190 M. R. Bunsen on the Laiv of Absorption of Gases. 



How far beyond the examined limits the law may be considered 

 as true cannot be a priori determined. It is, however, more 

 than probable that in this law, as in the law of Mariotte, a limit 

 exists beyond which the regularity of the action is disturbed by 

 varying molecular influences. The limits of the exact action of 

 the law are however quite extensive enough to enable us to draw 

 some very interesting conclusions from the subject. Eudiome- 

 try, for example, gains from the law of absorption an entirely 

 new sphere of action, enabling it not only to determine, without 

 any chemical experiments, the simple or complex constitution of 

 a gas, but also to recognize the nature of the component parts, 

 even indeed to estimate their several proportions, when once for 

 all the absorption-coefficients of the gases are known. To show 

 that such an absorptiometric determination can serve as a reaction 

 for the detection of gases, I chose an experiment with marsh 

 gas,, which satisfactorily proves that results are attainable even 

 when the values of the absorption-coefficients employed in the 

 calculation differ but little from each other. 



Relying on the results of eudiometrical analysis, it has been 

 hitherto supposed that the gas obtained by the action of a hy- 

 drated alkali upon an alkaline acetate at a high temperature 

 was marsh gas. Although this supposition has scarcely ever 

 been questioned, still all positive proof of the fact fails. Frank- 

 land and Kolbe have shown that two volumes of marsh gas by 

 eudiometrical explosion react exactly as a mixture of equal 

 volumes of hydrogen and methyle. Both give for every volume 

 a volume of carbonic acid, and require for their combustion the 

 double amount of oxygen. Eudiometric analysis leaves it then 

 undecided whether the gas evolved from the alkaline acetates is 

 to be considered as marsh gas, or as a mixture of methyle and 

 hydrogen. By means of absorptiometric analysis this question 

 is very readily and surely answered. If we start from the sup- 

 position that the gas in question is a mixture of equal volumes 

 of methyle and hydrogen, a volume V of the gas, at 0° and 

 under 076 pressure, measured in the absorptiometer would con- 

 sist under the pressure 076 of, — 



PV PV 



2^076 metl ^ e ' aud 27076 h y dl '° gen - 



If this gas be agitated with h x volumes of water, the observed 

 volume of the residual unabsorbed gas being V, under the pres- 

 sure P u the sum of the absorption-coefficients at the temperature 

 of absorption (for hydrogen a, and for methyle /3,) can be calcu- 

 lated from the observations. If we call the residual hydrogen 

 #1, and the residual methyle y^ (both reduced to 0° and 0-76), 

 this x x will, in consequence of its dilution with methyle, be 



