230 Mr Barlow, On the Osmotic Pressure of Aqueous Solutions. 





Gauge 



levels 





Calculated 



Time (year 1903) 







Tempera- 

 ture 



pressure 

 corrected for 









narrow- 

 limb 



wide-limb 



(degrees C.) 



temperature 





f open 









Thursday, Oct. 29, 4.15 



1 202-6 

 ] closed 



196-8 



— 



— 





[ 204 



196-6 



. — 



— 



Friday, Oct. 30, 12.0 



231 



— 



— 



— 



Friday, Nov. 6, 10.0 



335 



— 



— 



— 



Tuesday, 12.30 



363 



168 



— 



— 



Wednesday, 1.50 



368-6 



167-2 



— 



— 



Friday, Nov. 13, 10.0 



375-5 



166 



12-8 



1-57 atmos. 



Monday, 12.50 



382-6 



164-6 



12 



— 



Wednesday, 10.20 



386-5 



164 



12 



1 "84 atmos. 



Thursday, 4.0 



388-2 



164 



13-2 



— 



Friday, Nov. 20, 10.15 



375 



165-2 



9-2 



(Falling) 



From these readings it is seen that it took nearly three weeks' 

 time for the pressure to reach the value of 1'84 atmosphere. 

 Both the pressures calculated are above the theoretical value. 

 This is probably due to two causes, — a trace of alcohol from 

 the experiment in which cell XIV was last used, and partial 

 inversion of the sugar during the three weeks of the experiment. 

 If the latter were the sole cause of the excess of pressure, we 

 should have 



. _ observed pressure _ T84 _ 



theoretical pressure 1'26 ' 



a = i - 1 = 45. 

 That is 45 °/ of the sugar was inverted. 



I think this is too high to represent the actual state of affairs, 

 and though some of the sugar might be inverted, still most of the 

 excess must be due to some trace of alcohol. This experiment 

 thus affords an example of the length of time that must be 

 allowed in this kind of work for a cell to become clean for osmotic 

 purposes. 



The experiments with cells XIII and e were performed with 

 more dilute solutions. In each case reference is made to the 

 immediately previous history of the cell. 



(1) Cell XIII. '002 N cane-sugar solution. Theoretical 

 pressure = 34 mm. Previous history of cell. On Feb. 9, after 

 washing for more than two months in distilled water which was 

 often changed, the cell was used with a solution of KC1 for a week. 

 Then it was washing in water from Feb. 24 to Mar. 15. It was 



