NITRIC ACID. 



91 



Fig. 6. — Decorticator. 



iVlthough Dufour's experiments, which could not destroy the grubs 

 of the cochylis by steeping them for some seconds in 50 per cent 

 nitric acid, do not speak in favour of the insecticide action of this acid, 

 the results obtained in actual practice have been very favourable. 

 Sourdon and Castel, as well as Debray, have recommended for the 

 winter treatment of the vine the use of commercial nitric acid diluted 

 with six times its weight of water. After having barked the vine by 

 Sabate's iron glove, the eyes, the runners, and the body of the stem 

 are coated with nitric acid. The method may be applied in all weathers, 

 and its efficacy is almost always absolute. Debray is of opinion that 

 nitric acid msby replace eboiiillantage, "scalding," which is a compli- 

 cated method, and often inapplicable. Like the latter, it frees the vine 

 from all cryptogamic parasites, and from all insects which seek a refuge 

 in winter in the corners of the bark. Barbut's observations which in- 



FiG. 7.— Sabate's Glove. 

 duced him to affirm that 10 per cent nitric acid only kills 50 per cent 

 of pyralis and 40 per cent of cochylis, that the chrysales of lyyi'cd^^ can 

 stand steeping in that acid for several hours without injury, and that 

 treatment by nitric acid retards, moreover, the growth of the vine, in 

 no way diminishes the good results obtained in actual practice, and the 

 success of the winter treatment of the vine by nitric acid. 



