CANE SUGAR. 127 



tion. In other words, it was proved at last that the observed loss in 

 rotation was due to dilution and not to inversion. 



Having found that the uncertainty regarding the osmotic pressures of 

 the solutions was due to dilution, and knowing the extent of the dilution, 

 the question arises whether it is legitimate to correct the observed pres- 

 sures of Series II for dilution as they were originally corrected for inversion. 

 The author is of the opinion that, with certain reservations, this may be 

 done, and that the results will thereby acquire a new standing in the his- 

 tory of the investigation which is more in accordance with their merits. 



The absolute futility of attempting to correct observed pressures for 

 dilution which is due to leakage of the membranes has been emphasized 

 in another chapter. The reason given was that one has no means 

 of ascertaining the magnitude of the counter pressure which is exerted by 

 the escaped solute, even when one knows how much of it has passed 

 through the membrane, since the lost material does not distribute itself 

 quickly and uniformly throughout the whole body of solvent which is 

 exterior to the membrane, but remains, for the greater part, in the pores 

 of the cell, giving a solution next to the membrane whose concentration 

 is unknown and can not be determined. 



The dilution in the case under consideration was effected without 

 the loss of solute, and solely through the acquisition of solvent at three 

 different periods. Moreover, the concentration of the solutions was 

 determined by the polari scope after the dilution had ceased. There 

 can be no question as to the propriety of correcting for the dilution 

 which occurred during the closing of the cells or for that which occurred 

 while they were in the bath, since both were finished before the obser- 

 vations on the osmotic pressures of the solutions were taken. The 

 dilution of the third or opening period is of a different order, in that 

 it occurred after the measurements of pressure and previous to the 

 determinations of concentration by the polariscope. It had not, there- 

 fore, affected the pressures in the cells, and it should be deducted from 

 the total before correcting the observed pressures for dilution. There 

 are, however, no means of ascertaining how much of the known total 

 dilution occurred during the opening of the cells. It is probable, 

 therefore, that pressures which are corrected for the total dilution will 

 be slightly over-corrected. The excess can not be large, because the 

 dilution occurring when the cells were opened was brought under 

 control quite early in the investigation. 



With this intimation that the results are somewhat, but probably 

 not largely, overcorrected, the observed pressures of Series II, which 

 are recorded in Table 14, are given in Table 17 as corrected for dilution 

 instead of inversion, yet no higher degree of accuracy can be claimed for 

 these corrected pressures; the uncertainty pertaining to the correction 

 for dilution, the large thermometer effects which must have followed 

 the considerable fluctuations in bath temperature, and the generally 



