230 Testing Milk and Its Products. 



diluted.^ The same constituents are determined as in 

 case of whole milk, viz., solids, fat, casein and albumen, 

 ash, milk sugar, and cane sugar (if any has been added 

 to the milk) . The cane sugar is determined by the dif- 

 ference between the solids not fat and the sum of the 

 casein, albumen, milk sugar and ash ; if the student has 

 a knowledge of the manipulation' of the polariscope and 

 has had experience in gravimetric sugar analysis, the 

 milk sugar is determined gravimetrieally, and the cane 

 sugar by the difference between the polariscope reading 

 after inversion and the milk sugar present. 



The specific gravity of condensed milk may be deter- 

 mined by a method similar to that of McGill.^ 50 gr. 

 of the thoroughly mixed sample are weighed into a 

 tared beaker and washed with warm water into a 250 cc. 

 flask, cooled to 60°, filled to the mark and carefully 

 mixed. The specific gravity of this solution (a) is then 

 taken and the original density is calculated by means 

 of the following formula: 



Sp. gr. of condensed milk= ^ 



6-5a 



Concentration. The extent of concentration of con- 

 densed milk may be determined approximately by the 

 formula devised by McGill (loc. cit.) : 

 Concentration (c)=_5lJ_ 



aiSi 



where a and s designate the solids not fat and specific 

 gravity, respectively, of the condensed milk, and a^ and 

 Si the corresponding data for the milk used. If s,= 



^A second extraction following leaching and subsequent drying of 

 the tubes is necessary to extract all the fat In condensed milk ; see 

 Bull. 104, Bur. of Chem., U. S. Dept. of Apr., p. 102 and 154. 



' Bulletin 54, Laboratory Inland Rev. Dept., Ottawa, Canada. 



