ESTIMATIOX OF MILK-SI ■(;AR. 



m 



Wiley-Ewell Method. — Wiley and Ewell give the following 

 method as the best for estimating milk-sugar by the polariscope : — 

 They used a .Schmidt & Haensch polarimeter, with which HJ} 

 millimetre.s of a solution of 3"2'01 gi-ammes of milk-sugar in 

 100 c.c. read 10() divisions of the scale. They take 65 '82 grammes 

 of milk, add 10 c.c. of acid mercuric nitrate solution (in this case 

 the solution of mercury in nitric acid is diluted with 5 volumes 

 of water), and dilute to 100 c.c. .\ similar quantity of milk is 

 taken, 10 c.c. of acid mercuric nitrate added and diluted to 

 2(K) c.c. Each of these solutions is well mixed, filtered, and 

 polarised in a 40r) mm. tube. 



Fig. (i. — PolarisL-opo. 



Calling the reading of the solution obtained from 100 c.c. .r, 

 and that obtained from 200 c.c. //. the true percentage of milk- 



susar i.s — . 



" 4(.- - y) 



Thi' double dilution does away with any correction for the 

 volume of the precipitated fat and protein. The rationale of 

 the process lies in the fact that, while the percentage of milk- 

 sugar and the volume of the precipitate are constant, the total 

 volume varii'-. 



