328 Report of the Horticultural Department of the 



will immediately change to a dark, reddish-brown color. More lime 

 must then be added until the ferrocyanide does not produce the red- 

 dish brown color. Even after the test shows no color more lime 

 should be added so as to be sure that all of the copper is precipitated, 

 for in case the mixture has not been thoroughly stirred some of the 

 copper may still remain in solution in the bottom of the barrel while 

 the test shows no color at the surface. 



If the formula calls for a quantity of lime equal to the copper sul- 

 phate in weight, a half more lime than is required to satisfy the 

 ferrocyanide test should be added to the mixture. Suppose for ex- 

 ample one wished to take 6 pounds of copper sulphate and 6 pounds 

 of lime with 60 gallons of water to make 60 gallons of bordeaux mix- 

 ture and to use the ferrocyanide test. When the test first shows that 

 enough lime is present to combine with all of the copper sulphate the 

 mixture will contain somewhat less than 4 pounds of lime. To com- 

 plete the mixture according to the 6-6-60 formula requires the addi- 

 tion of half as much lime as has already been used, that is to say, it 

 requires 2 pounds more of lime, or the equivalent amount of the lime 

 paste. 



Mixing tanks. — It is convenient to have special tanks for mixing 

 the bordeaux. Thus the tank for the lime may be placed so that its 

 contents may be drawn off into the tank in which the copper sulphate 

 solution is put and in which the mixture is made. This tank may 

 likewise be elevated so that the prepared bordeaux mixture may be 

 drawn off into the spray tank. By this arrangement it is possible to 

 avoid the necessity of dipping and lifting the mixture. If these tanks 

 are so located with relation to the water supply that the water may be 

 run into the lime tank it is possible to avoid the necessity of dipping 

 and lifting every gallon of mixture that goes into the spray tank; the 

 lime may also be strained both when it is put into the lime vat and 

 when it is run from there into the bordeaux vat, which is an advan- 

 tage. 



