2 HORTICULTURIST S RULE-BOOK. 



White arsenic, when applied in solution to foliage, is 

 injurious. The poison can be used with lime, however, 

 if treated as follows : Boil 1 pound of arsenic and 2 

 pounds of lime in 3 or 4 gallons of water, for half an 

 hour. The sediment, an arsenite of lime, can then be 

 used in about 100 gallons of water, with good results. 

 Arsenites. — A term popularly used for compound's of arsenic. 

 The leading arsenites used in destroying insects are Paris 

 green and London purple. 



Arsenate of Lead. — This compound of arsenic has re- 

 cently come into use, and it promises to be of much value. 

 It was first suggested by F. C. Moulton, in 1892, and has 

 since been tested in the extermination of the Gipsy-moth 

 in Massachusetts, When used at the rate of 2 pounds in 

 150 gallons of water, it was effective in destroying the 

 larvae of the moths, while the foliage of apple trees was 

 uninjured when the poison was used at the rate of 24 

 pounds in 150 gallons of water. The arsenate of lead 

 may be prepared by dissolving 11 ounces of the acetate 

 of lead in one vessel, and 4 ounces of arsenate of soda in 

 another. When these two solutions are mixed, there is 

 formed a fine white powder, which is sufi&cient for 150 

 gallons of water. 



London Purple. — An arsenite of lime, obtained as a by- 

 product in the manufacture of aniline dyes. The compo- 

 sition 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 per cent ; lime, 

 26.23 ; sulphuric 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. , 



