$68 PRINCIPLES t)p CHEMISTRY' 



1861, 4 in an empirical manner from accumulated materials available at that? 

 time, and on the basis of the limits to combinations worked out by Dr. Frank- 

 land for other elements. 



Of all the various substitutions the highest proportion of hjdrogen is 

 yielded by methylation, because in that operation alone does the quantity of 

 hydrogen increase; hence, taking methane as a point of departure, if we 

 imagine methylation effected (n - 1) time ,^.we obtain hydrocarbon compounds- 

 containing the highest quantities of hydrogen,- It is evident that they will 

 contain CH 4 + (n - ^CH^ or CH,jn + 2 , because methylation leads to the addi- 

 tion of CH 2 to the compound. 



It will thus be seen that by the principle of substitution that is to say, 

 by the third law of Newton we are able to deduce, in the simplest manner, 

 not only the individual composition, the isomerism, and relations of sub- 

 stances, but also the general laws which govern their most complex combina- 

 tions without having recourse either to statical constructions, to the definition 

 of atomicities, to the exclusion of free affinities, or to the recognition of those 

 single, double or treble bonds which are so indispensable to structuralists in the 

 explanation of the composition and construction of hydrocarbon compounds. 

 And yet, by the application of the dynamical principles of Newton, we can 

 attain to that chief and fundamental object, the comprehension of isomerism 

 in hydrocarbon compounds, and the forecasting of the Existence of combina- 

 tions as yet unknown, by which the edifice raised by structural teaching is 

 strengthened and supported. Besides and I count this for a circumstance 

 of special importance the process which I advocate, will make no difference 

 in those special cases which have been already so .well worked out, such as, 

 for example, the isomerism of the hydrocarbons and alcohols, even to the 

 extent of not interfering with the nomenclature which has been adopted, and 

 the structural system will retain all the glory of having worked up, in a 

 thoroughly scientific manner, the store of information which Gerhardt had 

 accumulated about the middle of the fifties, and the still higher glory of 

 establishing the rational synthesis of organic substances. Nothing will be 

 lost to the structural doctrine except its statical origin ; and as soon as it 

 will embrace the dynamic^ principles of Newton, and suffer itself to be guided 

 by them, I believe that we shall attain for chemistry that unity of principle, 

 which is now wanting. Many an adept will be attracted to that brilliant and 

 fascinating enterprise, the penetration .into the unseen worjd of the kinetid 

 relations of atoms, to the study of which the last twenty-five years have con- 

 tributed so much labour and such high inventive faculties. 



)' Alembert found in mechanics that if inertia be taken to represent force, 

 dynamic equations may be applied to statical questions, which are thereby 

 rendered more simple and more easily understood. 



The structural doctrine in chemistry has unconsciously followed the same 

 course, and therefore its terms are easily adopted ; they may retain their 

 present forms provided that a truly dynamical that is to say, Newtonian-?- 

 meaning be ascribed to them. 



Before finishing my task and demonstrating the possibility of adapting 



Essai d'une thgorie sur les limites des combinaisons organiques,' par D. MendelSeff, 

 $/ll aotit 1861, Bulletin de VAcadimie i. d. Sc. de St. Pttersbourg, t. v 



