Spray Calendar. 125 



Six pounds of sulfate of copper dissolved in fifty gallons of 

 water, when applied at the proper time, will prevent the growth of 

 fungi. However, if applied in this form, the sohition will burn tlie 

 foliage. Four pounds of quicklime in six pounds of copper will 

 neutralize the caustic action. When sulfate of copper and lime are 

 added in this proportion, the compound is Bordeaux mixture. 



AYeighing of copper and lime at time of mixing is very incon- 

 venient. Bordeaux mixture is best when used within a few hours 

 after being mixed. Therefore a stock mixture of Bordeaux is imprac- 

 ticable. It is, however, practicable to have stock preparations of 

 sulfate of copper and of lime ready for mixing when required. 



The lime should be " dry slacked " in a barrel or box, and when 

 slacked must alwavs be covered with water to exclude the air. In 

 this man ler lime can be kept all summer unimpaired. 



Sulfate of copper can be dissolved in water and held in solution 

 until needed. One gallon of water will hold in solution two pounds 

 of copper sulfate. To accomplish this the sulfate should be sus- 

 pended at the surface of the water in a bag. The water most 

 loaded with copper will sink to the bottom, and the water least 

 loaded will rise to the surface. If fifty pounds of sulfate are sus- 

 pended in twenty-five gallons of water on an evening, each gallon of 

 water, will when stirred the next morning, hold two pounds of sulfate. 



If three gallons of this solution are put in the spray barrel, it is 

 equivalent to six pounds of copper. Now fill the spray barrel half 

 full of water before adding any lime. This is important, for if the 

 lime is added to so strong a solution of sulfate of copper, a curd- 

 ling process will follow. Stir the water in the lime barrel so as to 

 make a dilute milk of lime, but never allow it to be dense enough 

 to be of a creamy thickness. If the latter condition, lumps of lime 

 will clog the spray nozzle. Continue to add to the mixture this 

 milk of lime so long as drops of ferrocyanide of potassium (yellow 

 prussiate of potash) continue to change from yellow to a brown 

 color. When no change of color is shown, add another pail of 

 milk of lime to make the necessary amount of lime a sure thing. 

 A small excess of lime does no harm. The barrel can now be filled 

 with water, and the Bordeaux mixture is ready for use. 



The preparation of ferrocyanide of potassium for this test may 



