Sir H. Davy’s researches on flame. 6 y 
however, evidently presents the limit to experiments of this 
kind, for bodies exposed to flame can never be hotter than 
flame itself ; whereas in the voltaic apparatus there seems to 
be no limit to the heat, except the volatilization of the con- 
ductors. 
The temperatures of flames are probably very different. 
Where, in chemical changes, there is no change of volume, as 
in the instance of the mutual action of chlorine and hydro- 
gene, prussic gas ( cyanogen ) and oxygene, approximations 
to their temperatures may be gained from the expansion in 
explosion. 
I have made some experiments of this kind by detonating 
the gases by the electrical spark in a curved tube containing 
mercury or water; and I judged of the expansion from the 
quantity of fluid thrown out of the tube: the resistance 
opposed by mercury, and its great cooling powers, rendered 
the results very unsatisfactory in the cases in which it was 
used; but with water, cyanogen and oxygene being em- 
ployed, they were more conclusive. Cyanogen and oxy- 
gene, in the proportion of one to two, detonated in a tube of 
about ~ of an inch in diameter, displaced a quantity of water 
which demonstrated an expansion of fifteen times their ori- 
ginal bulk. This would indicate a temperature of above 5000° 
of Fahrenheit, and the real temperature is probably much 
higher ; for heat must be lost by communication to the tube 
and the water. The heat of the gaseous carbon in combus- 
tion in this gas, appears more intense than that of hydrogene; 
for I found a filament of platinum was fused by a flame of 
cyanogen in the air which was not fused by a similar flame 
of hydrogene. 
Ka 
