308 PHYSIOLOGICAL CHEMISTRY. 



OH 



/ 

 Cu 

 \ 

 OH 



2Cu - OH + H 2 O 



OTT Cuprous hydroxide 



^ A (yellow). 



Cu 



\ 

 OH 



Cu-OH 

 Cu-OH 



*B 



Cuprous hydroxide Cuprous oxide 

 (yellow). (brownish-red). 



The chemical equations here discussed are exemplified in Trom- 

 mer's and Fehling's tests. 



(a) Trammer's Test. To 5 c.c. of urine in a test-tube add one- 

 half its volume of KOH or NaOH. Mix thoroughly and add, drop 

 by drop, agitating after the addition of each drop, a very dilute 

 solution of cupric sulphate. Continue the addition until there is 

 a slight permanent precipitate of cupric hydroxide and in con- 

 sequence the solution is slightly turbid. Heat, and the cupric hy- 

 droxide is reduced to yellow cuprous hydroxide or to brownish-red 

 cuprous oxide. If the solution of cupric sulphate used is too strong, 

 a small brownish-red precipitate produced in the presence of a 

 low percentage of dextrose may be entirely masked. On the other 

 hand, if too little cupric sulphate is used a light-colored precipitate 

 formed by uric acid and purine bases may obscure the brownish- 

 red precipitate of cuprous oxide. The action of KOH or NaOH 

 in the presence of an excess of sugar and insufficient copper will 

 produce a brownish color. Phosphates of the alkaline earths may 

 also be precipitated in the alkaline solution and be mistaken for 

 cuprous hydroxide. Trommer's test is not very satisfactory. 



(b) Fehling's Test. To about i c.c. of Fehling's solution 1 in 



1 Fehling's solution is composed of two definite solutions a cupric sulphate 

 solution and an alkaline tartrate solution, which may be prepared as follows : 



Cupric sulphate solution = 34.65 grams of cupric sulphate dissolved in water 

 and made up to 500 c.c. 



Alkaline tartrate solution =125 grams of potassium hydroxide and 173 

 grams of Rochelle salt dissolved in water and made up to 500 c.c. 



