640 REPORT— 1895. 



in divining the nature and relations of bodies from the appellations attached to 

 them. Nor do I find this deficiency supplied in a manner which to me appears 

 satisfactory when I turn to the writings of Continental chemists.' In a 

 subsequent portion of the report Dr. Daubeny adds: — ' No name ought, for the 

 sake of convenience, to exceed in length six or seven syllables.' I am afraid the 

 requirements of modern organic chemistry have not enabled us to comply with 

 this condition. 



Among other physical discoveries which have exerted an important influence 

 on chemical theory the law of Dulong and Petit, indicating the relationship 

 between specific heat and atomic weight, had been announced in 1819, had been 

 subsequently extended to compounds by Neumann, and still later had been placed 

 upon a sure basis by the classical researches of Regnault in 1839. But here, 

 again, it was not till after 1851 that Cannizzaro (1858) gave this law the im- 

 portance which it now possesses in connection with the determination of atomic 

 weights. Thermo-chemistry as a distinct branch of our science may also be 

 considered to have arisen since 1851, although the foundations were laid before 

 this period by the work of Favre and Silbermann, Andrews, Graham, and 

 especially Hess, whose important generalisation was announced in 1840, and 

 whose claim to just recognition in the history of phj'sical chemistry has been 

 ably advocated in recent times by Ostwald. But the elaboration of thermo- 

 chemical facts and views in the light of the dynamical theory of heat was first 

 commenced in 1853 by Julius Thomsen, and has since been carried on con- 

 currently with the work of Berthelot in the same field which the latter investi- 

 gator entered in 1865. Electro-chemistry in 1851 was in an equally rudimentary 

 condition. Davy had published his electro-chemical theory in 1807, and in 1812 

 Berzelius h ad put forward those views on electric afiinity which became the basis 

 of his dualistic system of formulation. In 1833 Faraday announced his famous 

 law of electro-chemical equivalence, which gave a fatal blow to the conception of 

 Berzelius, and which later (1839-1840) was made use of by Daniell in order to 

 show the untenability of the dualistic system. By 1851 the views of Berzelius 

 bad been abandoned, and, so far as chemical theory is concerned, the M'hole 

 subject may be considered to have been in abeyance at that time. It is of 

 interest to note, however, that in that year AVilliamson advanced on quite distinct 

 grounds his now well-known theory of atomic interchange between molecules, 

 which theory in a more extended form was developed independently from the 

 physical side and applied to electrolytes by Clausius in 1867. The modern theory 

 of electrolysis associated with the names of Arrhenius, van 't Hoff, and Ostwald 

 is of comparatively recent growth. It appears that Hittorf in 1878 was the first 

 to point out the relationship between electrolytic conductivity and chemical 

 activity, this same author as far back as 1856 having combated the prevailing 

 view that the electric current during electrolysis does the work of overcoming 

 the affinities of the ions. Arrhenius formulated his theory of electrolytic disso- 

 ciation in 1887, Planck having almost simultaneously arrived at similar views on 

 other grounds. 



Closely connected with electrolysis is the question of the constitution of solu- 

 tions, and here again a convergence of work from several distinct fields has led 

 to the creation of a new branch of physical chemistry which may be considered 

 a modern growth. The relationship between the strength of a solution and its 

 freezing point had been discovered by Blagden towards the end of the last 

 century, but in 1851 chemists had no notion that this observation would have any 

 influence on the future development of their science. Another decade elapsed 

 before the law was rediscovered by Rlidorft' (1861 ( and ten years later was 

 further elaborated by de Coppet. Racult published his first, wonc on the freezing 

 point of solutions in 1882, and two years later the relationship between osmotic 

 pressure and the lowering of freezing point was established by H. de Yries, who 

 first approached the subject as a physiologist, through observations on the cell 

 contents of living plants. As the work done in connection with osmotic pressure 

 has had such an important influence on the ' dissociation ' theory of solutions, it 

 ■will be of Interest to note that at tlie last Ipswich meeting Thomas Graham made 



