IMPROVED METHODS FOR FAT ANALYSIS. 



109 



See derivation of formula (14) and table "Percentage of Fatty Acids 

 and Glycerol in Triglycerides." 



Mean Molecular Weight and Saponification Number of the Glycerides of 

 Soluble Acids. — The mean molecular weight (m2) and saponification 

 number ($2) of the glycerides of the soluble acids can be calculated from 

 the molecular weight (m) of the soluble acids: — 



m2= 3 m+ 38.016 

 _ 3X56108 



See table "Saponification Number of Triglycerides." 



From the above formulas factors were deduced for the soluble acids 

 enumerated below, by means of which the percentage of triglycerides and 

 of glycerol may be calculated readily from the percentage of fatty acids. 



Acid. 



Factor for Per 



Cent, of 

 Triglycerides. 



Factor for 



Per Cent, of 



Glycerol. 



Acetic, 



Butyric, 



Valeric, 



Caproic, 



Caprylic, 



Capric, 



1.21109 

 1.14390 

 1.12414 

 1.10915 

 1.08792 

 1.07361 



.51119 

 .34847 

 .30063 

 .26433 

 .21292 

 .17825 



Reichert-Meissl Number. 



The Reichert-Meissl number^ indicates the number of cubic centi- 

 meters of N/10 potassium hydroxide required to neutralize that portion 

 of the volatile fatty acids which is obtained from 5 grams of an oil, fat 

 or wax by the Reichert distillation process.^ 



Reagents. — Glycerol potash solution: 120 grams of potassium hydroxide, 

 free from carbonate, to 1,000 cubic centimeters of pure glycerol, heated 

 sufficiently to dissolve the alkali (about 115° C.). 



Sulfuric acid: 1 to 4. 



N/10 potassium (or sodium) hydroxide. 



Phenolphthalein solution: 1 gram to 100 cubic centimeters of alcohol, 

 neutralized. 



Method. — Into an Erlenmeyer flask of 300 cubic centimeters capacity 

 are brought 5 grams of fat, care being taken to avoid getting any fat on 

 the sides of the flask, together with 20 cubic centimeters of glycerol 

 potash, heated over a small naked flame and rotated continuously until 

 the saponification is complete, as shown by the solution becoming per- 



' The Reichert-Meissl number is about 2.2 times as great as the Reichert. — Lewkowitsch, Anal- 

 ysis of Oils, Fats and Waxes, 1, p. 417, 0913). 

 » Ztachr. Analyt. Chem. 18, pp. 68-73 (1879). 



