DETERMINATIONS ON FATS 199 
number of cubic centimeters of iodine used in the blank minus the num- 
her used for the sample gives the thiosulphate value of the sample. 
Saponification Number or Koettstorfer Number. Since the amount 
of alkali which will react with a fat is dependent upon the glycerides in it, 
the saponification number is valuable for identifying fats and oils. The 
saponification is the number of milligrams of sodium hydroxide neces- 
sary to saponify 1 gm. fat. 
Reagents. Sodium Hydroxide. Use a N/10 solution each cubic 
centimeter of which contains 0.0040 gm. NaOH and neutralizes 0.0088 
gm. of butyric acid. 
Alcoholic Potash Solution. Dissolve 40 gms. of pure potassium 
hydroxide in 1000 c.c. 95 per cent alcohol. 
Acid Solution. N/2 HCl. 
Indicator. Phenolphthalein. 
Procedure. Conduct the saponification in wide-mouth Erlenmeyer 
flasks of 250 c.c. capacity. Place about 5 gms. of the fat in a tarred 
flask and weigh. Add exactly 2 cubic centimeters of the alcoholic 
potash solution, connect with a reflux condenser and boil for thirty 
minutes or until the fat is completely saponified. Cool and titrate with 
the N/2 hydrochloric acid. The Koettstorfer number is determined 
as follows: Subtract the number of cubic centimeters of hydrochloric 
acid used to neutralize the excess of alkali after saponification from the 
number of cubic centimeters necessary to neutralize the 50 c.c. of alkali 
added; multiply the result by 28.06 and divide by the number of grams 
of fat used. Conduct two blanks using the same pipettes and con- 
ditions. (Official and Provisional Methods, 1912. A. O. A. C.) 
Determination of Volatile Fatty Acids (Reichert-Meissl Method). 
This determination must be carried out under standard conditions. 
Under these, the Reichert-Meissl number is the number of cubic cen- 
timeters of N/10 sodium hydroxide required by the soluble fatty acids 
distilled from 5 gms. of fat. 
Procedure. Into two clean Erlenmeyer flasks weigh 5 gms. of 
the fat. Add 10 c.c. of 95 per cent alcohol and 2 ¢.c. of sodium hydrox- 
ide (100 gms. in 100 c.c. H2O). Attach to a reflux condenser and heat 
on the steam bath until saponification is complete. After the sapon- 
ification, in case alcohol was used, remove this by dipping the flasks in a 
steam bath up to their necks. When the alcohol is nearly gone frothing 
may occur. Dissolve the soap by adding 1385 c.c. of boiled water and 
warming on the water bath until a clear solution results. After the 
solution has cooled to about 60° C., free the fatty acids by adding 8 c.c. 
of dilute sulphuric acid (200 c.c. in 1000 c.c. of water). Connect to a 
