8 The Horticulturist' s Rule- Book. 



Arsenites (Paris green), continued. 



mixture now recommended is 1 part of poison to 50 of the 

 diluent, but if the mixing is very thoroughly done, 1 part to 

 100 or even 200 is sufficient. 



Paris green is practically insoluble in water. When mixed 

 with water, the mixture must be kept in a constant state of 

 agitation, else the poison will settle and the liquid from the 

 bottom of the cask will be so strong as to do serious damage, 

 while that from the top will be useless. For potatoes, apple 

 trees and most species of shade-trees, 1 pound of poison to 

 200 gallons of water is a good mixture. For the stone-fruits, 

 1 pound to 300 or even 350 gallons of water is a strong enough 

 mixture. Peach trees are very apt to be injured by arsen- 

 ites, and for them the mixture should be no stronger than 

 1 pound to 300 gallons. In all cases, the liquid should be 

 applied with force in a very fine spray. At some seasons of 

 the year foliage is more liable to injury than at others, 

 London purple. An arsenite of lime, obtained as a by-product 

 in the manufacture of aniline dyes. The composition is 

 variable. The amount of arsenic varies from 30 to over 50 

 per cent. The two following analyses show its composition : 



1. Arsenic, 43.65 per cent.; rose aniline, 12.46; lime, 21.82; 

 insoluble residue, 14.57; iron oxide, 1.16; and water, 2.27. 



2. Arsenic, 55.35 percent.; lime, 26.23; sulphuric acid, ,22 ; 

 carbonic acid, ,27 ; moisture, 5.29. It is a finer powder than 

 Paris green, and therefore remains longer in suspension in 

 water. It is used in the same manner as Paris green, but is 

 sometimes found to be more caustic on foliage. This injury 

 is due to the presence of much soluble arsenic. London pur- 

 ple should not be used on peach trees. 



Combinations of arsenites and fungicides. The arsenites 

 may be used in connection with some fungicides, and both 

 insects and plant-diseases in this manner may be combated 

 at the same time. An ounce of the arsenites may be added 

 to ten gallons of Bordeaux mixture, for potatoes, and other 

 combinations will occur to the operator. The arsenites are 

 also sometimes added to soap and other washes. 



The addition of lime to Paris green and London purple 

 mixtures greatly lessens injury to foliage, and, as a conse- 

 quence, they can be applied several times stronger than ordi- 



