44 The Spraying of Plants 



It was stated l by Patrigeon that the addition of 500 grams 

 of dextrine per hectoliter of those fungicides having a solution 

 of copper carbonate for their principal ingredient, would render 

 them more adhesive. The dextrine should first be dissolved in 

 warm water, and then added to the copper solution. 



George Bencker gives an account of the treatments for mil- 

 dew as carried on in 1890, at the School of Agriculture, at 

 Montpellier, France. 2 The experiments were conducted by 

 Duchien. The list of substances used is interesting from the 

 fact that it shows which materials the French at that time con- 

 sidered as having value. The liquids tested were as follows : 



Bordeaux mixture; Bordeaux mixture celeste, containing 

 copper sulphate, lime, sugar, and aluminum calcide ; Bordeaux 

 mixture and glue ; mixture of carbonate of soda and sulphate 

 of copper; gelatinous hydrocarbon ate of copper; verdet ; and 

 a mixture of chloride of calcium and alum. The powders : 

 Skawinski's powder; Skawinski's sulphur; cuprosteatite ; sul- 

 phosteatite ; sulphocyanide of copper ; sulpfaated verdet ; sulphur 

 with the hydrate of copper; sulphated sulphur; cuprophos- 

 phate ; 8 and sulphur and cuprophosphate. 



Verdet was selected as being the most valuable of the above 

 materials, but later work has not substantiated this conclu- 

 sion. Verdet is an acetate of copper. There are many such 

 combinations, all being known under the general name of ver- 

 det, or verdigris. The form used by Bencker was that techni- 

 cally known as the dibasic acetate of copper. It requires to be 

 soaked in water three or four days before it is used, so that as 

 milch as possible will dissolve. It may be applied at the rate 

 of one or two kilos in a hectoliter of water. 



De Capol prepared the hydrate of copper as follows: 4 Dis- 

 solve 2 kilos of copper sulphate in 20 liters of water. To this 

 add 1 liter ammonia. The oxide of copper is precipitated, and 

 when it has settled to the bottom of the vessel the liquid above 

 is drawn off. This liquid contains sulphate of ammonia iu 



1 RuUetin de la Societe des Agriculteurs de Fi ance, 1889, Oct. 15, 795. Also, 

 Jour. d'Ag. Prat. 1890, May 15, 703. 



2 Progres Agrieole, 1890, Dec. 7, 510; Annals Hort. 1890, 82. 



3 This material is easily made by uniting solutions of sodium phosphate and 

 copper sulphate. It is thrown down as a precipitate, the other compounds remain- 

 ing in solution. 



* Jour. d'Ag. Prat. 1889, March 7, 367- 



