.5,2 . Dr. Gr. Gore on a Method of Measuring 



alkali" metal; but with the halogen salts of the calcium and 

 magnesium group of metals, and with oxygen salts of the 

 alkali metals, the influence of the atomic weight of the metal 

 was less manifest. (See also " Some Relations of Electro- 

 motive Force to Atomic Weight" &c, Proc. Birm. Phil. Soc. 

 1891, vol. vii. part 2, p. 253.) 



I beg to offer the following simple explanation of the chief 

 result, viz. that the loss or gain of mean amount of electro- 

 motive force coincided with the presence and absence of 

 chemical action. The electromotive force appears to depend 

 essentially upon the degree of freedom of molecular motion. 

 The substance which most strongly attacks the positive metal, 

 and by neutralizing some of its molecular motion excites 

 electromotive force, is the most electronegative constituent of 

 the liquid. When this substance (acid or halogen) chemically 

 combines with any ingredient of the mixture it usually loses 

 heat and energy freely ; by this act of union its molecules 

 acquire less freedom of motion, and consequently can only 

 excite a decreased mean amount of electromotive force with 

 the electropositive metal. But when the solution of this sub- 

 stance is only diluted by the second liquid, a much less amount 

 of its molecular motion is neutralized or lost, and the mole- 

 cules of the substance acquire by the dilution a larger sphere 

 of action and an increased degree of freedom of motion, 

 which usually more than compensates the small amount of 

 loss of energy and of contraction of total volume of the two 

 liquids, so that the molecules of the substance can now excite 

 an increased mean amount of electromotive force. These 

 remarks must apply in some degree to the oxygen of the 

 water, because the water itself excites some degree of volta- 

 . electromotive force. 



All the results obtained appear to be consistent with a 

 kinetic theory of chemical action, and the magnitudes of the 

 amounts of electromotive force obtained appear to be deter- 

 mined by the amount of incompatible molecular motions of 

 the mutually acting positive metal and the electronegative 

 -constituent of the liquid. As the amounts of action and 

 reaction are equal, the degree of energy excited, both between 

 the two liquids on mixing, and between the positive metal 

 and the liquids before mixing and after, must be limited by 

 the amount of incompatible molecular motion ; the greater 

 the amount of such motion in the two liquids before mixing 

 the larger the quantity of energy lost by neutralization of 

 those motions during mixing, and the less the total amount 

 of energy left in the liquid substances. According to these 

 views, voltaic electromotive force is directly proportional to 

 the degree of freedom of the incompatible molecular motions 



