DOCTRINE OF MIXED GASKS. ^^ 



After all that has been faid about the conftitution of gafes, 

 the notion is incorreft, ftri6lly fpeaking, which fuppofes each 

 gas to be as a vacuum to every other. The foregoing obferva* 

 tion may alfo be extended to mixtures of carbonic acid gas 

 with water; and the following inftances may be adduced in 

 confirmation of the propofition : When a particular gas is de- Proved by cxpc* 

 veloped in a vetTel containing common air, the firft portion *^'°**°'* 

 that comes over has in it lefs of the fpecific gas than the fe- 

 cond ; nor is the fecond equal to the third in purity. This 

 circum fiance fliews, that the new-formed gas does not find a 

 vacuum in the air of the veflel ; on the contrary, the two 

 fluids produce a mechanical mixture, which is gradually ex- 

 pelled, until no part of the air remains in the tube or bottle. 

 In like manner, if a bottle of highly asrated water be opened 

 fuddenly, the rapid expanfion of the liberated gas eje6ls a 

 great part of the contents, thereby proving that water oppofes 

 an obftacle to the dilatation of this gas. In reality, Mr. Dalton 

 allows one gas to be an impediment to the motions of another; 

 but at the fame time he maintains, that two fuch fluids finally 

 overcome their mutual obflruftions, and occupy the fame 

 fpace in a /late of perfect independence. This is a propofi- 

 tion which may be juftly fufpe6ted of being a folecifm in pneu- 

 matics, until the author of it has proved the contrary by a ri- 

 gorous demonftration. 



Amongfl the many probabilities which have been oflfered in A new theory •£ 

 fupport of the hypothefis, perhaps none are more ingenious ^*i^*^ ^ ''" 

 than the remarks of Mr. Henry ; and the part which I have 

 taken in the prefent letter, obliges me to place them in a new 

 light. This attempt muft, however, be preceded by a theory, 

 which will explain the relations of thofe gafes that neither 

 attrad nor repel each other : fuch an explanation became a 

 neceflary part of pneumatics, from the time when Dr. Prieflley 

 made his experiments upon mixtures of this defcription. The 

 following, then, is a flietch of a theory, having for its founda^- 

 tions the mutual repulfion of homogeneous particles, and ihe 

 reciprocal refiftance which gafes have been fliewnto poffefs. 



When two fuch gafes come into conta6l, parcels of each Sketch of the j 

 will be detached by every flight force, and enveloped in the ^^^°^y^ 

 fubfiance of the other. In this manner, the two fluids will be 

 broken to pieces, and blended in one mafs forrning a mechci- 

 3i «ic^l 



