1228 ACIDS OF THE ACETIC SEMES. 



Laurie or Laurostearic acid. C n H 23 . COOH. 

 Myristic acid. C 13 H 27 . COOH. 



These occur as neutral fats in spermaceti, in butter and 

 other fats. They present no points of interest. 



Palmitic acid. C 15 H 31 . COOH. 



Stearic acid. C 17 H 35 . COOH. 



These are solid, colourless when pure, tasteless, odourless, 

 crystalline bodies, the former melting at 62° C, the latter at 

 69*2° C. In water they are quite insoluble; palmitic acid is 

 more readily soluble in cold alcohol than stearic : both are 

 readily dissolved by hot alcohol, ether, or chloroform. Glacial 

 acetic acid dissolves them in large quantity, the solution being 

 assisted by warming. They readily form soaps with the alkalis, 

 also with many other metals. The varying solubilities of their 

 barium salts afford the means of separating them when mixed : 

 this method may also be applied to many others of the higher 

 members of this series. 



These acids in combination with glycerin (see below), to- 

 gether with the analogous compound of oleic acid, form the 

 principal constituents of human fat. As salts of calcium they 

 occur in the freces and in k adipocire,' and probably in chyle, 

 blood and serous fluids, as salts of sodium. They are found in 

 the free state in decomposing pus, and in the caseous deposits 

 of tuberculosis. 



Adipocire. When animal (proteid) tissues are buried for 

 some time in damp ground or otherwise exposed to moisture in 

 the absence of any free supply of oxygen they are frequently 

 found to have undergone a peculiar change by which they are 

 converted into a waxy or fatty substance. This is known as 

 adipocire. It consists not of true neutral fats but of the am- 

 monium, and in some cases calcium, salts of the highest fatty 

 acids palmitic and stearic, or of the free acids themselves. 

 Practically nothing is definitely known as to the agencies and 

 mode of this conversion. It may be the result of a purely 

 chemical change or perhaps it is more probably due to the 

 action of some micro-organism. On either view of its forma- 

 tion the occurrence of adipocire is of extreme interest as shew- 

 ing a possible direct formation of the higher fatty acids and 

 hence of fats from proteids. It is however supposed by some 

 authors that the adipocire is formed entirely by change and 

 aggregation from the fats present in the tissues at death. This 

 view is probably incorrect. 



