The sulphides of ammonium are formed by saturating the solution with well-washed sulphu retted hydrogen, or by distilling a mixture of tho alkaline sulphides or iron pyrites with sal-ammoniac or tho sulphate.
Ammonia exists, or rather is found sfter a short time, in animal excreta, the earliest source of this substance, as far as we know, being the excrement of the camel, in which the Egyptians at one time carried on an extensive trade. It exists ready formed in the excreta of certain serpents, as the boa, in the form of urate of ammonia, and which a few years ago was largely prescribed for con sumptive patients by an eminent London physician. Human urine yields, when fermented, a large quautity of ammonia, which results from the oxidation of urea ; this has been utilized as a source of ammonia. Schoenbein has shown that ammonia is formed when water is evaporated in atme spherio air, and that nitrate of ammonia is produced in many cases of combustion. He accouuts for the presence of ammoniacal salts in volcanic vapours, &c., by evaporation only, since he con siders it impossible that nitrogenized matters can be present in volcanoes.
In 1861, Mr. Manning patented au arrangeuient for collecting ammonia from the waste gases arising from combustion, as in factories. It is obvious that this is scarcely practicable where the conduction of the furnace smoke into chambers or other reservoirs is likely to interfere with the draught. Ou the other hand, the sooty matter from chimneys was for a long time an important source of sal-ammoniac. Ammonia exists in chimney soot, principally as carbonate, sulphate, and chloride; to the agriculturist it is an important fertilizer. The ammoniacal salts from soot are easily extracted by percolation with warm ivater, but better still by digestion with agitation. By sublimation, the ammoniacal ealts are driven over, mixed with tarry matter, from which they are separated by conversion into sulphate, and crystallized. Although this substance is so rich in ammonia, it does not appear to be used for its productiou. The liquid obtained from the soot boiling does not give riso to that objectionable frothing, when heated with milk of lime, which takes place with gas or bone liquor ; it seems, therefore, eminentli adapted for the production of liquor ammonia, espeoially on the small scale. The gas, after washing, may be passed into a suitable veesel or receiver containing acid, for the production of its salts. For the collection of ammouiacal salts from the waste gases given off during the combustion of coal in factories, It is necessary to avoid any obstruction to the draught. But still there is a very promising field open for the application of a well-devised method for condensing and collecting the ammoniacal salts given off when coal is consumed in a factory furnace.
In 1841, a patent was obtained for the application of a particular apparatus, which was hitherto used in this country for distilling alcohol, to the production of ammonia. It is shown in Fig. 194, and consists of an upright vessel W, divided into compartments d, by perforated
diaphragms of sheet iron. Fitted to each diaphragm are several small valves, weighted so as to rise whenever the accumulated gas has attained a desirable amount of pressure ; the valve being lifted or forced up allows the gas to enter the second compartment, and so on through each succes sive division. A pipe A is attached to each diaphragm, which projects about an inch above its upper surface, and reaches below nearly to the bottom of a small cup B, fitted on the upper side of the next diaphragm. This pipe allows the downward flow of the liquid, which enters for distilla tion at K, in the upper part of the apparatus. When these small cups are filled with liquid, the ends of the tubes reaching into them are closed, which prevents the upward passage of the gas through these tubes. The apparatus is connected to an air-tight receiver E, in which the descending liquid is accumulated. The receiver is supplied with an outlet G, and stopcock for drawing off the liquid, and near the top a pipe 'or inlet for steam S.
The liquid undergoing distillation covers the upper surface of these perforated diaphragms, as the pressure of the steam being upwards prevents the liquid falling through the small perforations, and as the steam cannot ascend but through these small holes, the liquid lying on them becomes heated, and in consequence readily parts with its gaseous or volatile matters. The object of this arrangement is simply to expose a large surface•of the liquid to the action of the heat ; the liberated ammonia escapes by the weighted valves to the outlet H at the top. According to the inventor, the management of the apparatus varies in some measure with the form in which it is desired to obtain the ammonia. If the ammonia he required to leave the chamber as gas, the steam, which ascends, and the ammoniacal liquid, which descends, must be so adjusted that the ammoniacal liquid is only slightly heated during its passage through some of the upper compartments, becoming progressively hotter as it descends. If the ammonia is to be collected and condensed with the vapour of water, the supply of steam must be such that the ammoniacal liquid in the upper part of the apparatus is maintained at the boiling point. The advantages possessed by this arrangement are, that a large evaporating surface is obtained, and a continuous flow of the liquid to be distilled can he main tained. The apparatus is generally made of wood lined with lead. There is no particular limit to the number of compartments ; but the distillation will be more complete by Increasing the number of them. In the figure P is n pump for supplying from the tank T a steady flow of fresh liquid into the still. The gas may be passed through coolers, or direct into water or acid. The fluid collecting in E may be maintained at the boiling point for a short time before being allowed to run away, so as to make sure that all the ammonia is expelled.