1901.] on Metals as Fuel. 499 



Heat Evolved by Burning One Gramme of the Following Elements. 



E — *• JBS32. Calories. 



Aluminium A1„0 3 7250 



Magnesium MgO 6000 



Nickel NiO 2200 



Manganese MnO, 2110 



Iron Fe„o 3 1790 



Fe 3 4 1580 



FeO 1190 



Cobalt CoO 1090 



Copper CuO 600 



Lead PbO 240 



Barium BaO 90 



Chromium Cr„0 3 60 



Silver Ag 2 30 



Carbon CO, 8080 



CO 2417 



Silicon Si0 2 7830 



pared. If they are in a chemically active state, as lead is which has 

 been prepared from tartrate of lead, they will, in many cases, take fire 

 in air and. burn at the ordinary temperature. Such lead burns readily 

 when shaken in air. If this mass of uranium, for which I am 

 indebted to M. Moissan, be filed in air, the detached particles will 

 ignite. Metallic iron which has been reduced by hydrogen from its 

 oxide at a temperature below 700° C. will also take fire and burn in 

 air at the ordinary temperature, a point of extraordinary interest in 

 relation to the allotropy of iron.* Metals in this chemically active 

 state are said to be " pyrophoric." 



So far as I am aware, metals in this chemically active state have 

 not been used as fuels. Neither am I aware that any use has been 

 made of the allotropy of metals as enabling them to be used as fuel, 

 but Professor Graham once told me that pyrophorie iron had been 

 suggested for warming ladies' muffs, the intention being to place the 

 iron in a small receptacle and to admit air gradually as warmth was 

 needed. Sir Henry Trueman Wood also remembers the suggestion, 

 but tells me that he can find no record of it in the ' Journal ' of the 

 Society of Arts. I may just mention that the burning of metallic 

 antimony plays a very important part in roasting silver ores, and the 

 behaviour of the metal is so pecular while burning that I must pause 

 to show it you. [A melted globule of antimony, if thrown on to a 

 tray of paper, darts about and cannons from the sides, leaving a track 

 of dark oxide on the paper.] 



The metal I am going to employ as fuel is aluminium, the oxygen 

 for its combustion being supplied by metallic oxides, which readily 

 part with their oxygen to aluminium if it be raised to certain definite 



* Osmond and Cartaud, Ann. des Mines, vol. xviii. 1S95, p. 113. 



2 l 2 



