CLASSIFICATION OF CHEMICAL AGSNTS. .g|. 



acquired its pt^inciples; the study of chemistry is therefor^ with its pciKcU 



properly begun by an attentive conf»ideration of those prini- ^ ^^' 



ciples^ by wluch its operations are produced and explained; 



«ud. consequently that arrangement would appear to be the 



most proper, iu whijih these are made to occupy the first 



place. 



But [ proceed to speak of the three classes, which are pe- Classes pecn- 

 culiar to the arrangement proposed. The first of these con- rangemeiu. 

 tains one substance only, namely oxigen. My reason for 

 devoting to this matter one whole class is founded on it^ . ,„ 



very extensive importance, and more especially on the rela- Importance « 

 tion which in ibis plan it bear# to the two classes that follow. ^ » 

 1 believe there is no substance in nature,which is not capable 

 «f entering into combination with oxigen, except those sub- 

 stances which have already suii'ered a combination of this 

 kind : such is the universality, and consequently such the 

 high importance, of this chemical agent. 



This circumstance, added to the view of the relation of its 

 combinations to each otiier,.which 1 have partly given in my 

 former communication, will, I trust, justify the plan, which 

 1 have adopted. 



The fourth class compreheiids those substances, which Substances ia 



do not contain oxi2:en; the fifth comprises all substances, '.^^ ^''^ ^''^^* 

 1- • . • •• rr.1 • 1 o 1 * 1 do not coin, 



which do contam this matter. 1 he articles ot the fourth bine with 



class do all combine with oxigen, and (as has been formerly ^^^^^ '" ^^* 



stated) generally with each other: some of the individuals 



of the fifth class unite with a still farther quantity of oxigen, 



and, as in the last case, generally with each other. But no 



individual of the fourth class will enter into combination 



with any substance which is included under the fifth. 



It has been said, that, all the substances of the fourth e^^cept 

 class will combine wilh oxigen; they may therefore all be ^^'^^[[f^ ^^ * 

 converted into articles of the fifth class; and hence it be- oxigen. 

 comes possible, that any two substances whatever may, 

 through theinediuni of oxigen, be made to combine. 



I have alleged, that the snb^tances of the fifth class will Substances in 



generally combine with each other; this however is not 1 ** 



r> J comoin J gene* 



~ univeri^ally the case; for i^hen this combination does take rally, but »«.)t 

 place, certain states, or degrees of oxidation, in the respeo- "'"v^r^aliy, 

 nv^ articles, ai-e reqiiired. Many acids dissolve oxides in requiring a p«. 

 ' certain 



