AMMONIA. 143 



after all, it is by no means necessary that the metal should be isolated, for tho exist- 

 ence of numerous basic radicals has been assumed in organic chemistry which have 

 never been isolated. 



It is true, also, that the oxide of ammonium is unknown, but substitution-products 

 of it have been produced, which are solid bodies, soluble in water, exhibiting all the 

 characters of potash solution, being as powerfully caustic and alkaline. In fact, 

 ammonia is in reality but the type of a vast number of compounds. It is capable 

 of having its hydrogen replaced by metals (as copper, mercury, calcium, &c.), as 

 well as by metallic Or basic compound radicals, producing the endless number of 

 artificial organic bases, which are primary, secondary, or tertiary nitrides, according 

 as one, two, or three equivalents of the ammonia is replaced. "When the substitu- 

 tion of the hydrogen in ammonia is effected by acid radicals, the compounds are 

 called amides. 



Preparation of Ammonia. Ammonia is obtained by the decomposition of one of the 

 salts of ammonia, either the chloride of ammonium, NH 4 Cl (sal-ammoniac), or the 

 sulphate, by a metallic oxide, e.g. lime. 



NH'Cl + CaO.HO = CaCl + NH S + 2HO. 



2(WH 4 CI) + CaH 2 2 = CaCl 2 + 2WH 3 + 2H 2 O. 



On the small scale in the laboratory the powdered ammoniacal salt is mixed with 

 slaked lime, in a Florence flask or a small iron retort, and gently heated ; the am- 

 moniacal gas being dried by passing it through a bottle containing lime. Chloride of 

 calcium must not be employed in the desiccation of ammonia, since the ammonia is 

 absorbed by this salt, producing a curious compound, the chloride of caliammo- 

 nium. 



It has been proposed by Knab to make use of the property of chloride of calcium 

 to absorb ammonia and give it up again when heated, for the purpose of storing and 

 transporting it. Solution of ammonia of the usual commercial strength, specific 

 gravity 0-880, contains only 33-12 per cent., whilst the chloride of calcium compound 

 is said to retain 50 per cent. 



The gaseous ammonia must be collected over mercury, on account of its solubility 

 in water. 



This operation is carried out on the large scale for the purpose of making the 

 aqueous solution of ammonia (liquor ammonia, or spirits of hartshorn). 



Solution of Ammonia. 



Preparation. In preparing the aqueous solution, the gas is passed into water con- 

 tained in Woolfe's bottles, which on the small scale are of glass, whilst on the large 

 scale they are made of earthenware. 



A sufficiently capacious still or retort of iron or lead should be employed, which is 

 provided with a moveable neck ; and it is desirable to pass the gas through a worm, 

 to cool it, before it enters the first Woolfe's bottle. Each of the series of Woolfo's 

 bottles should be furnished with a safety-funnel in the third neck, to avoid accidents 

 by absorption. The whole of the condensing arrangements should be kept cool by 

 ice or cold water. 



Properties. In the London and in the Edinburgh ' Pharmacopeia ' two solutions 

 of ammonia are directed to bo prepared, the stronger having the specific gravity 

 0'882, and containing about 32'5 per cent, of ammonia ; the weaker of specific gravity 

 0-960, containing, therefore, about 10 per cent, of the gas. 



Sometimes the commercial solution of ammonia is made by treating impure ammo- 

 niacal salts with lime, and it then contains empyreumatic oils ; in fact, tho various 

 volatile products of the distillation of coal which are soluble in or miscible with 

 water. 



Pyrrol may be detected in ammonia by the purple colour which it strikes with an 

 excess of nitric or sulphuric acid. If the residue of its distillation bo mixed with 

 potash, Picoline is detected by its peculiar odour. Naphthaline is discovered not 

 only by its odour, but may also bo separated by sublimation or heating, after con- 

 verting the ammonia in the solution into a salt by sulphuric or hydrochloric acid. 

 Dr. Maclogan. 



"We imported into England of sulphate and liquor of ammonia as follows : 



Ammonia, sulphate of . . 1856 . . Ibs. 23,904 



. 1855 . . 343,609 



Ammonia, liquor . . 1855 . . 22,400 



Since, for the purpose of purification on tho large scale, ammonia is invariably 



