FATS AND FIXED OILS 43 



(1) Saturated compounds of the acetic series, (C n H 2n O 2 ). 



Name. Formula. Melting point. 



Butyric acid C 4 H 8 O 2 2 C. 



Caproic acid C 6 H 12 O 2 ~~ I '5 C. 



Capryllic acid . . . . C 8 H 16 O 2 16-5 C. 



Capric acid Ci H 20 O 2 31*4 C. 



Laurie acid C 12 H 24 O 2 43'5 C. 



Myristic acid Ci 4 H 28 O 2 53-8 C. 



Palmitic acid C 16 H 32 O 2 62*0 C. 



Stearic acid C 18 H 36 O 2 6g'2 C. 



Arachidic acid .... C 20 H 40 O 2 75'o C. 



Behenic acid ...'.. C 22 H 44 O 2 83*0 C. 



All these, from butyric acid to stearic acid, inclusive, enter 

 more or less largely into the composition of butter fat. Some 

 of them are present only in very small proportion, but butyric 

 acid, it is estimated, forms something like 5 per cent, of the 

 whole ; and as it is absent, or occurs only in very small pro- 

 portion in other fats, butter fat can be distinguished readily 

 and certainly from all others in this way (p. 26). The 

 butyric acid can be separated more or less completely from 

 the others either by solution in water or by distillation. 



Arachidic acid is a characteristic ingredient of oil of 

 earthnuts (Arachis hypogea). It appears to be practically 

 identical with the theobromic acid obtained from cocoa 

 butter, but the latter melts at a slightly higher temperature, 

 75C. 



(2) Unsaturated acids. 



(A) Series C H H 2n . 2 O 2 . The only important representa- 

 tive of this class is oleic acid, (C 18 H 34 O 2 ), which has 

 already been described. It is a constituent of nearly all 

 the common fats, but predominates in those of lower melting 

 point the oils which are chiefly of vegetable origin. 



(B) Series C n H 2n _ 4 O 2 . The most important member 

 of this series is linoleic acid, C 18 H 32 O 2 . It enters largely 

 into the composition of linseed, hemp, poppy, and nut oils, 

 and it occurs also, in smaller quantity, in olive oil, rapeseed 

 oil, fish oils, etc. 



