SELECTING AND PREPARING MATERIALS 287 



d : 2. Consider the preparation of Bordeaux mixture. 

 This is commonly made by the grower if needed in any quan- 

 tity. A common formula is 4-4-50, containing: 



The formula may be 3-3-50 or 5-5-50, etc., varying the 

 proportion of lime and copper sulfate to the water. One unit 

 more of lime than of copper sulfate, as 4-5-50, gives additional 

 insurance against burning and is frequently used by growers. 



Prepare a stock solution by dissolving the required amount of copper 

 sulfate crystals at the rate of 1 pound of copper sulfate to a gallon of 

 water. Put the copper sulfate in a sack at the surface of the water, 

 using a barrel or other wood container for the water. As the chemical 

 dissolves, being heavier than water, it will work toward the bottom, 

 keeping water in contact with the sack. If the sack is put in the bottom 

 of the barrel, the material will dissolve much more slowly. Start the 

 process at any convenient time before the material is to be used, since 

 it will keep indefinitely. 



Slake the required amount of lime, adding water slowly so that the 

 lime breaks down into a fine powder and then into a smooth milky 

 mixture. Add water until the proportions are 1 part of lime to 1 gallon 

 of water. Keep the mixture covered. 



It is evident that for a 4-4-50 formula it is only necessary to take 4 

 gallons of each stock solution to a 50-gallon unit. For a 200-gallon 

 spray tank, using this formula, 16 gallons of each stock solution would be 

 required. 



If large amounts of stock solution are needed, prepare the copper 

 sulfate at the rate of 2 pounds to a gallon of water. If only small 

 amounts are required, use hot water in slaking the lime, since cold 

 water on a small quantity of lime may check the slaking process. The 

 solutions will keep indefinitely so long as they are not mixed. Keep 

 them covered to prevent evaporation of water from them, since this 

 would change the strength of the stock solutions and lead to errors in 

 making dilutions. Put a few drops of oil on the surface of the stock 

 solutions to prevent evaporation, or replace the water that has evapo- 

 rated, before using. 



In combining the materials for spraying, never put the stock solutions 

 together, as the materials will curdle and settle rapidly in the form of 



Copper sulfate 



Burned lime or quicklime 

 Water 



4 pounds 

 4 pounds 

 50 gallons 



