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The excerpt represents the core issue or deciding factor on which you must meditate, and is drawn from Faraday as a Discoverer by John Tyndall: know, the action of an acid by turning red, turmeric reveals the
action of an alkali by turning brown. Sulphate of soda, you know,
is a salt compounded of the alkali soda and sulphuric acid.
The voltaic current passing through a solution of this salt so
decomposes it, that sulphuric acid appears at one pole of the
decomposing cell and alkali at the other. Faraday steeped a piece
of litmus paper and a piece of turmeric paper in a solution of
sulphate of soda: placing each of them upon a separate plate of
glass, he connected them together by means of a string moistened
with the same solution. He then attached one of them to the
positive conductor of an electric machine, and the other to the
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