GERBER'S FAT DETERMINATION 209 



The following appliances are necessary for this examination (see 

 Fig. 20): (1) three pipettes of 200, 60 and 10 c.c.; (2) several 

 half liter bottles; (3) two delicate areometers with thermometer, 

 one for whole milk and the other for skimmed milk; (4) one large 

 glass tube (A) adjusted for flowing water; (5) a smaller glass 

 tube (B) enclosed in A; (6) a rubber bulb with a tube; (7) a larger 

 container filled with water heated to 17 to 18 C. Besides these, the 

 following chemicals are necessary: (8) potassium hydroxide solution 

 of specific gravity 1.27 (400 gr. potassium hydroxide is dissolved in 

 water and after the solution has cooled it is made up to 1 liter) ; (9) 

 ether, shaken with one-fifth its volume of water and decanted off; 

 (10) ordinary ether. 



The milk to be examined is warmed in a water bath to 18 C. and 

 is well shaken. By means of a pipette, 200 c.c. of this are drawn 

 off and mixed in a bottle with 10 c.c. of the potassium hydroxide 

 solution. Then, 60 c.c. of ether are added. The bottle is immediately 

 closed by a perfectly tight stopper, is violently shaken and allowed to 

 stand one-fourth hour in water at 18 C., during which time it must be 

 shaken frequently. Gradually, the ether dissolves the fat and a 

 transparent layer is formed on the surface. Now the stopper of 

 the bottle is replaced by another (D) and, by means of a bulb, the 

 transparent fat-containing ether is driven up into the tube B which is 

 surrounded in tube A by water warmed to 18 C. The areometer 

 (C) is in the inner tube, and after the fluid rises so high that it 

 can float, the flow is checked by means of a valve q, then the 

 specific gravity is read. The quantity of fat dissolved is shown, and 

 from this the fat content of the milk can be calculated. Soxhlet's 

 apparatus is accompanied by tables from which the fat content of the 

 milk can easily be read, if one has determined the specific gravity 

 of the fat-ether, and has read its temperature. 



Gerber's acidobutyrometer affords a very convenient 

 and accurate way of determining fat, that is widely 

 used. The method consists in measuring the quantity 

 of fat in an accurately measured quantity of milk, after 

 the fat has been separated and dissolved in amyl-alco- 

 hol. Gerber's instrument (see figs. 21 and 22), consists 

 of a centrifuge, bottles (G) of special shape, and 3 

 pipettes, i.e. : 1 acid pipette to hold 10 c.c.(H) and 2 small 

 pipettes (I, K) of 1 and 11 c.c. capacity. These chem- 



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