1903-4.] Physico-Chemical Investigations in Amide Croup. 51 
Physico-Chemical Investigations in the Amide Group. 
By Charles E. Fawsitt, Ph.D., B.Sc. (Edin. and Lond.). 
Communicated by Professor Crum Brown. 
(MS. received December 14. Read December 21, 1903.) 
Some time ago, while studying the chemical dynamics of the 
changes which occur in solutions of urea or carbamide,* I came 
upon some rather unexpected results which led me to hope that 
investigations conducted on somewhat the same lines with other 
substances of the amide group might prove to yield results of some 
interest. The amides referred to are those derived from carboxylic 
acids. While proceeding to this investigation I noticed some 
measurements,! obtained in connection with the viscosity of 
aqueous solutions of carbamide, which appeared of sufficient 
interest to demand an inquiry into the nature of solutions of 
this class of substances before proceeding further with the subject 
of inquiry in the manner at first intended. 
The Viscosity of the Amides in Aqueous Solution. 
The viscosity of solutions is a problem on which a considerable 
amount of work has been carried out, and the way in which the 
viscosity of a solution changes with the concentration of the sub- 
stance dissolved has been found to be generally in agreement with 
the formula 
y x = A* (i), 
where rj x is the viscosity of a solution of concentration x, the 
viscosity of water being taken as unity and where A is a constant. 
Some observers have shown that results occasionally follow the 
formula 
rj x =l+ax (ii), 
where ‘ a ’ is a constant. It will be noticed, however, that if 
* Zeit. fur physical. Chemie, 41, 601 (1902). 
t Rudorf, Zeit. fur physical. Chemie , 43, 257 (1903). 
