432 SMITH'S INTERMEDIATE CHEMISTRY 



Fats and Oils. The fats and oils found in the bodies of 

 animals, or pressed from the seeds of plants, are composed mainly 

 of various esters (p. 349). As such, they are formed by the inter- 

 action of a tribasic alcohol, glycerine C 3 H 5 (OH) 3 , with higher 

 acids of the paraffin and olefine series of hydrocarbons, such as 

 the saturated acids Ci 5 H 3 i.COOH (palmitic acid) and CnHgs.COOH 

 (stearic acid), and the unsaturated acid Ci 7 H 3 3.COOH (oleic acid). 

 For example : 



C 3 H 5 (OH) 3 + 3H(COO.C 15 H 31 )<= C 3 H 5 (COO.C 15 H 31 ) 3 + 3H 2 O 



glycerine palmitic acid glyceryl palmitate 



The glycerine esters of the saturated acids are solid at ordinary 

 temperatures (fats), while those of the unsaturated acids are 

 liquid (oils). Beef suet is a mixture of about three-fourths 

 glyceryl palmitate (rj^lmiLiii) C 3 H 5 (C0 2 Ci 5 H 3 i) 3 and glyceryl 

 stearate (sj^rjn,) C 3 H 5 (C0 2 Ci7H 3 5) 3 , and one-fourth glyceryl 

 oleate (olejn) C 3 H 5 (C0 2 Ci 7 H 33 ) 3 . Hog lard contains about 40 

 per cent of the former and 60 per cent of the latter, and is 

 therefore softer. Butter includes the same esters, with about 

 14 per cent of water. When butter is dried, the remaining fat 

 contains about 8 per cent of glyceryl butyrate (butyrin) 

 CsHstCC^C-jH?)-?. Olive oil contains 75 per cent of olein. Cot- 

 ton seed oil is similar in nature. 



All these fats and oils contain, also, a small amount of the 

 free adds. They must not be confused with mineral oils like 

 petroleum, which are mixtures of hydrocarbons. 



Oleomargarine is an artificial butter. It is made by straining 

 melted beef fat and allowing it to stand at 24. Much of the 

 stearin crystallizes out and the remaining liquid (the " oleomar- 

 garine ") is pressed out and allowed to solidify. The solid is 

 finally mixed with a little of some oil, to render it softer, and is 

 churned with milk to impart the proper flavor. Although it 

 lacks the butyrin, the product is similar in chemical nature to 

 butter, and just as nutritious and wholesome. 



