DISTURBING AGENCIES, AS TEMPERATURE. 55 



the carbonic acid was increases in quantity. Now when, instead of a screen of stuc- 

 co, a thin lamina of India-rubber is used, which is found, upon trial, to condense one 

 atmosphere of carbonic acid, while it does not act upon air, the same rate of exchange 

 ensues ; but there is a diminution of gaseous matter on the side containing the acid, 

 and because the screen condenses one atmosphere, there should be found only half as 

 much gas as would represent the equivalent volume of diffusion had the screen pos- 

 sessed no condensing power. 



173. One hundred and sixty-one measures of carbonic acid gas were confined in a 

 tube under a thin sheet of India-rubber, and suffered to diffuse for thirty-six hours. To 

 prevent as much as possible any disturbing action of the fluid over which the experi- 

 ment was tried, a saturated solution of common salt, which absorbs carbonic acid slow- 

 ly, was made use of. The gaseous contents of the tube decreased in their dimensions 

 very rapidly, and when measured, were found to consist of 98 volumes only. In the 

 mean time, a tube closed at one end, filled with the same quantity of carbonic acid, and 

 placed by the side of the former, had decreased about five measures ; we may therefore 

 assume that the quantity of gas that should have been found in the diffusion tube ought 

 to have amounted to 100 measures nearly. Now the specific gravity of carbonic acid 

 gas is 1-527, the reciprocal of the square root of which is 0-8091. Hence, under ordi- 

 nary circumstances, one volume of air should replace 0-8091 of carbonic acid gas ; but 

 as, in the experiment here tried, the barrier produced a compression, one volume of air 

 should displace 1-6182 of carbonic acid, the amount observed very nearly. 



174. I would not here be understood to say that there are no other disturbing ac- 

 tions going on in cellular tissues except those which result from their absorbent power. 

 A great many facts show that, under peculiar conditions, they are able to produce de- 

 compositions of a certain sort. Often their regular action, as indicated by theory, seems 

 to be entirely departed from ; great disturbance arising from the fact, that when two gases 

 are absorbed together by any areolar tissue, they experience a greater condensation than 

 each would in a separate state. The presence of nitrogen or carbonic acid, in any 

 porous mass, increases the action of that mass on oxygen, more of the latter being con- 

 densed. A piece of charcoal, impregnated with oxygen, condenses more hydrogen than 

 it should do, and the presence of hydrogen facilitates the condensation of nitrogen. It 

 is, therefore, impossible to foretell what the result of diffusing one gas into another will 

 be, by simply ascertaining how many volumes of either alone will be absorbed by the 

 tissue, inasmuch as a greater or lesser condensation may happen when both are em- 

 ployed together. 



175. Variations of temperature, which probably affect the power of absorption, and 

 thereby the diffusion of volumes, are experienced by all tissues. When charcoal, or 

 any other porous mass, is placed in an atmosphere of gas, which it can condense rap- 

 idly, its temperature rises, the effect apparently depending more on the velocity of ab- 

 sorption than on the final amount. In the case of ammonia, it does not even require a 

 thermometer to discover this increase of temperature, for it is very sensible to the touch. 

 On the other hand, when this condensed gas makes its escape, a corresponding dimi- 

 nution of temperature happens : it is immaterial by what means the liberation of the gag 



