196 • "Theory of mixed Gases, 



gas should ascend into a lighter one without the aid of agi- 

 tation ; and, on the contrary, a lighter one should descend 

 into a heavier oue. That this is actually the fact, and under 

 circumstances very unfavourable to their mixture, your own 

 experiments have fully proved. 



2dly, The hypothesis explains why sulphuret of potash 

 w ; thdraws oxvgen from the air without agitation, and whe- 

 ther placed at the top or at the bottom of a jar ; for it acts 

 as if the absorbed gas were the only one present in the 

 vessel. 



3dly, It explains why the last portions of common air 

 are expelled from water by carbonic acid and other absorb- 

 able gases. For these gases act as a vacuum to the air con- 

 tained in the water, which must, therefore, necessarily quit 

 its place. It solves also the problem how to expel, com- 

 pletelv, any gas from water ; for, to effect this, the water 

 must successively be agitated with portions of some other 

 gas of the greatest attainable purity. Thus, to expel atmo- 

 spherical air entirely from water, it may be agitated with 

 pure carbonic acid gas; but as the liberated common air 

 presses on that remaining in the water, according to the 

 proportion it bears to the superincumbent carbonic acid, the 

 gas thus employed must be removed, and fresh and pure 

 portions used in succession. 



4thlv, By applying the same general law, we are taught 

 bow to effect the highest attainable impregnation of water 

 with anv gas. There could be no difficulty in accomplish- 

 ing this object if the gas and water were both absolutely 

 uncontaminated by admixture with other gases. But when 

 pure carbonic acid is agitated with water, atmospherical air 

 is extricated ; which, mingling with the carbonic acid, 

 lessens its density. To obviate this difficulty as much as 

 possible, a quantity of water, to be impregnated fully with 

 carbonic aeid, should be agitated with several successive 

 portions of the purest possible gas. The unabsorbed resi- 

 duum should also be very large, in order that the carbonic 

 acid may bear a large proportion to other aeriform substances 

 accident ally mixed with it. 



These are, doubtless, only a few of the phamomena, to 

 the explanation of which your theory may be successfully 

 applied ; and [ confidently expect that many facts hitherto 

 referred to chemical principles will be brought, in conse- 

 quence of your discoveries, within the department of me* 

 chanical philosophy. I am, dear sir, yours very truly, 



Manchester, WlLLIAM Hf.NKY. 



June zo, 1804. 



XXXIV. Area 



