Page:Text-book of Electrochemistry.djvu/103

 88 GENERAL CONDITIONS OF EQUILIBRIUM, chap.

��The coefficients of the chemical equation become ex- ponents in the equation of equilibrium, whilst the signs of addition become signs of multiplication; in place of the molecular formulae we have the concentrations of the substances, and the sign ^ is changed into = JT.

These equilibria have been studied both in gaseous and liquid systems. Lemoine (8) found for a mixture of iodine and hydrogen which combine partially to hydriodic acid according to the equation —

H2 4" I2 ^ 2HI,

the values contained in the following table, which apply to the temperature 440^. po denotes the partial pressure of the hydrogen at the beginning of the experiment, p\ is the corresponding value for the iodine gas, and x the proportion of hydrogen still free after the equilibrium has been established. It is evident from the. numbers quoted that the observed values of x agree satisfactorily with those calculated. The measurements were carried out by collecting the gas mixture over water, which absorbs the acid formed, and the quantity of hydrogen was then determined eudiometrically. The reaction proceeds so slowly at the ordinary temperature that there is no disturbance of the equilibrium during the measurement.

�� �f^o

� � �Po-

� �X (obs0rv6d).

�% (calcaUted).

�2'2 atmo.

�2-33 „

�2-33 „

�2-31 „

�115 „

�0-37 ,,

�0-45 „

�0-41 „

�0-676 (?) 0-614 (?)

�0-45 „

�0-46 „

�0-600 (?)

�0-48 „

�0-48 „

�25 „

�0-10 ,.

�� �