_Reagents._— 1. Ten per cent solution of copper sulfate
(CuSO_{4}.5H_{2}O).
2. Ten per cent solution of lead acetate
(Pb(C_{2}H_{3}O_{2})_{2}.3H_{2}O).
3. Fifty per cent solution of sodium hydroxide (NaOH) or
potassium hydroxide (KOH).
_Procedure._—To 50 cc. of the sample to be tested, diluted if necessary
with an equal volume of ammonia-free water, in a short tube, add a few
drops of the copper sulfate solution. After thoroughly mixing, add 1 cc.
of the alkali hydroxide solution and again thoroughly mix. Allow the
tube to stand for a few minutes, when a heavy precipitate should fall to
the bottom, leaving a colorless supernatant liquid. Nesslerize an
aliquot part. Compare with standards and compute the ammonia nitrogen in
the same manner as in the distillation procedure.
Samples containing hydrogen sulfide may require the use of lead acetate
in addition to the copper sulfate. Some samples may require a few trials
before the right combination of the three solutions to bring about the
best results can be found.
Instead of adding copper sulfate to sewages of high magnesium content
satisfactory clarification of the sample can be obtained by mixing it
with the alkali hydroxide alone.[54]