244 Neiv Theory of the Conjtitutkn sf mixed Aeriform Fluidst 



much embarraifment and uncertainty to the chemlil aad philofopher, which otherwife 

 needed not to have taken place. 



There may be four fuppofitions in refpe£l to the affeftlonjs of the particles of one elaflic 

 fluid towards thofe of another : 



1 . Particles of one elaftic fluid may repel thofe of another with the fame force as they 

 repel thofe of their own kind. 



2. The particles of one may repel thofe of another with forces greater or lefs than that 

 exerted upon thofe of their own kind. 



2- ^^^ particles of one may poflefs no repulfive (or attraftive) power, or be perfedly 

 inelaftic with regard to the particles of another ; and confequently the mutual a£lion of 

 fuch fluids, or the a£lian of the particles of one fluid on thofe of the other, will be fubje£l 

 to the laws of inelaftic bodies. 



4. The particles of one may have a chemical affinity, or attra£tIon, for thofe of another. 



Let us now confider the confequences refulting from each of thofe fuppofitions : accord- 

 ing to the firft, if there were two gafes A and B, the particles of which were of equal 

 fpecific gravity ; then if m meafures of A were mixed with n meafures of J5, in the pneu- 

 , matic apparatus, and under atmofpheric prefliire equal to 30 inches of mercury, the two 

 gafes would occupy m -\- n meafures of fpace, and would remain in fuch circumftances as 

 they were at any time placed; that is, either intermingled or feparate: but if .^ was of 

 lefs fpecific gravity than B, A would occupy the upper part of the veflel, and the volume 

 of the compound continue the fame as before. The preflurc on each particle of the mix- 

 ture would be the fame in both cafes, and equal to 30 inches of mercury. 



According to the fecond hypothefis, if the particles of A had a greater or lefs repulfioti 

 to thofe of B than to their own, ftill m meafures of A with n meafures of B, would oc- 

 cupy m -\- n meafures of fpace, and the preflure on each particle be the fame, and equal 

 to 30 inches of mercury. But the fluids could not be mixed, unlefs the repulfive powers 

 of their particles were as the cube roots of the fpecific gravities of thofe particles ; or, 

 which amounts to the fame thing, unlefs the two fluids were of equal fpecific gravities. 



Gn the third hypothefis, if m mcafuree of A be miypil with n meafures of B, the two 

 will in this cafe likewife occupy /» + « meafures of fpace; but the two fluids, whatever 

 their fpecific gravities may be, will immediately or in a fliort time, be intimately diffufed 

 through each other, in fuch manner that the denfity of each, confidered abftradedly, will 

 be- uniform throughout ; namely (calling the denfity of the compound, unity) that of A 



will be ~ , and that oi Bzr. ; becaufe, meeting with no repulfion but what 



m + n m+ u 



arifes from particles of the fame kindy they will difFufe themfelves through any given fpace, 



occupied by a very rare medium, in the fame manner as they would do in a vacuum, each 



particle being impelled as far as poffible from its neighbouring particle ; only the diflFufion 



of each may be a little retarded by the other. The preflure upon any one particle in this 



cafe will not be as the denfity of the compound, as before, but as the denfity of the particles 



3 "^ 



