110 Agricultural Experiment Station^ Ithaca, N. Y. 



Bordeaux mixture was, with two exceptions, always made according 

 to the formula : 



Copper sulphate 6 pounds. 



Quick lime 4 pounds. 



Water 45 gallons. 



Upon two occasions, the mixture was prepared with the assist- 

 ance of the ferrocyanide of potassium test. The value of this 

 chemical in the preparation of the Bordeaux mixture lies in the fact 

 that when in solution it will combine with dissolved salts of copper 

 and form a compound having a deep reddish-brown color. When 

 sufficient lime is added to the copper-sulphate solution in making 

 the Bordeaux mixture, several new compounds are formed, of which 

 all that contain copper are practically insoluble. If an insufficient 

 amount of lime is used, some of the copper salts remain in solution 

 and the addition of a few drops of the ferrocyanide of potassium 

 solution will produce the characteristic brown color in the mixture; 

 but as soon as enough lime is present to remove all dissolved copper, 

 the test will cause no change to take place. This test solution may 

 be made as follows : 



Ferrocyanide of jDotassium (yellow prussiate of potash) . . 1 ounce. 

 Water 1 pint. 



The chemical dissolves very readily, and is then ready for use. 



When the Bordeaux mixture is prepared in this maoner, it contains 

 the smallest amount of lime necessary to satisfy all immediate 

 chemical changes, and upon this fact rests the principal argunient 

 for the use of the method. The subject is more fully treated upon 

 pages 120-122. 



Copper sulphate 1 pound. 



Water 18 gallons. 



This was applied as soon as the crystals were dissolved, but it was 

 used only at the time of the first applications, before the buds had 

 fully opened. 



London purple was applied by using 



London purple ^ 1 pound. 



Air-slacked lime 1 pound. 



Water 250 gallons. 



The lime was added to prevent any caustic action of the poison. 



