110 



Perhaps the most common source of de-emulsification is the presence 

 of calcium or magnesium in the water that is used as a diluent. The 

 presence of these salts with the oil leads to the formation of an insoluble 

 calcium or magnesium soap, which are products of reversion and tend 

 to form "water in oil" emulsions. The addition of Bordeaux mixture 

 to the diluted spray solution prevents this reaction. This recommenda- 

 tion is based upon a statement made in the fore part of the discussion, 

 that a colloid solution has two phases — a solid and a liquid. A fuller 

 explanation is given in the following paragraphs. 



Although emulsions can be made with even extreme amounts of 

 water or soap, there is a practical optimum amount of each of these 

 constituents. Judging from our experiments, the optimum amount of 

 soap is from one to two pounds per gallon of oil, and that of water 

 from % to y2 gallon for each gallon of oil. It has been found neces- 

 sary, in order to get a good emulsion, to use from 1 J/2 to 2 pounds of 

 soap with many of the waters used by orchardists for spraying in this 

 state. Emulsions made with varying amounts of soap and water 

 were tested as to their ability to kill scale. The following tables show 



the results. 



Table III 



These tables would seem to indicate that as far as kill of scale is 

 concerned, there is little to choose between an emulsion made with either 

 one or two pounds of soap and % gallon or J4 gallon of water per gallon 

 of oil, but laboratory experiments showed conclusively that a stock 

 emulsion made with % gallon of water to each gallon of oil was less 

 likely to be broken down from cold, because of a lower freezing point. 

 In addition to this, an emulsion made with y^ gallon of water requires 

 less space for storage. Using this amount of water in the stock emulsion, 

 a dilution of three gallons in a hundred of water would give slightly 

 more than a 2% solution, and for a 3% strength, four gallons to the 

 hundred would be sufficient. 



