TRANSACTIONS OF THE SECTIONS. 35 



invented for tliis pm-pose could he emploj-ed only under tlio ordinary pressiu'e of 

 one atmosphere, and left untouched the relation established by Dr. Heniy and Dal- 

 ton bet\Yeen absorption and pressure. Ijatelj' Messrs. Roscoe, Ditmar, and Sinims 

 have made very interesting investigations on the absorption of some highly absorb- 

 able gases, and showed that the law of Henry and Dalton is only exact for elevated 

 temperatures. That was the reason which induced mj^ friend Dr. Louguinine and 

 myself to undertake a new series of experiments on a gas not so absorbable as 

 those investigated by Messrs. Eoscoe, Ditmar, and Siimns — namely, on carbonic 

 acid gas. 



Before all it was absolutely necessary to construct an apparatus which should 

 not have the above-mentioned imperfections of the apparatus of our celebrated 

 predecessor Dr. Henry. It was evident that it must consist of a glass vessel ex- 

 actly gauged and arranged in such a manner as to be easily put in connexion with 

 a large manometer, and separated from it in a very short time. Secondlj', the 

 absorption must be produced, not by shaking the apparatus by the hand, but by 

 moving it mechanically in a space with an invariable temperature. The first re- 

 quirement was easily obtained by luting to the open end of om- absorption-bell an 

 iron tube with a cork, and the second by takin^ the precaution of making the con- 

 tact of tlie absorbing liquid and the absorbable gas very perfect bj' revolving the 

 glass vessel, containing the liquid aud the gas, in a gi'eat mass of water, maintained 

 constantly at the same temperature. These are the two principal difterences between 

 oiu' apparatus and those of our predecessors ; and without entering into more details 

 on om- experiments, executed at the College de France in the laboratory of M. Keg- 

 nault, I pass directly to the results we obtained for carbonic acid gas, and at the 

 temperatiu-e of 15° C. or 58° F. 



If we designate by u^ the coefficient of absorption of a given gas under the pres- 

 sure Pj, and by «o the coefficient of the same kind, but under a higher pressure V^, 



by the law of Henry and Dalton we must have esa : *i = I'2 = Po oi' ~~iy — ^) or 

 a—h—0; if we designate by «, — ^, and by I, =55-^. The following Table contains 



«,j_l X» 1 



the values of a and b given by oiu' experiments : — 



a. h. a — h. 



1-2307 1-1595 0-0712 



1-9751 1-8480 0-1271 



2-2903 2-1068 0-1835 



.3-0797 2-8094 0-2103 



3-3644 3-1369 0-2275 



3-6920 3-3938 0-2982 



3-9351 3-6005 0-2746 



4-2401 3-9247 3152 



4-7671 4-4567 0-3104 



In spite of some small anomalies presented by these mmibers, it is evident that the 

 difl'erence a -bis constantly increasing with tlie pressure, so that this discrepancy 

 -with the law of Henry and Dalton caimot be ascribed exclusively to the inevitable 

 errors of observation. 



From the monient that the carbonic acid gas was liquefied, it was evident that 

 its coefficient of absorption by liquids must be zero for two dift'ercnt pressiu-es. 

 First, for a pressure of nearly zero ; and second, for the pressure which reduced 

 the gas, at a given temperature, to a liquid state. But if so, it was also evident 

 that the relation between the coefficient of absorption and the pressure could not 

 ba a simple algebraical and lineal function of these variables, as it was supposed 

 l)y Henry aud Dalton, but that this relation could be more nearly expressed by 



a = A-t-BP-hCP2, 



which for «=:0 nuist give two positive and real values for P, and also 



c4 z= - A-I-BP-CP2 and B>A and C<B. 



Applying to this equation, for the different values of « and P obtained by our 



o 



