FOODS 75 



grm. Then by proportion 10-305 : 100 : : 0-326 : x = 

 3-16 grm. of fat in 100 grm. of milk, or 3-16 per cent. 



Adams' Process. Using a Soxhlet apparatus is the 

 official method of the Society of Public Analysts. 



Take a strip of Adams' fat-free paper, and from a pipette 

 spot over it 5 c.c. of milk sample. Dry the paper high over 

 a Bunsen flame, and finally in the water-oven. Roll paper 

 up into a coil, and put it into a Soxhlet apparatus attached 

 below to a clean dry flask (wide-mouthed) of known weight 

 and above to an invert condenser. Sufficient ether (specific 

 gravity 0-720) should be used to fill the Soxhlet tube to the 

 top of the siphon one and a half times. The flask is sup- 

 ported in an evaporating-basin containing water. The 

 basin is heated by a small flame. The ether evaporates 

 and is condensed, running back over the paper, soaking it, 

 and filling the tube until, when the level reaches the top of 

 the siphon, the latter acts and empties the whole amount 

 back into the flask, carrying with it the dissolved fat. 

 Twelve such siphonings at least should take place, and 

 then (the flame being meanwhile withdrawn), the condenser 

 is fixed in the usual position, and the ether distilled over. 

 The flask is then detached and dried in the water-oven 

 (laid on its side) to a constant weight. The weight obtained, 

 less the weight of the flask, gives the weight of fat in 5 c.c. 

 of milk sample, and this is calculated out as in above 

 example to a percentage. 



Never heat the flask containing ether over a naked flame, 

 but in a vessel of water at about 60 C., keeping the ether 

 in a gentle state of ebullition. 



Gerber's Process is somewhat similar, using a Gerber 

 apparatus. 



Leffmann-Beam Process. Using a special set of graduated 

 bottles and a special centrifugal machine. Into one of 

 the bottles 15 c.c. of sample are introduced by means of a 

 pipette, and then 3 c.c. of a mixture of equal parts of amylic 

 alcohol and strong HC1, and these are thoroughly mixed. 

 Then 9 c.c. of pure concentrated sulphuric acid are added 

 slowly, i c.c. at a time, shaking after each addition. The 

 milk will gradually assume a chocolate colour passing on to 

 a deep brown. Now fill up bottle to zero mark with a hot 

 and freshly-made mixture of one part of sulphuric acid to 



