102 MASS. EXPERIMENT STATION BULLETIN 166. 



Monoglycerides and diglycerides apparently never occur in nature nor, 

 to any appreciable amount, in freshly prepared oils and fats. The pres- 

 ence of free fatty acids indicates previous hydrolysis of the triglycerides, 

 and hydrolysis conditions the presence of monoglycerides and diglycerides; 

 therefore the so-called ether number loses its definite character as free 

 acids increase. 



Calculated Data from Saponification, Acid and Ether Numbers. 

 Glycerol. — In the saponification of any triglyceride, 3 molecules, or 

 168.324 parts, of potassium hydroxide combine with 1 molecule of fat, 

 setting free 1 molecule, or 92.064 parts, of glycerol; therefore 1 gram of 

 potassium hydroxide is equivalent to .54695 gram of glycerol. 



(RCOO)3C3H5+3 KOH =C3H5(OH)3+3 RCOOK 

 fat alkali glycerol salt 



The percentage of glycerol (G) can be calculated from the ether number 

 (e) by means of the formula ^ — 



G =.00054695 e 



(1) 



This formula is not applicable in the case of fats containing monoglyc- 

 erides and diglycerides. The higher the saponification number or, in 

 other words, the lower the mean molecular weight of the constituent 

 acids, the greater the proportion of glycerol. Monoglycerides and diglyc- 

 erides contain a larger proportion of glycerol than the triglycerides. 



Total Fatty Acids. — In the saponification of a fat, 3 molecules, or 

 54.048 parts, of water are required for every molecule, or 92.064 parts, of 

 glycerol separated. 



(RCOO)3C3H6+3 H2O =C3H5(OH)3+3 RCOOH 

 54.048 92.064 



The percentage of total fatty acids (T) in 1.00 part of fat can be calcu- 

 lated from the percentage of glycerol (G) by means of the formula 2 — 



^•"" 92.064^ 

 and substituting the value of glycerol in terms of ether number (e) : — 



rn 1 r^r. /38.016 \ 



T = 1.00 - {^^^^ X .00054695 e j or 

 1.00 - .00022585 e ' (2) 



' Zulkowski, Ber. Deut. Chem. Gesell. 16, p. 1140. 2 Loc. cit., p. 1315. 



