56 FRUIT TREES AND THEIR ENEMIES 



the higher proportions being used for hardier trees, 

 or when the plants are not in leaf. 



The solution should be used as soon as it is made, 

 as it decomposes on being kept. Liver of sulphur 

 never dissolves entirely in water, as it always contains 

 an excess of sulphur. 



The addition of soft soap to this mixture — i to 2 

 lbs. to every lo gallons — makes it more effective as 

 an insecticide for aphis, etc., and still better results 

 may be obtained by combining it with a paraffin 

 emulsion ; this may be done by churning 1 6 to 24 ozs. 

 of paraffin and i to 2 lbs. of soap with the sulphide 

 solution, or making an emulsion with iron sulphate 

 similar to \6d, but using water with potassium sulphide 

 dissolved in it, instead of plain water. As the sulphide 

 reacts with the basic sulphate of iron, the proportion 

 of the former should be increased, and that of the 

 latter reduced. The following proportions will be 

 found suitable — 



(24^) Iron sulphate . . 2 ozs. 



Quicklime . . . i oz. 



Paraffin (solar distillate) 16 to 24 ozs. 



Potassium sulphide . 4 to 6 ozs. 



Water to make up to . 10 galls. 



The iron sulphate is dissolved in some of the water, 

 the lime, as a milk, is mixed with it, and the paraffin 

 churned in ; the rest of the water, with the sulphide 

 dissolved in it, is then added. 



Vegetable poisons. — Many of these have been 

 tried as insecticides, but few of them have been found 

 to be of much use, except Hellebore, Nicotine, 



