MISCELLANEOUS 225 



ing matter, obtained as a by-product in the manufacture of 

 certain coal-tar dyes. It, like Paris green, is very variable in 

 composition, but usually contains from 30 to 50 per cent, of 

 arsenious oxide, of which often a considerable proportion is 

 soluble in water. It is used in the same manner as Paris 

 green, but unless lime be also added it is even more liable to 

 injure foliage. 



An arsenice of lime can be made by dissolving arsenite of 

 soda in water, diluting largely, and then stirring in milk of 

 lime containing about ten times the weight of lime as of the 

 arsenite of soda taken. I^he lime is in large excess, but does 

 no harm. 



Lead Arsenate, which is insoluble in water, and therefore 

 does not injure foliage, is very valuable as a spraying material. 

 It can be bought ready prepared, or can be made as required 

 from " sugar of lead " {i.e.y acetate of lead) and arsenate of soda 

 — 11 ounces of the former and bounces of the latter, dissolved 

 in separate portions of water. When mixed they give a fine 

 white precipitate of arsenate of lead, which, when suspended 

 in 150 gallons of water, can be sprayed on trees without fear 

 of injury. Arsenate of lead is supplied either as a paste 

 (usually containing about 1 2 per cent, arsenious oxide) or in 

 powder. The former gives the better results. 



Scheele's Green. — Copper hydrogen arsenite is also sometimes 

 used for spraying. Like lead arsenate, it is very slightly 

 soluble in water, and therefore has but little injurious 

 action on foliage. It is, however, not often used as an in- 

 secticide. 



Caution as to Use of Arsenical Preparations. — Arsenic com- 

 pounds are so poisonous to man and the higher animals that 

 it is of the utmost importance tliat they be used with care. 

 Every precaution should be taken to prevent access of any of 

 the arsenical solutions to foods, water, (tc, which may 

 afterwards be consumed by animals. The lethal dose of 

 arsenious oxide depends very largely upon the individual ; for 

 man it has been given as probably 1 or 2 grains, for a 



