irrmoGEir AXD ITS COMPOUNDS.] 



CHEMISTRY. 



835 



A large quantity of ammonia is afforded at our gas- 

 works, by the distillation of coal in producing coal gas. 

 In fact, 'the ammoniacal liquor of the gas-works goes 

 largely to swell the dividends of the gas companies. 

 Coal contains but a small per-centage of nitrogen ; but 

 this uniting with the hydrogen, produces the ammonia, 

 which partly condenses, as a dark-coloured liquor, witli 

 the water evaporated from the coals. The presence of 

 ammonia in coal gas may be readily detected by holding 

 a piece of turmeric paper over an open gas-tap, when 

 the paper will speedily turn to a brown colour. An 

 immense quantity of ammonia is thus annually wasted ; 

 and during its passage through brass tubes and con- 

 nections, it exerts a very prejudicial effect. Besides 

 being thus produced from coal, ammonia may be ob- 

 tained from some kinds of vegetables amongst the 

 fiinspis or mushroom kind, is an instance. 



When we enter on the discussion of the constitution 

 of animal substances, and the uses of nitrogen in vital 

 organisation, we shall perceive how important a part 

 that element plays in those conditions. As we have 

 already observed, there are few animal bodies but what 

 contain it, and most of them produce ammonia on 

 being subjected to destructive distillation. 



The chief salts of ammonia are the sulphate, nitrate, 

 hydrochlorate, and carbonate. The sulphate is largely 

 nsed as a manure by farmers, and is always a component 

 part of common soot. Guano contains both free and 

 combined ammonia; and hence one of its great advan- 

 tages for agricultural purposes. The nitrate has not 

 much use in ordinary life : it is, as we have already 

 mentioned, employed to manufacture laughing gas. 



Sal-ammoniac, chloride of ammonium, or hydrochlorate 

 of ammonia, as the same salt is indifferently called, has 

 numerous uses in the arts and manufactures. It is 

 employed by metallurgists, dyers, and others, for various 

 purposes, and is an important article of commerce. 

 The carbonate forms what is commonly called "smelling 

 salts." Both sal-ammoniac and the carbonate may be 

 readily sublimed by means of heat ; and this plan is 

 employed for the purpose of their purification. 



The other salts of ammonia, such as the acetate, 

 oxalate, <tc., are of chief use in the laboratory the last 

 being employed as a test for lime, with which it forms 

 an insoluble salt. 



Nitrogen forms other compounds with hydrogen ; 

 namely, imidogcn, which contains one equivalent 

 symbol, NH ; amidogen, which contains two symbol, 

 NH : and the hypothetic ammonium, which we have 

 already noticed symbol, NH<. 



Chloride of Nitrogen. This is the most explosive sub- 

 stance with which we are acquainted. Its composition is 

 that of one equivalent of nitrogen to three of chlorine ; 

 symbol, N Cb. Its preparation is attended with extreme 

 danger, unless the utmost precaution be observed. The 

 best plan is to make a tray of sheet lead, which must 

 be perfectly free from dirt or grease, and into it a 

 strong solution of sal-ammoniac is to be poured. A jar 

 of chlorine gas, mouth downwards, is then to be placed 

 in the solution, when the chloride of nitrogen will gra- 

 dually form as small globules. After a little has been 

 formed, the jar may be removed, when the chloride will 

 be found at the bottom of the dish. If it be touched 

 by any greasy substance, it will instantly explode with 

 a loud report, and the dish will most probably be 

 bent or broken in all directions. It is impossible 

 to be too careful in preparing this substance ; and 

 we strongly recommend all our readers to be satisfied 

 with the description rather than the investigation of the 

 substance. 



Nitrogen forms alo an explosive compound with 

 iodine, which is analogous to the chloride ; its symbol is 

 NIi. This iodide of nitrogen is prepared by adding 

 some liquid ammonia to iodine the same precaution 

 being employed as in the last instance. 



The fulminates of different metals will be considered 

 under their respective heads ; and the various organic 

 compounds in which nitrogen plays a conspicuous part, 

 will be dealt with hereafter. The union of carbon and 



nitrogen, producing cyanogen and its compounds, will be 

 described in the section on Carbon. 



CARBON. 



CARBON, in its ordinary state, is universally distributed 

 in nature. We find it in nearly all animal and vegetable 

 substances. It is familiar to us in our coals ; and in this 

 I form is one of the most valuable products of our country. 

 It floats, as carbonic acid, in the air we breathe ; is part 

 of ourselves, and constitutes the major portion of the 

 plants of all kinds which surround us. Strange to say, 

 that most valued of all gems, the diamond, is but carbon 

 in a pure and crystallised state ; and exists in striking 

 contrast n-ith another form of carbon the soot which 

 defiles the appearance of our houses and persons. Com- 

 bined with hydrogen, it affords us coal gas ; with hydro- 

 gen and oxygen, it forms sugar and starch ; with oxygen, 

 in various proportions, it produces acids ; and to its 

 other combinations we are indebted for alcohol, ether, 

 animal and vegetable oils, with numerous other sub- 

 stances we cannot here stop to enumerate. 



The purest form of carbon with which we are ac- 

 quainted, is the diamond ; and next to this is the well- 

 known substance, "black-lead;" which, however, does 

 not contain a particle of lead in its composition. The 

 most ordinary form of carbon is that of wood charcoal, 

 which is, however, mixed with earthy and saline matters. 

 Its symbol is C ; equivalent = 6. 



Carbon combines with oxygen in two proportions, to 

 form carbonic oxide and carbonic acid. Carbonic oxide, 

 CO, equivalent 14, is often produced during the com- 

 bustion of substances containing carbon. It burns 

 with a pale-blue flame, and is the cause of the lambent 

 flame which is often noticed arising from brick-kilns. It 

 can only be found in the gaseous form ; and, during com- 

 bustion, produces carbonic acid gas by uniting with the 

 oxygen of the atmosphere. It may be prepared as 

 follows : 



Experiment 46. Heat, in a test tube, or Florence flask 

 fitted with a bent tube, some oxalic acid in crystals, to 

 which some strong sulphuric acid is to be added. Car- 

 bonic oxide will be produced, together with carbonic 

 acid. The gas may be received in the ordinary manner, 

 in jars, over the pneumatic trough ; which, however, 

 should be filled with water containing a solution of 

 potass ' A better plan is to pass the gas through a 

 solution of potass, in an intermediate vessel containing 

 potass in solution, in the manner represented in the 

 following engraving. 



Fig. si. 



When sufficient of the gas has been collected, a taper 

 may be applied to the mouth of the jar, with its riin 

 held downwards ; as the gas has a specific gravity of 0'97, 

 or less than that of the air. The colour of the flame 

 may thus be readily noticed. 



Carbonic acid results from the union of one equivalent 

 of carbon with two of oxygen: its symbol is COs ; equiva- 

 lent = 22. This gas has a greater specific gravity than 

 air, it being equal to 1'527. It is not poisonous, but 

 destroys life if respired, through the absence of oxygen. 

 It is produced in large quantities during respiration, 

 combustion, fermentation, <tc ; and we shall suggest a 

 few experiments illustrating these facts, and its general 

 characteristics. 



