Condensed Milk and Milk Powder 207 



there is no difficulty in determining the end point within a single 

 drop. One cubic centimeter of the thiosulphate solution will be 

 found to correspond to .00636 grams of copper." 



DETERMINATION OF COPPER 



"After washing the precipitated cuprous oxid, cover the gooch 

 with a watch glass and dissolve the oxid by means of 5 c.c. of warm 

 nitric acid (1:1) poured under the watch glass with a pipette. Catch 

 the nitrate in a flask of 250 c.c. capacity, wash watch glass and 

 gooch free of copper ; 50 c.c. of water will be sufficient. Boil to 

 expel red fumes, add 5 c.c. of bromin water, boil off the bromin, 

 and proceed exactly as in standardizing the thiosulphate." 



DETERMINATION OF LACTOSE 



Place 50 c.c. of the mixed copper reagent in a beaker and heat 

 to the boiling point. While boiling briskly add 100 c.c. of the lactose 

 solution containing not more than 0.300 gram of lactose and boil for 

 six minutes. Filter immediately through asbestos and wash. Ob- 

 tain the weight of lactose equivalent to the weight of copper found 

 from the following table. 



