MIXING SPRAY MATERIALS 207 



. 6. Graduated cylinder, 100 c.c. 



7. Balance weighing to one half gram. 



Directions. Dissolve thirty grams of copper sulphate in 

 two liters of water, in a two-gallon crock. Slack forty grams 

 of fresh lime by pouring water over it and mixing. Pour in 

 water to bring the solution up to two liters. Pour the two 

 solutions together into the large crock. The resulting solu- 

 tion is the Bordeaux mixture. 



The Bordeaux mixture should be alkaline in reaction. 

 Dissolve the ten grams of potassium ferrocyanide in 50 c.c. of 

 water. Pour a drop of potassium ferrocyanide solution into 

 the spray material. If it turns brown on striking the liquid, 

 the reaction is acid, and more limewater must be added to 

 make it alkaline. If the reaction is acid, add 50 c.c. of lime- 

 water and test again with a drop of potassium ferrocyanide 

 solution. Continue adding limewater and testing until the 

 solution no longer gives the brown color when potassium 

 ferrocyanide is added. 



