IMPKOVED METHODS FOK FAT ANALYSIS. 113 



Volatile Acids. 



The percentage of volatile acids (V) can be calculated from the weight 

 (w) of the salts obtained, the quantity (v) of N/10 alkali used (as shown 

 above), and the weight (wi) of fat taken for the Reichert-Meissl deter- 

 mination by the formula — 



y ^ 1.1 (w -.0021992 V ) 



Wi 



The percentage of volatile acids (V) can be calculated in a like manner 

 from the Reichert-Meissl number and the neutralization number (n) of 

 the volatile acids by the formula — 



V = 



0.2 R-M. No. X 5.6108 



Formulas for calculating the amount of triglycerides of the volatile 

 fatty acids, the mean molecular weight and sa'ponijication number of the 

 triglycerides, and glycerol content will be found under like headings of 

 "Soluble Acids." 



Polenske Number. 



The Polenske number indicates the number of cubic centimeters of 

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

 insoluble volatUe 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 hydrox- 

 ide, 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. 



Alcohol : redistilled, free from acids and aldehydes. 



N/10 potassium (or sodium) hydroxide. 



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

 neutralized. 



Cotton blue 6B solution: 2 grams to 100 cubic centimeters of alcohol. 

 The indicator should be boiled in a flask under a reflux condenser for two 

 hours and then filtered. 



Method. — The method can be conducted in connection with the 

 Reichert-Meissl test, and may be considered supplementary to it. A 

 vertical condenser should be employed with a circulation of water ad- 

 equate to chill the distillate to 20° C, and the test carried out as usual. 

 The resulting distillate is chilled fifteen minutes at 15° C, carefully 

 mixed by reversing the flask several times (avoiding any shaking), and 

 poured through a dry 11 centimeter filter. The condenser, 110 cubic cen- 

 timeter flask and filter are washed three times in succession with 15 cubic 

 centimeter portions of water to remove soluble acids, and the wash waters 

 thrown away. The insoluble volatile acids in the condenser, 110 cubic 



