ESTIMATIOX OP TOTAL PROTEINS. 



125 



bisulphate added, and a small drop of mercury. A funnel or 



pear-shaped bulb with an elongated projection is placed in the 



neck of the flask, and heat applied, the flame being gradually 



increased as frothing ceases. In about half an hour the Uquid 



becomes colourless ; it is allowed to cool, diluted with water, 



and transferred to the distillation flask. This may conveniently 



be of copper or brass, and, for ease of manufacture, can be in the 



form of a bottle ; the digestion flask is well washed with water, 



care being taken that any white crystals which form on cooling, 



and become yellow on dilution, are transferred to the distillation 



flask. A cork carrying a dropping funnel with stopcock, and a 



wide tube with one or more bulbs blown on it, which are loosely 



packed with asbestos, is fitted ; one end of the tube is connected 



with a condenser, the other end of which is made to dip just 



N 

 below the surface of 50 c.c. of — sulphuric acid. 



Fig. 11. — Kjoldahl Apparatus. 



One hundred c.c. (more or less) of a 30 per cent, solution of 

 caustic soda, followed by 10 c.c. of a 10 per cent, solution of 

 potassium sulphide, or 1 gramme of sodium hypophosphite, are 

 added through the dropping funnel, and the contents of the 

 flask mixed by rotatory shaking ; a flame is placed beneath 

 the distillation flask, cold water run through the condenser, 

 and the contents distilled till about 200 c.c. have passed over. 

 The tap of the dropping funnel is opened, the flame removed, 

 and the flask disconnected from the condenser ; after washing 

 the latter into the flask containing the distillate, it should be 



If moved. The distillate is titrated with ^ alkali solution,. 



