On Chemical Equivalents. 101 



as is represented by the diagram. The fractions show that the 

 chemical attraction of azote for oxvgen is nearly exhausted. This 

 is the state of colourless nitrous acid ; and, in my opinion, no 

 more oxygen can unite to the azote, having its whole force of 

 attraction expended in the particles a, b,c, d, e. This illustrates 

 the nature of saturation or definite proportions," 



" We can readily perceive from the foregoing demonstrations, 

 that oxygen is retained with less force in the colourless nitrous 

 acid than in the straw-coloured ; and the latter acid retains it 

 with less force than the red nitrous acid ; and nitrous gas holds 

 it with still more force than the red nitrous acid. This accounts 

 for the separation of oxygen gas from the colourless nitrous acid 

 (nitric acid) when exposed to the sun, at the same time that the 

 acid becomes coloured. Nitrous acid in any other state will af- 

 ford no oxygen, when exposed to the sun."' 



" Why the gaseous oxide should be more soluble in water 

 than the nitrous gas, is what I cannot account for, unless it be 

 occasioned by the smaller size of its calorific atmospheres, which 

 may admit its atoms to come within the gravitating influence of 

 that fluid." 



It is impossible to deny the praise, of singular ingenuity, and 

 justness, to the above passages ; and every one must be struck 

 with their analogy, both as to atomical doctrines, and the calorific 

 atmospheres of gases, single and compound, with the language 

 and views expanded at full length in Mr. Dalton's New System 

 of Chemical Philosophy, first framed about the year 1803, and 

 published in 180S. It appears that this philosopher, after medi- 

 tating on the definite proportions, in which oxvgen was shown 

 by M. Proust to exist in the two oxides of the same metal, on 

 the successive combinations of oxygen and azote, and the pro- 

 portions of various other chemical compounds, was finallv led to 

 conclude, that the uniformity which obtains in corpuscular com- 

 binations, results from the circumstance, that they consist of one 

 atom of the one constituent, united generally with one atom of 

 the other, or with two or three atoms. And he further inferred, 

 that the relative weights of these ultimate atoms might be ascer- 

 tained from the projjortion of the two constituents in a neutral 

 compound. 



Cliemistry is un(|uestional)ly under great obligations to Mr. 

 Dalton, for the pains with which he collated the various analyses 

 of chemical bodies, by different investigators; ami for establish- 

 ing, in opposition to the doctrine of indefinite allinity, taii!.^ht bv 

 the illustrious Pjcrthollet, that the diflcrent compounds of the 

 same principles did not jiass into each other by imperceptible 

 gradations, but jnocccded, fjcr sullum, in hucce;,sive j)roporli<)ns, 



caih 



