" Add 10 grams of
sodic acetate, and ferric chloride until the precipitate turns brown;
dilute with water to half a litre, boil, and titrate with standard baric
chloride, as described under _Sulphur_. Report as sulphur.
A sample of hardhead examined in this way gave--
Sulphur 3.00%
Arsenic 27.10
Tin 22.2
Copper 1.64
Iron 43.2
Cobalt 2.6
------
99.74
~Examination of Tin Slags.~--In tin smelting works the term "slag" is
applied to the unfused portion of the charge. It is made up of unburnt
anthracite and small lumps of slag proper together with some buttons of
metallic tin. This is rarely, if ever, assayed. The slag proper (or, as
it is generally called, "glass") is a silicate of iron, alumina, and
lime, containing from 3 to 7 per cent. of tin. It is thus examined:--The
sample after bruising on an iron plate, is reduced to a very fine powder
by grinding in an agate mortar. In this state it is in most cases
readily decomposed by hydrochloric acid.
~Determination of Tin.~--Where the percentage of tin only is required,
take 2 grams of the powdered slag and well mix with it 20 c.c. of
hydrochloric acid, and heat to boiling. Add 1 c.c. of nitric acid, allow
to stand for fifteen minutes, dilute with water, and filter.
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