THE URINE. 201 



dividing by 358 (the equivalent weight of copper is 63.6; of 

 cuprous oxide 71.6; and of cupric oxide 79.6). K. B. Leh- 

 mann 1 and von Riegler 2 have both given a method for the 

 determination of sugar, which consists in heating the solu- 

 tion in which the sugar is to be estimated with a measured 

 quantity of an excess of Fehling's solution, filtering from 

 the precipitated cuprous oxide (or letting it settle) , and deter- 

 mining by the iodometric method of de Haen the copper 

 which remains in solution. The difference between the 

 quantity of thiosulphate used and the amount of thio sul- 

 phate which the quantity of the Fehling's solution taken 

 would require corresponds to the cupric oxide reduced by 

 the sugar. This method has been tested and recommended 

 by Benjamin. 3 The method of procedure as given by the 

 two authors named is somewhat different. According to 

 Lehmann, 60 cc. of the Fehling's solution is boiled with 25 

 cc. of the sugar solution, the mixture is then placed in a 250- 

 cc. measuring-flask, and the flask filled up to the mark with 

 water. Mix thoroughly, filter through a dry filter (or let set- 

 tle), take out of the filtrate with a pipette 50 cc., make this 

 slightly acid with sulphuric acid, add 2 to 3 g. of potassium 

 iodide, about 3 cc. of starch paste (1 g. of arrowroot starch 

 boiled with 100 cc. of water), and titrate with 1/10 normal 

 thiosulphate solution the iodine set free: 



2CuS0 4 + 4KI = 2K 2 S0 4 + Cu 2 I 2 + 1 2 , 



2Na 2 S 2 3 + 1, = Na 2 S 4 6 + 2NaI. 



Twenty cubic centimeters of Fehling's solution require 

 27.74 cc. of 1/10 normal thiosulphate solution. One cubic 



1 Arch, der Hygiene, 30, 267; Maly's Jahresber. f. Thierchemie, 

 1897, 64. 



2 Zeitschr. f. analyt. Chem. 37, 22. 



8 Deutsche med. Wochenschr. 1898, 551. 



