160 SCIENCE AND FRUIT GROWING 



mixture, perfect emulsification occurs at once. To such emul- 

 sions caustic soda may be added without causing decomposition, 

 at any rate in the case of the emulsion with iron sulphate. With 

 the copper sulphate emulsion, decomposition does occur, but 

 only gradually, and only if the emulsion is concentrated : the 

 cause of this decomposition has been ascertained, but it is not 

 necessary to explain it here. In both cases it is preferable, 

 if a strong stock emulsion is required (i. e. of about ten times the 

 strength indicated below), not to add the caustic soda till the 

 emulsion has been diluted preparatory to its being used, for, 

 even in the case of the caustic iron emulsions, de-emulsification 

 is liable to occur on shaking when the emulsions are very con- 

 centrated. Where a fungicidal effect is not required, iron instead 

 of copper sulphate should be used, and in all cases a com- 

 paratively high boiling paraffin oil, such as solar distillate, is 

 preferable to ordinary lighting oil. 



For use in summer as a fungicide and insecticide, where no 

 caustic action is required, the following recipe is given 



Copper sulphate . . .10 oz. 

 Water . . . . . ij gallons 

 Clear lime water . . 8J gallons 



Paraffin ..... 22\ oz. 



The sulphate is dissolved in the water, and the solution added 

 to the lime water, after which the paraffin is churned up with 

 the mixture. The resulting emulsion will be of about the same 

 density as water, and will, therefore, show very little tendency 

 either to rise or to sink. This emulsion can be manufactured 

 of ten times the strength indicated, and diluted with water 

 when required. 



For winter use, as a fungicide and detergent, the following 

 are the proportions recommended 



Copper sulphate . . ij Ibs. 



Quick lime . . . . J to J Ib. ' 



Water . . . . 9i gallons 



Paraffin . . . . .5 pints 



Caustic soda . . . . 2j Ibs. 



The emulsion is made as in the previous case (though the 

 lime water need not be clear), the caustic soda being added just 

 before use. 



