Bauhaus-Universität Weimar

Titel:
Handbook for the Physiological Laboratory. Text
Person:
Burdon-Sanderson, John Scott E. Klein Michael Foster T. Lauder Brunton
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit18583/564/
BY DR. LAUDER BRUNTON. 
555 
secondly, by determining the quantity of urine which has to be 
boiled with a standard solution of a cupric salt, in order to reduce 
the whole of the copper to the condition of red cuprous oxide. 
In order to determine the quantity of sugar by the last method, 
which is known as that of Fehling, we require to prepare a 
standard solution in the following manner :—34*65 grammes of 
pure and well crystallized copper sulphate are dissolved in about 
160 cubic centimeters of water, and 173 grammes of Rochelle salts 
(tartrate of potash and soda) are dissolved in about 600 cubic 
centimeters of solution of caustic soda, having a specific gravity of 
1120. The solution of sulphate of copper is added gradually to 
the alkaline solution of Rochelle salts, the fluid being continually 
stirred. A deep blue solution is thus obtained, which is diluted 
with distilled water to the volume of one litre. Ten cubic centi¬ 
meters of this solution are reduced by 0*05 grammes of diabetic 
sugar. 
The following is the process which has to be followed in deter¬ 
mining the quantity of sugar in urine :— 
The urine to be examined is diluted to a known extent ; thus in 
the case of a diabetic urine, having a specific gravity of 1040, 100 
cubic centimeters are diluted with distilled water to the volume of 
1,000 cubic centimeters. 
Ten cubic centimeters of the standard copper solution are then 
accurately measured out, and poured into a porcelain capsule. Forty 
cubic centimeters of distilled water are added, and the solution in 
the capsule boiled. 
The previously diluted urine is then allowed to flow in from a 
burette ; after a few cubic centimeters have been added, the fluid 
in the capsule is briskly boiled, and then the application of heat 
discontinued for a few seconds. 
The solution, which, after the saccharine fluid has been boiled 
with it, assumes a red colour, deposits a red sediment of cuprous 
oxide, whilst the supernatant fluid retains a more or less blue 
colour, in consequence of a portion of the copper remaining in 
solution. 
Successive portions of the diluted urine are then added, and the 
fluid boiled after each addition. As the operation proceeds, the 
addition of the diluted urine is performed with great care, only a 
few drops being poured in at a time. A point is at last reached 
when the bottom of the capsule is coated with a deposit of red 
cuprous oxide, and when, on tilting the capsule so as to bring 
the fluid which it contains over the clean white sides, no tint of 
blue is perceived. 
The number of cubic centimeters of sugar solution added is 
then read off and marked. It is advisable, however, to pursue the 
operation one step further. A few more drops of diluted urine
        

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