i MILK 53 



60 C., and on evaporation should not leave the least trace 

 behind. After the above-mentioned final shaking the 

 measuring cylinder and its contents are left undisturbed for 

 6 hours, so as to give the fat-containing ether time to separate 

 completely. 1 



The ethereal solution of fat is now taken from the cylinder 

 with the help of two tubes, which are fitted into a cork that 

 exactly fits the mouth of the cylinder. One of the tubes which 

 is bent at right angles only just passes through the cork, the 

 other is longer and more bent, and has an internal diameter of 

 3-4 mm. The cork with the tubes it contains is fitted to the 

 mouth of the cylinder, and the longer tube, which is to serve 

 as a syphon, is pushed down into the ether until it is exactly 

 1*5 c.c. above the dividing line of the two liquids. By blowing 

 carefully into the shorter tube, the ether is forced into the 

 longer one, and as this is arranged as a syphon the ether flows 

 of its own accord. Instead of blowing into the tube, the 

 rubber ball and tube used in Soxhlet's apparatus (p. 38) 

 may be employed. The ether-benzine solution is collected in 

 a tared flask of 100-150 c.c. contents with a fairly wide neck. 

 By blowing carefully into the shorter tube the last few drops 

 can be forced from the syphon, but care must be exercised, 

 otherwise the liquid below the ether passes over as well. The 

 1*5 c.c. ether- fat solution which remain in the cylinder are 

 exactly equivalent to the weight of 0'27 g. milk. As the 

 amount of milk taken for the test was 10'27 g., the . fat, 

 dissolved in ether-benzine, from 10 g. of milk has been 

 removed by the syphon. 



After evaporating or distilling off the ether-benzine the fat 

 which remains is dried at 100 C. for several hours and weighed. 

 The dry fat must be clear and fluid like oil, and not possess the 

 least smell of benzine. When the weight of the fat which is 

 left is multiplied by 10, the percentage of fat in the milk is 

 obtained without further calculation. With whole milk the 

 Rose-Gottlieb and the extraction methods give results which 

 agree very closely, but with separated milk and buttermilk the 

 former always shows higher values. The differences, on an 



1 M. Popp, Milch-Zeitung, 1904, No. 20, has shown that the result is not 

 influenced if only one hour is allowed for the separation. He also states that 

 the specific gravity of the ammonia does not need to be exactly 0'96, but that 

 it may vary between 0*91 and 0*96 without introducing an error. 



