The Students' Guide in Quantitative Analysis - Free Ebooks Library

ANALYSIS OF URINE. 113
2. Test witji Litmus Pa pek, and note whether acid or
alkaline.
3. Pour a sample into a stop-cock funnel, and let stand
12 hours. If a deposit forms, filter, and examine the filtrate
and sediment separately. Filtered urine leaves a scum of
mucus. (For sedunents, see Schemes, page 117 and 118.)
4. Determine Total Solids. Evaporate 4 to 6 c. c,
weighed, to dryness in a weighed dish. Dry at 115 c. (In-
accurate).
5. Ash. Evaporate 100 c. c. urine and ignite residue.
6. Determination of Ukea. CHjNiO.
A. — Lieb ig$ Method.
Principle : Mercuric nitrate added to a solution of urea
gives a white, gelatinous ppt. containing i molecule urea,
and 2HgO. (Absence of NaCl necessary.)
Requirements
:
{a) Standard solution Hg (NO3),.
{b) Baryta solution.
{/) Carbonate of soda test paper.
(«) Standard solution of mercuric nitrate. Dissolve
72 grms. pure dry HgO in strong HNOs, (50 grms.,)
evaporate until syrupy, and dilute to i litre. If a yellow
ppt, is produced by dilution, too little acid is present. It
must be evaporated down, fresh acid added, and again di-
luted. I c. c, =0.01 grm. urea. ^To test the strength of
the mercuric nitrate dissolve 2 grms. cryst. urea in 100 c, c.
water, i c, c. mercuric solution should equal o.oi grm. urea.
(^) Solution of Ba(NO,).+BaHA- Mix i part cold
saturated solution Ba(N03X, with 2 parts cold saturated
solution BalijOa, and add 3 parts distilled water.
[c] Soda test paper. Dip a sheet white filter paper into
cone. sol. Na. (CO.,) and dry.