10 Dec, 1918.] Copper Fungicides for Vine Diseases. 737 



In 1911, they recommended a formula for what they termed a 

 colloidal copper soap, as follows: — 



(a) Dissolve 500 grammes (1.1 lbs.) in 50 litres (11 gallons) 

 water. 



{h) Dissolve 2,000 grammes (4.4 lbs.) in 50 litres water. 

 When mixing the two solutions, the usual procedure should be reversed, 

 and the copper _ poured into the soap solution, in.stead of soap into 

 copper. Operating thus, instead of a voluminous greasy precipitate of 

 copper soap, an opaque bluish-green liquid is obtained, which has a 

 surface tension as low as that of a simple solution of alkaline soap, 

 which wets the bunches, just as alcohol would. The same authors 

 recommended, a couple of years later, in view of the difficulty of 

 procuring soaps rich in soda oleate, the preparation of a home-made 

 castor-oil soap, as follows : — 



Castor oil, 1 kilo. (2.2 lbs.). 



Caustic soda, 150 grammes (5^ ozs.). 



Water, 250 c.c. (9 fluid ounces). 



The caustic soda is dissolved in the water, and the hot solution stirred 

 into the oil. The mixture soon thickens to such an extent as to prevent 

 further stirring; it should then be left to itself for twelve hours. This 

 soap is extremely soluble in water. 



Rosin soap mixture (Bouillie a la colophane) figures in most French 

 viticultural text books. This may be dealt with here, though, strictly- 

 speaking, it should be considered under the heading of copper soda, since 

 rosin is more usually added to that spray mixture than to Bordeaux. 

 Ravaz* mentions it as follows — it is worthy of note that he does not say 

 much for or against its use : — 



Colophane (Rosin) is a mixture of dift'erent fatty acids; in combination with 

 soda it forms a soap which serves for the preparation of spray mixtures. The 

 rosin floats on the surface, forming a thick froth which thoroughly wets the green 

 parts of the vine. In order to prepare a mixture, dissolve 2i lbs. soda carbonate 

 in a gallon of water; heat to boiling point, and add 2^ lbs. powdered rosin. Stir 

 until dissolved. This soap is then poured into the copper sulphate solution, and 

 carbonate of soda added until neutralisation takes place. Tliis spray mixture 

 was first suggested by ^l. Perraud. Jt ha^ given good results. 



Several of the household soaps in general use here contain up to 20 

 per cent, of rosin. A rosin soap mixture may thus be made by simply 

 stirring a certain proportion of a solution of such a soap into the spray 

 mixture. The quantity required to communicate sufficient wetting 

 power can be determined, as recommended by Ravaz, by dipping a vine 

 leaf into the mixture. If this remains pi'operly wetted after withdrawal, 

 the proportion of rosin soap is. sufficient. 



Concerning the addition of soap to Bordeaux generally, it is worthy 

 of note that of late it has gone quite out of fashion in France. Casein 

 seems, in fact, to have altogether displaced it; this substance possesses 

 all the virtues of soap, in the direction of increased wetting power and 

 adhesiveness, without its defects; so much so that Vermorel and Dan- 

 tony, who have contributed so m.any interesting articles concerning soap 

 mixtures a few years back, have now abandoned their soap formulae in 

 favour of the addition of casein mixture to ordinary Bordeaux mixture. 



* Le M'ddion, p. 176. 

 17628.— 2 



