10 Feb., 1919.] Copper Fungicides for Vine Diseases. 105 



soda or potash, especially the latter, for the lime of Bordeaux mixture. 

 The pouring of soda carbonate crystals previously dissolved in water into 

 a solution of copper sulphate results in the formation of sulphate of 

 soda and copper hydro carbonate, which is a colloidal copper compound, 

 very adherent to the leaves. In the experiment of M. Aime Girard, the 

 cupro-sodic mixture, or Bouillie hourguignonne, or copper hydrocar- 

 bonate, Bouillie has proved one of the most adherent, a fact which has 

 been noted in the vineyards. . . . Bouillie hourguignonne does not 

 clog or obstruct spray pumps to such an extent as Bordeaux mixture, 

 but it has not proved superior to it in its effects. The addition of treacle, 

 according to M. Michel Perret, increases its adherence. The best 

 formula is as follows : — 



Copper sulphate (dissolved in 10 litres (2.2 gals.) water, 2 kilos 

 (4.4 lbs.). 



Soda carbonate crystals (dissolved in 10 litres water), 3 kilos 

 (6.6 lbs.). 



Water, SO litres (17^ gallons). 

 First dissolve the copper sulphate in water, hot if possible, and pour into 

 this solution the solution of the soda crystals, complete the mixture by 

 adding the water." 



Further improvements were subsequently made. As is now well 

 known, there is considerable advantage, so far as the fineness of the 

 precipitate is concerned, in mixing dilute instead of concentrated solu- 

 tions. The method of preparing copper soda most usually followed in 

 French vineyards of recent years has been as follows : — 



" On the one part a solution is made of the quantity of sulphate of 

 copper needed for a hectolitre (22 gallons) of spray mixture in 90 litres 

 of water (about 20 gallons). On the other part, the requisite quantity 

 of soda carbonate is dissolved in 10 litres of water (about 2 gallons). 

 The second solution is poured into the first with brisk stirring. In this 

 way a pale-blue mixture is obtained."* 



Anhydrous soda carbonate has of recent years been largely substi- 

 tuted for the soda carbonate crystals ordinary washing soda). In 

 France, the former is generally known as Solvay carbonate, and is much 

 the same as what is known here as soda ash, though the percentage of 

 pure soda carbonate in the two is not identical. 



As the carbonate of soda usually employed is anhydrous and of constant 

 strength ( Solvay carbonate of soda ) , the quantity of this salt necessary to 

 saturate to the desired measure the solution of copper sulphate can in practice 

 be fixed, and this is a great advantage of Bouillie hourguignonne. 



In other words, with copper soda the ingredients can be weighed 

 instead of it being necessary to check with test papers, as in the case of 

 Bordeairx mixture. 



Chemistry of Copper Soda. 

 Copper sulphate, being an acid salt, burns the green tissues of the 

 vine unless it be in solution so dilute as to provide insufficient protection. 

 This acidity must be neutralized for the double purpose of avoiding 

 damage to foliage, &c., and of leaving a sufiicient " reserve of copper " 

 to insure adequate protection, and for a sufficient length of time. In the 

 case of Bordeaux, this harmful acidity is neutralized with lime ; in that 



* L. Ravaz, in La Mildiou. 1914, p. 143. According to the usual French fonnula this would mean, 

 for 1 hectolitre (22 gallons), 2 kilos, (nearly 4} lbs) copper sulphate, and 3 kilos (just over 6^ lbs.) 

 washing soda. 



