232 SCIENCE PROGRESS 



proceeding, but with extreme slowness ; at the end of a week 

 some accidental disturbance set the change going, and at the 

 close of a second week a condition of equilibrium was attained. 

 In the second case (fig. 2) a larger quantity of a 5 per cent, 

 solution was prepared in a graduated flask, and a portion only 

 was transferred to a polarimeter tube for observation ; at the end 

 of a week a steady condition had been attained, and a second 

 week was then allowed to elapse before the remainder of the 

 liquid in the flask was examined ; the surprising observation 

 was then made that the rotatory power of this portion of the 

 solution was substantially identical with the value recorded 

 a fortnight previously, but when it had been transferred to 

 the tube a change of rotatory power immediately ensued exactly 

 as in the case of the portion first examined. 



It is of interest to note that shortly afterwards a similar 

 observation was made by Forster, 1 who stated that a solution 

 of enolic benzoylcamphor in chloroform " could be preserved 

 in darkness during twelve hours, exposed to bright sunlight 

 during two hours, and even sown with a crystal of the ketonic 

 isomeride without undergoing change." 



From these observations it was concluded that a catalyst of 

 some sort was necessary for isomeric change to take place, 

 even though the change was one which involved only the 

 transference of a single mobile hydrogen atom. It was not, 

 however, until several years later that an explanation was forth- 

 coming which accounted for the peculiar behaviour of these 

 chloroform solutions, and rendered it possible to make observa- 

 tions of a similar character in other solvents. 



This further discovery was made in the course of a series 

 of quantitative experiments on the " Influence of Impurities 

 on the Mutarotation of Nitrocamphor," 2 when it was found that 

 the solutions in chloroform again showed an altogether abnormal 

 behaviour. Thus the basic solutions, to which small quantities 

 of piperidine had been added, appeared at first to be more active 

 than the corresponding solutions in benzene, but were found 

 to be far less active after diluting with a further quantity of the 

 solvent; and finally at a dilution of N/ 1,000,000 it was found 

 that although isomeric change started in the ordinary way it 

 proceeded more and more slowly, and finally ceased altogether 



1 Trans. Chein. Soc. 1 901, 79, 999. 



2 Lowry and Magson, Trans. Chem. Soc. 1908, 93, 107. 



