COMPOSITION OF FAT. 



11 



C. A. Browne states that 1-0 per cent, of dioxystearic acid 

 occurs in butter, and 0-1 per cent, of unsaponifiable matter. 



In this table, butyric, caproic, and caprylic acids have been 

 classed as soluble in water, a"nd the others insoluble ; this is not, 

 strictly speaking, correct, as capric and, probably, lauric acids 

 are also slightly soluble ; on the other hand, caprylic acid pos- 

 sesses so slight a solubility in water that it probably is not wholly 

 dissolved. 



The figure 87-65 per cent, is, however, a near approximation 

 to the mean found for the insoluble fatty acids. The figure 

 for the total amount of glycerol 12-57 also agrees with that found. 



Besides the constituents enumerated above, there also exist 

 in the fat of milk traces of cholesterol (which doubtless replaces 

 a portion of the glycerol), lecithin, a colouring-matter, and 

 possibly also a hydrocarbon. 



Saponification. On boiling with a solution of caustic alkali, 

 the fat undergoes hydrolysis, thus 



R 

 C 3 H 5 R, + 3NaOH = C 3 H 5 (OH) 3 + NaR + NaR, + NaR,, 



R, R / and R /x , representing radicles of the fatty acids. 



If the hydrolysis be carried out in presence of alcohol a portion 

 of the caustic alkali is converted into an alkali ethoxide (alcohol- 

 ate) thus 



NaOH + aH 5 OH = C 2 H 5 OXa + H 2 0. 



This acts in a slightly different manner from the hydroxide, 

 though the ultimate products of hydrolysis are identical. 

 The actions are probably as follows : 



( R 

 *(i.) 3NaOC 2 H 5 + C 3 H 5 ] R^CACONaJg + CAR + CoHgR^-C^R^. 



( R // 



(ii.) C 3 H 5 (ONa) 3 + 30H 2 = C 3 H 5 (OH) 3 + 3NaOH. 

 (iii.) 3NaOH + O,H 5 R + C 2 H 5 R, + C 2 H 5 R, ; 



= 3C 2 H 5 OH + NaR + NaR, + NaR,,. 



* These reactions probably take place in stages, one acid radicle at a 

 time being attacked. 



