136 WORK OF M. R. SCHMIDT. 



although in one case it was as low as 0.9 X10 -7 . The value for the methyl alcohol 

 was about 1.5 X10~ 6 at 25. 



Work with mixtures containing acetone, which it was hoped would yield some 

 interesting results, had to be given up, since glycerol and acetone are only slightly 

 miscible. 



The mixed solvents are made up on a volume basis, and in every case throughout 

 the work, unless otherwise specified, "n per cent A and B" means n c.c. of solvent A 

 diluted to 100 c.c. with solvent B. 



SOLUTIONS. 



All solutions were made on a volume-normal basis, at 20, by direct weighing of 

 the anhydrous salts. A tenth-normal mother-solution was first made, from which 

 the fiftieth and hundredth normal solutions were prepared by dilution. The hun- 

 dredth-normal solution then served as a mother-solution for the two-, four-, and 

 eight-hundredth normal solutions, and from the last named the sixteen-hundredth 

 normal was prepared. The dilutions were made by means of calibrated flasks and 

 burettes. It was found that if a little time was given the solutions containing 25 

 and 50 per cent of glycerol would drain as completely as aqueous solutions, and the 

 same calibration was used for all three. With the 75 per cent solutions, and espe- 

 cially with those in pure glycerol, the draining was incomplete, even though the burette 

 stood two days. Accordingly, a different calibration was made for each of the three 

 mixed solvents containing 75 per cent of glycerol, and for the pure glycerol itself. 

 The amount to be delivered was run at a fixed rate of flow into a weighing-glass, and 

 its weight divided by the density of the solvent at 20. The difference between the 

 volume thus found and the volume read off was the amount clinging to the walls of 

 the burette, and this quantity, which was about 0.60 c.c. for 25 c.c. of glycerol, was 

 added with each measurement of the solutions. It was of course necessary to run 

 the solutions out between the same two points on the burette each time, as otherwise 

 the mean hydrostatic pressure would vary, causing corresponding variations in the 

 rate of flow, with a marked effect on the amount which did not drain out. This 

 precaution is important, as shown by the fact that a volume of glycerol drawn off 

 between and 25 on the burette lacked 0.65 c.c. of 25 c.c, while the same apparent 

 volume, taken between 24 and 49, was 0.35 c.c. less than the amount desired. The 

 water calibration showed that this difference was not due to a great irregularity in 

 the diameter of the burette. Another point that must be noted is the necessity of 

 keeping the temperature of the working room constant while measuring glycerol. 

 The changes in volume of the glycerol are inconsiderable compared with the great 

 changes in fluidity, and a calibration made for 20 would, by reason of the much 

 greater fluidity of glycerol at a higher temperature, be inaccurate at 22. 



In view of the fact that so little work has been done with solutions in glycerol, a 

 few details of a practical nature may not be out of place. In spite of the great solvent 

 power of glycerol, the actual rate of solution is very slow, and most substances can 

 be dissolved only after a great deal of shaking and heating. It was customary in 

 this work to heat the glycerol to almost 100 before adding it to the salt in the meas- 

 uring flask. At this temperature glycerol is quite fluid, and its solvent action is 

 greatly increased. Nevertheless, it required, with lithium bromide and cobalt 



