

31 



leutral fats. The neutral fats of the adipose tissue 



of thPWSy generally consist of a mixture of the neutral fats, 

 stea5Jri|i0alnjitin, and olein, the two former being- solid at 

 ordinary temperatures, while olein is fluid, and keeps the 

 other two in solution at the temperature of the body. They 

 are lighter than water : Sp. gr. 0.91-0.94. 



93. Try the reaction of a fresh fat, like lard or olive oil, 

 with a piece of litmus paper. It is neutral ; but, if the fat 

 has been standing for some time and has become rancid, it 

 may be slightly acid. 



94. Test the solubility of a few drops of olive oil in a 

 test tube of water. It mixes when shaken violently, but soon 

 separates at the top on standing. Add now a few drops of a 

 soap solution and shake again. The liquid becomes milky 

 and the fat does not separate. If the oil is not fresh it may 

 be necessary to add a few drops of sodium carbonate to neu- 

 tralize the free acid. 



95. Take a little lard or olive oil, and observe that fat is 

 soluble in ether, also chloroform. Take some of the ethereal 

 solution of lard and let some of it fall upon some paper. The 

 ether soon evaporates but a permanent greasy stain is left. 



96. Shake a few drops of cod-liver oil with a small 

 amount of dilute solution of sodium carbonate. The mass 

 should become white — an emulsion. In an emulsion the 

 particles of oil are broken up into innumerable fine| particles 

 which remain discrete, that is, do not run together. Milk is 

 a typical emulsion. Examine some of the cod-liver oil emul- 

 sion under the microscope. 



97. To about 10 grams (11 cc) of olive oil add 20 cc of a 

 10% solution of caustic potash. Boil the mixture, gently 

 stirring, meanwhile, until the odor of the oil has largely dis- 

 appeared and it appears homogeneous and no oil separates 

 when a few drops are poured into water. This may require 

 half an hour. Add water as the solution evaporates, to keep 

 the original volume. The product is a mixture of potassium 

 soap and glycerine. ' 



98. Convert a portion of the above soap into the sodium 

 or hard soap by adding some saturated salt solution and allow- 

 ing it to stand until cold. It will dissolve on warming. 



