24 MILK 



flask, lo grams of powdered potassium sulfate 

 and IS to 25 c.c. (ordinarily about 20 c.c.) of the 

 strong sulfuric acid are added and the diges- 

 tion conducted as follows: The flask is placed 

 in an inclined position and heated below the 

 boiling-point of the acid for from five to fifteen 

 minutes, or until frothing has ceased. Excessive 

 frothing may be prevented by the addition of 

 a small piece of paraffin. The heat is raised 

 until the acid boils briskly. A small, short- 

 stemmed funnel may be placed in the mouth 

 of the flask to restrict the circulation of air. 

 No further attention is required until the liquid 

 has become clear and colorless, or not deeper 

 than a pale straw. 



When Kjeldahl operations are carried out in 

 limited number, the arrangement used in my 

 laboratory has been found very satisfactory. A 

 double-Y, terra cotta drain-pipe, about 20 cm. 

 internal diameter, is connected by an elbow 

 directly with the chimney-stack. The digestion 

 flasks are supported as shown in the rough 

 sketch, figure i (not drawn exactly to scale). 

 Two flasks can be operated at once. The 

 central opening is convenient for other opera- 

 tions producing fumes. Openings not in use 

 are closed by circles of heavy asbestos. 



Apparatus for use when many determinations 

 are made are figured in the catalogs of supply- 



