[miller] 



IDEA IN CHEMICAL MECHANICS 



253 



This method has proved serviceable in some of the more complicated 

 cases, where even Harcourt's method was none too good. 



Then, in some special cases, a way has been found of keeping a con- 

 centration constant without using excess of the constituent;^® and most 

 valuable of aU, perhaps, it has been found possible to apply Harcourf s 

 principles to the study of chemical equilibrium. The equilibrium, in 

 solutions containing iodine, iodide, acid, arsenite, and arsenate, is (so 

 far as I know) the most complicated ye', studied; Mr. Roebuck "^^ cleared 

 the whole matter up in a few weeks by tlie application of a method analog- 

 ous to No. 1 of our table. 



I am very glad to have been afforded tliis opportunity, more than 

 forty years after Harcourt and Esson's first publication, to offer 

 this testimony to the value of the indispensable " idea " with which they 

 have endowed the study of chemical mechanics. No stronger testimony 

 could be offered of the power of the tool which they have placed in our 

 hands, than the fact that young chemists, most of them just completing 

 their college course, have attacked and solved problems which had been 

 left unsolved by some of the most able workers of the present day. 



And when I tiiink of a review "'^ of Harcourt and Esson's paper pub- 

 lished in 1895, in which — after expressing pleasure that these pioneers 

 had again returned to work in the old fields — the reviewer regretted that 

 they had taken so little notice of the progress made since their last visit, 

 I feel that these fathers of the science would have been justified in re- 

 plying, if they had had an opportunity of replying — you can't reply to a 

 reviewer — that so far as the method of working went, a great deal of the 

 progress since 1866 had been made down hill. 



«Jour. Phys. Chein., 8, 454 (1904). 

 '"Jour. Phys. Chem., 6', 365 (1902). 

 "Zeit. phys. Chem., 19, 177 (1906). 



