208 PROFESSOR THOMAS GRAHAm's SCIENTIFIC WORK. 



the pump. On examining the delivered gas, it was found to contain on 

 the average 41. G per cent, of oxygen ; and accordingly, to have the prop- 

 erty of re-inllaming a glowing splinter. Thus, by the simple suction of 

 atmospheric air through a caoutchouc film, the remarkable result was 

 arrived at of nearly doubling the proportion of 0x3' gen in the volume 

 of air sucked through. Unfortunately for the practical application of 

 the process, the entire volume of air sucked through proved to be very 

 small, about 2.25 cubic centimeters per minute, per square meter of sur- 

 face, at 20° C. At 60° C, however, the passage of air through the rub- 

 ber was almost exactly three times as rapid as at 20°. 



Instead of allowing the gases experimented on to pass through the 

 India rubber into a vacuous space, they were in some cases allowed to 

 l)ass into space already occupied with a different gas, somewhat as in 

 Dr. Mitchell's original experiments; but the conditions of the action 

 were then more complex. The constituent gases of atmospheric air, for 

 instance, pass through an India-rubber septum into a space containing 

 carbonic gas at the relative velocities with which they enter a vacuous 

 space ; but throughout the experiment, not only are oxygen and nitro- 

 gen continually entering the space, but carbonic gas is continually, and 

 very rapidly, escaping from it. Eventually, by the rapid escape of car- 

 bonic gas, the proportien or pressure of oxygen in the internal space 

 comes to exceed that in the external air ; whereupon a reverse trans- 

 mission, through the India rubber, of the excess of oxygen into the ex- 

 ternal air, at once begins. But by stopping the operation at an early 

 stage, and then absorbing the carbonic gas with caustic alkali, a residue 

 of hyperoxygenized air was left, capable, in some cases, of re-inflaming 

 a glowing splinter, and containing as much as 37.1 volumes of oxygen 

 to 02.9 volumes of nitrogen. 



The interpretation given by their discoverer to the above results 

 was in accordance with his slowly-developed views on the relations of 

 gases and liquids to each other and to soft solids. Having satisfied 

 himself that the merest film of India rubber is quite devoid of porosity, 

 and that oxygen is at least twice as absorbable by India rubber as by 

 water at ordinary temperature, (the absorbability of its own volume of 

 carbonic gas by India rubber, as by water, having been noticed by Dr. 

 Mitchell,) Mr. Graham came to view the entire phenomenon as having 

 a very complex character, as consisting in a dissolution of the gas in 

 the soft India rubber ; in a diffusion of the liquefied gas, as a liquid, 

 through the thickness of the India rubber; in an evaporation of the 

 liciuefied gas from the internal surface of the India rubber; and lastly 

 in a difi'usion of the evaporated gas into the internal space. Thus, in 

 reference to the remarks of Drs. Mitchell and Draper, he writes : 

 " These early speculations lose much of their fitness from not taking 

 into account the two considerations already alluded to, which appear 

 to be essential to the full comprehension of the phenomenon, namely, 

 that gases undergo liquefaction when absorlied by liquids and such 



