1908.] Woburn Experimental Fruit Farm. 57 



themselves round the oil globules, enclosing them in a sort of 

 skin, and thus preventing them from coming into contact with 

 each other and coalescing. Of many substances investigated, 

 the basic sulphates of copper, of iron and of some other metals 

 are amongst the best. It is only necessary to add a little lime 

 to a solution of sulphate of copper or sulphate of iron to obtain 

 a precipitate of the basic sulphates, and, when paraffin is 

 churned up with these, it immediately forms a bulky and fine- 

 grained emulsion, which is quite permanent, and is perfect for 

 spraying purposes. No heating is required, and one or two 

 strokes of a syringe are sufficient to ensure emulsification. 

 The great advantage in using such an emulsifier is that various 

 substances may be mixed with the emulsion, which, had soap 

 been used, could not be added without destroying the emulsion. 

 Thus caustic soda added to an emulsion of paraffin in soft soap 

 destroys the soft soap, and causes the separation of the paraffin ; 

 such a mixture can only be used if it is kept constantly agitated, 

 and, even then, the distribution of the paraffin on the trees is 

 very uneven. With copper or iron sulphates as emulsifiers, 

 the addition of caustic soda produces no de-emulsification. 



When the sulphate of copper is used, the wash will have 

 fungicidal properties, and will, as a matter of fact, contain 

 Bordeaux mixture ; if no fungicidal properties are required, 

 the cheaper sulphate of iron may be used. For winter-washing 

 an emulsion-soda wash, now known as the Woburn Wash, 

 may be made by dissolving 1} lb. of copper sulphate in 8 or 9 

 gallons of water in a wooden pail, adding to it \ lb. of fresh lime ; 

 this should be previously slaked, and made into a milk with 

 water, running it in through a piece of sacking so as to eliminate 

 grits ; the mixture is then churned with 5 pints of paraffin, 

 2 lb. of caustic soda are added and the whole made up to 10 

 gallons. 



When iron sulphate is used the amount of sulphate taken 

 may be reduced to 8 oz. for 10 gallons. It is also possible 

 with iron, but not with copper, to dispense with the lime, 

 increasing the amount of soda to 2\ lb., and adding this before 

 the paraffin, but in both cases lime gives the finest emulsion. 

 A high boiling paraffin, such as solar distillate (which is less than 

 half the price of lighting oil), gives the best results. 



For summer use as an insecticide for caterpillars and aphis, 



