I have already shown you that if we can liberate by any means
ammonia from a substance, we have practically proved the presence of
nitrogen in that substance, for ammonia is a nitrogen compound. As
regards sulphur and its compounds, that ill-smelling gas, sulphuretted
hydrogen, which occurs in rotten eggs, in organic effluvia from
cesspools and the like, and which in the case of bad eggs, and to some
extent with good eggs, turns the silver spoons black, and in the case of
white lead paints turns these brown or black, I can show you some still
more convincing proofs that sulphur is contained in wool, fur, and hair,
and not in silk nor in vegetable fibres. First, I will heat strongly
some cotton with a little soda-lime in a tube, and hold a piece of
moistened red litmus paper over the mouth of the tube. If nitrogen is
present it will take up hydrogen in the decomposition ensuing, and
escape as ammonia, which will turn the red litmus paper blue. With the
cotton, however, no ammonia escapes, no turning of the piece of red
litmus paper blue is observed, and so no nitrogen can be present in the
cotton fibre.
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