The following solutions must be prepared: 1. Dissolve 5 grammes of
nitrate of silver in 100 c.c. of distilled water, and add ammonia
until the precipitate first formed redissolves. 2. Dilute strong
nitric acid with about two volumes of distilled water; boil, to
destroy the lower oxides of nitrogen, and preserve in the dark. 3.
Dissolve about 8 grammes of ammonic thiocyanate (sulphocyanide)
crystals in a liter of water, and adjust to decinormal argentic
nitrate solution, by diluting till one volume is exactly equal to a
volume of the latter. Dilute the solution thus prepared with nine
volumes of distilled water, and label "Centinormal ammonic-thiocyanate
solution." 4. A saturated solution of ferric alum. 5. Strong solution
of ammonia (sp. gr. 0.880). The uric acid estimation is conducted as
follows: Place 25 per cent. of urine in a beaker with 1 gramme of
sodic bicarbonate. Add 2 or 3 c.c. of strong ammonia, and then 1 or 2
c.c. of the ammoniated silver solution. If, on allowing the
precipitate caused by the latter reagent to subside, a further
precipitate is produced by the addition of more solution, the urine
contains an iodide, and silver solution must be added till there is an
excess. The gelatinous urate must now be collected, the following
special procedure being necessary: Prepare an asbestos filter by
filling a 4 oz. glass funnel to about one-third with broken glass, and
covering this with a bed of asbestos to about a quarter of an inch
deep. This is best managed by shaking the latter in a flask with water
until the fibers are thoroughly separated, and then pouring the
emulsion so made in separate portions on to the broken glass. On
account of the nature of the precipitate and of the filter, it is
necessary to use a Sprengel pump, in order to suck the liquid through.
The small apparatus sold to students by chemical instrument makers
will answer the purpose admirably. Having collected the precipitate of
silver urate on the prepared filter, wash it repeatedly with distilled