772 



SCIENCE 



[N. S. Vol. XXVII. No. 698 



stances involved in the reaction— hence the 

 name catalytic agent. The acid does not 

 appear to combine with the ester simply 

 because the salt is almost completely 

 hydrolyzed under the conditions of equi- 

 librium between such a weak base and a 

 strong acid— and only very small quanti- 

 ties of the salt and its positive ion exist 

 at any moment. But still, if the concen- 

 tration of a component is increased, say, a 

 thousandfold by the addition of an acid, 

 its reactivity is increased proportionately 

 according to the law of mass action, no 

 matter whether a minute quantity has thus 

 been increased a thousandfold or a larger 

 mass. 



Thus far the development of the subject 

 was purely mathematical and theoretical, 

 although no assumption was made which 

 was not based on established facts of 

 organic chemistry. An experimental test 

 of the correctness of this theory necessarily 

 was a main object. The ordinary esters 

 were not considered suitable for the 

 purpose; they are such weak and unstable 

 bases that it was not considered wise to 

 attempt to measure exactly the actual con- 

 centration of their positive ions in given 

 cases — although this will now be at^ 

 tempted. Recourse was first taken to a 

 very closely related class of compounds, the 

 imido esters, RC( :NH)0CH3, in which the 

 stronger basic group ( :NH ) has replaced 

 an oxygen atom of the ordinary esters. 

 The imido esters are pronounced bases, 

 although weak ones, and form well-defined 

 salts. They are decomposed by water into 

 ammonia and an acid ester according to 



RC ( : NH) OCH3 + HOH -> RCOOCH3 + NH.. 



This action is enormously accelerated by 

 the addition of acids, just as is the decom- 

 position of an ordinary ester. On the basis 

 of the above theory, it was thought that 

 the acceleration of the decomposition of 

 the imido ester would also be due wholly 



to the formation of the salt, and, through 

 it, of its positive ion in larger masses; in 

 other words, the real decomposition must 

 be 



RC ( : NHj) OCHs + HOH -> RCOOCHs + N^, 



and the isothermal equation giving the 

 velocity of the action must be 



dx 

 Velocity = ^ =.^velocity X Cone. Pos.IonsXConC.uoH, 



the same as for the acid esters. 



In this case the theory could be put to 

 the test of experiment, for all the factors 

 could be determined— the velocity of the 

 reaction, the exact proportion of free ester, 

 its salt and its positive ion at any moment 

 were ascertained without difficulty. Not 

 to weary you with experimental details, it 

 may be said that the substance undergoing 

 decomposition was found, as a matter of 

 fact, to be the positive imido ester ion ; the 

 free base, the non-ionized salt do not de- 

 compose with water in this way. The 

 deeper the investigation was carried, the 

 more marked, too, was found the parallel 

 between the acid esters and the imido 

 esters, which have served for the experi- 

 mental verification of the theory; there is 

 an alkaline catalysis of imido esters, as 

 there is of esters, and the alkaline catalysis 

 in both cases is very much the faster one 

 and subject to the same law ; there is a salt 

 effect or salt catalysis for the imido esters 

 as there is for acid esters and for cane- 

 sugar, and our measurements help to ex- 

 plain, we believe, the nature of salt cata- 

 lysis in both cases. 



The proof of the soundness of a theory 

 is shown by the experimental verifications 

 of predictions which can be made on the 

 basis of it, and I would like to report two 

 such cases. Imido esters react also with 

 ammonia, as do ordinary esters, and the 

 products are quite analogous; we have: 



