426 ^Yof, Sir J. Dewar on Low Temperature Investigations. [1903. 



it appears that 100 volumes of mixed hydrogen and oxygen in the 

 solid state would after combination produce 55*2 volumes of ice, or 

 the contraction would amount to 45 per cent, of the initial volume 

 of the mixture. This value is of the order of magnitude of the con- 

 traction which results from the combination of oxygen (solid) with 

 metallic bodies like lithium and sodium, which is about 60 per cent. 

 On the other hand, the production of solid carbonic acid from the 

 diamond or graphite and solid oxygen, would in the former case 

 involve an expansion of 4J per cent., while in the latter the contraction 

 would not exceed some 3 per cent. Such considerations confirm the 

 view that what we call the molecular volume at zero is not the real 

 volume of the molecules, but includes a considerable amount of 

 unoccupied free space. 



[J. D.] 



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