]
[Footnote 13: Page 82. Potassium, the metallic basis of potash, was
discovered by Sir Humphrey Davy in 1807, who succeeded in separating it
from potash by means of a powerful voltaic battery. Its great affinity for
oxygen causes it to decompose water with evolution of hydrogen, which
takes fire with the heat produced.]
[Footnote 14: Page 98. Professor Faraday has calculated that there is as
much electricity required to decompose one grain of water as there is in a
very powerful flash of lightning.]
[Footnote 15: Page 101. A solution of acetate of lead submitted to the
action of the voltaic current, yields lead at the negative pole, and brown
peroxide of lead at the positive pole. A solution of nitrate of silver,
under the same circumstances, yields silver at the negative pole, and
peroxide of silver at the positive pole.]
[Footnote 16: Page 129. The gas which is thus employed as a test for the
presence of oxygen, is the binoxide of nitrogen, or nitrous oxide. It is a
colourless gas, which, when brought in contact with oxygen, unites with
it, forming hyponitric acid, the red gas referred to.]
[Footnote 17: Page 152. _Marble_ is a compound of carbonic acid and lime.
The muriatic acid being the stronger of the two, takes the place of the
carbonic acid, which escapes as a gas, the residue forming muriate of lime
or chloride of calcium.
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