624 



SCIENCE 



[N. S. Vol. XXX. No. 775 



the coneeutration of the hydrogen ions in 

 acid catalysis. 



Professor Bredig, who, with his students, 

 has made the chief contributions to the 

 theoretical and experimental development 

 of the idea that the catalyzer forms an 

 intermediate compound, has written me 

 that he too has recently discovered some 

 reactions in which the non-ionized salt 

 seems to be transformed into other sub- 

 stances. 



We see, then, that the question whether 

 the anion or cation (simple or complex) or 

 the molecular form of a given acid, base, 

 salt or other neutral substance, is the chief 

 constituent transformed directly into the 

 end products depends entirely upon the 

 relative magnitudes of the various con- 

 stants, and therefore varies widely in the 

 .different problems. 



Occupying our attention in this connec- 

 tion is another phase of this work which 

 should certainly be a great help to us in the 

 ■solution of such problems. There is no 

 method to-day for determining the concen- 

 trations of the constituents of such a react- 

 ing system as a mixture of acetamide, 

 hydrochloric acid and water, in which 



CHaCONHj-l- H-l- Ci -f CH3CONH3-I- CI -f- 

 CHjCONHaCl-t-H.O ?± CH3C00H-1-NH,-|-Ci, etc., 



the salt undergoing transformation is very 

 greatly hydrolyzed. The decrease in con- 

 ductivity produced by adding acetamide to 

 hydrochloric acid does not give us sufficient 

 knowns to solve for the unhnoivns in the 

 above equation. If some method were 

 devised for determining the concentration 

 of the hydrogen ions nearly instantaneously, 

 then these problems could be solved. A 

 eolorimetrie method involving the use of 

 indicators seems to be out of the question 

 with such concentrated solutions, but it 

 may, in certain cases, work well in dilute 

 solutions. But the use of the hydrogen 



electrode for the determination of the 

 changing hydrogen ion concentration at 

 any moment would seem to be very effective 

 in those cases in which no disturbing side 

 reactions take place, and this problem is 

 engaging Mr. Desha's attention. Such a 

 method, if successful, would be of great 

 help in the study of a large number of 

 reactions in acid, alkaline and other solu- 

 tions. 



Finally, organic chemistry is to-day a 

 ripe field for the study of energy changes 

 in reacting systems, as has been emphasized 

 especially by Michael. The total energy of 

 a system can in some cases be measured by 

 studying the rate of formation or absorp- 

 tion of heat during the reaction in an adi- 

 abatic system. This has been done very 

 satisfactorily by Bredig and Epstein in the 

 decomposition of hydrogen peroxide by 

 potassium iodide. Especially important is 

 the study of free energy by the use of 

 equilibrium and eleetrometric methods. A 

 large number of organic reactions can be 

 very easily arranged to take place in con- 

 centration cells in such a manner that the 

 electromotive force can be readily and accu- 

 rately measured. In order to study such 

 cases completely the mechanism of the reac- 

 tion must be known, and the values of all 

 the constants, especially the equilibrium 

 constant, must be determined accurately. 



We are further using electrometrie 

 methods in the study of the question 

 whether in the presence of platinum, iri- 

 dium, etc., such substances as methane, 

 ethylene, trimethylene, etc., can be made to 

 dissociate as follows in substitution and ad- 

 dition reactions: 



CH,=CH3-|-2 © -^ OIL— CH,-|-2Br -> CJ-I^Br,, 



CH;F=CH,-F2 e -» CHn— CtL+2H -^ aH„, 



CH,-|-2 © -^ CH3-f-H+2Br -^ CHjBr-l-HBr, 



CH^-^CHs+H. 



We see, then, that organic chemistry pre- 

 sents a large number of interesting prob- 



