44 MILK AND DAIRY PRODUCTS PART 



The author, though, has found that it is more satisfactory 

 to measure the ether and also the caustic potash solution from 

 a burette. 



Naumann 1 has carefully worked out the details of this 

 method, and the following description is based upon his 

 results. The necessary reagents are : 



Caustic Potash Solution. Eight hundred g. stick caustic potash are dis- 

 solved in a moderate quantity of water, and, after cooling, 600 g. glycerine 

 and 200 g. copper hydrate (to be obtained from Th. Schuchardt, Gorlitz) 

 are added, and the mixture made up to 3 litres. After three or four days, 

 during which time it should be shaken each day, the solution is ready for use. 

 The addition of the copper makes the dividing line between the light and 

 dark field more prominent. 



Ether. This should be saturated with -water, which can be done by shaking 

 the ether four times with distilled water, fresh water being added each time. 

 The ether must have a temperature of 17 '5 C. when it is used. 



Acetic Acid. Ordinary glacial. 



After the milk has been thoroughly mixed, 30 c.c. should 

 be drawn out by means of the self-filling pipette, which is done 

 by immersing the pipette completely, when a valve opens and 

 the milk fills the reservoir. When the pipette is raised again 

 the valve closes. The milk which adheres to the outside of the 

 pipette is carefully wiped off, and by raising the valve the milk 

 can flow into one of the tubes shown in Fig. 15, which it should 

 fill exactly to the mark. Then three or four drops of acetic 

 acid are added from a dropping bottle, and the tube shaken for 

 one or two minutes. This can be done very satisfactorily with 

 the help of the shaking machine made for the purpose by the 

 firm of Franz Hugershoff, of Leipsic, 2 the motive power being 

 either a small water or electric motor (see Fig. 15). 



When the samples are taken out of the shaking machine 

 they must be brought to a temperature of 17'5 C., and then 

 3 c.c. of caustic potash solution added from a burette. Then 

 the tubes are shaken again, this time for ten minutes, after 

 which they receive 6 c.c. of water-saturated ether, also from, a 

 burette, and are shaken once more in the machine for fifteen 

 minutes. In order to get the layer of ether to rise to the 



1 Naumann. " Uber die (Jntersuchung der Milch auf Fettgebalt mit dem 

 von der Firma Carl Zeiss, Jena hergestellten Wollnyschen Milchfett refrakto- 

 meter," Milch-Zeituny, 1900. No. 4 to C. Reprint from M. Heinsius 

 Nachfolger, Leipsic. 



2 Carolinenstrasse, No. 13. The pipettes, tubes, &c., which are used in the 

 above method, as well as all other apparatus required in the investigation of 

 milk and dairy products, can be obtained from this firm. 



