29 



manufacture of arsenate of lead; i. e., by precipitating a soluble 

 arsenate (arsenate of soda is probably the best from economic reasons) 

 in an alkaline medium with a soluble barium salt. Barium exists in 

 considerable quantities in nature as the carbonate (witherite). This 

 mineral may be treated with hydrochloric acid, and soluble barium 

 chloride results. When mixed with an alkaline solution of a soluble 

 arsenate, barium arsenate is thrown down as a .fine, floeculent, white pre- 

 cipitate, possessing physical qualities which render it easily suspended 

 in water. When prepared in a wholesale manner, its cost should not 

 greatly exceed that of arsenate of lead. In the reaction between 

 arsenate of soda and barium chloride there is, of course, a by-product 

 of sodium chloride (common salt) left in solution. This does not inter- 

 fere with the effect of barium arsenate upon either larvae or foliage, as 

 shown by careful comparison of experiments with salt-free v. salt- 

 containing barium arsenate. 



I am inclined to the belief that where arsenate of lead or arsenate of 

 barium is used in spraying better results will be obtained by dissolv- 

 ing the essential ingredients of either poison and adding them to the 

 contents of the spraying tank, thus allowing the reaction to take place 

 iu the tank. In this manner the original precipitate is left in suspen- 

 sion in the tank contents, and will stay suspended longer than when 

 dried and then remixed with water. 



The discussion of this paper was deferred until the reading of a 

 series of papers which had been arranged for during the afternoon 

 session, covering the general subject of insecticides and practical 

 operations with them against particular insects. 



The session adjourned until 2 p. in. 



AFTERNOON SESSION, AUGUST 21, 1896. 



The auditing committee, Messrs. Smith and Lintner, reported the 

 accounts of the secretary to be correct. The report was accepted and 

 the committee discharged. 



The committee appointed to arrange a joint meeting with the Society 

 for the Promotion of Agricultural Science reported that such joint 

 meeting would be held at 4 o'clock in the rooms occupied by the latter 

 society, and that papers by Messrs. Hopkins, Howard, and Dug-gar 

 would be presented. This report was also accepted and adopted. 



As arranged for at the morning session, the following three papers 

 were read, so that these, with the one presented by Mr. Kirkland in 

 the morning, could be discussed together. 



