Loss of Energy due to Chemical Union Sfc. 29 



venient quantity of an acid, such as an equivalent weight in 

 grains, dissolve itin about two thousand grains by weight of dis- 

 tilled water, measure the electromotive force of a small voltaic 

 couple of aluminium and platinum in the liquid and call the 

 amount "A." 2nd. Take a chemically equivalent weight of 

 an alkali, dissolve it in an equal quantity of water, measure 

 the electromotive force of the couple in the solution and call 

 the amount " B." 3rd. Take an equivalent weight of the 

 salt resulting from the union of the acid and alkali dissolved 

 in the same quantity of water, measure the electromotive force 

 in a similar manner and call the amount "C." We have 

 now the electromotive force "A" excited by the acid; "B" by 

 the alkali; and "C" by the salt formed by their union. 

 4th. Multiply the electromotive force "A" by the equi- 

 valent weight of the acid, and the one "B" by that of the 

 alkali, add the two products together, and divide the sum by 

 that of the two equivalent weights, and call the quotient " D." 

 "C" represents the mean electromotive force excited by the 

 compound as found by means of experiment, and "D" that 

 arrived at by calculation. 5th. Subtract the experimental 

 amount "C" from the calculated one " D " (or the reverse, 

 as the case may be), and a difference remains which repre- 

 sents the relative amount of loss (or gain) of energy which 

 has occurred during the act of chemical union, change, or 

 mixture of the acid and alkali or other substances employed, 

 as measured by the particular positive metal. And, 6th. 

 Ascertain the percentage amount of loss or gain of the calcu- 

 lated electromotive force " D " in various cases. By this 

 process we obtain a series of percentage numbers which we 

 may view as representing the relative amounts of loss (or 

 gain) of molecular energy which have occurred during the 

 actions with the different substances under the given con- 

 ditions. 



The method is essentially one for directly measuring the 

 differences of mean amount of electromotive force excited by 

 two different electrolytes, and by the liquid produced by 

 mixing them together, with particular positive metals, before 

 and after mixing ; and as these differences must indicate 

 the quantity of energy of some kind lost or gained during t\\c 

 mixing, the method is to a corresponding extent a means of 

 ascertaining the amount of relative loss or gain of energy 

 during the chemical union or mixture of electrolytes. If we 

 use only a single kind of positive metal, the method may be 

 regarded as a system of measurement of the relative Losses 

 and gains of energy as obtained by means of that particular 

 metal. Each positive metal is probably only affected by 



