384 On the Heat developed in Combustion 



Chemists may tell us whether the quantity of incom- 

 bustible matter separated from rape oil in purifying it 

 be sufficient, or not, to account for this difference. 



On comparing the results of the experiments made 

 with white wax and those with the purified oil, it 

 appears that equal weights of these substances afford 

 nearly equal quantities of heat in their combustion ; and 

 as, in fact, this ought to be the case, from the quantities 

 of combustible matter they contain, the result tends to 

 strengthen our confidence in this method of measuring 

 the heat developed in combustion. 



The combustion of 



I Ib. of white wax gave . 94.682 Ibs. of water heated 180. 

 I Ib. of purified oil . . 93.073 " " " " 



As the object I had chiefly in view in this series of 

 experiments was to ascertain the quantities of heat 

 developed in the combustion of pure hydrogen and 

 carbon, in order to render this method useful in some 

 chemical analyses, I examined particularly those in- 

 flammable substances that had been analyzed with most 

 care. 



Several attempts have been made to ascertain these in- 

 teresting questions by direct experiments, in burning 

 pure hydrogen, or pure hydrogen and carbon ; but the 

 results of these researches have varied so much that they 

 cannot be relied on. 



According to Crawford, the heat developed in the 

 combustion of one pound of hydrogen gas is sufficient 

 to raise the temperature of 410 pounds of water 180 F. 

 But the estimation of M. Lavoisier is much lower. 

 According to him, this heat would raise only 221.69 

 pounds of water the same number of degrees. 



