92 



DISEASES OF CROP-PLANTS 



but with ordinary washing soda (crystallized sodium carbonate) 

 substituted for the lime, using i| times the quantity. The 

 formulae for various strengths are given in the following table : — 



The 0.8 strength has been found by S. C. Harland to be the 

 maximum that can be applied to Sea Island cotton without severe 

 injury, and, according to E. J. Butler, the 0.4 mixture is popular in 

 some parts of France and Germany for spraying vines. The 

 addition of milk, ^ pint (5 oz.) to the gallon preserves and in- 

 creases the adhesion of the precipitate, or resin soap can be 

 added to increase adhesion as with Bordeaux. 



Burgundy mixture can be prepared by the ordinary Bordeaux 

 method of mixing equal amounts of the total water, one contain- 

 ing the copper and the other the soda. It may also be con- 

 veniently prepared by dissolving the copper in seven-eighths of 

 the water, and using the remaining one-eighth (as many pints 

 as there are to be gallons of mixture) to dissolve the soda. The 

 latter solution may be made in a bucket or a kerosene tin, the 

 copper solution being then stirred vigorously and the soda 

 solution steadily poured into it. The colder the solutions, the 

 better the precipitate. The mixture should be used fresh unless 

 a preservative has been added. Burgundy paste is prepared in a 

 similar way to Bordeaux paste, and should if possible have 

 milk added. 



Stock solution of copper can be used as for making Bordeaux, 

 but it is better to keep the soda in solid form. 



Testing. 



There is less need to test Burgundy than Bordeaux, provided 

 the soda is of good quality and the weighing accurate. The 

 soda should be crystalline, without much white powder. 



The test is best made with litmus paper, adding more soda if 

 blue litmus is turned red, and more copper solution if the turning 

 of red litmus blue shows that the mixture is more than mildly 

 alkaline. The results of the ferrocyanide test and the iron 

 test do not afford an index to the safety of Burgundy mixture. 



Advantages. 



Where spraying is done on a large scale and lime can be 



