Heat evolved in Chemical Combination. 



21 



Quantity of heat evolved in 

 combustion. 



IX. Mil). 



"':} 



70607 



33968 



12602 



2719 



3273S 



12080 



2452 



Mean. 



33254 



12269 



2602 



Substances and quantities 

 employed. 



Oil of turpentine, one litre" 

 in vapour, one experi- 

 ment 



iEther, one litre in vapour, 



two experiments 



One litre of cyanogen, three 



experiments . . . 

 One gramme of sulphur,' 

 three experiments 

 The following simple bodies evolved by combustion in oxy- 

 gen for every litre of oxygen used, the following proportional 

 quantities of heat : — 



Bodies. No. ofExps. Max. Min. Mean. 



Iron 2 6281 6152 6216 



Tin 3 6790 6325 6508 



Protoxide of tin .. . 3 6611 6262 6405 



Copper 3 3742 3503 3578 



Suboxide of copper. 1 3130 



Antimony 5 5875 5348 5552 



Zinc 3 7753 7378 7577 



Cobalt 1 5721 



Nickel 1 5333 



These results want probably the great accuracy which Du- 

 long would have given to them had he been longer spared to 

 science; but they probably fluctuate round the true numbers. 

 We cannot judge of what general conclusions he would have 

 deduced from them; but one important consequence appears 

 to follow naturally from the numbers now given, since it ap- 

 pears that the same quantity of oxygen does not evolve the 

 same quantity of heat in combining with various bodies. Thus 

 if we deduce from the first table the quantity of heat evolved 

 by each substance in perfect combustion with a litre of oxygen, 

 we obtain the following numbers: — 



Hydrogen 5204 



Carbon 7858 



Pond gas 4793 



Olefiant gas . 5113 



Alcohol 4792 



Carbonic oxide 6260 



Oil of turpentine . 5043 



Mther 5542 



Cyanogen 6135 



Sulphur 3744 



Amongst the metals similar deviations occur. 



