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Faraday to Charles Lyell   1824

The marl was heated in a glass tube to a red heat, upon which it gave out the smell peculiar to burnt animal matter. Turmeric paper, upon being brought near it, was tinged of a reddish brown colour, indicating the presence of ammonia; the tint disappearing upon the application of a moderate temperature.

The delicacy of this test is such, that it is necessary, not only that the glass tube should be previously examined, but that the specimen should be fresh from the centre of a mass and not handled. The importance of such attention will be shown by the following experiment.

Some sea-sand was heated in a crucible to red heat for half an hour, and then poured out on a copper plate and left to cool. A portion of it was then introduced into a glass tube by a platina spoon, and it caused no change of colour in the turmeric paper; but another portion of the sand which had been heated, upon being poured into the palm of the hand, turned over several times by the finger and then examined in the same manner, gave decided traces of ammonia. It may be interesting to enumerate the different substances, which when examined with due attention to the circumstances above stated, gave indications of ammonia. The result will serve as a caution against founding any theory on the presence of that alkali, except when it is very abundant.

Please cite as “Faraday4689u,”εpsilon: The Michael Faraday Collection accessed on 18 July 2019, https://epsilon.ac.uk/view/faraday/letters/Faraday4689u