FATS. 



509 



Glycerine is a tri-atomic alcohol, C 3 H 5 (OH)3, and unites with (1) the following 

 mono-basic /ay acids (those occurring in the body are printed in italics) : 



1. Formic 



2. Acetic 



3. Propionic 



4. Butyric 

 [Isobutyric 



5. Valerianic 



6. Caproic 



7. CEnanthylic 



8. Caprylic 



9. Pelargonic 



acid, 



CH 2 2 



2 

 C 4 H 8 2 

 C 4 H 8 2 ] 

 CsHio02 

 C 6 H 12 2 

 C 7 H 14 2 

 C 8 H 16 2 

 C 9 H 18 2 



10. Capric acid, CioH2o02 



11. Laurostearic Ci 2 H 24 2 



12. Myristic ,, Ci 4 H 28 2 



13. Palmitic CieH 32 02 

 [Margaric C 17 H 34 2 , 



is a mixture of 13 and 14.] 



14. Stearic acid, Ci 8 H 36 2 



15. Arachinic C 2 oH 40 2 



16. Hyanic C 2S H 50 02 



17. Cerotinic ,, C 



The acids form a homologous series with the formula C n H2n-iO(OH). With 

 every CH 2 added their boiling point rises 19. Those containing most carbon are 

 solid, and non-volatile; those containing less C (up to and including capric acid) 

 are fluid like oil, have a burning acid taste, and a rancid odour. 



The earlier members of the series may be obtained by oxidation from the later, 

 by CH 2 being removed, while C0 2 and H 2 are formed; thus, butyric acid ia 

 obtained from propionic acid. 



Nos. 13 and 14 are found in human and animal fat, less abundant and more 

 inconstant are 12, 11, 6, 8, 10, 4. Some occur in sweat, and in milk (p. 465). 

 Many of them are developed during the decomposition of albumin and gelatin. 

 Most of the above (except 15-17) occur in the contents of the large intestine 

 (p. 376). 



(2.) Glycerine also unites with the mono-basic oleic acid, which also forms a series, 

 whose general formula is CnHan sO(OH) ; and they all contain 2H less than the 

 corresponding members of the fatty acid series. The corresponding fatty acids 

 can be obtained from the oleic acid series and vice versa. Oleic acid (olein-elainic 

 acid), Ci 8 H 34 2 , is the only one found in the organism; united with glycerine, it 

 forms the fluid fat, olein (Gottlieb, 1846). The fat of new-born children contains 

 more glyceride of palmitic and stearic acid than that of adults, which contains 

 more glyceride of oleic acid (L. Langer). Oleic acid also occurs united with 

 alkalies (in soaps), and (like some fatty acids) in the lecithins (p. 36). If lecithin 

 be acted on with barium hydrate, we obtain insoluble stearic, or oleic, or palmitic 

 acids and barium oleate, together with dissolved neurin and baric glycerin- 

 phosphate. It appears as if there were several lecithins, of which the most 

 abundant are the one with stearic acid and that with palmitin + oleic acid radicle 

 (Diakonow). 



The neutral fats, the glycerides of fatty acids, and of oleic acid, are triple 

 ethers of the tri-atomic alcohol glycerine. 



With the neutral fats may be associated glycerin-phosphoric acid, an acid 

 glycerin-ether, formed by the union of glycerine and phosphoric acid, with the 

 giving off of a molecule of water (C 3 H 9 P0 6 ) ; it is a decomposition product of 

 lecithin (p. 36). 



(3.) The glycolic acids (acids of the lactic acid series) have the formula 

 CnH2n-20(OH) 2 . They are formed by oxidation from the fatty acid series by sub- 

 stituting OH (hydroxyl) for 1 atom of H of the fatty acids. Conversely, fatty 

 acids may be obtained from the glycolic acids. The following acids of this series 

 occur in the body : 



(a.) Carbonic Acid (oxy-formic acid) CO (OH) 2 ; in this form, however, it only 

 makes salts. Free carbonic acid or carbon dioxide is an anhydride of the same 

 = C0 2 . 



(6.) Glycolic Acid (oxy-acetic acid), C 2 H 2 (OH) 2 , does not occur free in the body. 



