MANNITE. 



207 



Measurements of the osmotic pressure of mannite have been made 

 at 10°, 20°, 30°, and 40°. At the three lower temperatures, the 0.1, 0.2, 

 0.3, 0.4, and 0.5 weight-normal solutions were investigated. At 40°, 

 the increased solubility of mannite in water made it practicable also 

 to measure the osmotic pressure of the 0.6 normal solution. 



Table 72. — Osmotic pressures of mannite at 10°, 20°, 30°, 40°. 



Osmotic pressures. 



At 10°. 



Observed pressures. 



Mean pressures 



Ratios of osmotic to gas pressures 



At 20°. 



Observed pressures 



Mean pressures 



Ratios of osmotic to gas pressures 



At 30°. 



Observed pressures 



Mean pressures 



Ratios of osmotic to gas pressures 



At 40°. 



Observed pressures 



Concentration. 



0.1 



2.322 

 2.310 

 2.314 



1.002 



2.391 



2 . 39,8 



2.395 

 1.002 



2.458 



2.479 



Mean pressures 



Ratios of osmotic to gas pressures 



2.407 

 0.999 



f 2.557 

 l 



2.557 

 0.998 



0.2 



0.3 



4.609 



4.609 

 0.998 



4.778 

 4.783 



4.781 

 1.000 



4.940 

 4 . 946 



4.943 

 1.000 



5.103 

 5.111 

 5.107 

 1.000 



6.950 

 6.930 

 6 . 940 

 1.002 



169 

 192 



7.181 

 1.001 



7.426 



7.434 



7.430 

 1.002 



7.664 



7.664 

 1.001 



0.4 



9.201 

 9.216 

 9.209 

 0.997 



9.613 

 9.572 

 9.524 

 9.570 

 1.001 



9.803 

 9.949 

 9.891 

 9.881 

 0.999 



10.230 

 10.201 

 10.216 



1.000 



0.5 



11.013 



11.613 

 1.006 



11.929 

 11.991 



11.960 

 1.001 



12.326 

 12.363 



12.345 

 0.998 



12.792 



12.816 



12 . 804 



1.003 



0.6 



15.319 



15.319 

 1.000 



The results are summed up in Table 73, in which are given the mean 

 osmotic pressures of mannite solutions, between 10° and 40°, and the 

 ratios of these pressures to the calculated gas pressures of the solute. 

 It will be seen that all the ratios approach unity, showing that, within 

 the limits thus far investigated, the aqueous solutions of mannite obey 

 the laws of Gay-Lussac and Boyle. 



Table 73. 



