A Calorimeter for the Human Body. 241 



known temperature and determining the rise of temperature of the 

 water; the burner was found to absorb 300 calories during the 

 experiment. The pointer showed on the scale of the bell-jar the 

 volume of hydrogen burnt, and the gauge the pressure the gas was 

 under in millimetres of water, while a thermometer gave the tem- 

 perature of the gas in the bell-jar, and a barometer the atmospheric 

 pressure ; the hydrogen gas was of course saturated with water 

 vapour. Hence we were in possession of every data for the reduc- 

 tion of the gas to the dry state, to C., and 760 mm. pressure. 



In the early experiments it did not occur to us to analyse the 

 hydrogen gas in order to ascertain its degree of purity, but we did 

 so subsequently, using for that purpose the eudiometer constructed 

 by one of us (W. M.), which for several years has been exclusively 

 adopted in this laboratory for the determination of oxygen in expired 

 air ; the analysis of the gas introduced but a very slight correction. 

 The following table gives the results of the experiments we made on 

 the heat emitted by the combustion of a given weight of hydrogen 

 gas. It might be added that the machine known as " Brunsviga " 

 was used for the calculations, which saved much time and trouble ; 

 by this means the whole of the calculations could be completed in 

 about fifteen minutes. 



Favre and Silbermann find 1 gram of H to give in burning 34,462 

 calories. 



Found. Difference. 



1 33,334 3'26 low per cent. 



2* 33,159 3-78 



3* 35,291 2-41 high 



4 35,186 2-10 



5* 34,212 0-73 low 



6* 35,610 3-33 high 



7 33,923 1-56 low 



8 34,079 1-11 



9 34,440 0-06 



10 35,048 1-70 high 



Mean.... 34,428 O'lO low 



Favre and Silbermann 34,462 



Marcet and Floris 34,428 



34 = O'l per cent. 



The present result is certainly convincing, and these figures are 

 plain statements of all the experiments we made. The greatest 



* In these experiments the hydrogen gas was not analysed ; it was analysed in 

 all the others and the correction therefrom introduced. 



