[206] Berzelius: Annales de Chimie, vol. lxi.
[207] On Transformations produced by Catalytic Bodies: by Lyon Playfair, Esq.; Phil. Mag., vol. xxxi. p. 191, 1847.—“Facts have been brought forward to show that there is at least as much probability in the view that the catalytic force is merely a modified form of chemical affinity exerted under peculiar conditions, as there is in ascribing it to an unknown power, or to the communication of an intestine motion to the atoms of a complex molecule. Numerous cases have been cited, in which the action results when the assisting or catalytic body is not in a state of change; and attempts have been made to prove, by new experiments, that the catalytic power exercises its peculiar power by acting in the same direction as the body decomposing, or entering into union, but under conditions in which its own affinity cannot always be gratified.”
[208] Consult Graham’s Chemistry, On Combining Proportions.
[209] Memoir on Atomic Volume and Specific Gravity. Messrs. Lyon Playfair and Joule.—Philosophical Magazine, vol. xxvii. p. 453, or Transactions of Chemical Society of London. Observations on the above, by Professor de Marignac.—Bibliothèque Universelle, Feb. 1846. On the Relation of the Volumes of bodies in the solid state, to their equivalents, or atomic weights: by Professor Otto. Studies on the connection between the atomic weights, crystalline form, and density of bodies: by M. Filhol. Translated for the Cavendish Society, and published in their Chemical Reports and Memoirs.
[210] Comptes Rendus de l’Académie des Sciences, 1840, No. 5. A good translation of Dumas’s Memoir appeared in the Philosophical Magazine, from which I extract the following familiar exposition of the laws of substitution:—“Let me make a comparison drawn from a familiar order of ideas. Let us put ourselves in the place of a man overlooking a game at chess without the slightest knowledge of the game. He would soon remark that the pieces must be used according to positive rules. In chemistry, the equivalents are our pieces, and the law of substitutions one of the rules which preside over their moves. And as in the oblique move of the pawns one pawn must be substituted for another, so in the phenomena of substitution one element must take the place of another. But this does not hinder the pawn from advancing without taking anything, as the law of substitution does not hinder an element from acting on a body without displacing or taking the place of any other element that it may contain.”—Memoir on the Law of Substitutions, and Theory of Chemical Types.
[211] Liebig’s Chemistry in its application to Agriculture and Physiology: translated by Lyon Playfair, Ph. D. Animal Chemistry, or Chemistry in its application to Physiology and Pathology: by Justus Liebig; translated by Wm. Gregory.
CHAPTER XII.
CHEMICAL PHENOMENA.