Tendency of Elastic Fluids to Diffusion, 1 1 



Third Class. 



Nitrous Gas, with Oxygenous Gas, Jtmospher'ic Air, 

 Hydrogenous and Azotic Gustos. 



The results of the preceding experiments upon gases that 

 have no known affinity for each other, were conformable 

 to what, a priori, I had conceived ; for, according to my 

 hypothesis, every gas diffuses itself equably through any 

 jriven space that may be assigned to it ; and no other gas 

 being in its way can prevent, though it may considerably 

 retard, this diffusion. But in some of the following ex- 

 periments, in which the two gases arc known to have a 

 chemical affinity for each other, I expected different results 

 from what were found ; perhaps without sufficient reason. 

 For chemical union cannot take place till the particles are 

 brought into contiguity ; and the elastic force which sets 

 them in motion appears, from the above experiments, to 

 be a principle diametrically opposite to affinity. That cir- 

 culation of elastic fluids, therefore, which we have now be- 

 fore us, cannot be accelerated by their having a chemical 

 affinity for each other. Another circumstance deserves ex- 

 planation : when nitrous and oxygenous gas are in the two 

 phials, the residuary gases after the experiment are nearly 

 as pure as before ; because those portions of them that meet 

 in the lube form nitrous acid vapour, which is absorbed by 

 the moisture in the phials, and therefore does not conta- 

 minate either gas. 



1. Two one-ounce phials were connected with the small 

 tube, the under containing nitrous gas, the upper atmo- 

 spheric air. After three hours the upper phial was taken 

 off, when a quantity of air was perceived to enter, as was 

 expected : the air in the upper phial was scarcely distin- 

 guishable from what it was at first ; that in the under phial 

 was still so nuich nitrous as to require its own bulk of 

 common air to saturate it. 



2. The above experiment was repeated, and the upper 

 phial drawn off when the whole was under water, in order 

 to prevent communication with the atmosphere. About 

 one-sixth of an ounce of water entered the phials^ to com- 



7 pcnsate 



