Canada's metals : a lecture delivered at the Toronto meeting of the British Association for the Advancement of Science, August 20, 1897 / by Professor Roberts-Austen.

  • William Chandler Roberts-Austen
Date:
1898
Catalogue details

Licence: Public Domain Mark

Credit: Canada's metals : a lecture delivered at the Toronto meeting of the British Association for the Advancement of Science, August 20, 1897 / by Professor Roberts-Austen. Source: Wellcome Collection.

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    metal. Evidence that there is such molecular move- ment in solid metals may be gathered in various ways. It can be shown that solid metals will diffuse into each other, slowly of course but, precisely in the same way that a salt diffuses against gravity into water or another solvent. The curves for the diffusion of gold or platinum into lead or bismuth are precisely of the same form as the curve which represents the diffusion of common salt into water.1 Another fruitful method of studying the changes which occur in solid metals and alloys is to measure the rate at which they cool, and to ascertain by the aid of curves not only what takes place as they pass from the fluid to the solid state, but what happens when they cool down to the ordinary temperature or below it. If a thermometer be placed in water which is steadily losing heat to a cold environment, the mercury will fall continuously until the water begins to freeze, then the fall will be arrested and the mercury will remain stationary until all the mass is frozen, and then the rate of fall will be resumed. It is just the same with a metal, say nickel, except that as the melting point of nickel is far above the range of the ordinary glass thermometer, some other means of measuring the temperature must be adopted, and this is afforded by the use of platinum wires. I 1 Roberts-Austen, “ Bakerian Lecture,” Phil. Trans. Roy. Soc., vol. 187, 1896, p. 383.
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