158 THE ESTIMATION OF SUGARS. 



100 - 

 r o*93 1 



= 1-041T X -iod - X T X ' 95 



m 1 = percentage of anhydrous milk-sugar by weight, 

 r = reading, 



F = percentage of fat by weight, 

 d = specific gravity of milk. 

 pi 7 



For the expression -TT-QO it is usually exact enough to employ 

 \j *y o 



the expression F x I'll. 



As an example, let us suppose that, using a 1984 mm. tube, 



r = 5-5 

 F = 4-1 

 d = 1-032 



5-5 1 



m 1 = x 0' 9 545 X X 0-95 = 4-58 per cent. 



Vieth states that when cream is analysed by this method, it 

 is necessary to dilute with an equal bulk of water, the result 

 being, of course, doubled. 



Richmond- Boseley Method. The author, in conjunction 

 with Boseley, has shown that the calculation necessary in Vieth's 

 method can be eliminated by adding to 100 c.c. of milk 



(a) A quantity of water in c.c. equal to T V degree of specific gravity. 

 (6) the fat x Ml. 



(c) ^ to reduce scale readings to percentages 



of milk-sugar. 



(d) 3 c.c. of acid mercuric nitrate. 



The percentage of milk-sugar can be read off directly in scale 

 readings. 



The values of c are : For polariscopes reading angular 

 degrees 



With 198-4 mm. tube, 10-0 c.c. 

 200 10-85 



500 10-85 (divide readings by 2-5). 



For the Laurent sugar scale (100 = 21-67 angular degrees) 



With 200 mm. tube, 2-33 c.c. (divide readings by 5). 

 400 2-33 ( 10). 



500 2-33 ( 12-5). 



For the Ventzke scale (100 = 34-64 angular degrees) 



With 200 mm. tube, 6-65 c.c. (divide readings by 3). 

 400 6-65 ( 6). 



500 6-65 ( 7-5). 



The author has shown that mercuric nitrate does not pre- 

 cipitate the whole of the proteins, and that a small further 

 precipitate is obtained by the addition of phospho-tungstic acid ; 

 the difference in the percentage of milk-sugar found after adding 



