Composition and Properties of Arsen.cals. 

 (1) Paris Green. 

 Form of Guaranty. — • The form of guaranty under which Paris green is 

 sold is as follows: — 



Per Cent. 

 Total arsenous oxide, not less than . . . . . . . 50 . 00 



Water soluble arsenous oxide, not more than . . . . . . 3 . 50 



This corresponds to the. Federal standard. Paris green as offered for 

 sale in this State fully meets this gu .ranty. The statement of total 

 arsenous oxide in the guaranty may be taken as representing the effective- 

 ness of the material in terms of the killing principle which it contains. 

 Soluble arsenic, however, injures the foliage; hence the statement of 

 soluble arsenous oxide indicates the maximum amount of injurious com- 

 pounds of arsenic present. 



Because of its chemical nature. Paris green is liable to cause foliage 

 injury unless applied with lime. Physically it has a low power of suspen- 

 sion, but admits of reasonably effective distribution. It does not color 

 the foliage; hence without lime it does not indicate sprayed and un- 

 sprayed portions of the plant. It is fairly adhesive and persistent under 

 average weather conditions. 



(2) Lead Arsenate. 

 Form of Guaranty. — ■ The usual form of guaranty under which dry lead 

 arsenate is sold is substantially as follows: — 



Per Cent. 



Active ingredients: — 



Lead arsenate, 7Wt less than . . . . . . . .98.00 



Total arsenic pentoxide, not less than . . . . 31.00 



Total arsenic {as metallic) , not less than . . . . 20.20 



Inert ingredients, not more than . . . . . . . . 2 . 00 



100.00 



Water Soluble. 



Per Cent. 

 Soluble arsenic pentoxide, not more than . . . . . . 0.75 



Soluble arsenic {as metallic) , not more than . . . . . .0.50 



The essential statements in the guaranty are those italicized. Naturally 

 the greater the percentage of total arsenic contained in the product the 

 less will be the amount needed to secure satisfactory results. Conversely, 

 the greater the proportion of water soluble arsenic the greater will be the 

 liability of foliage injury unless lime is used with the lead arsenate to 

 prevent foliage burning. 



Lead arsenate, as shown above, is of low arsenic content, and that 

 practically insoluble in water, and is safe to apply to most plants. It is 

 slow acting but effective, its fineness of particles and light flocculent 

 character insuring a high power of suspension and uniform distribution. 

 The white mixture readily indicates the leaf surface covered, and on 

 drving it forms a film which adheres with great persistence. 



