308 



Agricultural Chemistry. 



the so-called "normal" formula, or 1.6 per cent Bordeaux, which 

 consists of: 



Copper sulphate 6 Ibs. 



Quick lime 4 Ibs. 



Water 50 gallons 



The lime should be slightly in excess. This may be accom- 

 plished by weighing the pure salts for the mixture, or by testing 

 the product. 



Note the beneficial results from the control of potato diseases by Bor- 

 deaux mixture. 



The litmus test depends upon the fact that so long as copper 

 sulphate is in excess blue litmus will be turned red when moist- 

 ened with the Bordeaux mixture. Enough lime should be pres- 

 ent so that red litmus is turned blue. 



The ferro-cyanide test may be used also for this purpose. A 

 teaspoonful of the clear liquid, obtained by straining if necessary, 

 should be added to a few drops of potassium-ferrocyanide solu- 



