228 Report of the Horticulturist op the 



as is shown in Figure 15. When treated in this manner it will 

 keep indefinitely in the form of paste if the surface is kept 

 covered with a small amount of water. It will be economy to 

 buy a good quantity of fresh lime. Air slaked lime is worth- 

 less. 



Potassium fcrrocyanulc test. — Fill the spray tank two-thirds full 

 with the copper sulphate solution, then pour in the milk of lime. 

 Stir the mixture thoroughly and add a drop of the potassium 

 ferrocyanide. If enough lime has been added the drop will not 

 change color when it strikes the mixture, otherwise it will im- 

 mediately change to a dark reddish brown color. More lime 

 must then be added until the ferroc^'anide does not produce the 

 reddish brown color. Even after the test shows no color more 

 lime should be added so as to be sure that all of the copper will 

 be 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 sur- 

 face. 



An excess of lime will do no harm, while the free copper solu- 

 tion will injure the foliage. 



The potassium ferrocyanide, or yellow prussiate of potash, is 

 a poisonous yellow salt which readily dissolves in water. A few 

 cents worth dissolved in about ten times its volume of water will 

 last through the season. 



Stock solution of copper sulphate. — Where a good deal of spray- 

 ing is to be done it will be found advantageous to make up a 

 stock solution of copper suljjhate. This may be made by dis- 

 solving any number of pounds of the suli)hate in one-half as 

 many gallons of water. A gallon of the solution will contain 

 two pounds of the sulphate, therefore two gallons will contain 

 the required amount for a barrel of Bordeaux mixture. Suspend 

 the sulphate in the top of the water, otherwise it will not all 

 dissolve if the water is cold. The stock solution must be kept 

 well covered in order to prevent evaporation. 



Saturated solution of copper sulphate. — An up-to-date orchard ist 

 recently suggested that a saturated solution of copper sulphate 



