CONDENSED MILK 49 



well shaken to cause the ether to take up all the fat, taking care 

 not to bring the liquid up into the graduated tube. When the 

 fat is dissolved, the flask is placed in water at about 40°, kept 

 still and the temperature raised slowly until all ether is vaporized, 

 then rapidly until the boiling-point is reached, and this con- 

 tinued until the solution ceases to bubble, and the fat forms a 

 clear layer on the surface of the dark but clear acid solution. 

 The flask should not be shaken while evaporating the ether. 

 Water heated to nearly boiling is now run cautiously into the 

 side-tube until the flask is three-quarters full. If any fat is in 

 the side-tube, it may be removed by blowing gently into it. 

 If the liquid is producing but few bubbles, more hot water should 

 be run in until all the fat is within the limits of the graduation. 

 If the bubbling is still violent when the tube is only three-quarters 

 full, the lower half of the flask should be cooled by immersion 

 in cold water, when the bubbling will nearly cease, and the fat 

 may then be raised into the neck by adding more hot water. 

 The flask may stand for a minute, if necessary to allow the fat 

 column to unite, but it should be measured as soon as possible. 

 The graduation is percentage of fat by weight, based on 5 c.c. 

 of milk (say 5.16 grams). If the sample has been diluted, the 

 reading must be increased by the factor of dilution. 



The process is easy of accurate operation and is especially 

 adapted to materials that do not yield fat to common extraction 

 methods. The special point is to avoid prolonged or excessive 

 heating with the acid liquid, as this will produce lumps of partly 

 carbonized matter. If these form, the operation must be dis- 

 continued and the flask cleaned promptly. This lumpy ma- 

 terial should be distinguished from a brown flocculent matter 

 which rests between the acid and ether layer at the early part 

 of the operation, but which disappears later. 



For the examination of malted cereals, 1.72 grams are taken 

 and introduced by the side-tube, taking care that no more ma- 

 terial adheres than can be washed into the flask by not more 

 6 



