Page:Text-book of Electrochemistry.djvu/120

 vn.

��INFLUENCE OF TEMPERATURE.

��Inveksion of Caue SuOAtt.

��t

�f, (observed).

�p (calcnUted).

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�(9-67)

�(268-0)

��The change of velocity constant with the temperature is evidently very great. The velocity of saponification is doubled for a rise of 10°, corresponding with an increase of 7 per cent, per degree. With cane sugar the increase is even greater, for a rise of temperature of 15° causes an increase of the velocity of inversion in the ratio 1:8 = 1:2^; the velocity is therefore doubled by an increase of temperature through 5°, which is equivalent to an increase of 15 per cent, per degree. As is evident from the table, the increase is smaller at high temperatures than it is at low temperatures, and this is as would be expected from the formula.

Such an exponential increase with the temperature as that mentioned is scarcely ever met with for any other physical phenomenon except evaporation. A cubic centi- metre of saturated water vapour at 0° contains double as much water, namely 4*9 grams, as the same volume at — 10" when the amount is only 24 grams. This consideration led me to construct the following hypothesis (7). The cane sugar solution contains two kinds of molecules, one sort of w^hich can be attacked (inverted) by the acid, the other sort can not. The amount of the former sort is extremely small compared with that of the second, and both are in equilibrium. If we denote the concentrations of the two kinds by ci and ra respectively, we obtain —

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