Viscosity of Solutions. 275 



superseded by the recent careful measurements of Thorps and 

 Rodger (Phil. Trans. 1894). 



The object of the present experimental investigation is to 

 bring the data for some typical solutions up to at least the 

 standard of completeness attained by Thorpe and Rodger for 

 the commoner liquids ; for it is probable that in the next 

 important advance in the theory of solutions, viscosity will 

 have a considerable share. The solutions chosen for study 

 were those of NaCl I per cent., 5 per cent., 10 per cent., and 

 20 per cent., representing typical electrolytic solutions; and 

 of cane-sugar 1 per cent., 5 per cent., 10 per cent., 20 per 

 cent., and 40 per cent., representing typical non-electrolytic 

 solutions. Absolute values of the viscosity were obtained 

 over a range of temperature from 0° to 90° C. 



To ascertain whether the viscosities of these solutions had 

 been determined to the desired degree of accuracy, a pre- 

 liminary study of the viscosity of water over the same range 

 of temperature was undertaken ; and as it was found that the 

 results were in accord with the best determinations hitherto 

 made, such as those of Poiseuille, Sprung, Slotte, and Thorpe 

 and Rodger, it was concluded that the viscosities of solutions 

 obtained with the same apparatus could be taken to possess 

 the desired degree of accuracy. 



In the tables containing the data obtained in these experi- 

 ments, those for water will be given along with the values for 

 solutions. 



The method employed was that used by Thorpe and Rodger, 

 the general principles of which are here stated. 



A definite volume of the liquid under observation, under 

 the influence of a definite pressure, flows through a horizontal 

 capillary tube of known dimensions in a certain time, the 

 temperature of the liquid being observed and kept constant 

 during the interval. 



The liquid, for the purposes of experiment, was contained 

 in a glass glischrometer, similar to that employed by Thorpe 

 and Rodger, with the difference, however, that, the short 

 capillary tube, instead of being sealed to the two limbs, was 

 united to them by means of two indiarubber corks, one at 

 each end of the capillary tube. 



The glischrometer was almost completely immersed in a 

 water-bath, which was heated to the desired temperature by 

 gas-flames, and could be maintained at that temperature 

 by manipulation of a very small jet applied beneath it. 



On each vertical limb of the glischrometer two horizontal 

 marks were etched, in the restricted portions above and below 

 the long cylindrical bulbs ; the two limbs had been made 



