STEARIC ACID. Ill 



Stearic acid Margaric acid Fusing point 



1) .... 30 parts to 10 parts .... 65'5 



2) .... 25 10 .... 65 



3) .... 20 10 .... 64 



4) .... 15 10 ,, .... 61 



5) .... 10 10 .... 58 



6) .... 10 15 ... 57 



7) .... 10 20 .... 56'5 



8) .... 10 ,, 25 .... 56'3 



9) .... 10 30 .... 56 



Both pure margaric and pure stearic acids, after having been 

 fused and again allowed to solidify, are perfectly crystalline ; stearic 

 acid, however, forms small confused crystals, while margaric acid 

 forms larger acicular crystals ; a mixture of the two acids is however, 

 in this state, far less crystalline, and presents rather a porcelain- 

 like, opaque, and brittle appearance. 



Physiological Relations, 



Occurrence. Like margaric acid, stearic acid occurs in most 

 animal fats ; it is, however, always found in less quantity than 

 margaric acid, and in some cases appears to be altogether absent ; 

 or, at least, our present chemical appliances fail in detecting it. In 

 the fat of the cellular tissue it exists like margaric acid in combina- 

 tion with glycerine ; it never occurs free unless in association with 

 margaric acid ; it is, however, of much rarer occurrence than free 

 margaric acid, and occurs in much smaller quantity. 



Origin. As stearic acid is never found in vegetable fats, it 

 must be primarily formed in the animal body, where, indeed, its 

 formation may be readily explained. As it consists of 2 atoms of 

 margaric acid minus 1 atom of oxygen, we may regard it as pro- 

 duced from margaric acid, to which it stands, as we have seen, in 

 the same relation as hyposulphuric acid to sulphuric acid, for 

 S 2 5 : S0 3 =(C 34 H 33 ) 2 5 : (C 34 H 33 )O 3 . 



In which part of the system this conversion occurs we do not at 

 present know : that it takes place in the blood is improbable, 

 because we assume that the fats are directly oxidised in the blood, 

 and are decomposed into the oxides of simpler radicals. That this 

 conversion takes place in the primte vice is, at all events, incapable 

 of demonstration. 



We shall speak of the uses of stearic acid in the animal 

 organism, in our remarks on the fats in general. 



