134 WORK OF M. R. SCHMIDT. 



In spite of the ease with which very pure glycerol can be obtained in large quan- 

 tity, very little work has been clone with solutions in it. In various branches of 

 manufacture, and especially in pharmacy, it has long had extensive use as a solvent ; 

 but no systematic study has been made of the properties of its solutions. 



Cattaneo 1 measured the conductivity of a number of halogen salts of the metals 

 in glycerol, and found that the conductivities are smaller than the corresponding 

 values in water or alcohol, but greater than those in ether. He also states that the 

 molecular conductivity increases only in the case of chlorides. This last statement 

 is not at all confirmed by the present work. 



Schottner 2 carried out an extensive investigation on the viscosity of glycerol and 

 of some of its mixtures with water. Arrhenius 3 measured the viscosity of certain 

 organic substances, including glycerol, in aqueous solution, and found that the 

 decrease of 77 with rising temperature is greatest when 77 is large. Schall and van 

 Rijn 4 determined the relative times of flow of various mixtures of glycerol with small 

 quantities of water and alcohol. 



CONDUCTIVITY APPARATUS. 



The conductivity measurements were made by the Kohlrausch method, using a 

 wire bridge and telephone receiver. The bridge wire was calibrated and found to be 

 of uniform resistance throughout. The conductivity cells were of the form used by 

 Jones and Bingham and subsequent workers in this laboratory. For use with the 

 solutions in pure glycerol, two cells of a different type were used. The electrodes in 

 one cell consisted of two concentric platinum cylinders, about 7 cm. long, and 18 and 

 22 mm. in diameter. They were maintained at a constant distance apart of about 

 2 mm. b}^ means of several drops of fusion glass attached to the edges of the cylinders. 

 The constant was very low, about 4.30. The other cell had as electrodes three 

 cylinders, the outer and inner being joined by a thick branching platinum wire, and 

 forming one electrode, while the middle cylinder formed the other. Drops of fusion 

 glass also served here to keep the electrodes at a constant distance apart of about 

 1.5 mm. The cell constant was about 2.35. The electrodes of both cells were used 

 without being covered with platinum black, and it was possible to obtain very sharp 

 minima on the bridge with them. For instance, when the cell contained conduc- 

 tivity water, and a resistance of 1,000 or 2,000 ohms was introduced into the circuit, 

 the bridge could easily be read at points 2 mm. on each side of the true minimum. 

 This form of cell has proved itself to be especially adapted to work with very viscous 

 solutions. The large electrode surface permits of the cylinders being several milli- 

 meters apart, without making the " capacity" of the cell too great; and this feature 

 alone is of great advantage, as it allows very thick liquids to fill all the space be- 

 tween the electrodes, without the danger of imprisoning air bubbles. The escape of 

 the latter is further facilitated by the vertical position of the cell walls. The "con- 

 stants" of both cells showed only extremely slight variation throughout the work. 



The conductivity measurements are expressed in reciprocal Siemens's units, and 

 the cell constants were determined by means of a fiftieth-normal potassium chloride 

 solution, the molecular conductivity of which was taken as 129.7 at 25. 



Rend. Accad. Line. [51, 2, II, 112 (1893). *Zeit. phys. Chem., 1, 289 (1887). 



=Wien. Ber., 77, 2, 682 (1878). *Jbid., 23, 329 (1897). 



