^ "7 

 J/ 



12. A filtered solution from which the arsenic had been removed 

 was sprayed upon peach July nth. No injurs- resulted, showing 

 that it is the arsenic and not the dye which is injurious. f 



Our trials were made at nearly all times of day, and under vari- 

 ous meteorological conditions. Full records were made of all 

 these conditions, but as they appear to have exercised no influence 

 whatever, they need not be discussed here. The notion that fol- 

 iage may be scorched by spraying with pure water on a bright 

 and hot day has no foundation, else our trees would have been 

 scorched by the Paris green water, which was sometimes applied 

 in very hot and bright weather. 



Plums. Serious injury is said to have followed London purple 

 spray upon plum trees in this State, last year. One grower is 

 said to have permanently injured his orchard by the use of one 

 pound of purple to 300 gallons of water, particularly the Bavay 

 (yRcine Claude). Two tests were made upon vigorous young plum 

 trees : 



the arsenic in solution is in the same condition as that in the original sub- 

 stance. To determine the amount of dye that was soluble, the total nitro- 

 gen in the London purple was determined and found to be 1.56 per ct. 

 The nitrogen in the solution was then determined and found to be .30 per 

 ct.; now, since the nitrogen comes from no other source except the London 

 purple, .30 : 1.56 : x : 100 represents the per centage of dye (on the basis 

 of the total dye) soluble in water, and this was determined by difference 

 to be 23.04. 



The solubility of London purple is as follows : 



Calcium arsenite, 38.08 per ct. 

 Dye, 4- 61 



This represents 52.38 per ct. of the total calcium arsenite as being soluble 

 in water. 



The above samples of London purple were purchased in the open market, 

 and are the same as that used in the orchard tests. A sample direct from 

 the Hemingway Company was found to be equally soluble, containing 39. 11 

 per ct. of soluble calcium arsenite. 



Paris green is a compound coniaining copper, arsenious and acetic acids. 

 It is an aceto-arsenite of copper, having the formula, Cu(As 2 Oj 3 , Cu(C 2 H 3 

 C0 2 . This formula would require copper, 23.92 per ct.; arsenic, 44.47 per 

 ct.; oxygen, .53perct. ; acetic acid, 11.08 per ct. The sample under ex- 

 amination yielded 23. iS per ct. copper, and 44.16 per ct. arsenic. Some in- 

 soluble matter was present, but it was not determined. This represents 97 

 per ct. of aceto-arsenite of copper, all of which is insoluble in water. 



t In order to precipitate the arsenic, the solution was made acid with hy- 

 drochloric acid, and this was neutralized with ammonium hydrate, forming 

 ammonium chloride. This substance scorched the foliage, but the whole 

 injury was entirely different from that caused by London purple, and could 

 not be confounded with it for a moment. Moreover, a tree was sprayed at 

 the same time with ammonium chloride as a check, and the same injury 

 resulted. This explanation may be useful to those who desire to repeat the 

 experiment. 



