green. 



The specific gravity of insecticides. — An important ,point in 

 every insecticide applied with water is the time* it will remain 

 in suspension. If the arsenite sinks to the bottom of the barrel 

 in a few minutes, as does Paris green, there is an unequal distribu- 

 tion of the poison and the concentrated mixture at the bottom is 

 likely to burn the foliage. Frequent stirring is an inconvenience. 

 Generally speaking, the lighter and more fiocculent an insecticide 

 is, the longer it will stay in suspension. Assuming the Paris green 

 to be 10, the various insecticides compare with it in weight as fol- 

 lows : Green arsenite, 10; pink arsenoid, 9; paragrene, 7; green 

 arsenoid, 7 ; XX, 4 ; green arsenoid I^o. 53, 4. Equal amounts of 

 the above arsenites shaken in water followed approximately the 

 same order in settling, Paris green and green arsenite settling first 

 and No. 53 last. The heavy specific gravity of Paris green is one 

 of its weak points as an insecticide. 



Summary of Insecticides. 



Paragrene. — Manufactured by Fred L. Lavenburg, New York. 

 Price 14^ cents per pound in 14-pound pail. It has equal insecti- 

 cidal value with Paris green, is about as likely to burn the foliage 

 and remains longer in suspension. We consider it an excellent 

 substitute. 



Green arsenite. — (Arseniate of copper, Scheele's green.) This 

 is practically the same as Paris green in composition, and has the 

 same effect on foliage. Its fungicidal value is slightly greater than 

 Paris green owing to the higher percentage of copper oxid. When 

 it can be obtained as cheaply as Paris green, it may be given 

 preference. 



Phik arsenoid. — Manufactured by the Adler Color and Chemi- 

 cal Works, Brooklyn, N. Y. Petail price 15 cents per pound at 

 ]Sr. Y., f . o. b. It is slightly inferior to Paris green as an insecticide, 

 and has decidedly less fungicidal value, since the lead oxid it contains, 

 corresponding to the copper oxid of Paris green, has little if any 



