FUNGICIDES AND THEIR APPLICATION 93 



obtained, there is no particular advantage in substituting Bur- 

 gundy for Bordeaux mixture, and the latter will usually be the 

 cheaper. But where good lime is not available the use of soda is 

 necessary, and when only a small quantity of mixture is required 

 at a time it is much more convenient. Weighed quantities to 

 make i gallon (i^oz. copper sulphate and 2oz. soda) can be kept 

 in separate small bottles and made up as required with very 

 little trouble. 



Burgundy mixture is less likely than Bordeaux to contain 

 particles which will clog the nozzles of sprayers. 



Copper Sulphate Wash. 



At a strength of 31b. to 40 gallons of water copper sulphate 

 is sometimes used as a bark wash or disinfectant. It cannot be 

 applied to leaves or to tender tissues of any description. 



Cuprammonium Washes. 



The Cuprammonium washes, made by dissolving copper or 

 one of its compounds in ammonia water have no advantages, 

 and some disadvantages, as compared with Bordeaux mixture 

 for the purpose for which the latter is ordinarily used, i.e., pre- 

 vention of the germination of spores. They have, however, 

 retained an application to cases (1) where the visibility of the 

 deposit left by Bordeaux spraying is objected to as unsightly ; 

 (2) where direct effect on a developed fungus is required. The 

 results of a comparison are summed up by O. Butler to the effect 

 that the cuprammonium washes are more effective than Bordeaux 

 mixture when large amounts of soluble copper are required to 

 give protection, less effective when small amounts suffice. These 

 fungicides have the practical disadvantage in hot climates 

 that strong ammonia is difficult to keep and dangerous to handle. 

 It should be diluted with 5 times its volume of water as soon as 

 it is obtained. 



The original eau celeste (cuprammonium sulphate) is made by 

 adding ammonia to a solution of copper sulphate. Modified 

 eau celeste (cuprammonium hydrate) may be made by adding 

 ammonia to Burgundy mixture until the precipitate is dissolved. 

 The method of preparing cuprammonium hydrate usually 

 recommended is by dissolving commercial copper carbonate in 

 ammonia according to the formula : — 



Copper carbonate ... ... 5 ounces. 



Strong ammonia 3 pints. 



Water 40 gallons. 



The ammonia is diluted with i gallon of water, and the copper 

 carbonate, previously made into a paste with a little water, is 



