ARSENICALS 291 



then add the sal soda and water, and boil until dissolved. Add 

 water to replace any that has boiled away, so that one gallon of 

 stock solution is the result. Use one quart of this stock solution 

 to 50 gallons of bordeaux mixture for fruit-trees. Make sure 

 there is enough lime in the bordeaux mixture to prevent the caus- 

 tic action of the arsenic. 



For use without bordeaux mixture. Sal soda, 1 pound ; water, 1 

 gallon; white arsenic, 1 pound; quicklime, 2 pounds. Dissolve 

 the white arsenic with the water and sal soda as above, and use 

 this solution while hot to slake the 2 pounds of lime. Add 

 enough water to make 2 gallons. Use 2 quarts of this stock 

 solution in 50 gallons of water. 



Arsenicals. A term popularly used for compounds of arsenic. The 

 leading arsenicals used in destroying insects are arsenate of 

 lead, paris green, and london purple. 



ARSENATE OF LEAD. This can be applied in a stronger mixture than 

 other arsenical poisons, without injuring the foliage. It is, there- 

 fore, much used against beetles and other insects that are hard to 

 poison. It comes in the form of a paste or powder, and should be 

 mixed thoroughly with a small amount of water before placing in 

 the sprayer, else the nozzles will clog.' Arsenate of lead may be 

 used with either bordeaux mixture or lime-sulfur without lessen- 

 ing the value of either. It is used in strengths varying from 4 to 10 

 pounds per 100 gallons, depending on the kind of insect to be killed. 



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 50 per cent. The two 

 following analyses show its composition : (1) Arsenic, 43.65 per 

 cent; rose aniline, 12.46; lime, 12.82; insoluble residue, 14.57; 

 iron oxide, 1.16; and water, 2.27. (2) Arsenic, 55.35 per cent; 

 lime, 26.23; sulfuric acid, 0.22; carbonic acid, 0.27; 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; but it 

 can be averted by the use of lime, as advised under paris green. 



PARIS GREEN. An aceto-arsenite of copper. When pure it contains 

 about 58 per cent of arsenic. By the provisions of the federal 



