146 The Spraying of Plants. 



These ingredients are mixed in a definite order : 



(a) Dissolve the soap in the insecticide. 



(6) Add this solution to the water of preparation, and agitate. 



(c) The water of dilution may then be added, and the emul- 

 sion again thoroughly agitated. 



In America the method followed is to dissolve the soap in the 

 "water of preparation," after which the oil is added. This 

 mixture is then thoroughly agitated, commonly by means of a 

 force-pump, until all the oil is emulsified. If the liquids are 

 hot, an emulsion may be produced more easily. 



FERROCYANIDE OF POTASSIUM; YELLOW PRUSSIATE OF 

 POTASH; K 4 FECY 6 . The only value this material possesses in 

 connection with spraying is to assist in making the Bordeaux 

 mixture, and to serve as a test for discovering the presence 

 of sulphate of iron. The test solution may be made by dis- 

 solving the compound in water : 



Ferrocyanide of potassium 1 ounce. 



Water 1 pint. 



The test solution forms a reddish-brown precipitate, or discol- 

 oration (the ferrocyanide of copper, Cu 2 FeCy fi ), with a dissolved 

 copper salt, but a blue precipitate with an iron salt. See page 

 151. 



FISH-OIL SOAP. 



Crystal potash lye 1 pound. 



Fish-oil 3 pints. 



Soft water 3 gallons. 



Dissolve the lye in the water, and when boiling, add the oil, 

 and boil for two hours. One pound of the soap may be dissolved 

 in 5 to 10 gallons of water. This is of value as an insecticide 



FLOUR. Flour is sometimes added to liquids to render them 

 more adhesive. It may be used at the rate of 1 pound to 40 

 or 50 gallons of the preparation, but such additions are rarely, 

 if ever, advisable. An exception may be made in the case of 

 powders, especially those containing the arsenites. With these, 

 the addition of flour, at the rate of five to ten times the bulk of 

 the poison, may be of service in rendering the mixture more ad- 

 herent to the foliage. But this condition is often followed by 



