152-84 sec. 

 152-57 „ 



rj/ Vo = 0-9987. 



152-84 sec. 

 152-55 „ 



r)/r) = 0-9985. 



ON THE VISCOSITY OF SOLUTIONS. 399 



independent solutions of the same substance ; and from them the limits of variation 

 in the value of the viscosity may be ascertained. 



(1) 25° C. -1 m. KOI. 



(a) Nov. 22, 1905. 



Water . . . 97 -50 sec. V?o= l '° 002 - 



Solution . . . 97-05 „ 



(b) Jan. 31, 1906. 



Water . . . 206-06 sec. r)/ Vo = 0-9996. 



Solution . . . 204-96 „ 



Two different viscosity tubes were used in this case. 



(2) 8° C. -03125 m. carbamide. 



(a) June 14, 1906. 



Water 

 Solution . 



(b) June 18, 1906. 



Water 

 Solution . 



The tubes employed by us, up to the present, are all of the Ostwald pattern (as 

 figured in Ostwald-Luther's Phys. chem. Messungen, p. 260). The difference of time 

 of outflow is not caused to any considerable extent by differences in length or diameter 

 of the capillary, but is due to the fact that the bulbs immediately above the capillary 

 were of different capacities, and, indeed, were generally adjusted so as to give a suitable 

 time of outflow. 



The diameters of the two capillary tubes were measured, and were found to be as 

 follows : — 



(1) Greatest diameter, 0*56 mm. ; least diameter, 0*50 mm. 



(2) ,, „ 0-60 mm. ; „ „ 0*52 mm. 



The pycnometers with which the density determinations were made were of about 

 13 c.cm. capacity. The solutions and the water were carefully freed from air, and the 

 temperatures at which the adjustments of the volumes in the pycnometer were made 

 were extremely constant. The densities of the solutions may be taken to be accurate 

 to 1 in 10,000. The densities of water at the different temperatures were the values 

 given in the table of Thiesen, Scheel, and Diesselhorst (in Ostwald-Luther's Phys. 

 chem. Messungen, p. 128). The relative viscosity was calculated by means of the 

 formula 



y\jy] = dt/d't' , 



and not from the more accurate formula 



V / Vl = (d - \)t/(d' - X)t' , 



as the density of the air (A) would not introduce an error greater than 1 in 10,000, and 

 may therefore be neglected. 



