ii BUTTER 151 



soda (100 g. in 100 c.c. water) added. The flask is then heated 

 over a small flame, the contents being kept in movement for a 

 few minutes. When the water has all evaporated the liquid 

 ceases to boil and becomes quite clear. 



The soap is dissolved in 90 c.c. of boiling water, a few pieces 

 of pumice stone dropped into the flask, and then 50 c.c. of 

 sulphuric acid (25 c.c. concentrated acid per litre) added. The 

 caustic soda solution mentioned above ought to be neutralised 

 by 30-35 c.c. of this dilute sulphuric acid. After the addition 

 of the acid the flask is connected at once with the condenser 

 and 110 c.c. distilled over as usual, the time of distillation 



FIG. 61. Distillation Apparatus for Reichert-Meissl Method. 



being from 30 to 40 minutes. The distillate is then shaken, 

 filtered through a dry filter, and titrated with .2V/ 10 caustic 

 soda solution in the same way as before. 



Leffmann and Beam's modification is simpler and more 

 convenient than the original method, and as it is quite as 

 accurate it is to be preferred. 



Whether the original or modified method be used, a blank 

 experiment without the fat should always be made with the 

 reagents which are to be used in the analysis. Generally a 

 few tenths of a cubic centimetre of caustic soda are needed to 

 neutralise the distillate, and this quantity must be deducted 

 from the analysis. In Fig. 61 is shown the arrangement of 



