MILK 



55 



D.R.G.M. 



graduation marks is narrow. This tube possesses the advantage 

 that the volume of fat-containing ether which is drawn off 

 here with a pipette, not a syphon, can be easily read. 



Recently Rohrig has modified the original Gottlieb cylinder 

 by affixing to the side a glass tap through which an aliquot 

 part of the ethereal solution can be drawn off direct into a 

 tared flask. The apparatus is very convenient 

 to work with. 



Another modification of the Gottlieb 

 cylinder is in the form of a glass tube about 

 37 cm. long, and internal diameter 2 cm. 

 The tube is rounded at the bottom so that 

 it can be placed in a suitable support and 

 has only two marks, one at 19 c.c. and the 

 other at 70'5 c.c. As a rule the boundary 

 between the cloudy and the clear layer lies 

 at 17'5 c.c. (if the milk is not unusually 

 rich in fat). If, therefore, in syphoning off 

 the ether the lower end of the syphon is 

 placed at the division 19 c.c., there remains 

 behind exactly 1*5 c.c. On the other hand, 

 the total volume of liquid in the tube is 

 generally about 70'5 c.c. before any is drawn 

 off. 



For whole milk and for exact analyses of 

 separated milk the completely graduated 

 cylinder must be used, but for ordinary determination with 

 separated milk the above-described simpler and considerably 

 cheaper tube can be used. In the analysis of separated milk 

 the line between the two layers of liquid comes practically 

 always to the same position in the tube. 



FIG. 20. Rohrig's 

 Tube for Gottlieb 

 Method. 



5. Liebermann-Sztkelys l Method. 



In this method petroleum ether alone is used as a solvent for 

 the fat. 



After the specific gravity of the milk has been determined by 

 Soxhlet's lactometer or the Westphal balance, 50 c.c. of milk at 

 room temperature are brought into a graduated cylinder about 



1 Zeitschrift. f. anal. Ghemie, Vol. XXXII, 1893, p. 168. 



