140 



OSMOTIC PRESSURE OF AQUEOUS SOLUTIONS. 



Table 30. — Cane sugar, Series VI. Observed osmotic pressures corrected for dilution, and 

 ratios of osmotic to calculated gas pressure of the solute. 



Series VII.* 



While the work in Series V and VI was in progress, certain defects 

 of construction in the cooling system manifested themselves. The 

 principal difficulty experienced in this connection was with the gas 

 which was expelled from the hydrant water while passing through the 

 cooling system. Provision had been made in the beginning for the 

 easy escape of this gas by giving all the pipes in the cooling system a 

 slight upward inclination in the direction in which the water was to 

 run. It was found, however, that, despite the inclined position of the 

 pipes and the arrangement for constant pressure, no perfectly steady 

 flow of water could be secured when the stream passing through the 

 system was small. When it was very small, the flow of water would 

 cease altogether in a few hours. It was necessary, therefore, at stated 

 intervals throughout the day and night, to open wide for a few seconds 

 the regulating valve and flush the system. The cause of the difficulty 

 was finally located in the valve itself, which was found to be of such 

 construction that gas could accumulate in it and eventually stop the 

 flow of water whenever the stream passing through the system was 

 small. The valve was replaced by one of different construction, and 

 no further difficulty was experienced in securing a constant flow of water. 



There was no material variation in the temperature of the bath 

 during any experiment in Series VII, and it was apparent, therefore, 

 that one of the two great objects of the preliminary investigation had 

 been accomplished. The system of bath regulation had been improved 

 to the point where thermometer effects were no longer to be feared. Dilu- 

 tion, on the other hand, had not been entirely suppressed. In a total 



♦Measurements by H. N. Morse and W. W. Holland. Am. Chem. Jour., xli, 1. 



