FUNGICIDES 23 



be poured into the lime, rather than the lime into the 

 copper sulphate solution. 



"It is now necessary to determine whether the 

 mixture is perfect that is, if it will be safe to apply 

 it to tender foliage. To accomplish this, two simple 

 tests may be used. First insert the blade of a pen- 

 knife in the mixture, allowing it to remain there for 

 at least one minute. If metallic copper forms on the 

 blade, or, in other words, if the polished surface of 



Making Bordeaux Mixture 



Pouring together the lime milk and copper sulphate solution 



the steel assumes the color of copper plate, the mix- 

 ture is unsafe and more lime must be added. If, on 

 the other hand, the blade of the knife remains 

 unchanged, it is safe to conclude that the mixture is 

 as perfect as it can be made. As an additional test, 

 however, some of the mixture may be poured into 

 an old plate or saucer, and while held between the 

 eyes and the light the breath should be gently blown 

 upon the liquid for at least half a minute. If the 



