519 



manufacture. The copper in Bordeaux mixture paste is always in 

 such a physical condition as to be nearly worthless for the purposes 

 for which it is intended, and the purchase of Bordeaux mixture paste 

 is a waste of time and money. 



Rabat^ (E.). Les bouillies riches en sulfate de cuivre ; quality des 

 bouillies cupriques. [Sprays rich in copper sulphate ; the 

 properties of cupric sprays.] — Rev. Vilic, Paris, xUi, no. 1088, 

 6th May 1915, pp. 377-381. 



After recording the properties required of a good cupric spray 

 solution, various methods of determining the presence of small 

 quantities of copper are described. The following solutions are 

 particularly rich in copper : — A pure j per cent, solution of copper 

 sulphate ; a 1 per cent, solution of verdigris ; a solution of ammonia 

 and copper oxide ; a solution of 2 lb. copper sulphate and 47 liquid oz. 

 of 22° ammonia in 20 gals, water. The value of a spray depends 

 also on the quantity and quality of the copper deposit in reserve on 

 the foliage. In solutions very rich in soluble copper the clear fluid 

 above the precipitate is usually blue in colour, but some commercial 

 solutions were found to be coloured with methylene blue ; this gave 

 a beautiful blue colour, but no soluble copper was present. A 

 concentrated solution of sodium hyposulphite will remove all trace 

 of colour from a solution of copper sulphate. If a solution of sodium 

 carbonate is poured into the colourless fluid, no more precipitate is 

 formed, provided the sulphate is free from salts of iron or zinc. This 

 method is recommended as a test for purity. Another way of 

 detecting the presence of iron is provided by the addition, firstly of 

 a little nitric acid to the copper sulphate solution, in order to 

 superoxidize the iron, and then of an excess of ammonia ; the resultant 

 light blue fluid will be clear if the sulphate is pure, while flakes of 

 ferric oxide will be seen in the liquid if iron is present. In order not 

 to confuse necessary laboratory research with the results obtained in 

 cultural practice, it suffices to say that various acid, neutral or basic 

 sprays, rich in soluble copper, have proved of great value against 

 mildew. Among such may be mentioned Bordeaux mixture containing 

 2 per cent, of copper sulphate with the addition of one of the 

 following : — J per cent, of copper sulphate added just before use, 

 producing a slightly acid solution ; | per cent, of ammonia, producing 

 a light bhie alkaline solution ; yV to xV per cent, of casein mixed in 

 water with an equal quantity of powdered or paste lime ; 1 per cent, 

 of molasses thinned witli water. 



FoNZEs-DiACON (— ). Sur les bouillies cupriques. [Copper spray 

 mixtures.]— ^ev. Vitic, Paris, xhi, no. 1088, 6th May 1915, 

 pp. 384-385. 



It has been found by various chemists that in Bordeaux mixtures 

 the greater part of the copper is rendered insoluble in the form of 

 basic sulphates, the basicity varying more or less directly with the 

 quantity of lime used to precipitate a given weight of copper sulphate. 

 The bluish green precipitate of the acid mixtures consists principally 

 of tctracupric sulphate, which is present in greater proportion at the 



