200 BUTTER 



lower the proportion of the glycerides of the volatile fatty acids 

 present. 



This is the basis of the process originally proposed by 

 Reichert, and modified later by Meissl, Wollny, and Leffmann 

 and Beam. 



The Reichert-Meissl number may be defined as the number of 



N . . . 



C.C. of — alkali solution equivalent to the fatty acids volatile in 



steam and present in 5 grams of butter. 



192. The Determination of the Reichert-Meissl Nmnber 

 by the Modified Method of Leffmann and 

 Beam. 



Exactly 5 grams of butter-fat from a sample that 

 has been melted and filtered free from casein, etc., are 

 weighed out into a 300 c.c. round-bottomed flask, and 

 20 c.c. glycerine and 2 c.c. caustic-soda solution, con- 

 taining I gram NaOH per c.c, are added. 



By gently heating the flask the water is driven off, 

 as shown by the fact that the solution becomes clear, 

 and the heating should be continued until this clarifica- 

 tion has taken place. The glycerides present in the 

 butter have now been hydrolysed to glycerine and the 

 sodium salts of the various fatty acids. The fatty acids 

 themselves are then liberated from the sodium salts by 

 dissolving the latter in 90 c.c. hot water, and adding 

 50 c.c. of dilute H2SO4 (2J per cent, concentrated acid 

 by volume) to the mixture in the flask. The flask is 

 then connected to a water-trap fitted to a condenser 

 (see Fig. 28), and distillation immediately commenced 

 into a flask graduated on the neck to 100 c.c. 

 and no c.c. 



The rate of distillation should be so adjusted that 

 the 1 10 c.c. mark is reached in from thirty to forty 

 minutes. The distillate is then filtered through a dry 



