May 15, 1908] 



SCIENCE 



773 



C,H.COOCHa + NH,^ CeHjCONHj + CH3OH 

 and 



C.HjC ( : NH) OCH, + NH, -> 



CeHjC ( : NH) NHj + CH3OH. 

 The latter reaction proceeds very slowly 

 but is accelerated again enormously by the 

 addition of an acid. On the basis of the 

 general theory we supposed at once that 

 the real action does not involve the imido 

 ester itself at all, but only its positive ion, 

 so that we must have 



Velocity = ^ = •S'yeiocity X Cono. po^. i^^ X Cone. ^Hj. 



This action is interesting because almost 

 all of the added acid is taken by the 

 stronger base, the ammonia, to form an 

 ammonium salt, the weaker base, the imido 

 ester, taking only a very small share of it. 

 The same catalytic effect can, therefore, be 

 produced also by adding an ammonium salt 

 to the mixture; the weaker base will also 

 take a small part of the acid ; but this small 

 share, however minute, can be rigorously 

 ascertained with the aid of the equilibrium 

 law and of the experimentally ascertained 

 affinity constants of the two bases. The 

 mathematical development led to the rather 

 startling prediction that the reaction veloc- 

 ity would be found to be independent of 

 the concentration of free ammonia— one of 

 the reacting components— a result which 

 no one would anticipate from the old 

 view as expressed in the first equation. 

 That is, while accelerating the action pro- 

 portionately to its mass, the ammonia, ac- 

 cording to our view, should also retard it 

 to a like degree by driving the imido ester 

 proportionately out of its combination with 

 the acid and thus its concentration would 

 not affect the reaction. As a matter of ex- 

 periment, the velocity of the reaction was 

 found, as predicted, to be practically inde- 

 pendent of the concentration of free am- 

 monia. In the second place the degree of 

 ionization a of the ammonium salt figures 



in the final mathematical equation— the 

 velocity constant referred to the positive 

 imido ester ions being Ev/a. Now, am- 

 monium sulphate is ionized considerably 

 less than ammonium chloride in equivalent 

 solutions. When we determined the veloc- 

 ity of the action for methyl imido benzoate, 

 first using ammonium chloride as the cata- 

 lyzer, we found that it is 281 if a is left out 

 of consideration, and for the sulphate solu- 

 tion it is 212. The respective degrees of 

 ionization of the salts in the concentra- 

 tions used are 80 per cent, and 61 per 

 cent., respectively, and for Kv/a we have 

 281/0.80 = 351 and 212/0.61 = 351. The 

 third point of especial interest is that in 

 this reaction the actual concentration of 

 the reacting substance, the positive ester 

 ion, is exceedingly small ; for instance, only 

 0.000,018 gram molecules at the beginning 

 of our first series, and still smaller as the 

 reaction proceeds, but it is rigorously cal- 

 culable and it is noteworthy that the 

 velocity is really found proportionate to 

 this small but vital component. This, I 

 believe, also justifies completely the concep- 

 tion that the catalysis of ordinary esters is 

 also due to a very small but vital com- 

 ponent, which has hitherto escaped meas- 

 urement, but the assumption of whose pres- 

 ence enables us to give a rational explana- 

 tion of catalytic action of acids which is in 

 complete agreement with all experimental 

 facts and with the laws of dynamics. 



Another fact discovered as a result of 

 applying the theory is this: in all our 

 determinations we have found the rule to 

 hold that in the presence of an acid cat- 

 alyzer the tendency for action is for the 

 ion of a weaker base to change into the ion 

 of a stronger one— that is true for the 

 amidine reaction, for the action of water 

 on imido esters and on ordinary esters, and 

 even for the formation of esters from an 

 acid and alcohol; the rule is probably de- 



