152 



REPORTS ON INVESTIGATIONS AND PROJECTS. 



well for those of glucose. The measurement of the pressure of glucose 

 solutions was delayed somewhat by a persistent infection of the solutions 

 and membranes with penicillium. This necessitated a search for a poison 

 for the fungus which should be effective in such small quantities that the 

 pressure of the solutions would not be sensibly altered by its presence, and 

 which would not act injuriously upon the membranes. Thymol was found 

 to fulfill these conditions in a satisfactory manner. 



A Final Summary of Results. 



Weight- 

 normal 

 concentra- 

 tion. 



0.2 

 0-3 



0.4 

 0.5 

 0.6 



0.7 

 0.8 

 0.9 



I.O 



No. of 

 experi- 

 ment. 



Tempera- 

 ture of 

 solution. 



Observed 

 osmotic 

 pressure. 



24.05° 



24.23 



20.90 



21.47 



21.75 



21.65 



19.90 



21.62 



22.15 



22.60 



23.70 



24-35 



24.23 



24.1 



23.68 



24.03 



2359 

 23.68 



2478 

 24.78 



23.58 



2455 



Atmospheres. 

 2.51 

 2.55 

 4.72 



4.78 

 4.81 



7.24 



7.20 



9.64 



9.69 

 12.06 

 12.22 

 14.74 

 14.70 

 14.77 

 16.95 

 16.96 

 19.30 



19.39 

 21.82 

 21.91 



24.42 

 24.05 



Theoretical 

 gas pressure 



at same 

 temperature. 



Atmospheres. 

 2.42 

 2.43 

 4-79 

 4.80 

 4.81 

 7.21 

 7.16 

 9.61 



963 

 12.06 

 12.10 

 14.55 

 14-55 

 14-54 

 16.94 



16.93 

 19-35 

 19.36 

 21.86 

 21.86 

 24.19 

 24.28 



Differences 



betvreen 

 osmotic and 

 gas pressure. 



A tmosphere. 

 -I-O.09 

 -j-0.12 

 — 0.07 

 — 0.02 



0.00 

 +0.03 

 +0.04 

 +0.03 

 ■^-o 06 



0.00 

 +0.12 



+0.19 



+0.15 

 +0.23 



O.OI 



4-0.03 

 —0.05 

 +0.03 



— 0.04 



+0.05 

 4-0.23 

 —0.23 



Molecular 

 weight cal- 

 culate d from 

 osmotic 



pressure. 



327.85 

 322.56 



344.96 

 340.90 



339-74 

 338.37 

 338.20 



338.73 

 337.50 

 339-59 

 336.19 

 335-32 

 336.07 

 334-32 

 339-59 

 339-50 

 340.48 

 339.08 



340.19 

 338.82 



336.39 

 342.72 



Mean molec- 

 ular weight 



for each con- 

 centration. 



325.21 



341.87 

 338.29 

 338.12 

 337-89 



335.24 

 339-55 

 33978 

 339.51 

 339-56 



Simultaneously with the work indicated above, careful determinations 

 have been made of the freezing-points, and the densities at different tem- 

 peratures, of cane-sugar and glucose solutions, with a view to discovery, if 

 possible, what relations exist between the osmotic pressure of these solutions 

 and their other properties. It had been found, during the earlier work, 

 that if the factor of density is taken into account, the so-called abnormality 

 of the freezing-points of concentrated solutions of cane-sugar disappears, in 

 the sense that all concentrations then conform to the same rule, making it 

 practicable, in the case of cane-sugar, to calculate correctly the freezing- 

 point depression of any solution from its known osmotic pressure, and vice 

 versa. The existence of this relation has been confirmed, but its significance 

 has not been explained. 



