76 LATENT CALORIC OF HYDROGEN 1 . 



These vague hypotheses have been superseded 

 by the more definite views of the celebrated La- 

 voisier, who proved that hydrogen is composed of 

 a ponderable base, united with an igneous fluid, 

 which he termed caloric ; and which may be sepa- 

 rated from each other by chemical action. 



According to the experiments of Dr. Dalton, 

 caloric enough is decomposed and given out dur- 

 ing the combustion of I Ib. of hydrogen gas, to 

 melt 3*20 Ibs. of ice. According to Crawford, 

 480 Ibs. of ice are melted by the heat given out 

 during the combustion of 1 Ib. of hydrogen ; which 

 Dr. Thomson thinks is about as far beyond the 

 truth, as Dalton's estimate falls short: conse- 

 quently, that 400 Ibs. may be regarded as the 

 mean quantity of ice that will be melted during 

 the combustion of 1 Ib. of hydrogen. If then we 

 admit with Dr. Black, that 140 of caloric are 

 required to melt 1 Ib. of ice, 56,000 of heat must 

 be given out during the combustion of 1 Ib. of 

 hydrogen. 



It must however be observed, that during the 

 process, 2 volumes of hydrogen combine chemi- 

 cally with 1 of oxygen or that 1 atom of oxygen 

 combines with 1 of hydrogen ; and as the atomic 

 weight of oxygen is 8 times that of hydrogen, 

 8 Ibs. of oxygen must unite with 1 of hydrogen, 

 making 9 Ibs. of water. From which it is evi- 

 dent, that a certain proportion of the caloric dis- 

 engaged, is afforded by the oxygen ; for we find 



