﻿On the Heat Developed in the Combination of Acids and Bases, 29 



metals being impure, it is clear that there is no similarity between 

 the electric-tension series and that which the metals form as re- 

 gards the heat produced or absorbed on the passage of a current. 

 As, then, from the theoretical proofs which we gave in a former 

 paper, the quantities of heat in question furnish a measure of the 

 electromotive forces, it must be concluded that the electric-tension 

 series is in no close connexion with these forces. Hence it is 

 highly probable that the electrical tension does not exclusively 

 depend on the contact between the two metals, but on the layer 

 of gas or of water which is condensed on their surfaces — a view in 

 favour of which many reasons might be urged. On the other 

 hand, it was seen that the thermoelectric series is the same as 

 that for the electromotive forces. The metals which in contact 

 with each other produce the greatest electromotive force, also 

 produce the most powerful thermoelectric current when the place 

 of contact is heated ; but these thermoelectrical currents are not 

 in all combinations proportional to the corresponding electromo- 

 tive forces. 



V. On the Heat Developed in the Combination of Acids and Bases. 

 — Second Memoir. By Thomas Andrews, M.D., F.R.S., 

 Hon. F.R.S.E., Vice-President of Queen's College, Belfast*. 



IN a paper communicated to the Royal Irish Academy in 1 841, 

 I gave an account of a large number of experiments on the 

 heat disengaged when acids and bases, taken in the state of di- 

 lute solution, enter into combination, and when bases, insoluble 

 in water, are dissolved in dilute acids. The following general 

 conclusions or laws were deduced from those experiments : — 



Law 1. — The heat developed in the union of acids and bases 

 is determined by the base, and not by the acid — the same base 

 producing, when combined with an equivalent of different acids, 

 nearly the same quantity of heat, but different bases different 

 quantities. 



Law 2. — When a neutral is converted into an acid salt, by 

 combining with one or more atoms of acid, no change of tempe- 

 rature occurs. 



Law 3. — When a neutral is converted into a basic salt, by 

 combining with an additional proportion of base, the combina- 

 tion is accompanied with the evolution of heatf. 



Three years later I laid before the Royal Society of London 

 the results of an experimental investigation of the heat developed 

 when one base is substituted for another in chemical compounds. 



* From the Transactions of the Royal Society of Edinburgh, Session 

 1869-70. Communicated by the Author. 



t Transactions of the Royal Irish Academy, vol. xix. p. 228. [Phil. 

 Mag. Sept. 1841, p. 183]. 



