288 lAw or SUBSTITUTION. 



mately so.* It would be a beautiful exemplification of 

 the simplicity of Nature's operations, if it should be 

 clearly proved that the atomic volume of solid water 

 (ice) regulated the combining proportions by volume of 

 all other bodies,, that it was the standard by which 

 chemical combination and ordinary solution were 

 determined. 



In addition to the laws already indicated, there appeal* 

 to be some others of which, as yet, we have a less satis- 

 factory knowledge, and, as a remarkable case, we may 

 adduce the phenomena of substitution, or that power 

 which an elementary body, under certain conditions, 

 possesses, of turning out one of the elements of a com- 

 pound, and of taking its place.f Thus, the hydrogen 



* 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. Bibliotbeque Univer- 

 selle, 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. 



j Comptes Rendus de T Academic des Sciences, 1840, No. 

 "). A good translation of Dumas' s Memoir appeared in the Philo- 

 sophical Magazine, from which 1 extract the following familiar ex- 

 position 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 nothinder 

 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. 



