Page:Outlines of Physical Chemistry - 1899.djvu/163

 interval of twenty seconds between the tenth and eleventh readings the loss by radiation will be

Aid-,, - { - - a — hj — _- + A„

It is to be noticed that for t n we take the mean of the temperatures £ 10 and t u. Similarly,

and so on up to A 19 _ 20.

The sum of all these falls of temperature will be

By adding the number of degrees 2A to the last tem- perature observed in the second period we obtain the cor- rected maximum temperature :


 * 2o + 2A.

��Chemical Affinity and Calorimetry :

First Fundamental Principle

In a compound composed of the atoms a and b, these are disposed at a fixed distance from each other. Suppose that the molecule ab meets another cd under circum- stances which favour a double exchange, and that in the new compounds ad and be the atoms are more closely united than they were in the initial molecules. On coming together, the atoms will have traversed a path under the influence of a force of attraction. The system, therefore, will have lost a certain quantity of potential energy, which becomes externally manifest in some form. Molecules themselves may, on coming together, contribute to the same phenomenon.

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