CHEMISTRY. 



15 



Elements Such are the properties of the simple combustible 



bodies ; none of which, unless hydrogen be an excep- 



'^ tion, are, strictly speaking, simple substances, though 



Vr.nJ.rri w e are not in possession of any accurate method of 



1 1 1 -1 1 



of the sim- separating their constituents, and exhibiting them in 

 pic com- a separate state. It is very likely that the hydro- 

 buitible*. g en an( j oxygen separated from several of them, 

 may be owing to the presence of water in them, 

 from which it is very difficult to separate them com- 

 pletely. 



Tivo of them, boraciiim and carbon, are solids 

 which we are incapable of melting or altering by 

 heat ; two of them, sulphur and phosphorus, easily 

 melt, and may be exhibited in a solid, liquid, or even 

 gaseous state ; while one of them, hydrogen, is al- 

 W3ys, when pure, in the state of a gas. 



They all combine with oxygen, but in different 

 proportions, as is obvious from the following table, 

 exhibiting the quantity of oxygen capable of com- 

 bining with 100 parts of each. 



100 Hydrogen unites with 750 oxygen. 



100 Carbon 251.6 



100 Boracium 200 



100 Sulphur 150 



100 Phosphorus lit 



It has been supposed by some, that the affinity of 

 different bodies for oxygen, is proportioned to the 

 quantity of it with which they combine. According 

 to this notion, the affinity cf the simple combustibles 

 for oxygen is in the order of the preceding table. 



Chlorine has the property of combining with all 

 the simple combustibles except carbon. With hy- 

 drogen it forms muriatic acid ; with sulphur, phos- 

 phorus, and boracium, it forms compounds not yet 

 distinguished by specific names. 



Hydrogen unites with all the simple combustibles, 

 unless boracium be an exception. It is probable that 

 they are all capable of combining with each other, 

 at least, in one proportion, and gome are known to 

 combine in several. Chemists have agreed to give 

 such compounds a name derived from one of the in- 

 gredients and ending in uret, as sulphuret of phos- 

 phoriu, photphuret of cnrbon. When the compound 

 is gaseous, the term i converted into an adjective, as 

 xulphureted hydrogen gat, carbureted hydrogen gas. 



CHAP. III. 

 Of Simple Incombustibles. 



Simple in- BY simple incombustibles are meant all substances 



combusti- incapable of combustion which have not yet been 



blet. decompounded. We are acquainted with only one 



body of that nature at present, namely, azote. There 



can be little doubt that it is a compound, though all 



attempts at a regular analysis of it have hitherto 



failed. 



SSCT. I. Of Azote. 



Azote. 1. Azote, called also nitrogen, which was first 



particularly pointed out by Dr Rutherford in 1772, 

 constitutes four-fifths of the atmosphere. The other 



fifth is oxygen. To obtain it pure, we have only to ElemenY< 

 deprive any portion of air of the whole of its oxygen. p f 

 This is easily done by confining in it for some time L " einistr )'- 

 a mixture of sulphur and iron filings made up into a How'oli- 

 paste, or a quantity of phosphorus,. tained. 



L)r Priestley, who was one of the original experi- 

 menters on this substance, gave it the name of pklo- 

 gisticated air. The French chemists called it at 

 first miifete, and afterwards azotic gtis, because ani- 

 mals cannot breath it without dt-ath. The name 

 azoic, though it has prevailed, is without doubt ill 

 chosen. 



Azotic gas is invisible, and possesses the mechani- Its proper- 

 cal properties of common air. Its specific gravity, t ' es - 

 according to Kirwan, is O.Q85; according to Lavoi- 

 sier, 0.978; according to Biot and Arago, 0.969; 

 that of common air being 1.000. 



It neither supports flame nor animal life. Water 

 does not sensibly absorb it. 100 cubic inches ot wa- 

 ter, freed from air by boiling, absorb about 1^ inches 

 of this gas. 



2. Though incombustible, it is capable of com- 

 bining with oxygen gas. When electric sparks are 

 passed through a mixture of oxygen and azotic gases 

 for some time, the bulk of the mixture diminishes, 

 and an acid is formed. If the gases be mixed in the Nitrous 

 proper proportions, they disappear entirely, and are cid 

 of course totally converted into an acid. This acid 

 is the nitrous. Hence it follows, that nitrous acid 

 is composed of oxygen and azote. This important 

 discovery was made by Mr Cavendish. The result 

 of his experiments gives us nitrous acid composed 

 very nearly of 30 azote, 



70 oxygen. 



100 

 or one part azote united to 2 i of oxygen. 



Nitric acid is a yellow corrosive liquid, of great im- Mj trou ,' 

 portance in chemistry. It acts with great energy on g as . 

 most other bodies, in consequence of ttie facility 

 with which it parts with its oxjgen. If copper or 

 tilver, for example, be put into it, the metals absorb 

 oxygen and dissolve. The portion of acid which 

 loses a part of its oxygen, assumes the gaseous form, 

 and makes its escape out of the liquid, occasioning 

 an effervescence. The gas which escapes is a com- 

 pound of azote, and a smaller proportion of oxygen 

 than exists in nitric acid. It is usually called nitrous 

 gas. It has the curious property of combining with 

 oxygen gas whenever it comes in contact with it, 

 and of thus being again converted into nitric acid. 

 The mixture becomes yellow ; and, if standing over 

 water, its bulk diminishes very much, because the 

 water absoibs the acid as it forms. 



If iron filings be kept for some days in a jar of Gaseous 

 nitrous gas, its bulk diminishes, and it loses the pro- ox "le. 

 perty of becoming yellow whi-n mixed with common 

 air. Its properties are now changed, and it is called 

 gaseous oxide of azote. This new gas is composed 

 of the same constituents as the former, but it con- 

 tains a smaller proportion of oxygen. It supports 

 combustion, and bodies burn in it almost with as 

 much splendour as in oxygen gas. 



Thus it appears, that azote has the property of 

 combining with three different doses of oxygen. 



