in Combustion, and in the Condensatlo7i of Fapours. 295 



tion nearly equaf quantities of heat; and as this oiuiht to i^e 

 the case, in fact, according to the quantities of combustible 

 niatter which these substances contain, this result is made 

 in order to give confidence to the meihod of measuring tl e 

 titat which is developed in combustion. 



With ihe combustion of one pound of bees wax 91'632 

 pounds of water were heated 100% and with one pound of 

 refined oil 93-073 pounds of water were heated 180"^. 



As the object which 1 had chiefly in view in these ex- 

 periments was to determine the quantities of heat which are 

 developtd in the combustion of pure hydrogen a:id carbon; 

 in order to render this new method useful in chemical ana- 

 lyses, I attached myself particularly to inflammable sub- 

 stances which have been analysed with the greatest care. 



§ IV. Estimate of the Qiianlkies of Heat developed in the 

 Combustion of Hydrogen Gas and Carbon.. 



Several attemjits have been made to determine these in- 

 teresting questions by direct experiments, by burning p?//-^ 

 hydrogen, or hydrogen gas, and pure charcoal; but the re- 

 sults of these inquiries have been so variable that we can- 

 not rely upon them. 



According to Crawford, the heat developed in the com- 

 bustion of one pound of hydrogen gas is sufficient to raise 

 the temperature of 410 pounds of water to 180" F. but the 

 estimate of M. Lavoisier is much lower : according to him, 

 this heat could raise only 221 -eQiKJunds of water to this heat. 



In return, M. Lavoisier estimates the quantity of heat 

 developed in the combustion of charcoal much higher than 

 Mr. Crawford. I have a great many reasons for thinking 

 that botli estimate too highly ; and if this opinion be con- 

 firmed, we shall be obliged to estimate the heat developed 

 in the combustion of hydrogen even a little higher than 

 Mr. Crawford, in order to account for that which was ma- 

 nifested in my experiments. 



According to the results of several experiments made five 

 years ago, it appeared to me that the heat developed in the 

 combustion of one pound of charcoal, dried as well as possi- 

 ble before being weighed, by making it red hot in a crucible, 

 was not fit to raise more than 32 or 34 pounds of water 

 from the freezing to the boilins; point. 



According to Crawford, this heat ought to be sufficient 

 to boil 37-606 pounds, and according to M. Lavoisier 

 72-475 pounds. 



We shall see how these estimates agree with the results 

 of my experiments. 



T4 As 



