PREPARATION OF KEROSENE OIL EMULSIONS. 37 



of water, if first thinned with a small quantity of the liquid. In using 

 the emulsion for killing scale-insects (perhaps the most difificult of in- 

 sects to be destroyed by it), the kerosene butter should be diluted with 

 water from twelve to sixteen times, or one pint of butter to one gallon 

 and a half of water. Dilute only as needed for immediate use. {Re- 

 port of the Commissioner of Agriculture for the Years 1881, 1882, pp. 

 T13-114.) 



A soap emulsion. — Dr. J. C. Neal, also a special agent of the U. S. 

 Department of Agriculture — as the result of his experiments with 

 various emulsions of kerosene oil, recommends very highly the following: 



Four pounds of rosin soap — common bar or yellow soap, dissolved 

 in one gallon of water, with heat. Add gradually one gallon of kerosene 

 with constant agitation. A gelatinous compound is formed which is 

 very stable. 



A gallon of this emulsion, containing fifty per cent of kerosene, costs 

 twenty-six cents. 



Reducing the above by the addition of forty-nine gallons of water, 

 gives one per cent of kerosene, costing a little more than half a cent 

 per gallon. 



This reduced emulsion is of a milky color and is quite permanent. 

 Dr. Neal was satisfied that with it, thoroughly applied, all the cotton- 

 worms reached by it, were killed without injury to the plants. {Bulletin 

 No. I. U. S. Dept. Agricul. — Division of Entomology, 1883, pjD. 32, 42.) 



Later, Mr. H. G. Hubbard reports that further experiments made by 

 him with kerosene emulsions prove that various soaps can be readily 

 made to combine with the oil, and that the soap and kerosene emulsions 

 are as effective as those formed with milk. The use of soap materially 

 reduces the cost, except where milk is abundant and cheap. 



Common bar soap, soft soap and whale oil soap have been tried and 

 found to be almost equally good. The following formula is one which 

 has proved in practice useful where a moderate quantity of emulsion is 

 required: 



Kerosene 2 gallons ==67 per cent. 



Common soap or whale oil soap \ pound, ) 



Water i gallon, f ^^ Percent. 



Heat the solution of soap and add it boiling hot to the kerosene. 

 Churn the mixture by means of force-pump and spray nozzle for five or 

 ten minutes. The emulsion, if perfect, forms a cream, which thickens 

 on cooling, and should adhere without oiliness to the surface of glass. 

 Dilute before using, one part of the emulsion with nine parts of cold 

 water. 



The above formula gives three gallons of the emulsion, and makes, 



