X PROCEEDINGS. 



It was long, however, before the next organic synthesis was 

 effected. This was the synthesis of acetic acid, the acid of vinegar, 

 and was carried out by Kolbe in 1845. Two relatively simple 

 organic compounds had thus been synthesized in somewhat less 

 than twenty years. This was slow progress. And in learning 

 why advance had not been more rapid we shall learn something of 

 the nature of the problem presented by organic synthesis. 



Let us suppose that a clever workman who had never seen a 

 watch finds one some day and, observing its usefulness, wishes to 

 construct one for himself. Let us further suppose that he is 

 permitted to experiment with the watch and to observe its exterior 

 but that he cannot open it and that, therefore, the internal mechan- 

 ism is invisible to him. Having learned everything possible from 

 observation, his next step would be to make an hypothesis about 

 the structure of the watch that would satisfactorily explain its 

 observed behaviour. Then, having purchased the necessary parts 

 from a dealer, he would proceed to put them together in accord- 

 ance with his hypothesis. If the latter were well-founded the result 

 would be a watch, the counterpart of that studied. 



Now the problem which our amateur w r atch-maker had to solve 

 is crudely analogous to the much more complex problem which 

 confronts the chemist who attempts to synthesize an organic 

 compound. First he has to determine the composition of the given 

 compound ; then to observe its behaviour under various conditions ; 

 then to make an hypothesis about its structure that satisfactorily 

 explains the observed behaviour ; finally, he has to cause the proper 

 kinds of matter to unite in such a way as to give a compound of 

 the assumed structure. If the assumed structure were correct, the 

 result will now be the desired compound. 



In the time of Wohler, to determine the composition of a 

 substance was in general much the easiest part of this problem; 

 for methods of analysis had already been perfected. It was only 

 necessary to obtain a pure specimen of the substance to be analyzed. 

 This, indeed, sometimes was, and still is, a very difficult task. But 

 as a rule, the nature and proportions of the constituents of a com- 

 pound could be accurately ascertained without great difficulty. 



It was far otherwise with the structure. Dalton's atomic 

 hypothesis was already nearly quarter of a century old when Wohler 



