No. 6. DEPARTMENT OF AGRICULTURE. 409 



SPRAYING MATERIALS. 



The chief materials for spraying here suggested are Paris green, 

 arsenate of lead and kerosene emulsion. It is well to speak more 

 fullj of these substances as one-half of the value of spraying depends 

 upon whether the}' are properly made or not, while the other half is 

 determined by when and how they are applied. Combinations of 

 insecticides and fungicides are also important for if these can be ap- 

 j)lied together rather than separately much time and labor can be 

 saved. A short consideration of these points, therefore, should be of 

 value. 



Paris Green. 



This insecticide which has been used in quantities for the destruc- 

 tion of insects longer than any other, is a chemical combination of 

 arsenic, copper and acetic acid. The arsenic (arsenious oxide) is of 

 course the poisonous substance, and a good Paris green should con- 

 tain over fifty per cent, of it. Much that is on the market, however, 

 contains less than this amount, and is known as "Low grade Paris 

 green," and is worth less for use than the higher grades (though it is 

 generally sold at about the same price as the better article), as the 

 farmer who uses it is putting less poison on his crops than he sup- 

 poses. 



In some States, laws have been enacted requiring that all Paris 

 green sold should contain at least fifty per cent, of arsenic — a law 

 that has frequently done more harm than good — and in order to com- 

 ply with it, manufacturers sometimes produce a low grade article, 

 and during its manufacture or afterwards, add enough arsenic to 

 bring the percentage of this substance up to that required by the law. 

 But the arsenic thus added does not chemically combine with the 

 other substances present in the Paris green, but remains as free ar- 

 senic which burns the leaves badly as everyone who has used much 

 Paris green knows. In this way a poor quality of Paris green which 

 would cause little or no burning of the foliage, becomes, by the addi- 

 tion of the free arsenic, a dangerous substance to apply to leaves of 

 any kind. 



Another objection to Paris green is that it is frequently adul- 

 terated with other substances, such as flour or plaster. Though such 

 adulterations do no harm when applied to foliage, the purchase of 

 such Paris green is much more expensive than it would be to buy 

 these materials separately and mix them. 



A further objection to Paris green is that some of the arsenic ao- 



