WORK OF M. R. SCHMIDT. 137 



chloride, nearly three hours of practically continuous shaking, with the temperature 

 at about 80 to 100, to effect the complete solution of 1 or 2 grams of the salts in 

 100 c.c. of glycerol. Potassium iodide, on the other hand, dissolved as soon as the 

 glycerol was warmed slightly, and gave a clear solution in less than five minutes. 

 In view of the close relation of glycerol to the alcohols, and of the very slight solu- 

 bility of potassium iodide in absolute alcohol, this behavior is surprising. 



Much annoyance is caused by the ease with which glycerol imprisons air bubbles, 

 which may require hours to rise. Especially is this likely to occur when the sub- 

 stance is poured into a burette. This difficulty may be obviated, however, by pour- 

 ing the solutions in while hot, in which case the air bubbles will rise fairly rapidly; 

 or by pouring the solutions in such a manner that the descending stream does not 

 strike the walls of the burette except at the highest point to which the burette is 

 to be filled. Thus manipulated, the glycerol flows down the burette walls without 

 inclosing any air, and moreover, no time is lost in waiting for the upper part of the 

 burette to drain before taking the initial reading. 



VISCOSITY. 



The determinations of viscosity were made by means of several Ostwald viscosi- 

 meters, 1 or this form as modified by Jones and Veazey. 2 For the solutions in pure 

 glycerol, as well as for the solutions containing 75 per cent of glycerol, viscosimeters 

 of very large bore were necessary. Two of these, made for us by Eimer and Amend, 

 were very satisfactory. The small bulb had a capacity of about 4 c.c, and the larger 

 of about 30 c.c. The " capillaries," having internal diameters of 1.1 and 2 mm., 

 respectively, were 12 cm. long. As the time of flow of water through these viscosi- 

 meters was less than 10 seconds, it was of course necessary to calibrate them by using 

 a more viscous liquid, the viscosity of which was known. For this purpose the 

 viscosities of several solutions, containing about 50 per cent of glycerol, were deter- 

 mined in the smaller instruments, and then the times of flow of these liquids through 

 the large viscosimeters were noted. A fixed amount of solution was introduced into 

 the viscosimeter from a pipette, and after being raised to the upper mark by air 

 pressure, was allowed to run through the capillary by its own weight. The times of 

 flow were read with an accurate stop-watch. The viscosities were calculated from 

 the formula si 



where 170, s , and t are the viscosity, density, and time of flow, respectively, of pure 

 water, and 77, s, and t the corresponding values for the liquid in question. The values 

 of T70 at 25 and 35 are taken from Thorpe and Rodger's work on viscosity, being 



0.00891 at 25 and 0.00720 at 35. Fluidity, expressed by <, is equal to -, and 



V 



the temperature coefficients of fluidity are calculated from the formula 



, j 1 (/>35-tf>25 

 temp.coef.^=^5-- ir - 



The densities of the solutions were determined in pycnometers of the form 

 described by Jones and Veazey. 3 



iPhysiko-Chemische Messungen, 2d ed., p. 260. 2 Phil. Trans., 185 A, 307 (1S94). 3 Zeit. phya. Chem., 61, 651 (1908). 



