1.8 On the Absorption, of Gases 



metallic or sulphureous mixtures, or any other article to 

 which the effect could be ascribed*. The quantity of azotic 

 gas is not materially diminished by stagnation, it' at all. 

 These circumstances, not being duly noticed, have been 

 the source of great diversity in the results of different phi- 

 losophers upon the quantity and quality of atmospheric air 

 in water. By article 4, it appears that aln)ospheric air 

 expelled from water ought fo have 38 per cent, oxygen; 

 w-hereas by this article air may be expelled from water that 

 shall contain from 38 to per cent, of oxygen. The dis- 

 appearance of oxygenous gas in water, I presume, must be 

 owing to some impurities in the water which combine with 

 the oxygen. Pure rain water that had stood more than a 

 year in an earthen-ware bottle had lost none of its oxygen. 



11. If water free from air be agitated with a small 

 portion of atmosp''jric air (as l-13th of its bulk), the resi- 

 duum of such air will have proportionally less oxygen than 

 the original : if we take l-15th, as above, then the resi- 

 duum will have only 17 per cent, oxygen, agreeably to the 

 principle established in article 4. This circumstance ac- 

 counts for the observations made by Dr. Priestley and 

 Mr. William Henry, that water absorbs oxygen in pre- 

 ference to azote. 



12. If a tall glass vessel, containing a small portion of 

 gas, be inverted into a deep trough of water, and the gas 

 thus confined by the glass and ihe water be briskly agitated, 

 it will gradually disappear. 



It is a v.onder that Dr. Priestley, who seems to have 

 been the first to notice this fact, should have made anv 

 difficulty of it : the loss of gas has evidently a mechanical 

 cause ; the agitation divides the air into an infinite number 

 of minute bubbles, which may be seen pervading the whole 

 water; these are successively driven out from under the 

 margin of the glass into the trough, and so escape, 



13. If old stagnant water be in the trough in the last 

 experiment, and atmospheric air be the subject, the oxy- 

 genous gas will Aery soon be almost wholly extracted, and 

 leave a residuum of azotic gas ; but if the water be fully 



• h was drawn from a leaden ci;tern. 



impregnated 



