358 CARNEGIE INSTITUTION OF WASHINGTON. 



were employed, ranging from 0.1 to 1.0 weight-normal. The ratios 

 of osmotic to gas pressure which were observed are, respectively: 

 1.001, 1.004, 1.001, 0.999, 0.999, 1.001, 1.001, 1.001, 1.002, and 1.001 : 

 showing that at 60°, as well as between 30° and 50°, the osmotic pres- 

 sure of glucose solutions obeys the gas laws. Material for future 

 work has been prepared bj^ subjecting large quantities of glucose 

 (Traubenzucker Kahlbaum) to the elaborate i)rocess of purification 

 which was described in the monograph previously cited. 



In the case of cane-sugar it had been shown also that, at low tempera- 

 tures, the ratio of osmotic to calculated gas pressure is always consider- 

 ably above unit^^; but that, at some temperature between 30° and 80°, 

 the ratio in every concentration of solution up to 1.0 weight-normal 

 declines to unitj-. It was suggested, as in the case of glucose, that the 

 excessive ratios observed at low temperatures, and their gradual decline 

 through a higher range of temperature — eventually to unity — could be 

 explained most readily by imputing to the solute a definite hydration 

 at the lower temperatures. It was presumed that such hydrates, if 

 formed, would necessarily become unstable at some more elevated 

 temperatures and begin to dilute the solutions by increasing the propor- 

 tion of solvent, and that we should therefore observe, above the initial 

 temperature of instability, a progressive decline in the ratio of osmotic to 

 gas pressure, which would continue until the solute becomes anhydrous. 



The measurement of the osmotic pressure of cane-sugar solutions 

 had previously been carried to 60° for the 0.1, 0.2, 0.3, and 0.4 weight- 

 normal solutions; to 70° for the 0.5, 0.6, and 0.7 solutions; and to 80° 

 for the 0.8, 0.9, and 1.0 concentrations. In other words, the measure- 

 ment of the pressure of all the solutions had been carried at least up to 

 the temperature at which the ratio of osmotic to gas pressure became 

 unity, and the solute appeared, therefore, to be obeying the gas laws. 



It was regarded as highly important to carry the measurement 

 of the osmotic pressure of cane-sugar solutions to still higher tempera- 

 tures, not only for the purpose of ascertaining whether the gas laws 

 continue to prevail, but also to secure additional evidence as to the 

 cause of the excessive ratios of osmotic to gas pressure at low tempera- 

 tures. For more than a year we had been preparing and developing a 

 new series of cells with which it was intended to resume the work on 

 cane-sugar at high temperatures. When, however, it was attempted 

 to use these cells, it was found that they were 'Hoo slow," that the time 

 required for the establishment of ''equilibrium pressures" in them was 

 so great that the slow auto-inversion of cane-sugar which takes place 

 at high temperatures became sensible in quantity — that is, detectable 

 by the method of Fehhng and by the polariscope. It was therefore 

 necessary to suspend the work on cane-sugar at high temperatures 

 until a new series of " quicker" cells could be prepared. The magnitude 

 and difficulty of such an undertaking can be realized only by those who 

 are actively engaged in the investigation; but a statement regarding 



