130 EXPERIMENT STATION. [Jan. 



(6) Neutralization Number. 

 The neutralization number (n) of the volatile fatty acids can 

 be readily calculated from the mean molecular weight (m) by 

 means of the formula : — 



56158 



6. Soluble Fatty Acids. 

 The soluble fatty acids indicate the percentage of fatty acids 

 in an oil, fat or wax that is soluble in water. ^ The percentage 

 of soluble fatty acids can be readily calculated by difference, — 

 total fatty acids less the insoluble. 



(a) Neutralization Numher. 



The neutralization number indicates the milligrams of po- 

 tassium hydrate required to saturate 1 gram of soluble fatty 

 acids. The difference between the saponification number of the 

 fat and the product of the percentage of insoluble fatty acids 

 times their neutralization number indicates the milligrams of 

 potassium hydrate required to neutralize the soluble fatty acids 

 in 1 gram of fat, which, divided by the percentage of soluble 

 fatty acids, gives the neutralization number of the soluble fatty 

 acids. 



(b) Mean Molecular Weight. 



The molecular weight (m) of the soluble fatty acids can be 

 calculated from the neutralization number (n) by means of the 

 formula : — 



56158 



7. Insoluble Fatty Acids and Unsaponifiable Matter 

 (IIehner Number). 



The Hehner number indicates the percentage of insoluble 

 fatty acids and unsaponifiable matter in an oil, fat or wax. 



Reagents. — Glycerol-soda solution, 100 cubic centimeters 

 of sodium hydrate solution (equal parts of soda and water fil- 



1 This may mean either hot or cold water, according to the method employed. 



