iv
his elaborate memoir, "On the Specific Heat of Compound Sub-
stances," in which he sought to develop Neumann's law, was published
by the Royal Society. The Royal Society Catalogue of Scientific
Papers gives the number of his papers as 65.
Kopp enjoys an almost unique position as an investigator. The one consistent purpose of his work was to establish a connexion between the physical and chemical nature of substanoes; to prove, in fact, that all physical constants are to be regarded as functions of the chemical nature of molecules. It is not implied, of course, that the conception of such an interdependence originated with him. As a matter of fact, almost immediately after the pnblication of Dalton's New System of Chemical Philosophy,' in which the doctrine of atoms was revived to account for the fundamental facts of chemical union, the endeavour was made to connect the chemical attributes of a substance with one of its best defined physical constants, viz., its atomic mass. Prout's hypothesis is, n reality, the generalised expression of such an attempt; it is an adumbration of Mende léeff's great discovery of the Law of Periodicity be justly claimed for Kopp that no one before him made any systematic effort to connect such of the physical qualities of sub stances as admit of quantitative statement with the stoichiometrical valnes of such bodies. The sporadic attempts made prior to 1840 were practically fruitless on account of the imperfect nature of the physical data up to that time extant.
When Kopp began his inquiries, very few boiling points were known, even approximately; and he had, as a preliminary step, to ascertain the conditions under which such observatious must be made in order that accurate and comparable results could be obtained The thermal expansions of barely half a dozen liquids had been measured, and the very methods of making such measurements with precision had to be worked out
At the outset of his investigations, Kopp found the physical con- stants with which he was more immediately concerned very much as Berzelius found Dalton's values of the relative weights of the atoms at the close of his work they were hardly less accurately known than were those stoichiometric numbers to the ascertainment of which the great Swedish chemist had dedicated his life.
Kopp's more important memoirs readily and naturally fall into comparatively few groups, viz., (1) those concerning the relations between the specific gravities of substances and their molecular weights; (2) those treating of the relations between boiling point and chemical composition; and (3) the papers relating to the specific heats of solids and liquids. As regards the other papers, only the briefest notice is here possible. Much of this work was of a pioneer character, and his conclusions have necessarily been modified by But it may
