URINE 



527 



reduced. Multiply this result by the value of i c.c. of thiosulphate expressed as 

 Cu, and obtain the number of milligrams of copper reduced. Then by consulting 

 the table of values (below) determine the weight of glucose equivalent to this 

 amount of copper. 



Cole 1 has determined the copper values for lactose using this method exactly 

 as outlined. He has also suggested the following empirical formula which agrees 

 well with the values derived from his table: 



Mg. anhydrous lactose = 1.25 + 0.778 X mg. Cu. 

 Interpretation. See page 523. 



TABLE FOR THE DETERMINATION OF GLUCOSE 



According to Peters 



Copper, Glucose 

 mg. ~^ 



Copper, Glucose 



ratio 



5. Bertrand's Method. 2 Principle. The sugar is boiled with alkaline copper 

 sulphate solution and the precipitated cuprous oxide filtered off, dissolved in an 

 acid solution of ferric sulphate and the resultant ferrous salt titrated with potassium 

 permanganate. This method of titrating cuprous oxide may be conveniently used 

 where other reduction procedures such as that of Peters or of Munson and Walker, 3 

 have been employed. In this case the tables corresponding to the particular 

 method and not the Bertrand tables must be consulted in calculating the sugar 

 equivalent. 



The following reactions are involved in the Bertrand titration: 



Cu 2 O + Fe 2 (S0 4 )3 + H 2 SO 4 = 2CuSO 4 + 2FeSO 4 + H 2 O 

 ioFeSO 4 + 2KMnO 4 -f 8H 2 SO 4 = 5Fe 2 (SO 4 ) 3 + K 2 SO 4 + 2MnS0 4 + 8H 2 O. 



Procedure. Introduce into an Erlenmeyer flask of 150 c.c. capacity, 20 c.c. of 

 the sugar solution (of a concentration of 0.5 per cent or less), 20 c.c. of the copper 



: Biochem. /., 8, 134, 1914. 



2 Bertrand: Bull. Soc. Chim. de France, 35, 1285, 1906. 



3 Munson and Walker: Bull. 107, U. S. Dept. of Agriculture. 



