92 



FOODS AND FOOD ADULTERANTS. 



The following chemists, in addition to those already mentioned, have 

 given the method their entire approval : Egger, Kellner, Schrodt, Fried- 

 lander, Meissel, Fleischinan, Hofmeister, Deitzell, Moser, Schreiner, 

 Janke, Gerner, and Angstrom. 



I will give now some of my own experiences with the areometric 

 method : 



The milk examined by me was mostly obtained from a neighboring 

 dairy arid was a mixture from forty cows. Samples were also bought 

 from dealers in the city. The milk from the dairy mentioned was drawn 

 at 5 p. m., and the examination made the following morning. This may 

 partially account for the small success I had in securing a good separa- 

 tion of the ether'- fat. The work extended from March 23 to May 7, 1886. 



With the first series of samples in which the method of separation 

 recommended by Soxhlet was followed ninety-three trials were made. 

 In only four cases was the separation sufficiently good to get a reading 

 within thirty minutes. A larger number of readings was obtained within 

 an hour, and about half the number could be read at the end of three 

 or four hours. Of the remainder about one-half could be read after 

 twenty-four hours, and the rest did not separate at all. The results of 

 reading the areometer at different times, however, showed that the 

 density of the either-fat solution underwent quite a change. The fol- 

 lowing data will show the nature and extent of this change: 



From the above it is seen that there is no uniformity in the character 

 of this change, but in the greater number of cases the areometer shows 

 an increase in the percentage of fat on standing. 



Attempts also to obtain a more perfect separation by varying the 

 quantity of potash employed gave only conflicting results. 



I was, therefore, forced to the conclusion that for general work 

 Soxhlet's method would prove useless unless some method could be de- 

 vised to secure a prompt and uniform separation of the ether-fat solu- 

 tion. 



Various theories have been proposed to account for this peculiarity 

 of milk in refusing to allow the ether solution to separate. Caldweli 

 and Parr have supposed it to be due to the bran in the cow's food ; Lieber- 

 mann ascribes it to failure of manipulation ; Schinoeger that it is caused 



