62 MILK PRODUCTS. 



a total change of 133. The following formula is to be 

 used for calculation. 



IPO D 

 C= 144- (/- 32) 



3-6 



in which C equals the angular rotation due to the 

 uninverted cane sugar, D the difference in the polari- 

 metric reading before and after inversion, and t the 

 temperature in Fahrenheit degrees. Since, in the 

 performance of the inversion, the liquid has been di- 

 luted from 50 to 55 c. c., the polarimetric reading 

 must be increased in proportion, before the value of 

 D is found. The value of C found by the equation, 

 deducted from the reading before inversion, will give 

 the angular rotation due to the milk sugar. 



The specific rotatory power of cane sugar varies 

 slightly with the concentration. Tollens gives the 

 following formula, in which 5 is the sepecific rotatory 

 power and 7 the concentration in grams per 100 c. c. 

 5 == 66.386 + .015035 C .0003986 C* 



A method which has given good results in our 

 hands, is to take the reading for milk and cane sugars 

 as described above and determine, in another portion 

 of the sample, the milk sugar by Fehling's solution, 

 which is not reduced by cane sugar. About three 

 grams of the condensed milk (corresponding to about 

 ten grams of ordinary milk) are accurately weighed, 

 diluted with water, treated with copper sulfate and 

 sodium hydroxid as described under the determination 



