146 AMMONIA, SULPHATE OF 



OtJifr Carbonates of Ammonia. Besides the neutral or monocarbonato of ammonia 

 before alluded to, the true bicarbonate NH'O, CO 2 ; HO, CO* [(WH 4 ) 2 CO 3 ; H-CO S ] 

 and the sesquicarbonato of the shops, Rose has described about a dozen other 

 definite compounds ; but, for their description, wo must refer to Watts's ' Dictionary 

 of Chemistry.' 



AMMONIACUM, OUM. Gum-resin. ( Gomme Ammoniaquc, Fr. ; Ammoniak, 

 Gor.) This is the inspissated juice of an umbelliferous plant (the Dorcma ammoniacum), 

 the gum-bearing heracleum, which grows in Persia, the East Indies, and Africa. In 

 the French colony of Algiers this plant grows naturally, and it appears likely to 

 become an object of cultivation. It comes to us either in small white tears clustered 

 together, or in brownish lumps, containing many impurities. It possesses a peculiar 

 smell, somewhat like that of assafcetida, and a bitterish taste. It is employed in 

 medicine. Its only use in the arts is for forming a cement to join broken pieces of 

 china and glass, which may be prepared as follows : ' Take isinglass 1 ounce, distilled 

 water 6 ounces, boil together down to 3 ounces, and add l ounce of strong spirit of 

 wine ; boil this mixture for a minute or two ; strain it ; add while hot ; first, half 

 an ounce of milky emulsion of gum ammoniac, and then 5 drachms of an alcoholic 

 solution of resin mastic.' 



AMMONIA, NITRATE OF. This salt is not made on an extensive scale ; 

 but as it has a certain consumption for making the protoxide of nitrogen (laughing 

 gas), now largely used by dentists as an aneesthetic, a few remarks respecting it may 

 not be out of place here. 



It is obtained by saturating solution of ammonia, or the carbonate, with nitric acid, 

 and then evaporating the solution till crystallisation takes place. It ought to be per- 

 fectly free from chloride of ammonium. 



This salt crystallises in six-sided prisms, being isomorphous with nitrate of 

 potash. 



Its composition is NH J 0, NO 5 [(WH 4 )W O 3 .] It is incapable of existing without the 

 presence of an equivalent of water, in addition to NH 3 and NO 5 . If heat be applied, 

 the salt is entirely decomposed into protoxide of nitrogen and water ; thus 



NH0, NO* - 2NO + 4HO. 

 N'O + 2H-0. 



Besides its use in the laboratory for making protoxide of nitrogen, it is a con- 

 stituent of frigorific mixtures, on account of the cold which it produces on dissolving 

 in water. 



Lastly, it is very convenient for promoting the deflagration of organic bodies, both 

 its constituents being volatile on heating. 



AMMONIA, SULPHATE OF. NH J 0, SO 3 [(NH l )-SO 4 ]. This salt is found 

 native in fissures near volcanoes, under the name of Mascagnin, associated with sal- 

 ammoniac. It also forms in ignited coal-beds as at Bradley, in Staffordshire with 

 chloride of ammonium. 



This salt is prepared by saturating the solution of ammonia, obtained by any of the 

 processes before described (either from animal refuse, from coal, in the manufacture 

 of coal gas, from guano, or from any other source), with sulphuric acid, and then 

 evaporating the solution till the salt crystallises out. 



Frequently, instead of adding the acid to the ammoniacal liquor, the crude ammo- 

 niacal liquor is distilled in a boiler, either alone or with lime, and the evolved am- 

 monia is passed into the sulphuric acid, contained in a largo tun or in a series of 

 Woolfe's bottles ; or a modification of Coffey's still may be used with advantage, as 

 in the case of the saturation of hydrochloric acid by ammonia. 



If Coffey's still be employed, a considerable concentration of the liquor is effected 

 during the process of saturation, which is subsequently completed generally in iron 

 pans ; but great care has to be taken not to carry the evaporation too far, to avoid 

 decomposition of the sulphate by the organic matter invariably present, which reduces 

 it to the state of sulphite, hyposulphite, and even to sulphide, of ammonium. 



The salt obtained by this first crystallisation is much purer than the chloride produced 

 under similar circumstances, and one or two recrystallisations effect its purification 

 sufficiently for all commercial purposes. 



It is on account of the greater facility of purification which the sulphate affords 

 by crystallisation than the chloride of ammonium, that the former is often produced 

 as a preliminary stage in the manufacture of the latter compound, the purified 

 sulphate being then converted into sal-ammoniac by sublimation with common salt. 

 The acid mother-liquor left in the first crystallisation is returned to be again treated, 

 together with some additional acid, with a fresh quantity of ammonia. 



Preparation, Modifications in details and patents. Since it is in the production of 



