New York AGRICULTURAL EXPERIMENT STATION. 213 
considerable risk. Injury to the foliage resulted from the use of 
8 pints of arsenite of soda per acre in the first spraying and 9 
pints per acre in the second and fourth sprayings. Based on the 
arsenic it contains, nine pints of the arsenite-of-soda stock solution 
are equivalent in poisoning properties to 36 ounces of paris green 
which is not an excessively large quantity to apply per acre. 
In the paris green experiment twice this amount of paris green 
per acre was used without the least injury to the foliage. (See 
pages 201, 206.) 
Why injury resulted from the fourth treatment with arsenite > 
of soda in lime water and not from the third is not clear. The 
spray mixture was prepared and applied in identically the same 
manner in both cases, except that a slightly greater quantity was 
used in the fourth spraying. The difference in rainfall may 
have had something to do with it. The third spraying was made 
August 1. On the night of the same day .52 inch of rain fell; 
an August 2, .J2 inch and on August 5, .07 inch. After this 
there was no more rain until August 18. The fourth spraying was 
made August 12, following which date the rainfall was as fol- 
lows: August 13, .18 inch; 16, .16 inch; 17, .31 inch; 19, .76 
inch. The injury was not observed until August 20, but it is possi- 
ble that it occurred earlier. 
An interesting result of the experiment was the discovery of 
the part which copper sulphate plays, in connection with the 
lime, in preventing the caustic effect of the arsenite of soda. 
When arsenite of soda was applied with lime water injury to the 
foliage resulted; but when the same quantity of arsenite was 
applied with bordeaux mixture there was no injury. This hap- 
pened three times. In the fourth spraying the quantities of 
arsenite, lime and water were the same in both cases the only 
difference being that one mixture contained copper sulphate 
while the other did not. The conclusion is plain that the copper 
sulphate was, in some way, responsible for the absence of spray 
injury on the rows to which it was applied. It appears that the 
caustic effect of the arsenite of soda is prevented more effectively 
by copper sulphate and lime acting together than by either one 
alone. In fact there is no evidence that copper sulphate alone is 
of any value whatever for this purpose. On the contrary it has 
