72 N. S. ENTOMOLOGICAL SOCIETY 



addition of lead acetate to take the arsenic out of solution, and 

 obviate the difficulty. Since that time arsenate of soda, has 

 been used by growers as a basis for making home made arsenate 

 of lead, and by some manufacturers for the same purpose. The 

 practice of adding arsenate of soda to Bordeaux mixture grew 

 into favor with some potato growers, and the practice spread 

 in some districts. 



At the present time arsenate of soda is used in Bordeaux 

 mixture by some potato growers, particularly in New Bruns- 

 wick. It is completely soluble in water and consequently its 

 use is limited to the combination with Bordeaux. When in 

 that mixture it forms arsenate of lime, and to some extent ar- 

 senate of copper. On the potato this is very satisfactory, and 

 the arsenic in this form is fairly cheap. 



In Nova Scotia arsenate of soda is used but little. At 

 prices ruling in this Province the arsenic in this form, is no 

 cheaper than that in arsenate of lime, and consequently the 

 latter is preferred. 



Arsenite of Soda. 



Arsenite of soda was developed for use in Bordeaux mix- 

 ture, as a substitute for Paris green. It seems to have been 

 used by several persons about the same time, but the formula 

 generally used for making it was devised by Prof. Kedzie of the 

 Michigan Agricultural College about 1899. The product was 

 made by boiling together sal soda and white arsenic, and the re- 

 sulting liquid used as a stock solution of poison. The use of 

 this both on the potato and in the orchard spread rapidly, but 

 sometimes foliage injuries resulted, and later the combination 

 lost its popularity. 



At the present time arsenite of soda is used to some ex- 

 tent. Being completely soluble in water it can only be used in 

 Bordeaux mixture, where it forms arsenites of lime and copper. 

 Even in this combination it sometimes causes burning, espec- 

 ially where heavy applications are made. It can be purchased 

 in either solid or liquid form,and is the cheapest form in which 

 to buy arsenic, with the exception of white arsenic. 



In Nova Scotia arsenite of soda was once extensively used 

 but is now almost abandoned. It has been noted here that 

 the danger of foliage injury can be considerably lessened by add- 

 ing the arsenite to the copper sulphate solution, rather than 

 by adding it to the completed Bordeaux mixture. But even 

 with this modification it is doutbful if its use will ever be ex- 

 tensive. 



