

DAIRY PRODUCTS-. 99 



tance that all the measurements be made with the greatest exactitude, 

 since a single drop too much or too little will influence the result. 



In case some small particles of the butter fat are detached and swim 

 about in the liquid no fear need be entertained that the results of the 

 measurement will be influenced thereby. 



It will appear at once that the difference between the volume of water 

 >riginally held by the flask, and that which was necessary to fill it after 

 iie fat had been added, will represent the volume of the fat which was 



mtaiued in the 20cc. of the ether solution. This number multiplied by 



will give the volume per cent, of the fat at the temperature at which 

 the experiment was made. 



For converting volume per cent, into weight per cent, the following 

 ible is used: 



Table for converting volume per cent, into weiyht per cent. 



At temperature 15 C., volume per ceiit.X. 9 1109=^ weight per cent. 



160 . 90831 



170 . 90642 



18 . 90377 



19 .90170 



200 . 90034 



210 . 89897 



220 . 89626 



23 . 89216 



24 . 88822 



250 . 88703 



26 . 87584 



27 . 87463 



28 . 87327 



290 . 87191 



30 . 87055 



The following example will show the manner in which the above-de- 

 scribed method of analysis may be reckoned. 



The graduation of the flask shows a volume of 48cc. and 25cc. After 

 the evaporation of the 20cc. of the ether solution 47.3cc. water was neces- 

 sary to fill the flask. The volume of fat which was contained in the 

 JOcc. of the ether solution is therefore 48.25 47.38=. 95cc. This number 

 multiplied by 5 gives 4.75cc. volume per cent, of fat. The temperature 



which the estimation was made was 17 0. 



Looking now in the table, opposite 17 C. we find the factor ,90642 

 'his number multiplied by 4.75 gives 4.3, which is equal to the per cent 



fat by weight. 



If it is wished to determine the per cent, by weight of butter per 

 LOO grams, and not cubic centimeters as before, it is necessary to de- 

 termine the specific gravity of the milk and to proceed according to 

 the following formula : 



p 1000 



In this formula P denotes the number sought, p the quantity of fat 

 found for 100 cubb centimeters, and S the specific gravity of the milk. 

 I According to Wolfl the percentage of fat obtained by the method 

 ust mentioned is too high, because a part of the ether used for separat- 



