286 Chemical Analysis of the Atmosphere. 



of the volume of air to that of dry air, or rather to the degree of 

 humidity shown by the experiment, appears to me too minute to 

 have any sensible influence on the very feeble proportion of carbonic 

 acid existing in the air. 



To determine the limits of the proportion of carbonic acid appre- 

 ciable by this method, I operated upon air taken from two feet above 

 a small charcoal fire, and passed it through barylic water, after it had 

 passed through the lime tube. Although the carbonic acid was 

 found to be near one per cent, in the volume of air, the barytic water 

 was not troubled. When I repeated it with a similar air, but more 

 highly charged, viz. two per cent, of carbonic acid, the barytic water 

 was decidedly affected. But this proportion of carbonic acid sur- 

 passes, by more than thirty times, the maximum found by de Saus- 

 sure in the atmosphere. I would observe, that in the latter experi- 

 ments, I let the water flow in a natural stream. By slackening the 

 current, or by lengthening the lime tube, we might probably operate 

 upon air more highly charged with carbonic acid. 



To be certain that the current of air does not bring with it any 

 sensible quantity of water, I placed a second hygrometric tube be- 

 tween the lime tube and the vessel A. In several experiments of 

 this kind, I never observed the least increase of weight in this tube. 



In a series of experiments undertaken with a view of studying my 

 apparatus, I constantly obtained results included within the limits of 

 those obtained by de Saussure. 



It appears therefore that the method now described furnishes an 

 easy and certain means for ascertaining the proportion of the two ac- 

 cidental principles of the atmosphere. I think it susceptible of being 

 extended to those researches which are properly styled eudiomet- 

 ric* Perhaps a method may be derived from it, more exact than 

 those now practised to determine the proportion of the oxygen, which 

 has hitherto been scarcely brought within one hundreth of the point 

 of rigorous exactness. It would also be desirable to employ some anal- 

 ogous methods in researches into the other elements which the at- 

 mosphere appears to contain. For this purpose currents of air should 

 be passed, for some time, through different reagents, which might be 

 enclosed either in tubes similar to those above described, or through 

 Wolfs bottles, and in order to act upon large masses of air, an appa- 



* Is it not to be regretted that the term eudiometry and eudiometer should be ap- 

 plied exclusively to the art of determining the quantity of oxygen in the air and the 

 instruments for that purpose ? Would not the terms oximetry and oximeter be more 

 appropriate ? — TV. 



