COMPOUNDS OF NITROGEN WITH HYDROGEN AND OXYGEN 245 



for the preparation of coal gas. This ammoniacal liquor is placed in a 

 retort with lime and heated ; the ammonia is then evolved together 

 with steam. 4 In practice, only a small amount of ammonia is used in 

 a free state that is, in an aqueous solution ; the greater portion of it 

 is converted into different salts having technical uses, especially sal- 

 ammoniac, NH 4 C1, and ammonia sulphate, (NH 4 ) 2 SO 4 . They are saline 

 substances which are formed because ammonia, NH 3 , combines with all 

 acids, HX, forming ammonia salts, NH 4 X. Sal-ammoniac, NH 4 C1, is 



I'n,. -i:5. Method of abstracting ammonia, on a large scale, from ammonia water obtained at gas 

 \\orks 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 

 boiln- is heated directly over a furnace, and therefore no ammonia remains in solution after the 

 liquid liits been boiled io it. The liquid is therefore then thrown away. The ammonia vapour and 

 steiiiii 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, from thence into the 

 Wouite's bottle P, where the solution of ammonia is collected, and from whence the still uncon- 

 densed ammonia vapour is led into the flat vessel R, containing acid which retains traces of 

 ammoniii. 



a compound of ammonia with hydrochloric acid. It is prepared by 

 passing the vapours of ammonia and water, evolved, as above described, 

 from ammoniacal liquor, into an aqueous solution of hydrochloric acid, 

 and on evaporating the solution sal-ammoniac is obtained in the form 

 of soluble crystals 5 resembling common salt in appearance and pro- 



4 The technical methods for the preparation of ammonia water, and for the extraction 

 of ammonia from it, are to a certain extent explained in the figures accompanying the 

 text. 



5 Usually these crystals are sublimed by heating them in crucibles or pots, when the 

 vapours of sal-ammoniac condense on the cold covers as a crust, in which form it cornea 

 into the market. 



