and on the Sulphur ets of Lime. 399 



time stagnant in the cistern, though preserved carefully from 

 any material impurities, always affects the remaining air, 

 though the phial be well corked and immersed in a cup of 

 water. The cause is obvious to those acquainted with the 

 laws that regulate the absorption of gases by water. The 

 common air in the water (the quantity of which varies much 

 as to the oxygen part) is continually either making its escape 

 into the incumbent air of the phial, or this last air is entering 

 the water, so that the degree of purity is continually changing 

 in a small degree. This renders it necessary to test the actual 

 state of this gas after it has been some time in the phial, be- 

 fore we recommence the use of it. A phial of air may be 

 pure at first, and only 90 per cent, at its conclusion. I have 

 known samples of common air kept in bottles at first contain- 

 ing 21 per cent, of oxygen, and after some months a small 

 residue was found to contain only 19 per cent. 



4. It may not be improper here to relate some unpublished 

 results which I formerly obtained when experimenting on 

 subjects here discussed. In my memoranda for 1816, I find 

 that I took water well boiled (supposed | of an hour or more) 

 and then poured it gently into a Florence flask, filling it up 

 into the narrowest part of the neck, and left it so, exposed to 

 the atmosphere for three days without any agitation. At the 

 end of this, 2700 grains of water imbibed 49 grain measures 

 of atmospheric air by agitation, which is about f of a full 

 share; hence j of a full share must have been, both the air 

 that was left in after boiling, and that acquired from the 

 atmosphere in three days by absorption from the small ex- 

 posed surface. 



Water boiled in a kettle for three or four minutes, then 

 suddenly cooled and transferred without agitation into a bottle 

 containing 2700 grains, and then agitated with atmospheric 

 air, imbibed 32 measures, which are about half a charge; 

 whence it may be inferred that water boiled for three or four 

 minutes loses about half of its air. 



I boiled a kettle full of water for a quarter of an hour; let 

 it stand a day or two to cool, then transferred it carefully by a 

 siphon into a cylindric jar of 8 inches diameter and 10 inches 

 deep; afterwards drew off daily by a siphon 2700 grain mea- 

 sures from the middle or near the bottom of the jar, and 

 charged it with air to the full by agitation. The bottle of 

 water imbibed 



The first day ... 16 measures. 



The second day 15 measures. 



The third day.. 12 measures. 



The fourth day 10 measures. 



The fifth day ... 10 measures. 



