2. A modification of Coffey’s still,[43] patented by Mr W. E. Newton (1841), under the name of the ‘AMMONIA STILL,’ is now extensively and successfully employed in this manufacture. By its use ammonia may be obtained from ‘gas-liquor,’ ‘bone-spirit,’ or any other ammoniacal liquor or solution, and even from solutions of the salts of ammonia, of almost any density, and of considerable purity; and this by a process which is continuous and inexpensive. The body of the apparatus is formed of wood, the chambers are lined with lead, and the diaphragms are of perforated sheet iron. The management of the apparatus varies with the form in which it is desired to obtain the product. When the ammonia is required to leave the upper chamber of the rectifier in the form of gas, either pure or impure, the steam which ascends, and the current of ‘ammoniacal liquor’ which descends, are regulated in such relative proportions that the latter remains at or near the atmospheric temperature during its passage through some of the upper chambers, becoming successively hotter as it descends, until at length it enters into ebullition; in which state it passes through the lower chambers, either to make its escape, or to enter a cistern provided to receive it. If, on the contrary, the ammonia is required to leave the upper chamber in combination with the vapour of water, the supply of steam entering below must be in such proportion to that of the ammoniacal liquor supplied from above, that the latter may be at or near the boiling temperature in the upper part of the apparatus. Crude liquor and ammonia-salts, before being thus submitted to distillation, are, of course, first treated with a proper quantity of quick-lime——in the one case to remove most of the impurities, and in the other to set the ammonia free by seizing on its acid.[44] [Footnote 43: An _engr._ and description of this still, as employed for spirit, is given under DISTILLATION (which _see_).] [Footnote 44: For a full description of the “AMMONIA-STILL,” _see_ Newton’s ‘Patent Journ.,’ ‘Pharm Journ.,’ xiii, 64; &c.] The water or solution contained in the first bottle or the first receiver is found to be the strongest, provided it has been kept well cooled; and that in the others, of progressively decreasing strength. By mixing the contents of one bottle with another a solution of almost any strength may be made. It is also easy to prepare liquor of ammonia of any required strength, or to ascertain the strength of that in the receivers, by observing the expansion of the liquid. Water, when fully saturated with ammonia, expands from 3 volumes to 5 vols.; and in less, but corresponding proportion, according to the quantity absorbed. All that is necessary in practice is, that each receiver be furnished with a gauge-pipe by which the degree of expansion may be noted. On the small scale, graduated glass receivers may be used.