FUNGICIDES, ETC. 277 



Put the lime in another vessel, and add a little warm 

 water. Continue to add small quantities of water until 

 the lime is thoroughly slaked and in a smooth paste. 

 Now add enough water to make a total of twenty-five 

 gallons, and stir thoroughly. Pour the two prepara- 

 tions together slowly into a third container, and stir 

 thoroughly. 1 



The mixture should now be tested to determine if 

 there is enough lime to counteract the injurious effects 

 of the copper sulphate on the foliage. This can be done 

 as follows : Pour a little of the mixture on a porcelain 

 plate or saucer, hold between the light and the eyes, and 

 blow the breath gently upon the surface for a minute or 

 longer. If the mixture is properly made a thin pellicle, 

 having the appearance of oil on water, will form on the 

 surface ; or, add a drop of potassium ferrocyanide 

 (poison) to the mixture, and if it changes colour it will 

 be necessary to add more lime. The second is better 

 than the first, and, in fact, is the only strictly reliable 

 method. 



The mixture should be strained before using, but if 

 the lime has been strained and all the preparations made 

 and kept in clean vessels, this will not be necessary. 



The proportions of lime and copper sulphate are 

 varied in amount for different purposes. Sometimes 

 as much as six pounds of copper sulphate is used, 

 while in other cases on]y one pound is used with one 

 and a half pounds of lime. 



Considerable difficulty is experienced in climates 

 where the humidity is great from air-slaking of the lime. 

 Air-slaked lime will not make good Bordeaux mixture. 

 However, the difficulty can be overcome by slaking 

 a quantity of lime and keeping it in concentrated 

 stock for use. It keeps well if kept moist, but is 

 worthless if allowed to become dry. In fact, the two 

 preparations are frequently made separately in con- 

 centrated form and kept in stock, to be diluted and 



1 If desirable, only one preparation need be diluted previous to mixing. 

 Never mix the two in a concentrated form. 



