It decomposes at a
low temperature into potassium nitrite (KNO_{2}) and free oxygen; and at
a higher temperature leaves potash (K_{2}O). It oxidizes sulphur and
carbon with explosive violence. This action may be moderated by mixing
the nitre with carbonate of soda, common salt, or some other inert body.
~Potassium Nitrite~, KNO_{2}.--The commercial article is not pure, but
is sufficiently so for the purpose required. A saturated solution is
used in the separation of cobalt; the solution is made when wanted.
~Potassium Permanganate~, KMnO_{4}.--This salt can be purchased
sufficiently pure. It is much used as an oxidizing agent.
~Potassium Bisulphate~ (KHSO_{4}) is used as a dry reagent for opening
up minerals. It fuses; and at a much higher temperature is converted
into potassium sulphate with loss of sulphuric acid.
~Potassium Sulphocyanate~ (KCNS) is used for the detection and
determination of traces of ferric iron; as also in the separation of
silver and copper from some of the other metals. Make a 10 per cent.
solution. It should show no colour on the addition of hydrochloric acid.
"~Red Lead~" (Pb_{3}O_{4}) is used in the dry assay as a flux instead of
litharge, from which it differs in containing a little more oxygen. When
acted on by nitric acid a brown residue of lead dioxide is left, nitrate
of lead going into solution.
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