ll from
6 per cent. to 8 per cent. Distillation with a moderate quantity of
hydrate of lime increased the yield of ammonia only by 1 per cent. to
11/2 per cent. A rather better result was obtained by distilling the
ground residual carbon with hydrate of lime, but this operation
proceeded very slowly, and the total yield of ammonia still remained
very far below the quantity theoretically obtainable, so that I came
to the conclusion that it was more rational to utilize the leather,
reduced to powder by mechanical means, by mixing it directly with
other manures.

A few years later I became connected with a large animal charcoal
works, in which sulphate of ammonia was obtained as a by-product. Here
again I was met with the fact that the yield of ammonia by no means
corresponded with the nitrogen in the raw material and that the
charcoal remaining in the retorts contained still about half as much
nitrogen as had been present in the bones used.

From this time forward my attention was for many years given
exclusively to the soda manufacture, and it was only in 1879 that I
again took up the question of ammonia. I then determined to submit the
various processes which had been proposed for obtaining ammonia from
the nitrogen of the air to a searching investigation, and engaged Mr.
Joseph Hawliczek to carry out the experimental work.

These processes may be broadly divided into three classes:

(1.) Processes which propose to combine nascent hydrogen with
nitrogen at high temperatures or by electricity, with or without
the presence of acid gases.

(2.) Processes in which nitrides are first formed, from which
ammonia is obtained by the action of hydrogen or steam.

(3.) Processes in which cyanides are first formed and the ammonia
obtained from these by the action of steam.

We began with an investigation of those processes in which a mixture
of steam and nitrogen or of steam and air is made to act upon coke at
a high temperature, sometimes in the presence of lime, baryta, or an
alkali, sometimes in the presence of hydrochloric acid.

Very numerous patents have been taken out in this direction and there
is no doubt that ammonia has been obtained by these processes by many
inventors, but as I was aware that coke contains a considerable
quantity of nitrogen, frequently as much as 1.5 per cent., which might
be the source of the ammonia obtained, I determined to carry on the
investigation in such a way as to make