MR HAYCRAFT on the Specific Heat of the Gases. 203 



In these experiments it will be perceived, that the two first 

 indicate that carbonic acid has a less capacity for caloric than 

 common air. The three last, however, which do not differ ma- 

 terially from each other, will indicate an equal capacity, if we 

 take the average of their results. The cause of the two first 

 experiments indicating a lesser capacity, I suppose to arise 

 from the gas not being perfectly freed from watery vapours. In 

 the experiments I made last year, I observed that it was neces- 

 sary to expose this Gas to the drying influence of muriate of 

 lime, for 35 minutes at least, before it indicated the same speci- 

 fic heat as atmospheric air. This is not the case with all the 

 other Gases : from hence I would infer, that it has a greater af- 

 finity with watery vapour. 



The Gas contained in the gasometer, as indicated by lime- 

 water, contained 99 per cent, of carbonic acid ; that taken from 

 the apparatus after the experiments were concluded, by the same 

 test, contained 90 per cent. The temperatures of the Gases while 

 entering the calorimeters were equal, as indicated by the thermo- 

 meters. It is worthy of remark, however, that these tempera- 

 tures appeared several degrees lower than that of the water con- 

 tained in the heating apparatus through which they passed. 

 This will be easily explained, when we consider that a thermo- 

 meter can never indicate the true temperature of any gas or 

 vapour, which is itself pervious to the radiation of heat or cold 

 from surrounding bodies. On this account the thermometers 

 indicated a temperature of the Gases much lower than the true 

 one, they being necessarily placed so near the calorimeters, 

 which usually contained water of a temperature nearly 100 

 lower than that of the gases. In the same manner, the gases 

 issuing from the calorimeters appeared to have a temperature 

 something lower than that of the calorimeters themselves, being 

 surrounded with objects of a lower temperature than that of the 

 calorimeter! 



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