WORK OF M. R. SCHMIDT. 135 



Measurements were made at 25 and 35. Glycerol, when maintained at for a 

 long period, undergoes a gradual change, resulting sometimes in the deposition of 

 crystals. On this account, and for the reason that at low temperatures the substance 

 is so extremely immobile that viscosity determinations are almost impossible, no 

 measurements were made at 0, as has been the custom in these investigations. The 

 temperature coefficients of conductivity and viscosity are therefore not strictly 

 comparable with those obtained by other workers for the same solutions between 

 and 25. 



The constant-temperature baths were of the form previously described, and were 

 maintained constant to within 0.03 of the desired temperatures. The thermometers 

 were compared with a certificated Reichsanstalt instrument. The measuring flasks 

 were calibrated to hold aliquot parts of the true liter at 20, and solutions were 

 brought to within 0.2 of this temperature before filling to the mark. 



SOLVENTS. 



Glycerol. The glycerol used was Kahlbaum's "Glycerin, 1.26." Two determin- 

 ations of different lots gave the same density, D25= 1.2586. The specific conduc- 

 tivity varied from 0.5 X 10~ 7 to 0.7 X 10~ 7 at 25. Some of the glycerol was distilled 

 under diminished pressure, boiling at 160 under a pressure of 6 mm. The specific 

 conductivity was not changed by this process, and the remainder of the glycerol 

 was used without further treatment. 



Water. The water was purified essentially by the method of Jones and Mackay, 1 

 with a slight modification. The practice heretofore has been to distil ordinary dis- 

 tilled water from acidified potassium dichromate to destroy organic matter and retain 

 ammonia, and then to redistil from a weaker chromic acid solution, forcing the steam 

 from the second distillation through a solution of barium hydroxide. There can be 

 no doubt that water prepared in this way still contains large quantities of carbon 

 dioxide. The extreme rapidity with which the current of steam passes through the 

 alkaline solution makes it impossible for the latter to come in contact with all of the 

 vapor, and some of the carbon dioxide escapes with the steam to be condensed, 

 giving water with a conductivity which has generally been about 2 X 10~ 6 at 25. If, 

 however, the second distillation is made from a solution containing barium hydroxide 

 instead of acidified dichromate, the conductivity of the water is lowered considerably. 

 Nearly all of the carbon dioxide is retained, and the conductivity of the water thus 

 purified has rarely risen over 1.5 X10 -6 , and was many times as low as 1.2. In 

 addition, the alkaline solution, probably owing to the presence of the fine crystals of 

 barium carbonate, boils more quietly than the acid solution, with entire absence 

 of bumping. 



Ethyl and Methyl Alcohols. These were purified by boiling the commercial prod- 

 ucts with fresh lime for a day, and then distilling again from more lime without trans- 

 ferring the alcohol in the air. A third distillation from lime was made if the specific 

 gravity of the second distillate showed the presence of any appreciable amount of 

 water. Several more distillations were then made through a block-tin condenser. 

 The conductivity of the ethyl alcohol ranged between 1.2Xl0 _r and 1.8X10 -7 , 



Amer. Chem. Journ., 17, 83 (1895). 



