166 



OSMOTIC PRESSURE OF AQUEOUS SOLUTIONS. 



activity of membranes, but they need not be discussed in the present con- 

 nection. In many cases, the record could have been begun earlier than it 

 was, but there is need of caution in the measurement of pressure with 

 "slow" cells, because of the persistence of thermometer effects in them. 

 There is always some danger, when using slow cells, that a thermometer 

 effect may be mistaken for an equilibrium pressure. 



Table 48. — Determinations of osmotic pressure at 5°. 



(Measurements by H. N. Morse, W. W. Holland, and E. E. Gill.) 



[W. N. S. = Weight normal solution. C. G. P. = Calculated gas pressure.] 



0.1 W.N. S. at 5° 

 C. G. P. 2.267. 



0.2 W. N. S. at 5° 



C.G.S. 4.535.. 



0.3 W. N. S. at 5° 



C.G.P. 6.802. 



0.4 W.N. S. at 5° 

 C. G. P. 9.07.. 



0.5 W. N. 



C.G.P 

 0.6 W. N. 



C.G.P 

 0.7 W.N. 



C.G.P 

 0.SW. N. 



C.G.P 

 0.9 W. N. 



C.G.P 



S. at 5° 

 .11.34. 

 S. at 5° 

 . 13.604 

 S. at 5° 

 . 15.872 

 S. at 5° 

 . 18.139 

 S. at 5° 

 . 20.406 



LOW. N. S. at 5° 

 C.G.P. 22.67. 



O 



K 3 



U 



Js 



F 3 



J 3 



J 3 



K 3 



F 3 



E 3 



K 3 



H 3 



E 3 



J 3 



Li 



M, 



J 3 



J 3 



B 3 



B 3 



Q 3 



F 3 



S 3 



K 3 



J 3 



G 3 



— i 



a 





366,000 

 550,000 

 228,000 

 565,000 

 270,000 

 366,000 

 224,000 

 550,000 

 550,000 

 550,000 

 500,000 

 550,000 

 360,000 

 370,000 

 275,000 

 270,000 

 275,000 

 550.000 

 500,000 

 550 , 000 

 1,000,000 

 550,000 

 1,100,000 

 1,000,000 

 550,000 



3 



m 



v 



a 



13 



6 



13 



6 



9 



6 



9 



13 



22 



9 



9 



13 



11 



20 



2. 

 2. 

 2, 



4, 

 4 

 5 

 6. 

 7 

 8, 

 9 

 12 

 10 

 10. 

 13 

 9J 15, 

 6' 16. 

 20 ! 19. 

 9i 16. 

 9 17 



20 22 



21 18 

 20' 20 



9 21 

 21! 20 

 22! 20 



30 



39 

 30 

 55 



70 

 60 

 89 

 27 

 79 

 28 

 00 

 74 

 28 

 59 

 51 

 00 

 50 

 01 

 11 



oo 

 56 



12 

 83 



15 

 91 



Observed mean daily osmotic pressure. 





c3 



•o 



a 

 o 

 o 

 o 



W 



2.455 

 2.453 

 2.454 



4.83S 

 7.189 



9.591 



9.644 

 12.10 

 12.11 

 14.611 

 14 . 605 

 17.228 

 17.191 

 19.797 

 19.849 



25.32 

 25.23 



25.31 



25.31 

 25.25 

 25 . 26 







2. 

 2. 



2. 

 4. 

 4. 



449 

 449 

 452 

 815 

 822 

 7.186 

 7.213 

 • 9.622 

 9.577 

 9.631 

 12.10 

 12.09 

 14.597 

 14 . 608 

 17.207 

 17.198 

 19.795 

 19.850 

 22.46 

 22.44S 

 25.29 

 25.29 

 25.26 

 25.24 

 25.25 



>> 



3 

 O 



4.810 



7.198 



9.624 



9.517 

 12.09 



19.793 



22.53 

 22.439 

 25.30 

 25.31 





19.793 



22.53 



5 « 





2.452 

 2.451 

 2.453 

 4.812 

 4.825 

 7.187 

 7.209 

 9.623 

 9.584 

 9.617 

 12.10 

 12.10 

 14.604 

 14.606 

 17.217 

 17.194 

 19.795 

 19.849 

 22.51 

 22.443 

 25.30 

 25.30 

 25.30 

 25.24 

 25.26 



i£ 



oi a 

 P. a 





T: ft 



o 



2.452 1.082 



1.063 

 1.058 



9.608 1.059 



^25. 2S 



1.115 



The length of the record which the cells were allowed to make, after 

 having reached equilibrium pressure, varies in general from 2 to 15 days. 

 In one case — that of the 0.5 weight-normal solution at 15° — the record 

 was prolonged to 60 days, in order to test the endurance of the membrane. 

 As a rule, however, the length of time a cell was allowed to continue its 

 record depended principally upon the activity of the membrane. If the 

 cell was slow in coming to equilibrium, it was allowed to remain longer in 

 the bath, in order to lessen the errors due to thermometer and barometer 

 effects. Sometimes a cell was allowed to continue its record simply 

 because its manometer was not needed for another cell. 



