Loss of Energy due to Chemical Union Sfc. 53 



of the electropositive metal and of the electronegative acid or 

 halogen of the liquid. 



We may regard every instance of chemical union, mixture, 

 or dilution in this research as a case of balance and change of 

 molecular motion of all the substances composing the liquid 

 in the particular case. Previous to mixing, the molecular 

 movements of the liquid are mutually compatible, and there- 

 fore coexist without neutralizing one another : they are in a 

 balanced condition, the liquid is in a state of " rest," and no 

 heat or other form of energy is being evolved or absorbed. 

 During mixing, a more or less profound change and redistri- 

 bution of the movements takes place, those portions of them 

 in the two liquids which are mutually incompatible neutralize 

 one another, heat is either evolved or absorbed, contraction or 

 expansion of the total volume of liquid occurs, and a change 

 of the mean amount of those portions of molecular motion of 

 the liquid, which are incompatible with some of the molecular 

 motions of the positive metal, takes place. 



The amount of each of these several alterations differs in 

 every different case ; in cases of chemical union there nearly 

 always occur contraction of volume, evolution of heat, and 

 decrease of the mean amount of incompatible molecular motion 

 in relation to that of the positive metal, but in those of simple 

 dilution an increase of the latter effect very usually takes 

 place. After mixing, a new state of balance of molecular 

 motion occurs, and the amount of change which has happened, 

 and the point or state of balance attained, depend upon 

 the various conditions already mentioned. In a few cases, a 

 temporary or unstable intermediate state of balance occurs, 

 and the more fixed or final condition is only attained on the , 

 application of heat &c. (see Sections J and K). Immer- 

 sion of the positive metal and closing the electric circuit 

 introduce new conditions, which again disturb the balance. 



Applications of the Method. — The examples given show that 

 the method is applicable to the examination of a large variety 

 of chemical and physical changes in dissolved electrolytic 

 substances, including cases of chemical union and decom- 

 position by whatever causes determined ; simple physical 

 mixture and dilution ; the investigation of the relations of 

 voltaic electromotive force to temperature, specific gravity, 

 atomic weight, amount of chemical heat, &c, and that it is 

 capable of detecting small amounts of molecular change in 

 electrolytes, such as those which occur when neutral salts are 

 dissolved together without any manifest chemical action. 



