ADULTERATION OF MILK 191 



184. WeibuWs Method. 



The approximate volume of the sample is estimated 

 by inspection and 10 percent, of this volume of ammonia 

 solution is added. On shaking, the casein will dissolve, 

 and the liquid becomes homogeneous. 



The volume of the ammoniacal milk is then 

 accurately measured by means of a measuring glass or 

 burette, and by subtraction of the volume of ammonia 

 solution added the original volume of the milk is 

 obtained. 



The ordinary analytical operations, such as deter- 

 minations of total solids, fat, casein, etc., may be carried 

 out with the mixture of milk and ammonia, and from a 

 knowledge of the percentage of the original milk in the 

 ammoniacal liquid accurate values can be obtained for 

 the milk. 



In the case of the determination of the density, 

 allowance must be made for the density of the ammonia 

 solution added. 



This is best done by means of the formula originally 

 proposed by Weibull : — 



(M + A)D'-^AD'' 



^- M 



where 



D = density of original milk 



D' = density of ammoniacal mixture 



D" = density of ammonia 



M = volume of milk 



A = volume of ammonia. 



Adulteration of Milk. 



As distinct from the addition of those substances employed as 

 preservatives, the commoner methods of adulteration or falsifica- 

 tion are as follows : — 



(i.) The addition of water. 



