Dr. Thomas Martin Lowry [April IS, 



Form of the Curves. 



In most cases the change of rotatory power proceeds according to 

 a very simple law, the rate of change being directly proportional to 

 the distance still remaining to be traversed. 



But I have recently found a number of cases in which the curves 

 are far more complex. In such instances it is necessary to assume a 

 series of successive isomeric changes ; but this assumption presents 

 no difficulty, as the substances in question can all be formulated in 

 at least five different ways. 



Acceleration by Catalysts. 



The mutarotation of glucose is accelerated to a moderate extent 

 by acids and very largely indeed by alkalis. Similar observations 

 have been made in the case of nitrocamphor. Piperidine added to a 

 solution of nitrocamphor in benzene produces a remarkable accelera- 

 tion which can be detected even at a concentration of N/10,000,000, 

 i.e. 1 part in 100 million or 1 centigram per ton. Aniline is 100,000 

 times less active. 



Arrest of Isomeric Change. 



The fortunate selection of chloroform as one of a series of solvents 

 led to the discovery of one of the most important facts that has come 

 to light in the course of fifteen years' work on mutarotation. In the 

 very earliest stages of the work it was found that solutions in 

 chloroform behaved in a very irregular and surprising way ; the 

 mutarotation in this solvent seemed sometimes to " hang fire " until 

 set going by some accidental stimulus. These observations were 

 evidently important as proving that isomeric change was not spon- 

 taneous, even after the nitrocamphor had been dissolved. But for 

 ten years no explanation was forthcoming to show why this 

 phenomenon was observed in chloroform, and in chloroform only. 

 About five years ago, however, an arrest of isomeric change was 

 again observed in the case of chloroform solutions to which a trace 

 of acid had been added. These solutions (the rotatory power of one 

 of which " held up " absolutely during twenty-four days) acquired a 

 pungent and horrible odour, and had evidently undergone marked 

 decomposition. It was not long before the odour was recognized as 

 being due to carbonyl chloride — a well-known and (in ansesthetic 

 chloroform) a dangerous impurity, formed by oxidation of the chloro- 

 form according to^ the equation CHCI3 + = COCl, + HCl. This 

 substance has the property of attacking ammonia and organic bases 

 such as piperidine and converting them into neutral ureas, as shown 

 by the equations : 



COCI, + 2NH3 = CO(NH,) + 2HC1 

 COCl, + 2NC5H11 = CO(NC,Hi,)o + 2HC1. 



