56 MILK ANALYSIS 



volumetrically in the filtrate by means of standard silver nitrate 

 and potassium chromate indicator and calculated to sodium 

 chlorid. 



Adulteration with Foreign Fats. — The chief adulteiration of 

 butter consists in the substitution of foreign fats, especially the 

 product known as oleomargarin. 



When fats are saponified and the soap treated with acid, the 

 individual fatty acids are obtained. It is upon the recognition 

 of the peculiar acid radicles existing in butter that the most 

 satisfactory method of distinguishing it from other fats is based. 

 Since the relative proportion of these radicles differs in dif- 

 ferent samples, the quantitative estimation cannot be made 

 with accuracy; but when the foreign fats are substituted to 

 the extent of 20 per cent, or more, the adulteration can be 

 detected with certainty and an approximate quantitative deter- 

 mination made. 



The detection of adulteration of butter-fat by other fats is 

 generally carried out by the determination of the volatile acid, 

 but some other confirmatory processes are occasionally em- 

 ployed. 



Volatile Acids. — This method was first suggested by Hehner 

 & Angell, but was systematized by Reichert, and hence is gen- 

 erally called the Reichert process. In this form it is carried 

 out by saponifying 2.5 grams of the fat, adding excess of sul- 

 furic acid, distilling a definite portion of the liquid, and titrat- 

 ing the distillate with ~- alkali. The number of cubic centi- 

 meters of this solution required to overcome the acidity of the 

 distillate is called the Reichert number. E. Meissl suggested 

 the use of 5 grams, and the number so obtained is called the 

 Reichcrt-Mcissl number. Alcoholic solution of potassium hy- 

 droxid was originally used for saponification, but the solution 

 devised by Leffmann & Beam, namely, sodium hydroxid in 

 glycerol, is more satisfactory. The reagents and operation 

 arc as follows: 



