i8o Bulletin 156. 



thoroughly slake all the lime and keep well stirred so that the 

 water may come in contact with all particles. This thorough 

 stirring is important and the lime should be carefully watched and 

 stirred for several minutes or otherwise it is likely to Vjecome dry 

 and hard. After the lime is all slaked, cover it over with 

 water and it is then ready for use and may be kept for any length 

 of time desired if it is always kept covered with water. Ferro- 

 cyanide of potassium may be purchased from the drug store, and 

 comes as a solid. One ounce of ferrocyanide of potassium dis- 

 solved in one ounce of water will be sufficient for testing many 

 barrels of the Bordeaux mixture. When it is desired to begin 

 spraying, there should be provided two empty barrels. Into one 

 barrel dip three gallons of the copper sulfate solution after it has 

 been thoroughly stirred. This will provide the six pounds of cop- 

 per sulfate in case two pounds were dissolved per gallon of water 

 and will be sufficient for making one barrel, or 45 gallons of Bor- 

 deaux mixture. Dilute the three gallons with ten or more 

 gallons of water. 



From the lime box dip from five to ten pounds of slaked lime 

 into the empty barrel. Add water and stir thoroughly until the 

 milk of limeis produced, after which dilute with some ten gallons 

 more of water. Pour the milk of lime thus diluted through a 

 sieve into the dilute copper sulfate solution. The quantity of 

 lime to be added to the copper sulfate is to be determined by the 

 ferrocyanide of potassium test. After adding a small amount of 

 the milk of lime to the copper sulfate solution, add to the mix- 

 ture a drop of ferrocyanide of potassium. If a brick red color 

 is produced w^here the drop strikes, it indicates that more lime is 

 needed. Continue adding the milk of lime until no reddish 

 color will be produced when the ferrocyanide of potassium is 

 used. A few trials will enable one to judge very accurately as to 

 the amount of lime required. A little surplus lime will do no 

 harm. 



If Paris green is to be used it should now be added. Take 4 

 ounces of Paris green and place it in a dish and add water 

 just sufficient to make a paste, and stir thoroughly until a 

 homogeneous mixture is formed. Pour this paste into the mix- 

 ture of lime and copper sulfate and stir vigorously. 



Pour the lime and copper sulfate mixture into the spray barrel, 



