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 by 

 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, 

 outlmed 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 

 pi p,o nival p,nt of — 



the equivalent of — 



0.64 per cent 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 U. 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 U. 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 U. 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 U. S. gallons of the 

 stock limewater, and make up the total volume to 50 U. S. gallons. 



1 Throughout this bulletin capital letters in parenthesis following "Pickering" indicate the formula 

 used in making the spray. 



