FUNGICIDES AND THEIR APPLICATION 91 



gallon, previously slaked as directed with part of the water, 

 in the other. To make i per cent, mixture an equal quantity 

 of each is separately diluted by the addition of four times as 

 much water, and the two lots then mixed as before, so that to 

 make 50 gallons of mixture, 5 gallons of copper stock solution 

 is mixed with 20 gallons of water, and 5 gallons of lime stock 

 solution with the like amount. The stock solutions may, if 

 desired, be made up at double the strength given above. They 

 keep well if covered, but if evaporation has taken place should 

 be made up with water to the previous level. 



Where water at the required level is available, it is an advan- 

 tage to have the stock solutions and dilution barrels on a raised 

 platform, so that the solutions can be run by gravity into the 

 mixing barrel, and if this is also raised the mixture can be again 

 run into the sprayers. 



Testing. 



When the indicated amount of good lime has been used the 

 mixture cannot contain unaltered copper sulphate, but to guard 

 against mistakes, and when the quality of the lime is uncertain, 

 it is advisable to test the mixture. There are three ways of 

 doing this : — 



(i) A fresh solution of potassium ferrocyanide is prepared by 

 dissolving a crystal of this substance in a few spoonfuls of water. 

 A piece of white blotting paper is moistened with the Bordeaux, 

 or a little is poured into a white plate, and a drop or two of the 

 testing solution added. A brown discoloration indicates that 

 more milk of lime is required. 



(2) A piece of blue litmus paper is dipped into the mixture. 

 If it turns red, add more milk of lime. 



(3) A bright iron nail (avoid steel) is allowed to stand for 

 some minutes in a little of the mixture. If a black deposit or a 

 coating of metallic copper is formed on the nail, add more milk 

 of lime. 



Bordeaux Paste. 

 The thick creamy compound known as Bordeaux paste is 

 used for application to bark or exposed wood, or for any similar 

 purpose in which a temporary paint protective against fungus 

 infection is required. It is prepared by dissolving i lb. of copper 

 sulphate in i gallon of water (or using i gallon of 10 per cent, 

 stock solution) and separately slaking 2 lb. of lime in \ gallon of 

 water. When the latter is cooled the two are stirred together. 

 The addition of milk (i pint or more to the gallon) or sugar 

 (4 ounces to the gallon) greatly improves its keeping qualities. 



Burgundy Mixture. 

 Preparation. 



A mixture which closely resembles Bordeaux and is regarded 

 as interchangeable with it in use is prepared in a similar way 



