230 Proceedings of the Royal Irish Academy. 



XXXYI. FURTHEE E,ESE.4Ji,CH:ES OX THE DISSOCIATION OF MoLECULES 



, . nf SoLUTioi^. By Chaeles E. C. Tichboe:s-e, Ph. D., E. C. S., &c. 



[Eead June 14, 1875.] 



Iif my previous researclies in conrLexion Tvitli the dissociation of the mole- 

 cules, which are generally known as salts, I have shown that there is 

 probably in every case a partial sej)aration of the base, cleterniinecl by 

 the thermal force acting upon these molecules when in solution.^ The 

 first basic salt produced does not differ much from the original molecule, 

 but its basicity goes on increasing with the increment of heat, ob- 

 tained, we will say, by increased pressure, until a complete temporary 

 analysis of the salt is effected, even if the result of the action is not a 

 permanent decomposition. We may also view these extreme cases as 

 partaking of the nature of gaseous dissociation, it having been proved 

 by Dr. Andrews that there is no hard line of demarcation between the 

 liquid and gaseous state of matter. 



I have also determined that the first thermanalytic action of heat 

 upon hydrated salts, although still in the presence of water, is to gra- 

 dually and completely dehydi-ate the salts, and to render them anhy- 

 drous. The water of hydration, so called, being merely the last and 

 crowning portion of the compound molecule, and therefore the portion 

 of the molecule least amenable to the chemical or molecular force, f 

 it is not necessary to dwell upon this point of the subject any further 

 than to bear in mind that we are actually operatiiLg upon the anhy- 

 drous salt. Presuming, then, that the thermanalytic force being 

 antagonistic to the chemical force, and that, step by step, the com- 

 pound is analyzed to its elementary molecules, it follows that as the 

 basylous molecules are separated, so the stylous or acid molecules must ^ 

 be also liberated or separated. The following experiments, whil^- 

 establishing tliis fact, are merely taken as examples fi'om many others 

 in consideration of their simplicity. 



It becomes evident that, in working under pressure, there cannot 

 be any indications of molecular change better than colour tests, similar 

 to those which serve us so well in ordinaiy qualitative analysis, and, 

 therefore, it is better to confine ourselves, as much as possible, to such 

 reactions. 



There are many instances which may be cited as setting forth with 

 the dissociation of the stylous group, but which would not come under 

 my designation of dissociation, because they are attended with perma- 

 nent decomposition. As an example of dissociation, let us take the 

 well-known salts formed by the combination of chromic acid and 



* Eeport on the Molecular Dissociation by Heat of Compounds in Solution. 

 Proceedings Eoyal Irisli Academy, Vol. i., Ser. ii., Science, p. 169. 



t On the Action of Heat upon Solutions of Hydi-ated Salts. Proceedings 

 Royal Irish Academy, Vol. i., Ser. ii., Science, p. 247. 



