CHEMIC COMPOSITION OF THE HUMAN BODY n 



sazone is the most characteristic, and occurs in the form of long, yellow 

 needles. It may be obtained from dextrose by the following method: 

 To 50 c.c. of a dextrose solution add 2 gm. of phenyl-hydrazin and 2 gm. 

 of sodium acetate, and boil for an hour. On cooling, the osazone crystal- 

 lizes in the form of long, yellow needles. 



THE FATS 



The fats constitute a group of organic bodies found in the tissues of 

 both vegetables and animals. In the vegetable world they are largely 

 found in fruits, seeds, and nuts, where they probably originate from a 

 transformation of the carbohydrates. In the animal body the fats are 

 found largely in the subcutaneous tissue, in the marrow of bones, in and 

 around various internal organs and in milk. In these situations fat is 

 contained in small, round or polygon-shaped vesicles, which i are united by 

 areolar tissue and surrounded by blood-vessels. At the temperature of the 

 body the fat is liquid, but after death it soon solidifies from the loss of heat. 



The fats are compounds consisting of carbon, hydrogen, and oxygen. 

 The percentage composition of fat (stearin) is as follows: Carbon, 76.86; 

 hydrogen, 12.36; oxygen, 10.78. The fat found in animals is a mixture, in 

 varying proportions in different animals, of three neutral fats stearin, 

 palmitin, and olein. Each fat is a derivative of glycerin and the particular 

 acid indicated by its name e.g., stearic acid, in the case of stearin, etc. 

 The reaction which takes place in the combination of glycerin and the 

 acid is expressed in the following equation: 



C 3 H 6 (OH) 3 + 3 H.C 18 H 3 50 2 -. C 3 H ft (C 18 H 3fi 2 ) 3 + 3 H 2 O. 

 Glycerin. Stearic Acid. Stearin. Water. 



Hence, strictly speaking, the fats are compound ethers, in which the 

 hydrogen of the organic acid is replaced by the trivalent radical, tritenyl, 

 C 3 H 5 . 



Stearin, C 3 H 5 (C 18 H 35 O 2 ) 3 , is the chief constituent of the more solid 

 fats. It is solid at ordinary temperatures, melting at 55C., then solidify- 

 ing again as the temperature rises, until at 7iC. it melts permanently. It 

 crystallizes in square tables. 



Palmitin, C 3 H 5 (C 16 H 31 O 2 ) 3 is a semifluid fat, solid at 45C. and 

 melting at 62C. It crystallizes in fine needles, and is soluble in ether. 



Olein, C 3 H 5 (C 18 H 33 O 2 ) 3 , is a colorless, transparent fluid, liquid at 

 ordinary temperatures, only solidifying at oC. It possesses marked 

 solvent powers, and holds stearin and palmitin in solution at the temperature 

 of the body. 



Saponification. When subjected to the action of superheated steam, 

 a neutral fat is saponified i.e., decomposed into glycerin and the particular 

 acid indicated by the name of the fat used: e.g., stearic, palmitic, or oleic. 

 The reaction is expressed as follows: 



CACC, 8 H 83 2 ) S + 3H 2 - C 3 H S (OH) 3 + 3 C 18 H 34 2 

 Olein. Water. Glycerin. Oleic Acid. 



The fat acids thus obtained are characterized by certain chemic fea- 

 tures, as follows: 



Stearic acid is a firm, white solid, fusible at 69C. It is soluble in 

 ether and alcohol, but not in water. 



