436 On the Determination of the [Dfcc. 



Specific heat. 



Azote 0-2/54 



Oxide of azote 0*2369 



defiant gas 0.4207 



Carbonic oxide 0'2884 



Vapour of water 0*8 i/0 



From this table it appears tbat, if we except hydrogen, which 

 has the greatest specific heat of all known bodies, all the gases 

 that we have examined have a smaller specific heat than water, 

 and a greater specific heat than any of the metals. 



The results which we have obtained by comparing the specific 

 heat of the gases with that of water, enable us to decide 

 whether, as some have thought, it would be attended with a 

 saving of fuel, to employ the action of dilated air, instead of 

 steam, in steam-engines. ^ e consider the question here under 

 a point of view entirely theoretic, abstracting both the difficulty 

 of constructing such machines, and the loss of power which 

 could not be entirely avoided. Setting out from the specific 

 heats of water and air contained in the preceding table, we have 

 found that with the same quantity of heat employed in the one 

 case to convert water of 32° into steam, but without raising its 

 temperature higher than 212°, and in the other to bring the 

 temperature of atmospherical air from 32° to 212°, the effects 

 produced in the first case would be to those produced in the 

 second case as 1 to 1*285 : but the advantage in favour of air 

 would be much greater if the temperature were laised still 

 higher.* It is obvious that, from the knowledge which we 

 already possess of the quantity of heat given out by steam when 

 it is condensed, and from the data furnished by our experiments 

 on the specific heats of the gases, it was very possible to arrive 

 at the solution of this question ; but the calculations being 

 somewhat complicated, and requiring, in order to be presented 

 with clearness, details which might appear foreign to the subject 

 proposed by the Institute, we will not give them here. 



§ IV. — Specific Heat of the Vapour of Water, compared with 

 that of Water itself. 



It would have been very interesting to have determined with 

 accuracy the specific heats of different vapours, and to have 

 compared them with the fluids which they form by condensation. 

 The prodigious quantity of heat disengaged during this change 



* Thus, if ins'ead of applying the same quantity of heat to raise a mass of 

 air Eroin 32 J to 212°, it was employed to raise the temperature of -| of it from 

 32° to 572°, the effect produced in this case would be 3*043, or thrice as great 

 as would he produced by employing the same quantity of heat to convert uater 

 into steam. 



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