1903-4.] Physico-Chemical Investigations in Amide Croup. 55 
by making measurements of the electrical conductivity. On the 
addition of urea we have the ion CO(NH 2 ) 2 H* forming at the 
expense of the H* ion, but the mobility of this new ion, as indeed 
of all other kations, is considerably less than that of H\ Below 
are results I have obtained for urea and hydrochloric acid at 
34 ’2° C. (The relations are practically unaltered at other tempera- 
tures between 25° and 100° C.) 
Urea and Hydrochloric Acid. 
Concentration. 
Molec. Conductivity. 
h norm. HC1 
,, + £ mol CO(NH 2 ) 2 
55 +4 '5 55 
55 +1 5 5 5 5 
„ + 1-6 „ 
55 +3‘2 ,, ,, 
406-8 
353 
312 
250 
206 
147 '6 
These results are reproduced in figure 2, giving a curve very 
similar to that in figure 1. It will be noticed in these curves that 
the effect produced by the urea falls off greatly in the higher 
concentrations.* 
To show the effect of urea on the electrical conductivity of a 
neutral salt in solution, I have measured the conductivity of a 
solution of potassium chloride with varying additions of urea. 
Urea and Potassium Chloride ; 25° C. 
Concentration. 
i norm. KC1 
,, +f mol. CO(NH 2 ) 2 
5 5 4 ” 2 5 5 5 5 
+ 1 5 , 
„ + 1*6 „ 
55 +3 2 ,, ,, 
It will be seen that the percentage decrease here is very much 
less than in the last case. The results are given in the curve 
(fig. 3). The form of the curve is also different from the last 
case, being almost a straight line, but slightly concave towards the 
abscissa axis. 
In the present case we may assume that there is no measurable 
salt formation in solution. The decrease of conductivity may be 
Molec. Conductivity. 
116-4 
115-3 
114-6 
111-9 
108-7 
100-1 
Compare also Journ. Clievi. Soc., 79, 707 (1901). 
