Chemistry / [Raphael Meldola].

  • Meldola, Raphael, 1849-1915.
Date:
[1914?]
Catalogue details

Licence: In copyright

Credit: Chemistry / [Raphael Meldola]. Source: Wellcome Collection.

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    of heat. This is a point of fundamental significance, and will require further elabora- tion. It is not always possible to detect the heat of chemical combination, because in many cases the transformation takes place very slowly, and the heat is dissipated too rapidly to enable us to measure it. The com- bination of iron with oxygen is a case in point. There is no doubt that heat is developed when iron rusts, but that is a case of slow chemical combination. Now, although the state of physical aggregation of the matter entering into combination is, as already stated, of minor importance so far as concerns the nature of the final product, yet it is obvious that the state of physical aggregation may influence the rate of combination. In the case of a solid combining with another solid, or with a liquid or a gas, it is evident that the more intimately the combining materials are brought into contact the more rapid will be the chemical combination. That is why, in such experiments with iron as have been described, it was thought desirable to use the metal in a finely divided form. It is simply a case of presenting as large a surface as possible to the other substance. But, how- ever finely we may divide iron by mechanical processes, it is not possible to increase the rate