CHEMISTRY. 



9 



PART I. 

 ELEMENTS OF CHEMISTRY. 



Elements AS the object of chemistry is to ascertain the con- 

 el stituents of bodies, the way in which these constitu- 

 Chemistry. etits combine, and the nature of the combinations 

 ^TT'Y"" 1 **' which they form, the science naturally divides itself 

 ec ' into three parts : 1. A description of the component 

 parts of bodies, or of simple substances, as they are 

 called. 2. An account of the compound bodies form- 

 ed by the union of the simple substances. 8. An 

 account of the nature of the power which induces 

 the particles of bodies to unite. This power is usu- 

 ally called affinity. These three particulars will form 

 the subject of the three following Bjoks. 



BOOK I. 

 OF SIMPLE SUBSTANCES. 



Simple sub. E are probably ignorant at present of bodies, 



Ktance*. itrictly speaking, elementary or simple. All that 

 is understood in chemistry by a simple tubttance, is 

 a substance not yet decomposed, and which we can- 

 not shew to he a compound. Those of that kind 

 at present known are about forty-eight. They may 

 be divided into two classes ; those which can be con- 

 fined in vessels, and of course exhibited in a sepa- 

 rate state ; and those which cannot be confined in 

 any ve?sel that we possess, and the existence of 

 which it> only inferred from certain phenomena exhi- 

 bited by the first class of bodies in certain circum- 

 stances. The first class of bodies may be called con- 

 finable, the second vnconjinable. 



DIVISION I. 



Op CONFIXABLE Borne*. 



Onfiuablc un containable bodies may be arranged under the 



bodies. f ur following heads : 



1. Simple supporters of combustion. 



'_'. Simple combustibles. 



3. Simple incombustibles. 



4. Metals. 



These classes shall be treated of in order in the 

 four following Chapters. 



CHAP. I. 



Of Simple Supporters of Combustion. 



bustible substances will burn. Thus air is a sup- 

 porter of combustion, because a candle will not burn 

 unless it be supplied with air. All supporters, not 

 yet decompounded, are called simple. 



We are at present acquainted with two simple sup- 

 porters of combustion, namely, oxygen and chlorine. 



SECT. I. Of Oxygen. 



This substance is an air, or, as chemists use to 

 call aerial bodies, a gaf. * It was discovered by Dr 

 Priestlty, on the 1st of August 177*. It may be 

 obtained by heating black oxide of manganese in an 

 iron bottle fitted with a long iron tube. The extre- 

 mity of the tube is plunged into a trough of water, 

 having a shelf a little below the surface, on which 

 stands an inverted glass cylinder full of water. The 

 open mouth of this cylinder is brought over the ex- 

 tremity of the iron tube. As soon as the manganese 

 is red hot, air issues from the extremity of the tube, 

 and gradually fills the glass vessel, displacing the 

 water. In this way any quantity of oxygen gas may 

 be procured. Red lead, or red precipitate, may be 

 substituted for the manganese, but they do not yield 

 so much oxygen. The salt called hyperoxymuriate 

 of potash may also be used, and it yields a very great 

 proportion of pure oxygen. Oxygen gas may also 

 be obtained, by putting the manganese in powder in- 

 to a glass retort, and pouring on it as much sulphuric 

 acid as will make it into a thin paste. The heat of 

 a lamp being applied to the retort while its beak it 

 plunged into the water trough, the gas is disengaged 

 in considerable quantity. 



This gas was called by its discoverer depfilogisii- 

 caled air ; Scheele, who likewise discovered it, cal- 

 led it empyrial air ; Condorcet gave it the name of 

 rital air ; aud at last Lavoisier, from an hypothe- 

 sis respecting the formation of acids, distinguished 

 it by the appellation of oxygen gas, which it now 

 bears. 



Oxygen gas possesses the mechanical properties 

 of common air. It is colourless, invisible, and ca- 

 pable of indefinite expansion and compression. 



Combustibles burn in it better and brighter than 

 in common air. Animals can breathe it longer than 

 common air without suffocation. 



It has been ascertained, that one-fifth of the air 

 of the atmosphere is oxygen gas, and that when thit 

 portion is abstracted, the air can neither support com- 

 bustion nor animal life. 



When substances are burnt in oxygen gas or air, 

 or when animals breathe them, a portion of the oxy- 



Elements 



of 

 Chemistry. 



Oxygen. 



How pro- 

 cured. 



Fu proper- 

 tiei. 



gen always disappears, and, in some cases, even the 

 whole of it. 



Simpleiup. THE term, supporter of combustion, is applied to 

 portti> of those substances which mut be present before com- 

 combiu- 



The term gti it applied by chemists to all oir except common air. 

 VOL. VI. PART I. B 



