GLUCOSE. 28-f 



Trommer's test may also be successfully employed in the quan- 

 titative determination of the sugar in diabetic urine ; Barreswil,* 

 Falck,t and Scharlau,t have recommended different methods of 

 applying it with this view ; the most generally applicable one, 

 however, is that of Fehling. As a test he uses a solution of 

 40 grammes of crystallised sulphate of copper in 160 grammes of 

 water ; this is mixed with a concentrated solution of 160 grammes of 

 tartrate of potash and 560 grammes of a solution of caustic-soda 

 (specific gravity =1*1 2), and water is then added till the volume of 

 th e fluid at + 15 amounts to 1 litre. ll'5c.c. of a saccharine solution 

 containing 5 grammes of dry sugar(=i C 12 H 12 O 12 ) in a litre, are neces- 

 sary to cause the perfect reduction of the oxide to the suboxide of 

 copper in lOc.c. of the test-fluid. Hence it follows that 100 parts 

 of oxide of copper are completely reduced to the state of suboxide 

 by 45*25 parts of sugar, or 10 atoms of oxide of copper by 1 atom 

 of sugar. In order to determine with the greatest certainty the 

 weight of the sugar from the volumetric measurement, and to render 

 the errors of observation as small as possible, Fehling recommends 

 that the urine to be examined for sugar should be diluted with 

 water to 10 or 20 times its volume, that is to say, that 50 grammes 

 of urine should be treated with 450 or 950 of water : 10 c.c. of 

 the test-fluid are then to be diluted with about 40 c.c. of water, 

 boiled, and so much of the diluted urine (which must be kept in a 

 burette or graduated tube in order that we may be able to estimate 

 the quantity used) added to it, as to effect as nearly as possible the 

 complete decomposition of the sugar and of the oxide of copper. 

 If any uridecomposed oxide of copper be contained in the fluid 

 after the removal of the suboxide by filtration, it may be recog- 

 nised by the blue tint, and by its reaction with sulphuretted 

 hydrogen : if, on the other hand, too much urine be added, the 

 filtered fluid appears yellow from the action of the caustic alkali on 

 the sugar. The point of thorough mutual decomposition is easily 

 attained by a few repetitions of the experiment. As 10 c.c. of the 

 test-fluid require 0'0577 of a gramme of sugar for the reduction of 

 the oxide of copper contained in them, there must be exactly that 

 amount of sugar in the quantity of urine used in the experiment, 

 and hence the proportion of sugar in any given quantity of urine 

 may be easily calculated. 



Those who are not in the habit of using French weights an:l 



* Journ. de Pliarm. T. 6, p. 301. 



f Oesterlen's Jahrb. f. pr. Heilk. Bd. 1, S. 501). 



Die Zuckerharnruhr. Berlin, 1846. 



Arch. f. phys. Heilk. Bd. 7, S. (J4-73. 



