PICKERING SPRAYS. 7 
(3) To compare the fungicidal values of certain of the more prom- 
ising Pickering sprays with those of standard Bordeaux mixture per 
unit of copper. 
(4) To determine the injurious action of the more promising 
Pickering sprays on various kinds of vegetation as compared with 
that of standard Bordeaux. 
(5) To compare the adherence of Pickering sprays with that of 
standard Bordeaux. 
PREPARATION OF SPRAYS USED. 
Pickering sprays made according to Formulas A and C (p. 3) 
were used in such proportions that the finished sprays prepared hy 
Formula A would contain the equivalent of 0.64, 0.38, 0.13, and 
0.065 per cent of copper sulphate, and those prepared by Formula 
C, 0.36, 0.23, and 0.115 per cent of copper sulphate. In making the 
stock solutions of limewater and copper sulphate these directions, 
outlined by Bedford and Pickering (4), were followed: 
Dissolve the copper sulphate by suspending it in a piece of sacking, near the top 
of the water, in a wooden or earthenware container. Place not less than 2 or 3 pounds 
of some good quicklime (CaO) in a wooden container, slake with a little water, and 
add the desired amount of soft water. After making a smooth paste, add water, stir 
the lime and water two or three times, and let settle. Cover the container. Carbonate 
of lime found on top of the water does no harm. Run off the desired amount of the clear 
limewater, and mix with the required amount of copper sulphate solution. Test to 
be sure that all the copper has been combined with lime, and dilute to the required 
volume with water.. To test for free copper, put a few drops of a solution of ferro- 
cyanide of potash in a white saucer with water and drop into this some of the clear 
liquid obtained after the limewater Bordeaux has settled. If a brownish-red color- 
ation appears, it indicates that copper remains in solution, a little more limewater 
must be added, and the solution retested. 
To prepare Pickering (A) 1 sprays containing in the finished product 
the equivalent of — 
0.64 2 jer cen t copper sulphate: Mix enough of the stock solution of copper sulphate 
(prepared so that 1 gallon is equivalent to 1 pound of copper sulphate) to obtain 2 
pounds, 10.7 ounces of crystallized copper sulphate with 42.88 U. S. gallons of the 
stock limewater, and make up the total volume to 50 IT. S. gallons. 
0.38 per cent copper sulphate: Mix enough of the stock solution of copper sulphate 
to obtain 1 pound, 9.3 ounces of crystallized copper sulphate with 25.47 U. S. gallons 
of the stock limewater, and make up the total volume to 50 XJ. S. gallons. 
0.13 per cent copper sulphate: Mix enough of the stock solution of copper sulphate 
to obtain 8.67 ounces of crystallized copper sulphate with 8.71 IT. S. gallons of the 
stock limewater, and make up the total volume to 50 U. S. gallons. 
0.065 per cent copper sulphate: Mix enough of the stock solution of copper sulphate 
to obtain 4.33 ounces of crystallized copper sulphate with 4.36 TJ. S. gallons of the 
stock limewater, and make up the total volume to 50 TJ. S. gallons. 
1 Throughout this bulletin capital letters in parenthesis following "Pickering" indicate the formula 
used in making the spray. 
