138 M. Berzelius on the [Aug. 



mercury, and introduced into it a bit of hydrate of potash. It 

 was so completely absorbed, that the minute bubble of air re- 

 maining could not be accurately measured, and could not at the 

 utmost have amounted to more than a thousandth part of the 

 original volume. A quantity of gas collected in a similar way 

 at Theresia's spring, left one per cent, of a gas which appeared 

 to be azote, as it was not sensibly absorbed by a solution of sul- 

 phuret of potash. 



I now calculated the quantity of carbonic acid gas which the 

 water in the reservoir should contain, on the supposition that 

 100 volumes of it absorb 104 volumes of the gas, at the tem- 

 perature 164-f- , making allowance at the same time for the addi- 

 tional pressure to which it is subjected, and which may be esti- 

 mated by the height to which the jet of the Sprudel rises 

 above the surface of the water in the reservoir. The result was, 

 that the disengaged carbonic acid gas, taken at the temperature 

 32°, should constitute three-fourths of the volume of the water. 

 If we add to this the carbonic acid of the bicarbonates, which 

 by weight constitutes 0*075 per cent, of the water, and at 32° 

 would occupy 0*396 of its volume, it will follow that the water, 

 when boiled, should emit at least l-,\ times its volume of car- 

 bonic acid gas, measured at the temperature of 32°. But the 

 taste alone of the water is sufficient to convince us that the 

 quantity thus indicated is greatly in excess. JBy direct experi- 

 ment, Beccher found precisely as much gas in the water as 

 would be requisite to convert the whole of the carbonates into 

 bicarbonates ; Klaproth found rather less than this quantity ; 

 Reuss found rather more. I am of opinion that the quantity of 

 gas contained in the water when it first issues from the earth, is 

 rather greater than what would convert the carbonates into 

 bicarbonates. 



This seeming anomaly is probably occasioned by a circum- 

 stance, to which no attention has hitherto been paid in deter- 

 minations respecting the solubility of gases in water, because it 

 exerts but little influence at the ordinary temperatures. Water, 

 under every temperature and pressure, possesses a determinate 

 tension, and any gas standing over the surface of water, 

 always contains an admixture of its vapour, which in this situa- 

 tion acts in exactly the same manner as a permanently elastic 

 gas. When a mixture of carbonic acid gas, and of the gas 

 (or vapour) of water stands over the surface of water, the inter- 

 stices of the liquid must contain a portion of this gaseous mix- 

 ture, that is, both of the carbonic acid gas, and of the gas of 

 water. The apparent absorption by water, therefore, of any 

 pure gas, as for example, carbonic acid gas, in a given tempe- 

 rature and pressure, is in fact the quantity which, in that tem- 

 perature and pressure, is necessary to maintain the equilibrium 

 between the carbonic acid gas and the gas of water, both 



