i MILK 105 



Appendix. Dr. Ackermann has constructed an apparatus, 1 

 shown in Fig. 50, which is very useful where a number of calcu- 

 lations have to be made. If it is found that the total solids are 

 below the usual limit of 10*3 per cent., then it may be concluded 

 with almost absolute certainty that there has been an addition 

 of water. In order to have a further check upon the result the 

 amount of total solids minus fat, which = tf, as well as the 

 percentage of fat in the total solids, which is 100//2, should be 

 considered. 



If the specific gravity, the fat contents, the total solids, and 

 the solids minus fat are abnormally low (see the data on p. 100) 

 then the milk has been adulterated with water. The percentage 

 amount of fat in the total solids undergoes, of course, no change 

 by the addition of water. 



3. Determination of the Specific Gravity of the Milk Serum. 



Often when -milk is suspected of being adulterated with water 

 a determination is made of the specific gravity of the milk 

 serum, because this is very constant for at least three days 

 after the milk has been drawn. 2 As different numbers are 

 obtained for the specific gravity of milk serum according to the 

 different methods of obtaining the serum, Bialon 3 has proposed 

 to use for such calculations a number which is independent of 

 the total solids and of the milk serum. This number is the 

 specific gravity of a hypothetical fat-free milk, <r, which is got 

 from the formula : 



100*-/_ 

 00- // 0-933 



in which s is the specific gravity of the milk, / the percentage 

 amount of milk which it contains, and 0*933 the average specific 

 gravity of the milk fat. 



If the number a sinks below 1*0323 the milk is to be suspected, 

 for this number is the lowest that has been obtained in a long 

 series of estimations of the specific gravity of fat-free milk. 



1 Made solely by Auer Co., Zurich. 



2 Reinsch und Liihrig, Zeitschrift fur Untersuchnng der Nahrungs- nnd 

 Genussmittel, 1900, p. 521. 



3 Milchwirthschaftliches Zentralblatt, Vol. I, 1905, p. 363 ; see also J. Nisius, 

 " Uber das spezifische Gewicht und den prozentischen Wassergehalt des 

 Milchplasmas," Milch-Zeituny, 1902, No. 27. 



