Secondly, I will similarly treat some silk. Ammonia
escapes, turns the red litmus paper blue, possesses the smell like
hartshorn, and produces, with hydrochloric acid on the stopper of a
bottle, dense white fumes of sal-ammoniac (ammonium chloride). Hence
silk contains nitrogen. Thirdly, I will heat some fur with soda-lime.
Ammonia escapes, giving all the reactions described under silk. Hence
fur, wool, etc., contain nitrogen. As regards proofs of all three of
these classes of fibres containing carbon, hydrogen, and oxygen, the
char they all leave behind on heating in a closed vessel is the carbon
itself present. For the hydrogen and oxygen, a perfectly dry sample of
any of these fabrics is taken, of course in quantity, and heated
strongly in a closed vessel furnished with a condensing worm like a
still. You will find all give you water as a condensate--the vegetable
fibre, acid water; the animal fibres, alkaline water from the ammonia.
The presence of water proves both hydrogen and oxygen, since water is a
compound of these elements.
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