l by steam alone at a
temperature at which the ammonia formed should not be dissociated,
although it yielded more ammonia, would not lead to an economic
process, because it would require apparatus heated from the outside,
of great complication, bulk, and costliness, on account of the immense
quantity of raw material to be treated for a small amount of ammonia
obtainable.

On the other hand, if the coal could be burned in gas producers by a
mixture of air and steam, the plant and working of it would be simple
and inexpensive, the gas obtained could be utilized in the same way as
ordinary producer gas, and would pay to a large extent for the coal
used in the operation, so that although only one-half of the ammonia
would be obtained, it seemed probable that the result would be
economical.

I consequently constructed gas producers and absorbing plant of
various designs and carried on experiments for a number of years.
These experiments were superintended by Mr. G. H. Beckett, Dr. Carl
Markel, and, during the last four years, by Dr. Adolf Staub, to whose
zeal and energy I am much indebted for the success that has been
achieved. The object of these experiments was to determine the most
favorable conditions for the economic working of the process with
respect to both the cost of manufacture as well as the first cost and
simplicity of plant. The cost of manufacture depends mainly upon the
yield of ammonia, as the expenses remain almost the same whether a
large or a small amount of ammonia is obtained; the only other item of
importance is the quantity of steam used in the process. We found the
yield of ammonia to vary with the temperature at which the producer
was working, and to be highest when the producer was worked as cool as
was compatible with a good combustion of the fuel. The temperature
again depended upon the amount of steam introduced into the producer,
and of course decreased the more steam increased. We obtained the best
practical results by introducing about two tons of steam for every ton
of fuel consumed. We experimented upon numerous kinds of fuel, common
slack and burgy of the Lancashire, Staffordshire, and Nottinghamshire
districts. We found not much difference in the amount of nitrogen
contained in these fuels, which varied between 1.2 and 1.6 per cent.,
nor did we find much difference in the ammonia obtained from these
fuels if worked under similar conditions. Employing the quantity of
steam just named we