recovered about half the nitrogen in the form of
ammonia, yielding on an average 0.8 per cent. of ammonia, equal to 32
kilos, of sulphate per ton of fuel. In order to obtain regular results
we found it necessary to work with a great depth of fuel in the
producers, so that slight irregularities in the working would not
affect results. Open burning kinds of slack do of course work with the
greater ease, but there is no difficulty in using a caking fuel, as
the low temperature at which the producers work prevents clinkering
and diminishes the tendency of such fuels to cake together.

The quantity of steam thus required to obtain a good yield of ammonia
is rather considerable, and threatened to become a serious item of
expense. Only one-third of this steam is decomposed, in its passage
through the producer, and two-thirds remain mixed with the gases which
leave the producer. My endeavors were consequently directed toward
finding means to recover this steam, and to return it to the
producers, and also to utilize the heat of the gases which leave the
producers with a temperature of 450 deg. to 500 deg. C., for raising steam for
the same purpose. The difficulties in the way of attaining this end
and at the same time of recovering, in a simple manner, the small
amount of ammonia contained in the immense volume of gas we have to
deal with, were very great. We obtain from one ton of coal 160,000
cubic feet of dry gas at 0 deg. C. and atmospheric pressure. The steam
mixed with this gas as it leaves the producer adds another 80,000
cubic feet to this, and the large amount of latent heat in this
quantity of steam makes the problem still more difficult. The
application of cooling arrangements, such as have been successfully
applied to blast furnace gases, in which there is no steam present,
and which depend upon the cooling through the metallic sides of the
apparatus, is here practically out of the question. After trying a
number of different kinds of apparatus, I have succeeded in solving
the problem in the following way:

The gases issuing from the producers are led through a rectangular
chamber partly filled with water, which is thrown up in a fine spray
by revolving beaters so as to fill the whole area of the chamber. This
water, of course, becomes hot; a certain quantity of it evaporates,
the spray produced washes all dust and soot out of the gases, and also
condenses the fixed ammonia. The water thus becomes, to a certain
de