The Use of Sulphuric Acid. 45 



solution, and should be used for fertilizing purposes. The pre- 

 cipitate is then treated with 10 liters of ammonia and there is 

 obtained a normal solution. Dilute forty times when applying. 

 De Capol believed this to be an excellent preventive against the 

 mildew, and he also said that it would not burn the foliage. 

 The preparation, however, never came into general use. 



Messrs. Skawinski were among the first in France to use 

 Schnorf's remedy for authracnose. But their experience sug- 

 gested to them a change in the preparation, which led to a 

 general modification of the old formula. They remarked that 

 the action of the iron sulphate was stronger when sulphuric 

 acid was present in considerable quantities with the crystals. 

 They consequently adopted the following: 



Iron sulphate 50 kilos. 



Sulphuric acid, 53 1 1 liter. 



Warm water 1 hectoliter. 



The best method of making the solution is to pour the acid 

 upon the crystals of iron sulphate, and then slowly to add the 

 water. The amount to be used during the day is made in 

 the morning ; if the material is allowed to stand for twenty- 

 four hours or more the salt re-crystallizes, and the applications 

 will not be so efficacious. Skawinski washed the grape wood 

 once during the first days of February. The immediate effect 

 upon the wood is to blacken it, and if this color is not uni- 

 formly shown, a second application is made to those portions 

 which were not touched by the first treatment. The above 

 formula has not been uniformly adopted in France, for some 

 growers prefer to increase the amount of acid, and others de- 

 crease the amount of iron salt. But as the practice of spraying 

 with such a solution has been well established, and since good 

 results generally follow the treatment, it is safe to say that so 

 long as the plants are uninjured, the use of a definite formula 

 is of minor importance. 



In 1890 Dr. G. Patrigeon gave the following directions re- 

 garding the treatment of grape mildew. 2 He advised that the 

 first application be made about the middle of May in southern 

 France, and during the first week in June in the more northern 



1 This grade of acid was used because it is less dangerous to handle. 



2 Jour. <.VAg. Prat. 1890, May 8, 660. 



