u8 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



Lavoisier (1784) decomposes water by means of iron. 



Having shown that water must be regarded as a compound 

 of inflammable air with oxygen, Lavoisier argued that it 

 should be possible to obtain inflammable air by the removal 

 of oxygen from water. This he succeeded in doing by 

 passing steam through an iron gun-barrel (Fig. 25) heated 

 in a charcoal furnace (Meusnier and Lavoisier, " Decom- 

 position of Water," 1784; Works, II. 360 373). 



Lavoisier writes : 



" If, when the gun-barrel is red and incandescent, water 

 is allowed to flow drop by drop in very small quantities, it 

 is decomposed completely, and none of it escapes from the 

 lower opening of the gun ; the oxygen of the water combines 

 with the iron and calcines it ; at the same time the 

 inflammable constituent of the water, set free, passes into 

 the gaseous state, with a specific weight about 2/25 of that 

 of common air. At the beginning of the experiment, the 

 production of inflammable air is very rapid ; it soon 

 becomes slower, and reaches a uniform condition, which lasts 

 several hours ; finally, at the end of eight to ten hours, more 

 or less, according to the thickness of the barrel, the passage 

 of inflammable air becomes slower, and the water ends by 

 escaping entirely from the gun, as it entered it, without 

 decomposing. If this operation has been pushed to the 

 end, all the substance of the iron which composed the 

 gun-barrel is converted into a black, brilliant substance, 

 crystallised in facets like specular iron ore . . . : this 

 substance occupies a much greater volume than the iron 

 from which it was produced ; the gun-barrel is consequently 

 increased in thickness, and its internal diameter considerably 

 diminished." 



" The phenomena are very different if a metal is used for 

 which oxygen has less affinity than for inflammable air : if, 

 for example, one substitutes, in the preceding experiment, a 

 copper barrel for one of iron, the water is reduced to vapour 

 by passing through the incandescent part of the tube, but it 

 condenses by cooling in the worm ; the process is then only 

 an ample distillation without loss, and there is neither 



