CANE SUGAR. 



115 



were ours, the changes in temperature would be so moderate and 

 gradual that thermometer effects were not to be apprehended; in other 

 words, that the solutions would at all times exhibit their true osmotic 

 pressure, whatever their temperatures might be. It was soon discov- 

 ered, however, that the speed with which the membrane is accustomed 

 to compensate changes in volume through dilution or concentration 

 of the solution had been greatly overestimated. There is no doubt, 

 therefore, that the thermometer effects in Series I were very large. 



The material employed in Series I to VIII, inclusive, was the purest 

 obtainable "rock candy." It was not recrystallized, but was analyzed 

 and examined by the polariscope, and was judged to be sufficiently pure 

 for preliminary experiments. 



Table 10.— Cane sugar, Series I. 



All the solutions except one were made up on the "weight-normal" 

 basis — that is, by dissolving a gram-molecular weight of the sugar, or 

 some decimal part of the same, in 1,000 grams of water. 



Table 10 gives, for Series I, the weight-normal concentrations of 

 the solutions ; the extreme temperature of the bath during each experi- 

 ment; the observed osmotic pressure; the mean osmotic pressure for 

 each concentration; the mean calculated gas pressures of the solute 

 if its volume is reduced to that of the solvent; and, finally, the molecular 

 weights which are calculated from the mean osmotic pressures by the 



