246 IIT. CHEMISTRY OF NEUTRAL FATS 



the values are from 6 to 8, while in the case of other edible fats the lleichert- 

 Meissl values are less than 1.0. However, the figures in the case of palm 

 QJpo9 jj^g^y glightly exceed 1 (0.9-1.9). Porpoise and dolphin oils give ex- 

 tremely high Reichert-Meissl numbers (40-90) ; this is to be traced to the 

 isovaleric acid which makes up such a large proportion of the triglycerides 

 of these marine fats. However, these are not classed as edible fats and 

 their odor prevents their use for the adulteration of butter. Wool fat is re- 

 ported^"^ as having a Reichert-Meissl value as high as 8. 



The presence of animal fats or of coconut oil in butter in appreciable 

 amounts can readily be detected by the application of this test. Lewko- 

 witsch^^* has stated that, although it is possible to prepare a fat mixture 

 which duplicates butter insofar as refractive index, saponification value, 

 iodine number, and melting point are concerned, such a mixture invariably 

 falls short in simulating the Reichert-Meissl value of butter. 



(.9) Polenske Numher^^'^-^^^ 



This constant is the number of milliliters of 0.1 N alkali required to neu- 

 tralize the insoluble volatile fatty acid distilled from five grams of fat. Ap- 

 preciable values for this constant are given only by those fats which have a 

 sizable proportion of capric, lauric, and/or myristic acids in their tri- 

 glycerides. Coconut oil gives the highest Polenske values (16.8-17.8), 

 while palm oil is another edible fat which also gives a high figure (8.5- 

 11.0); butter fats yield values which vary between 1.5 and 3.0. Wood- 

 man^'^^ indicates that the addition of coconut oil to butter fat, to the extent 

 of 10%, will increase the Polenske number by about 1.0. 



The so-called Kirschner^^*'^^^ value is sometimes employed to assist in the 

 determination of the proportion of butter fat in a mixture. This value is 

 obtained from the titrated Reichert-Meissl distillate by precipitation of the 

 higher volatile soluble fatty acids as the silver salts and by a reestimation 

 of the remaining soluble volatile fatty acids on the filtrate. The Kirsch- 

 ner values for butter fat are reported as 19 to 2G, while coconut oil gives a 

 figure of 1.9 and palm kernel oil one of 1.0. For the majority of fats and 

 oils, the values range^^^ between 0.1 and 0.2. The appreciable Kirschner 

 values given by coconut oil and palm kernel oil, neither of which contains 

 butyric acid, indicate that the method for separation of butyric from ca- 

 proic and caprylic acids on the basis of solubility of the silver salts is not an 

 absolute one. 



(10) Acetyl Number 



The acetyl value is the number of milligrams of potassium hydroxide re- 

 quired to neutralize the acetic acid liberated from one gram of acetylated fat or 



352 E. Polenske, Arb. kaiserl. Gesundh., 20, 545-558 (1904). 



353 H. Leffmann and W. Beam, Analyst, 16, 153 (1891). 



'" A. Kirschner, Z. Untersuch. Nahr. Genussm., 9, 65-70 (1905). 

 "s C. Revis and E. R. Bolton, Analyst, 36, 333-342 (1911). 



