MATERIALS 27 



A wooden or stoneware vessel must be used for the 

 solution, as it acts on iron and zinc. 



9. Copper basic sulphate {Bordeaux mixture). — A 

 number of different compounds are formed when 

 lime is added to copper sulphate, according to the 

 proportions used, but they all behave similarly in 

 reproducing by exposure to air a certain amount of 

 ordinary copper sulphate, which acts as a fungicide ; 

 but the proportion of this which is thus reproduced 

 varies in different cases, so that some of the mixtures 

 are much more effective than others, or, what comes 

 to the same thing, the same degree of effectiveness 

 may be obtained at the expense of different amounts 

 of copper taken. The amount of lime used in making 

 Bordeaux mixture can only be regulated accurately 

 when used in the form of the clear solution known as 

 lime-water (see p. 37). The instructions for making 

 Bordeaux mixture with this are — 



(9^:) Copper sulphate . . .10 ozs. 

 Lime-water . . . .8^ galls. 

 Water to make up to . .10 galls. 



Dissolve the copper sulphate separately in about 

 half a gallon of the water. Put about half a pound 

 of quicklime, previously slaked (see p.'36), in a tub 

 with 12 to 15 gallons of water; stir this up once or 

 twice, and then leave it to settle. When the liquid 

 is quite clear, run S^- gallons of it off into the solution 

 of copper sulphate. Add whatever extra water is 

 required to make the whole up to 10 gallons. 



The lime-water may vary a little in strength, so 

 that it is absolutely necessary to test the mixture to 



