LEFFMANN-BEAM METHOD. 



349 



is mixed with a small quantity of a mixture of amyl alcohol, 

 C 5 H n OH, and hydrochloric acid, whereby the casein is coagu- 

 lated. Strong sulphuric acid is then added, in which the casein 

 dissolves, the whole liquid becoming hot from the action of the 

 sulphuric acid upon the water. The amyl alcohol aids in the 

 separation of the fat, most probably because it is a common 

 solvent for fat and the acid liquid. The emulsified fat thus 

 speedily separates and by centrifugal action forms a distinct 

 and clear layer above the acid liquor, which usually takes a 

 dark purple colour. The operation is carried out in small 



Leffniann-Beam flask. One-half natural size. 



flask-like vessels provided with narrow graduated necks, and 

 the separation of the fatty layer is effected by a centrifuge 

 driven by toothed gearing. The mode of performing the test 

 may briefly be described thus : 15 c.c. of milk are run into the 

 vessel from a pipette, 3 c.c. of a mixture of equal volumes of 

 amyl alcohol and strong hydrochloric are then added and the 

 whole shaken. 9 c.c. of sulphuric acid of specific gravity 1'835 

 at 15 C. are then run slowly into the vessel with frequent 

 mixing ; the mixing is best done by rotating the flask in the 

 hand, care being taken to avoid loss of the contents and also 



