2 8 FRUIT TREES AND THEIR ENEMIES 



make sure that the whole of the copper has been 

 thrown down : therefore, before adding the additional 

 water, ladle out a little of the mixture, and add one 

 or two drops of it to a weak solution of potassium 

 ferrocyanide in a white saucer (the ferrocyanide may 

 be obtained from any chemist) : if there is any brown 

 coloration, the copper has not all been thrown down ; 

 a little more lime-water must then be added, and the 

 test repeated. Another test for unprecipitated copper 

 consists in immersing the blade of a knife in the 

 liquid, and seeing whether it becomes stained : but 

 this test is neither very delicate nor reliable. 



Bordeaux mixture made with lime-water in this 

 way is as efficient as that made in the ordinary way 

 (No. 9<:), though the latter contains two-and-a-half 

 times as much copper sulphate. It also presents the 

 advantages of being much finer in texture, and, 

 therefore, less liable to settle to the bottom of the 

 liquid ; it also contains no particles of solid lime, 

 which wear the spraying nozzles, and cause loss of 

 material, by being easily knocked off the leaves, and, 

 further, it exhibits its fungicidal action at once after 

 it is applied, instead of necessitating a certain time to 

 elapse before such action begins, as in the case of the 

 ordinary mixture. 



Bordeaux mixture may be emulsified with paraffin 

 oil, and thus gives us a combined fungicide and 

 insecticide of great efficiency. The mixture should 

 be made exactly as described above, and then the 

 paraffin added, and churned up with it by a few 

 strokes with a syringe fitted with a rose-jet. This 

 has been named Bordeaux Emulsion. 



