NEW THEORY OF MIXED GASES. 271 



There are but three fuppofitions we can make eftentially Where gafes 

 different refpeaing the mutual adion of heterogeneous par- ™*' s |£*|J£ 

 tides of gas: \jt, When two gafes are mixed their particles ther, (i.) repel, 

 may reciprocally repel one another, juft as they ad on their own °*2j^ ha ^ e tt £ 

 kind in an unmixed ftate : 2d, They may be neutral, or have attract, 

 neither attraction nor repulfion for each other : 3d, They may 

 have a chemical affinity or attraction for each other. The ad- The gafes do not 

 vocates for the chemical adhefion of gafes will agree with me^ /; iScf 

 in exploding the. firft, becaufe where nothing but repulfion is have no aclion 

 manifeft, we can afcribe no efTeft to attradion : The fecond, *^ j™^ 9 . **■ 

 which is the one I adopt, is obviouily inconfiftent with their and, 

 hypotheiis; and as for the third, I can conceive no other ex- 

 planation than the following : \Jl, Two or more heterogeneous if the particles 

 particles may unite and become a new centre for the caloric the become one 

 to adhere to; but in this cafe the gafes are no longer two but gas, and not t<wc 9 

 one; and oxigenous and hidrogenous would become aqueous ^ n . 1 e um 

 vapor : This therefore is not a cafe of two gafes being held 

 together by chemical affinity. 2d, The two gafes may fepa- Or if they at- 



rately retain their caloric and ft ill be held by chemical affinity ; *** *"£ do ** • 

 J J J ' unite, they mutt 



that is, there may be an equilibrium between the powers of come nearer to- 

 attracrion and repulfion ; but this is evidently inconfiftent with gether, contrary 



' - , r . r to the third law 



the third law of condenfation and rarefaction oblerved in luch r facl above 

 compounds. ftatcd. 



I am, &c. 



J. DALTON. 



I thank you for the notice you have taken of my Eflays, and 

 particularly for the note fubjoined to that on the Expanfion of 

 Gafes. I have lately read a Paper to the Literary and Philofo- 

 phical Society of this place, in which I have fhewn that the 

 quantity of carbonic acid gas found in a given volume of at- 

 mofpheric air, is not more than y—^ part of the whole ; and 

 that the ("aid gas is held in water, not by chemical affinity, but 

 merely by the preflure of the gas abftracledly confidered oxx 

 the furface, forcing it into the pores of the water. 



VIII. A Method 



