1910.] PUBLIC DOCUMENT — No. 31. 139 



ADDITIONAL NOTES FOR METHODS IN 

 FAT ANALYSIS.' 



BT E. B. HOLLAND^ M.SC. 



In the titration of saponification and acid nnmbcrs of the 

 fat, and neutralization number of the insoluble acids, 1 cubic 

 centimeter of indicator should be used. This has been our prac- 

 tice for some years, though not so stated in the methods, and 

 gives a more definite end point, especially in the case of acid 

 number. The writer has also noted the rather ambiguous state- 

 ments relative to desired temperature for the above titrations. 

 A temperature of 40° to 4,5° C. has proved very satisfactory. 

 It is sufficiently high to maintain the soaps and fatty acids in 

 solution and yet not destroy the sensitiveness of the indicator. 

 Slight saponification may take place in the determination of 

 acid number, but the error is less than the opposite fault of too 

 great chilling. 



Sulfuric acid is preferable to hydrochloric for the decompo- 

 sition of the soap in the determination of insoluble acids; 150 

 cubic centimeters of water together with 5 cubic centimeters of 

 sulfuric acid (1-4) clears the solution rapidly with little appar- 

 ent action on the fatty acids. 



The variable results in iodine number at a high temperature 

 are evidently due to volatilization of iodine and not to a second- 

 ary reaction. Moistening of the cork stopper with potassium 

 iodide solution will reduce the loss, but not prevent it, if the 

 temperature exceeds 10° to 15° C. 



' Massachusetts Agricultural Experiment Station, twenty-first report (1909), pp. 120-138. 



