Chemical Absorption of Gases. 357 



given, selected from about 126, in which the readings of the 

 manometer after sixty minutes were nearly the same ; the pres- 

 sures being in all cases corrected for capillarity and alteration 

 of level of the water-reservoir of the manometer. 



The barometric pressures show slight differences ; but some 

 experiments made at differences of five and eight millimetres 

 of mercury exhibited no appreciable difference in the results, 

 indicating that this want of uniformity in the whole set of 

 experiments may be overlooked. 



If it be assumed that the rate of absorption of a gas varies 

 as its pressure, the volume remaining constant, then, Q being 

 the original quantity of the gas, and q that which has been 

 absorbed, 



dq = /cpdt ; 

 but 



Q"~9 r = A 6 P an( i —dq = fj,p; 

 then 



dp k 



The object of the present work was to determine the co- 

 efficient c for the various gases with a view to forming an esti- 

 mate of their rates of interdiffusion in atmospheres of air and 

 hydrogen ; for the reason, how r ever, that experiment does not 

 show the validity of this equation, the quantities e~ c are only 

 calculated. 



Integrating the equation, we get p = ^€~ ci } N being the 

 initial pressure of the gas. This factor was not determined, 

 nor was it necessary in order to establish the formula ; for if 

 W, n r , n n ', &c be the readings of the manometer after equal 

 consecutive intervals of time t, andp,^/, p", &c. the pressures, 

 then 



p =N— n =Ne- cf , 



n r — n =Ne- c '(l— €~ ct ), 

 and 



This ratio, taking the intervals of time t as the unit (one 

 minute in the experiments), should be constant ; this, however, 

 is not shown by experiment to be the case, but that the ratio 

 increases as the pressure diminishes. 



Carbonic Dioxide. — This gas was obtained by the action of 



