~--In addition to the determination just given,
the following determinations are also required:--
~Water.~--Take about 2 grams and heat to tranquil fusion in a platinum
crucible. Count the loss in weight as water.
~Sulphuric Oxide.~--Take 2 grams, dissolve in water, acidify with
hydrochloric acid, filter, and precipitate with barium chloride. Wash
the precipitate, ignite, and weigh as barium sulphate (see _Sulphur_).
~Chlorine.~--Take 2 grams, dissolve in water, acidify with nitric acid,
filter, and add silver nitrate. Collect, wash, and weigh the precipitate
as silver chloride.
~Alumina.~--Take 5 or 10 grams, dissolve in water, boil, add ammonia in
slight excess, and filter off the precipitate when it has settled. Wash
with hot water, ignite, and weigh as alumina (Al_{2}O_{3}).
FOOTNOTES:
[113] If the dishes show a manganese stain, wash them out with a few
drops of hydrochloric and sulphurous acids. Pass the acid liquor through
the same small filter but collect the liquor apart. Make ammoniacal and
again pass through the filter, this time collecting the liquid with the
main filtrate.
[114] This rarely amounts to more than 1 milligram.
[115] To make this, dissolve 1 gram of titanium oxide by fusing for some
time with an excess of bisulphate of potash and dissolve out with cold
water and sulphuric acid.
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