for ease of application and delicacy of end-reaction, combined with
considerable accuracy. His solution differs from that of Fehling in
containing ammonia, which dissolves the cuprous oxide as soon as it is
formed, yielding a colorless solution. It is only necessary,
therefore, to note the moment that the blue color of the liquid is
exactly discharged, in order to tell when all the copper present has
been reduced. Pavy's solution is prepared as follows: Dissolve 356
grains of Rochelle salt and the same weight of caustic potash in
distilled water; dissolve separately 73 grains of recrystallized
cupric sulphate in more water with heat. Add the copper solution to
that first prepared, and when cold add 12 fluid oz. of strong ammonia
(sp. gr. 0.880), and distilled water to 40 fluid oz. The estimation is
thus conducted: Dilute 10 c.c. of the ammoniated cupric
solution--equivalent to 5 milligrammes of glucose--with 20 c.c. of
distilled water, and place in a 6 or 8 oz. flask. Attach this by means
of a cork to the nozzle of an ordinary Mohr's burette, _b_, preferably
fitted with a glass stopcock, and filled previously with the diluted
urine. The small tube, _c_, which traverses the cork is intended to
permit the escape of steam. Now raise the blue liquid in the flask to
active ebullition--not too violent--by the aid of a spirit lamp or
small Bunsen flame. Turn the stopcock in order to allow the urine to
flow into the boiling solution at the rate of about 100 drops per
minute (not more or much less) until the azure tint is exactly
discharged. Then stop the flow, and note the number of cubic
centimeters used. That amount of dilute urine will contain 5
milligrammes of glucose. To render the determination as accurate as
possible, the urine should be diluted to such an extent that not less
than 4 or more than 7 c.c. are required to decolorize the solution,
and the proportions necessary will be found to vary from 1 part of
urine in 2½ to 1 in 30 or 40. The subsequent calculation is very