the haws of Affinity. 137 



fub (lances *, This fubjecl: w ill require (till further explana- 

 tion. 



13. The refulting affinity ought always to be confidered as 

 a (ingle force, while the fubttances from which it is derived 

 remain in combination : but when a feparation takes place, 

 it is neceffary to confider the elements of which it is com- 

 pofed; for the reful t will then be conformable to what has 

 been explained in the divifion of fubttances, in proportion to 

 the oppofite powers which a& upon them. 



14. It often happens that a fubltance acls partly by a re- 

 fulting affinity and partly by its elementary affinities. When 

 a metal is diifolved by the nitric acid, one part of the acid 

 exerts a refulting affinity, and another a&s by its elementary 

 affinities; fo that the oxygen of the latter part is divided be- 

 tween the metal and the azote, and the oxide which is formed 

 is diifolved in the undeeompofed acid. 



15. It is obvious, from what has jufl been explained rela- 

 tive to refulting affinity, that a falfe idea may be adopted of 

 the properties of a body, when we confine ourfelves, as 

 is too often done, to the determination of its conftituent 

 parts, without paying attention to the other conditions of its 

 conftitution, if among thofe conftituent parts there chance to 

 be fome whofe itate has undergone a confklerable alteration. 

 A quantity of oxygen gas does not polfefs the fame chemical 

 power when it is in the elaftic ftate, as when it exerts a re- 

 fulting force in its combination with azote, hydrogen, car- 

 bon, fulphur, or a metal. For example, the oxygen does 

 not exert the fame action, and has not the fame refulting 

 affinity, in the fulphuric and the fulphurous aeid : though in 

 the fulphuric acid a fmaller proportion of fulphur is com- 

 bined, yet it adheres much more ftrongly than in the ful- 

 phurous acid, and, being more condenfed, it exerts a much 

 more powerful chemical action f. We ought not to con- 

 found the oxygen gas which is held in folution by water, 

 with the oxygen whieh, by its combination with hydrogen, 

 forms this liquid : the difference caufed between them by the 

 ftate of condenfation, produces two fubftances very different 

 in their chemical action. It is therefore necellary, either to 

 confider the whole conftitution of a body, in order to ex- 

 plain its chemical properties, or to content ourfelves with 



* I have often reforted to this change of conftitution in the chemical 

 explanations which I have had occafion to give, and particularly • rhe 

 lectures of the National School, where I defined the refulting aftlnitv by 

 the name of collctii've aj/imty, and diftinguiihed it from dementaty <<jfz- 

 nuies. 



\ I have obferved the efFccls of condenfation in a memoir on the ful- 

 phyrous acid. (Annates de Cbimie 1789.) 



eftablifhing 



