46 DAIRY ANALYSIS 



the increment of specific gravity due to the addition is 

 deduced, and subtracting this from the specific gravity 

 found, the specific gravity of the milk is obtained. From 

 this last figure and the fat the solids not fat can be 

 calculated, and from this the amount of added water 

 deduced by the formula on p. 52, or the formula which 

 is based on the above factors, 



added water = 



N 



/ c.c. ^silver solution -aldehyde fig. x o.i 71 \ 



V 2.?. ) 



x 100 



36 



may be used. 



Whey is treated as milk; it contains, however, no 

 casein, but gives a small precipitate consisting of 

 albumoses, which by the methods given would be 

 estimated as casein. The aldehyde figure multiplied by 

 0.125 gives the percentage of proteins. 



Sterilised milk can be analysed by the methods 

 given for milk ; the polarimetric estimation of milk 

 sugar tends to be low, owing to change in the milk 

 sugar on heating, and the gravimetric method should 

 be used. The albumin behaves like casein, as it is 

 rendered insoluble in dilute acetic acid and magnesium 

 sulphate solutions ; the estimation of casein and albu- 

 min can, however, be made by the indirect method from 

 organic phosphorus and sulphur. The total nitrogen is 

 unaffected. Ritthausen's method should not be used 

 for the estimation of fat in sterilised or condensed 

 milk. 



Condensed milk, if unsweetened, may be analysed 

 by diluting one part by weight with two parts of water, 

 and boiling and treating in the same way as steri- 

 lised milk ; the results must, of course, be multiplied 



by 3- 



Sweetened condensed milk should be similarly 

 diluted and analysed. Great care must be taken to 

 well mix the contents of the tin, as the milk suga r 



