552 



SCIENCE. 



[N. S. Vol. XII. No. 302. 



liand and the stable inorganic on tlie other, 

 then, too, the labile compounds of pro- 

 toplasm occupy an intermediate position. 

 The chemical phenomena of life, are as 

 close to those of the inorganic as to those of 

 the stable organic bodies. It is not so much 

 by emphasizing the differences between car- 

 bon and the inorganic elements that we 

 shall aid in the explanation of life as by 

 looking for those features in which carbon 

 approximates to the inorganic. 



Hitherto the organic chemist has occu- 

 pied himself mainly with the end-products 

 of chemical reactions. With those impor- 

 tant factors, the time and the yield, he has 

 seldom concerned himself, further than to 

 obtain the greatest possible yield in the 

 shortest possible time, and he has reached 

 this end by purely empirical processes. 

 Now we know that most, if not all, reac- 

 tions do not proceed to an end in the 

 sense expressed by the chemical equation.* 

 Every equation is true, not only when read 

 from left to righ t but from right to left like- 

 wise ; there is always a state of equilibrium, 

 lying between the two extremes, sometimes 

 so far from each that the reaction is ob- 

 viously incomplete, sometimes so near one 

 extreme that for practical purposes it may 

 be considered as coinciding with it, but in 

 reality never absolutely does so. This state 

 of equilibrium is influenced hy the relative 

 amounts or active masses of the reacting 

 bodies, and is approached with a velocity 

 varying from what is practically instanta- 

 neous to a slowness which can be measured 

 only by ages. The ionized bodies reach 

 equilibrium with exceeding rapidity, while 

 undissociated substances, or those disso- 

 ciating slowly, usually show a much smaller 

 reaction velocity. The reactions of organic 

 chemistry are to a great extent comparatively 

 slow, and the equilibrium lies at a consider- 

 able distance from both extremes, hence the 



* This of course does not apply to the so-called 

 ' condensed systems. ' 



almost invariable wide deviation from the 

 ' theoretical ' yield of the desired products. 

 It seems, therefore, that the study of reac- 

 tion velocities and of the laws of equilibrium 

 has a most important bearing on the work 

 of the organic chemist, a study which he 

 has been most tardy in taking up. The 

 precious ' Ausgangsmaterial,' which he has 

 spent months in preparing, is often wasted 

 unnecessarily through ignorance of these 

 laws, while in technical processes the case 

 is no better ; this, too, quite apart from the 

 contributions which could be made to phys- 

 ical chemistry by duly considering these 

 points. As organic chemistry advances, 

 relatively more and more attention will be 

 devoted to the way in which the reaction 

 takes place. In physiological chemistry 

 especially is this important, because here 

 it is not the final products themselves, as a 

 rule, which are interesting, but the mode 

 of their formation ; physiological chemistry 

 is not a science of compounds, but a science 

 of processes ; it is the most physico-chemical 

 branch next to physical chemistry itself. 



Most important for organic chemistry 

 and its applications is the study of the 

 influence which certain substances exert 

 on the course of a reaction, without being 

 themselves permanently changed. Such 

 phenomena have long been known, and to 

 them the name catalytic was applied by 

 Berzelius. The most obvious character- 

 istics of such reactions are that the foreign 

 substance, or catalyzer, is able to exert an 

 influence altogether out of proportion to its 

 quantity and that it remains unaltered at 

 the end of the process. Such catalytic re- 

 actions are well known both in inorganic 

 and in organic chemistry. In the former I 

 may cite the well-known influence of small 

 quantities of platinum in decomposing 

 hydrogen peroxide, and the influence of 

 the oxides of nitrogen or of spongy plati- 

 num in the formation of sulphuric acid, in 

 the latter, the inversion of cane sugar by 



