4. On dissolving 0.3 gram of mercury in hot nitric acid, and passing
sulphuretted hydrogen in excess through the diluted solution, what
weight of precipitate will be got?
FOOTNOTES:
[9] Lead may be granulated by heating it to a little above the melting
point, pouring it into a closed wooden box, and rapidly agitating it as
it solidifies.
[10] A rod of iron placed in the crucible with the assays will decompose
any regulus that may be formed.
[11] With buttons poor in silver the lowering of the temperature at this
stage is not a matter of importance.
[12] 100 grams of the lead, or of its oxide, will contain from 1.5 to
2.5 milligrams.
[13] Still the precautions of having cupels well made from bone ash in
fine powder, and of working the cupellation at as low a temperature as
possible are very proper ones, provided they are not carried to an
absurd excess.
[14] Be careful to remove the crucible before taking the bottle out of
the basin of water; if this is not done the chloride may be washed out
of it.
[15] 1 c.c. of this dilute acid will precipitate 8 or 9 milligrams of
silver.
[16] Chlorides interfere not merely by removing silver as insoluble
silver chloride, but also by making it difficult to get a good finishing
point, owing to the silver chloride removing the colour from the
reddened solution.
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