CANE SUGAR. 



117 



concentrated of them that the amount sufficed for even an approximate 

 quantitative estimation. The osmotic-pressure correction equivalents 

 of the quantities found are given in Table 12. 



Table 12. — Cane sugar, Series I. Correction for inversion found by Fehling's method. 



The quantities given in the table are not the full osmotic equivalents 

 of the invert sugar. They are equal to one-half the pressure which is 

 exerted by the products of inversion, since that is the proportion which 

 is to be deducted from the observed pressures in correcting sucrose 

 for the presence of hexoses. 



A very noteworthy feature of Series I was the close agreement 

 between the known molecular weight of cane sugar and that calculated 

 from the observed pressures, on the presumption that the osmotic 

 pressure of solutions obeys the laws of Gay-Lussac and Boyle. It 

 will be seen, in Table 10, that the mean molecular weight derived 

 from 25 determinations, on 13 different concentrations of solution, 

 was 341.41; while the theoretical value (if oxygen = 16) is 342.22. 

 The coincidence is better expressed in the form of the ratio of osmotic 

 to theoretical gas pressure, as in Table 13. The disagreement appears 



Table 13. — Cane sugar, Series I. Ratio of osmotic to calculated gas pressure. 



to be large in the case of the most dilute solution, but of this it is to be 

 said that an experimental error of 0.1 atmosphere in the measurement 

 of the osmotic pressure of the 0.05 weight-normal solution leads to an 

 error of 30.4 units in the estimated molecular weight, or of 0.09 in 



