Viscosity of Solutions. 225 



The results of the experiments recorded in the Tables are 

 shown graphically in the curves marked fig. 1 (Plate XL), 

 the ordinates of points of which are given by the numbers in 

 the last column (less 75) ; the abscissae being the temperatures 

 given in the first column. 



At first the most viscous solution is that denoted by B ; 

 the others follow in the order C, A, D, E. The A curve 

 crosses that of C at about 37°, and that of B at about 65°, so 

 that at temperatures higher than this the order of the viscosi- 

 ties of the solutions is the same as that of their concentrations. 



In fig. 2 the coordinates are viscosity and concentration, 

 expressed by the amount of water added to 100 of H 2 S0 4 

 and the viscosities of the different solutions, at intervals of ten 

 degrees, are marked. Definite curves are not drawn at the 

 lower temperatures, but the different points corresponding to 

 the same temperature are joined by straight lines. If more 

 solutions had been used curves might have been drawn 

 throughout in this diagram, which would then have been 

 much more satisfactory. 



These results may be explained as being due to the in- 

 creasing dissociation of the hydrate H 2 S0 4 . H 2 as the 

 temperature rises. It is noteworthy that these experiments 

 show r , as far as they go, that the viscosity of solutions of sul- 

 phuric acid varies with the concentration and temperature in 

 the same kind of way as the electrical resistance as determined 

 by Kohlrausch. 



For subsequent experiments an improved apparatus was 

 fitted up suitable for liquids less viscous than those previously 

 used. The capacity of the bulb of the new apparatus was 

 52*5 cub. centim. The beaker of water, by which the bulb 

 and capillary tube were kept at the required temperature, was 

 in these experiments jacketed by being put in a box and sur- 

 rounded with cotton w T aste. Two apertures, in opposite sides 

 of the box, enabled the bulb to be seen. The pressures were 

 measured by means of a water-gauge, the height of which 

 was observed by a cathetometer. 



Experiment on Acetic-acid Solutions. 



A similar set of experiments was made on solutions of 

 acetic acid, but more solutions were used. The viscosity of 

 each was observed at temperatures varying between 20° and 

 80°. Some experiments w r ere tried at 100°, but they are not 

 recorded here since they were vitiated to a great extent, 

 owing to the formation of bubbles in the bulb and tube. The 

 experimental numbers are given in Tables VI. to XVII. 

 From these numbers a set of viscosity-temperature curves 



