106 _ Professors W. B. and R. E. Rogers 
pressure. But further experiments are, we think, needed, to de- 
termine with precision the law of absorption as dependent on 
pressure, and in the mean time, the law of Henry can only be 
looked upon as approximately true. From observations on this 
subject in which we have lately been engaged, and which we 
nope to continue, we have been led to infer that, in comparing 
widely variant pressures, there is a marked departure from this law. 
Although therefore, from the small difference of gaseous pres- 
sure (that between p and p—/) in our experiments, we believe 
that no sensible error could be introduced by applying the law of 
Dr. Henry to the results, we have thought it proper in reporting 
them, to state the volume of dry gas absorbed and the reduced 
pressure, as well as the apparent absorption and entire barometric 
pressure. 
Having now presented all the details of our mode of operating, 
and of the precautions and corrections we have used, we proceed 
to give an account of the results, treating of them in the follow- 
ing order: 
I. Of the absorption by water. 
If. Of that by sulphuric and other acids, and by other un- 
mixed liquids. 
If. Of that by various saline aqueous solutions. 
I. Absorption of Carbonic Acid by Water.—The water used in 
ese experiments, as well as in making the solutions employe 
in others to be described hereafter, was prepared by careful distil- 
lation in a copper vessel. Its purity was such, that several cubic 
inches evaporated in a platinum capsule, gave no indication of 
alkaline matter to the most delicate test paper, and when entirely 
volatilized, left scarcely a trace of residuum. Before being used, 
it was briskly boiled for half an hour, quickly transferred to a 
well stopped bottle, and when sufficiently cooled, exposed to the 
& 
exhausting action of a good air-pump. ‘The bottle was then sus- — 
pended in the large reservoir, to bring it to the proper tempera- 
ture, before the charge was introduced into the flask. se 
The absorption was seen to begin as soon as the first drop de- 
scended from the flask, and with brisk agitation, the process was 
completed in about five minutes after the liquid was brought in 
contact with the gas. To satisfy ourselves that no further ab- 
sorption would occur, we repeatedly prolonged the agitation to 
fifteen or twenty minutes, allowed the apparatus to rest, and again 
resumed the shaking, but without producing any appreciable 
change in the column of the measuring tube. 
Although, from the purity of the gas used, the closeness of the 
apparatus, and the care with which it was charged with gas, we 
had no reason to apprehend any dilution of the CO,, yet as such 
a change would cause the absorption to terminate short of the 
saturation of the liquid proper to an unmixed atmosphere of the 
eal 
