426 Experimental Researches on the Depressions [July, 



This fourth series, on which every care was bestowed to ensure accu- 

 racy, confirming as it does the ratio of the prior experiments, certainly 

 tends to prove that hydrogen produces a less depression than common 

 air in the proportion of 82 to 100 ; and consequently that the specific 

 heat of this gas for equal volumes should be 1.22, that of atmospheric 

 air being 1 . 



Tab. XI. — Depressions with Carbonic Acid. 



1. 



CU! 



Temp, 

 air. 

 t 

 rrent through ° 



Wet- 

 bulb. 



C 



o 



Depres 



sion. 



d 



o 



Hair 

 hygr. 





Tabular 



depression 

 for dry air. 

 D 



Ratio. 

 d 

 D 



2. 



3. 



steam pipe 

 Do. steam 

 Do. quicker 



, .. 91.7 



on, 161.0 



draft, 160.0 



66.2 

 85.0 

 81.5 



25.5 

 76.0 



78.5 



(acquired moisture 

 Nearly dry ? 

 ditto, 



.20 



?) 36.3 

 82.2 \ 

 81.5 J 



.94 



4. Common air, .. 86.8 60.8 26.0 34.3 



The experiment with common air shews that the passages still im- 

 parted moisture to the amount of full ' 1 2, and therefore vitiated the 

 result as with hydrogen. The trial was renewed with the precaution 

 of employing the hair hygrometer. h d o d~B 



5. Short glass tube, 83.6 55.0 28.6 5 Corrected 30.1 32.6 .92 



6. Ditto 86.2 55.2 31.0 3 for dry 32.0 34.0 .94 



7. Ditto, 83.7 53.6 30.0 3 air or 31.0 32.6 .95 



8. Common air 88.2 54.5 33.7 3 max. dep. 34.8 35.0 



Here again the depression in carbonic acid gas is proved to be 

 94 hundredths of that in common air, whence the specific heat of 

 this gas should turn out 1 .06, air being 1 .00. A third series was taken : 



8. Well dried, .. 88.7 56.2 32.5 32.5 35.3 91 



9. Ditto, 84.8 55.1 29.7 0.5 29.9 33.2 90 



10. Ditto, 89.6 57.2 32.4 1 32.8 35.8 90 



In the last three experiments which were made with the precautions 

 I have described, in the hydrogen experiments, (13-15) a little of the 

 latter gas was mixed (gsth) with the carbonic acid ; while in experi- 

 ments 6, 7, common air may have been present to the same extent. 

 We may therefore assume the maximum depression in dry carbonic 

 acid to be about 92 per cent, of that in atmospheric air; and its spec, 

 heat = 1-087. 



Although these unexpected results are supported by their great 

 uniformity, I still feel hesitation in inviting for them the implicit con- 

 fidence of chemists, in opposition to the very opposite conclusions of 

 other experimenters. Had the specific heat of one gas proved in de- 

 fect and the other in excess, it would have been more consonant with 

 the analogy of their specific gravity, — but that two gases so strongly 

 contrasted, should both err, on the same side, I own to be plausible 

 evidence against me. Still I hardly think that the 8 per cent, discre- 

 pancy in the carbonic acid experiments is within the limits of experi- 

 mental error ; and the 18 per cent, of the hydrogen is certainly more 

 than I am willing to allow to be attributable to such a cause. 



