ENEMIES OF PLANTS. 301 



that it does not contain acetic acid, and in the 

 per cent, of arsenic. It has the advantages of 

 being held longer in suspension, as it is a finer 

 powder, and of costing onl)' about half as much. 

 Home preparation insures purer and better 

 arsenical spraying mixtures — as, arsenite of soda 

 and arsenate of lead. 



White arsenic i pound 



Sal soda 4-5 pounds 



Water 2 gallons 



Mix the above ingredients and boil until clear 

 — about fifteen minutes. Add enouorh water to 

 replace that which boiled away. This forms a 

 stock solution which should be placed in Mason 

 jars, labeled poison, and kept until needed. 

 This stock solution is used similarly to Paris 

 green. Since it is soluble in water, and hence 

 would damage the foliage, it is prepared for use 

 by mixing two quarts of the stock solution and 

 eight or ten pounds of freshly slaked lime with 

 one hundred gallons of water. 



Arsenate of Lead.*^ — -This insecticide has 

 several advantages over the others just men- 

 tioned: (i) it can be used in stronger solutions 

 and in larger quantities without injuring tender 

 foliage, since it is absolutely insoluble in water; 

 (2) it will remain longer in suspension ; (3) 



* Commercial arsenate of lead sold under the name of dis- 

 parene, is said to be perfectly reliable. It comes in paste form, 

 and sticks on the foliage well. 



