AMMONIA, SULPHATE OF 147 



tlio sulphate of ammonia that tho modification of Coffey's still, called the ammonia 

 still, is generally employed, it may be well to introduce hero a detailed account of its 

 arrangement. 



This apparatus is an upright vessel, divided by horizontal diaphragms or partitions 

 into a number of chambers. It ds proposed to construct tho vessel of wood, lined 

 with lead, and tho diaphragms of sheet iron. Each diaphragm is perforated with 

 many small holes, so regulated, both with regard to number and size, as to afford, 

 under some pressure, passage for the elastic vapours which ascend, during the use of 

 tho apparatus, to make their exit by a pipe opening from the upper chamber. Fitted 

 to each diaphragm are several small valves, so weighted as to rise whenever elastic 

 vapours accumulate under them in such quantity as to exert more than a certain 

 amount of pressure on the diaphragm. A pipe also is attached to each diaphragm, 

 passing from about an inch above its upper surface to near the bottom of a cup or 

 small reservoir, fixed to the upper surface of the diaphragms next underneath. This 

 pipe is sufficiently largo to transmit freely downwards tho whole of the liquid which 

 enters for distillation at the upper part of the upright vessel ; and the cup or reservoir 

 into which the pipe dips forms, when full of liquid, a trap by which the upward 

 passage of elastic vapours by the pipe is prevented. The vessel may rest on a close 

 cistern, contrived to receive the descending liquid as it leaves the lowest chamber, 

 and from this cistern it may be run off, by a valve or cock, whenever expedient. The 

 cistern, or in its absence the lowest chamber, contains the orifice of a pipe which 

 supplies the steam for working the apparatus. The exact number of chambers into 

 which the upright vessel is divided is not of essential importance ; but the quantity 

 of liquid and the surface of each diaphragm being given, tho distillation, within certain 

 limits, will be more complete the greater tho number of chambers used in the pro- 

 cess. The liquid undergoing distillation in this apparatus necessarily covers the 

 upper surface of each diaphragm to the depth of about an inch, being prevented from 

 passing downward through the small perforations by tho upward pressure of the 

 rising steam and other elastic vapours ; and, on the other hand, the steam being 

 prevented, by the traps, from passing upwards by the pipes, is forced to ascend by 

 the perforations in the diaphragms ; so that tho liquid lying on them becomes heated, 

 and in consequence gives off its volatile matters. When tho ammoniacal liquid ac- 

 cumulates on one of the diaphragms to the depth of an inch, it flows over one of the 

 short pipes into tho trap below, and overflows into the next diaphragm, and so on. 

 See DISTILLATION. 



The management of the apparatus varies in some measure with the form in which 

 it is desirable to obtain the ammonia. When the ammonia is required to leave the 

 upper chamber in the form of gas, either pure or impure, it is necessary that the 

 steam which ascends and the current of ammoniacal liquid which descends, should be 

 in such relative proportions that the latter remains at or near tho atmospheric tempera- 

 ture during its passage through some of the upper chambers, becoming progressively 

 hotter as it descends, until it reaches the boiling temperature ; in which state it 

 passes through the lower chambers, either to make its escape, or to enter a cistern 

 provided to receive it, and in which it may for some time be maintained at a boiling 

 heat. On the contrary, if the ammonia, either pure or impure, bo required to leave 

 the upper chamber in combination with tho vapour of water, tho supply of steam 

 entering below must bear such proportion to that of tho ammoniacal liquid supplied 

 above, that the latter may be at a boiling temperature in tho tipper part of the 

 apparatus. 1 



The use of this apparatus was patented in the name of Mr. W. E. Newton, 

 Nov. 9, 1841. 



Mr. Hills' process, patented Oct. 19, 1848, for concentrating ammoniacal solutions 

 by causing them to descend through a tower of coke through which steam is ascend- 

 ing, is, in fact, nothing more than a rough mode of carrying out the same principle, 

 which is more effectually and elegantly performed by the modification of Coffey's still 

 above described. The concentrated ammonia liquor is then treated with acid and 

 evaporated in the usual way. 



Mr. Wilson patented, Dec. 7, 1850, another method of saturating tho ammonia 

 with the acid by passing the crude ammonia vapour, obtained by heating the ammo- 

 niacal liquor of the gas-works, in at the bottom of a high tower filled with coke, 

 whilst the sulphuric acid descends in a continuous current from the top ; in this 

 manner the acid and ammonia are exposed to each other over a greatly extended 

 surface. 



Dr. Richardson (patent, Jan. 26, 1850) mixes the crude ammonia liquors with 

 sulphate of magnesia, then evaporates tho solution, and submits tho double sulphate 



1 I'h.irm. Journal, xiii. 64. 

 1,2 



