EXAMINATION OF NORMAL AND ABNORMAL URINE. 387 



Trommer's test, A few drops (2-4) of a 5 per cent, solution 

 of cupric sulphate are added to about 5 to 8 c.c. of urine in a 

 test-tube and then an equal volume of potassium (or sodium) 

 hydrate solution is added. The alkaline hydrate precipitates 

 both earthy phosphates and cupric hydrate, the latter however 

 dissolving (especially if sugar be present) in the excess of the 

 alkali, producing a beautiful blue transparent liquid. (If no 

 sugar is present, the color is less blue, but more of a greenish 

 hue.) The liquid is now boiled for a few seconds, when, if 

 sugar be present, a yellow precipitate of cuprous hydrate is 

 formed which subsequently loses its water and becomes the red 

 cuprous oxide, which falls to the bottom or adheres to the sides 

 of the test-tube. 



As various organic substances (other than sugar) have a ten- 

 dency to reduce cupric oxide at a temperature of 100, it is 

 well to set aside a test-tube prepared as above (without heating it) 

 for from 6 to 24 hours. If sugar be present, the formation of 

 cuprous hydrate will gradually take place, whilst most other 

 organic matters do not act upon cupric oxide at ordinary tem- 

 perature. 



In drawing conclusions from the above test, it should be re- 

 membered that a change of color does not indicate sugar; that 

 a precipitate of earthy phosphates must not be mistaken for 

 cuprous oxide; and that substances other than sugar may 

 deoxidize cupric oxide at the temperature of 100. 



Fehling's test differs from Trommer's test merely in using a 

 previously mixed reagent instead of producing this reagent, 

 as it were, in the urine by adding to it cupric sulphate and an 

 alkaline hydrate successively. This reagent, known as Fehl- 

 ing's solution, is made as follows : 



Crystallized cupric sulphate, ...... 34.65 grams. 



Dissolved in 

 Pure water, 200 



This solution is poured gradually into a solution of 

 Crystallized sodium potassium tartrate, .... 173 



Dissolved in 

 Solution of sodium hydrate of sp. gr. 1.12, . . . 500 



The clear, well-mixed fluid is diluted to 1000 c.c. 



The addition of sodium-potassium tartrate in Fehling's solu- 

 tion prevents the precipitation of cupric hydrate by the alka- 



