CHAPTER IV 

 FATS AND PHOSPHATIDES 



I. Fats 



The fats found in the animal body are mainly the triglycerides 

 of palmitic, stearic and oleic acids. Olive oil and lard are con- 

 venient materials for laboratory study. Butter or mutton tallow 

 may be used with equal advantage. 



1. Solubility. Test the solubility of olive oil and lard in 

 water, cold and hot alcohol, ether and chloroform. To 3 c.c. of 

 solvent add 2 drops of oil or a small piece of lard. Note : Do 

 not heat alcohol over the free flame. Heat some water to the 

 boiling point in a small beaker. Turn out the flame and warm 

 the alcohol by dipping the test tube in the hot water. 



2. Formation of Crystals. Many fats will crystallize in small 

 needles from warm alcohol, benzol, etc. 



3. Place a drop of oil or a small piece of lard on a filter 

 paper. Observe the transparent spot. This test may be used to 

 detect the presence of a fat in a solvent. On evaporation of the 

 solvent a transparent spot remains on the paper if fat was pres- 

 ent in solution. 



4. Preparation of a Neutral Oil (Mathews). Most commer- 

 cial fats and oils contain some free fatty acid. To get a neutral 

 oil this free acid must be neutralized. 



To about 25 c.c. of 95% alcohol in a small flask add about !/2 

 c.c. phenolphthalein solution. Heat to boiling on the steam bath 

 and from a pipette add 0.5% NaOH (dilute 10% twenty times) 

 until a faint pink coloration remains. Now add 6 c.c. of oil. 

 Again heat to boiling, then stopper the flask and shake gently. 

 The alkaline alcohol becomes colorless as the alkali is neutralized 

 by the fatty acids present. Continue the addition of NaOH as 



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