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dinary mixture, institutes strong arguments in its favour. The latter 

 argument, however, has now been found to have been much un- 

 derstated, for direct determinations of the copper sulphate recover- 

 able from these mixtures by the action of carbon dioxide, prove 

 the existence of secondary reactions, which greatly increase the 

 above mentioned proportion. In the case of reaction 4), the ord- 

 inary Bordeaux mixture, a secondary reaction sets in between the 

 calcium carbonate and the copper sulphate which further reduces 

 its efficiency. 



The Soda Bordeaux, a mixture of copper sulphate and sodium 

 carbonate has been suggested as a substitute for ordinary Bordeaux, 

 as being less likely to scorch the foliage. 



The reaction requires the addition of 1.84 parts of the crystal- 

 lised carbonate (ordinary washing soda) to one part of the crystal- 

 lised sulphate; but the mixture on standing becomes altered and 

 nearly all the copper remaining in solution, changes into carbo- 

 nate 2 Cu 2, C o 2 , H 2 o, which is malachite. This change is not 

 prevented in practice but only delayed and only o.ooi to 0.002 of 

 the copper remains in solution and this amount is probably too 

 small to have an appreciable fungicidal action. 



The action of soluble copper compounds on foliage was in- 

 vestigated by immerging leaves in the solutions. In the case ot 

 compounds which are insoluble to start with, the leaves had to be 

 wetted with them and then exposed to the action of the air. 



A further investigation of the action of various copper com- 

 pounds on foliage was made by spraying them on growing trees. 



Numerous series of experiments made in these ways with the 

 various Bordeaux compounds, gave values which agreed remark- 

 ably well with the conclusions drawn as to their relative efficiency 

 from the study of their chemical composition and behaviour alluded 

 to above. 



This is of special importance with reference to the Bordeaux 

 paste, which has already come into extensive use as a cheap and 

 labour-saving substitute for the ordinary mixture. So far as re- 

 ports received up to the present are concerned, its effect seems 

 to be satisfactory, and to be equal to that of the ordinary freshly 

 prepared Bordeaux mixture. 



The Woburn Bordeaux requires i ounce of copper sulphate, 6 3 /4 

 pints of lime water and 4 l / 2 gallons of water. Sulphate of copper 

 gr. 28.35. kime water, 1. 3.83. Water, 1. 29.53. 



Messrs W. Voss of Slengall Road Millwall E. who have been 



