1912.] 



Studies on Enzyme Action. 



Ill 



The observed rate of change may be accounted for in two ways : either on the 

 assumption that when the cyanate is dissolved in water it is in part resolved 

 into cyanic acid and ammonia; or on the assumption that the cyanate is 

 dissociated electrolytically into the two ions, the ammonic ion and the 

 cyanic ion — the process measured in either case being the rate at which 

 the reverse interaction takes place by which the cyanate is reconstituted and 

 transformed into urea. 



Walker and Hambly have proved that whereas a neutral salt such as 

 potassic sulphate and also ammonia have but a slight retarding effect, ammonic 

 sulphate and potassic cyanate both hasten the rate at which cyanate is 

 changed into urea. 



The same observers have shown that a variety of non-electrolytes — 

 methylic and ethylic alcohol, glycol, glycerol, acetone and cane sugar — have 

 also a marked influence in accelerating the rate of change ; they express 

 themselves unable to account for the acceleration, though they have no doubt 

 as to the interpretation to be given to the results they obtained with electro- 

 lytes, as they remark " On no other theory (than that of electrolytic 

 dissociation), as it appears to us, can even a qualitative explanation of our 

 results be given." 



We venture to differ. To us it appears easy to interpret the results on 

 ordinary simple principles without invoking the aid of a mysterious, 

 electrolytic-ionic dissociation. It is sufficient to assume that amnionic 

 cyanate undergoes hydrolytic dissociation (dissociation through the agency 

 of water) into cyanic acid and ammonia and that urea is formed by the 

 gradual interaction of these substances and water ; the effects electrolytes 

 produce in altering the rate of change may be accounted for as easily on this 

 assumption as on that of ionic dissociation favoured by Walker and Hambly. 

 The fact is the observations may be interpreted from either point of view : 

 as in so many other cases, the ionic explanation is merely an ornate 

 paraphrase of the ordinary chemical point of view. 



Walker' and Hambly offer no explanation of the formation of urea. It 

 appears from their observations that when ammonic cyanate is dissolved in 

 water it is to some extent resolved into its components ; the slowness with 

 which urea is formed at moderate temperatures is attributable, it may be 

 supposed, to the slowness with which cyanic acid, ammonia and water 

 interact and with which the product of their interaction gives rise to urea, 

 the slowness arising perhaps from the frequent reversals which attend the 

 changes. In any case, the process is to be regarded as one of considerable 

 complexity, in no way as a mere structural change in a single molecule. 



The uncertainty we feel as to the structure of cyanic acid is of little 



