CHAPTER VI THE COMPOUNDS OF NITROGEN WITH HYDROGEN AND OXYGEN
Fig. 43.—Method of abstracting ammonia, on a large scale, from ammonia water obtained at gas
works by the dry distillation of coal, or by the fermentation of urine, &c. This water is mixed
with lime and poured into the boiler C″, and from thence into C′ and C consecutively. The last
boiler is heated directly over a furnace, and hence no ammonia remains in solution after the
liquid has been boiled in it. The liquid is therefore then thrown away. The ammonia vapour
and steam pass from the boiler C, through the tube T, into the boiler C′, and then into C″, so that
the solution in C′ becomes stronger than that in C, and still stronger in C″. The boilers are furnished
with stirrers A, A′, and A″ to prevent the lime settling. From C″ the ammonia and steam
pass through the tube T″ into worm condensers surrounded with cold water, thence into the
Woulfe's bottle P, where the solution of ammonia is collected, and finally the still uncondensed
ammonia vapour is led into the flat vessel R, containing acid which absorbs the last traces of
ammonia.
It must be observed that all the complex nitrogenous substances of plants, animals, and soils are decomposed when heated with an excess of sulphuric acid, the whole of their nitrogen being converted into ammonium sulphate, from which it may be liberated by treatment with an excess of alkali. This reaction is so complete that it forms the basis of Kjeldahl's method for estimating the amount of nitrogen in its compounds.
Fig. 45.—The liquefaction of
ammonia in a thick bent
glass tube. A compound
of chloride of silver and
ammonia is placed in the
end a , and the end c is
then sealed up.
Ammonia is a colourless gas, resembling those with which we are already acquainted in its outward appearance, but clearly distinguishable from any other gas by its very characteristic and pungent smell. It irritates the eyes, and it is positively impossible to inhale it. Animals die in it. Its density, referred to hydrogen, is 8·5; hence it is lighter than air. It belongs to the class of gases which are easily liquefied.7
