EXPERIMENTS WITH INSECTICIDES UPON POTATOES. l8l 



The farmer must know the grade of goods he is working with 

 and establish a new formula with each change of percentage." 



The experience of the other company is practically the same. 

 In answer to the question why ready made was superior to home 

 made arsenate of lead, they said (in part) as follows : 



"In regard to your inquiries regarding the manufacture of 

 arsenate of lead, would say that it is made from arsenate of soda 

 with either acetate or nitrate of lead. Each salt is dissolved 

 separately, filtered and the solutions added together, when arsen- 

 ate of lead precipitates out chemically. It is very necessary to 

 have exactly the right proportions of the two salts, as an excess 

 of either (particularly the arsenate of soda) will burn the foli- 

 age. As commercial arsenate of soda runs from 50 per cent to 

 68 per cent arsenious acid and acetate of lead varies somewhat, 

 the correct proportions cannot be obtained without a chemical 

 analysis. 



"The remarkable adhesiveness of arsenate of lead is principally 

 due to the extreme fineness of the particles in the precipitate. 

 This we have been able to obtain only by a great many experi- 

 ments to find the right conditions. 



"Both arsenate of soda and acetate of lead are deadly poisons, 

 and would be much more dangerous to have around than a dis- 

 infectant plainly marked, and understood to be poisonous. 



"Taking all these facts into consideration, in our opinion the 

 making and use of arsenate of lead by persons without a chem- 

 ical knowledge would be dangerous and unsatisfactory." 



While both of these companies have made the difficulties of 

 preparation fully as great as they really are, there is no doubt 

 that the average man had far better buy prepared arsenate of 

 lead than attempt its manufacture. 



As sold, arsenate of lead (including disparene) is put up in 

 paste form, and carries from 60 to 70 per cent of arsenate of lead. 



In the experiments here reported upon Swift's arsenate of lead 

 and Bowker's boxal (in which the poison is lead arsenate) were 

 used. Disparene was sent, but it was received too late to be used 

 for the first spraying. 



Swift's arsenate of lead. Rows 97 to 112 were treated four, 

 times with Bordeaux mixture and Swift's arsenate of lead at the 

 rate of one pound to the acre. The field notes are as follows : 



