DAIRY PRODUCTS. 97 



and caustic potash are employed, wheu the volume of the ether-fat so- 

 lution separated is sensibly constant and the time employed in separa- 

 tion sensibly the same. These conditions can only be secured by the 

 use of the centrifugal machine described. 



I propose to use a centrifugal apparatus also for assisting in the sepa- 

 ration of the ether-fat solution in the lactobutyrometer ; and it has al- 

 ready proved its usefulness in separating precipitates which subside 

 very slowly. 



I am of the opinion that such a machine would prove of great value 

 jn every chemical laboratory aside from its utility in determining the 

 fats in milk. 



Cronander 1 has proposed the following method of estimating the fat 

 in milk : 



A glass flask of 200 to 250cc. capacity, and two glass tubes constitute 

 the chief parts of the apparatus. One of the tubes is furnished with 

 a scale dividing it into ten equal parts. Below the last division the 

 scale is expanded into a bulb, below which the tube extends for about 

 5cm. The other tube is bent to an obtuse angle and serves for the in- 

 troduction of hot water into the flask to drive the fat into the measur- 

 ing tube at the end of the operation. Both tubes are fastened to a cork 

 stopper in such a manner as to have the measuring-tube end even with 

 the under surface of the stopper, while the other extends almost to the 

 bottom of the flask. 



Of the milk to be analyzed lOOcc. are taken at 17.5 0., lOcc. potash lye 

 (200 grams to the litre) added and 30cc. aqueous ether. The flask is 

 corked and thoroughly shaken. The ether-fat solution collects at the 

 top (after one hour), and after evaporating the ether the residual fat is 

 forced into the measuring tube by pouring water at 70 C. to 80 0. into 

 the flask. The volume of the fat is thus determined and its per cent, 

 can be calculated. 



LIEBERMANN'S METHOD. 2 



This method, like that of Soxhlet's, depends on the separation of a 

 fat from a mixture of milk and caustic potash by shaking it with 

 ether. 



Apparatus. (1) A glass cylinder with ground glass-stopper, 26cm. 

 higli and 3.5cm. diameter. (2) Burettes of the form shown in Figs. 3, 4. 

 (3) A glass flask holding from 45 to 47cc., according to size of burette 

 employed ; neck 1cm. diameter, with edge ground accurately in a hori- 

 zontal plane. (4) Four pipettes, two of 50cc. and one each of 20cc. and 

 5cc. Before beginning the operation the flask is graduated as follows: 



The burette, Fig. 3, is filled to the zero-point with pure water at the 

 temperature of the working room. The water is now run out of the 



1 Milchzeitung, vol. 11, pp. 161-164. 



2 Zeit. Anal. Clicm., 1883, p. 383; 1884, p. 476; 1884, p. 87, 

 19330 No. 13 7 



