TUE MONTHLY lUII-LETIN. 175 



juUlcd (a slijilit cxc&ss of allcali is better than to have free oil). Too 

 imicli nlkiili will izivo a frothy npixmrinico to llic soap in eookinf^; to 

 DVi'rcouie this more oil may he; added and the cookinj^ continued a short 

 time. If a dark brown liquid settles out durinj? the cooking with a 

 layer of soap floating on the surface, the alkali used was largely soda 

 and a hnrd snap lias i-esulted. A little soap left in the kettle will assist 

 the sapouiiyiiig action of the next soap making. 



MISCIBLE OILS. 



Oil and water are very incompatible and, in order that a uniform 

 mixture or emulsion may be made, a third substance must be employed, 

 such as soap, which will dissolve in oil and in this way prepare the two 

 for mixing. Ordinary soap is but slightly solu])le in petroleum oils, 

 but the presence of cresylic acid adds very greatly to the solubility of 

 the soap in oil, so that cresylic acid, in the form of cresol soap, has 

 become one of the most important emulsifiers of petroleum oils. 



The chief use of cresol soap is in making miscible oils, or for making 

 petroleum oil emulsions, instead of by means of fish oil soap or other 

 emulsifiers. The commercial form of cresolated oil emulsions may con- 

 tain 85 to 90 per cent petroleum oil, w^liile other forms of commercial 

 oil emulsions generally contain about 60 per cent of petroleum oils. 



Cresol Soap. 



FORMULA. 



Fish oil 1 gallon (Heat to 290 or 300 degrees 



Cresylic acid 1-5 gallon - Fahrenheit and then add 



Caustic soda 0.5 pound ( kerosene and water. 



Kerosene 3 gallons 



"Water 2 gallons 



(Petroleum oil, either kerosene or distillate or crude oil, to be added 

 to the above soap when spray solution is wanted.) 



Place the soda and the oil in the kettle and heat until the alkali is 

 dissolved ; if desired a little water may be used for dissolving the 

 potash, then add the cresylic acid^ and heat the mixture to 290 or 300 

 degrees Fahrenheit. When this point is reached the boiling slakens 

 and a quantity of very heavy dark fumes is given off; the mixture 

 should now be removed from the fire ; while still warm — but at a dis- 

 tance from the fire — add the kerosene and afterwards add tw^o gallons 

 of water. If this is added before the kerosene an explosion may re^sult. 



Liquid cresol soap may be kept indefinitely without breaking down, 

 but not after making into a miscible oil. The soap is mixed cold with 

 distillate or crude oil ; the volume of oil used can only be determined 

 by experiment, but will probably vary from five to ten times the volume 

 of soap. This combination of soap and oil is called a miscible oil, and 

 upon the addition of water should give a good emulsion with no free oil. 

 If free oil is present an insufficient quantity of soap was used or else 

 the preparation was not mixed well. The soap and oil may be com- 

 bined at any time to form the miscible oil, but if the latter stands 

 after the mixing it should be stirred well before being used for making 

 emulsions. When water is added to the miscible oil it should be done 



'Delaware Bui. No. 75. In tliis bulletin several formulae are given for cresol 

 emulsifiers, but instead of cresylic acid, the grade of carbolic acid known as "straw 

 color," 100 per cent pure, is recommended. 



