MILK-SUGAR POLARISCOPE. 



155 



Wiley's Method. The investigations of Wiley have shown 

 that mercury compounds are the most efficient for this purpose, 

 of which " acid mercuric nitrate " is the most convenient. This 

 is prepared as follows : Mercury is dis olved in twice its weight 

 of nitric acid of specific gravity 142, and, after solution, an equal 

 bulk of water is added. 



Basic lead acetate has also been used to remove fat and protein, 

 but Wiley has proved that the results are not accurate, owing to 

 the incomplete removal of protein. Still more inaccurate is the 

 use of acetic acid, followed by boiling, which has been recom- 

 mended by Blyth. 



Fig. 22. Polariscope. 



Wiley-Ewell Method. Wiley and Ewell give the following 

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

 They used -a Schmidt & Hsensch polarimeter, with which 200 

 millimetres of a solution of 32-91 grammes of milk-sugar in 

 100 c.c. read 100 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. A similar quantity of milk is 

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

 200 c.c. Each of these solutions is mixed well, filtered, and 

 polarised in a 400 mm. tube. 



