2l8 



REPORTS OF INVESTIGATIONS AND PROJECTS. 



Series 3, 4, and 5, at 0°, 5°, and 10°, were executed under the best con- 

 ditions which we are able at present to command. There was not, in any 

 case, a sensible loss of concentration while the solutions were in the cells; 

 the maximum variation in the temperature of the bath during any series of 

 measurements did not exceed 0.02°. The thermometer effects were therefore 

 small and every possible precaution was taken to insure the correctness of 

 the manometers and of the readings. 



In order to prepare uniform material for these and later measurements of 

 pressure, 75 kilograms of the purest obtainable rock-candy were purified by 

 three successive precipitations from aqueous solution with ethyl alcohol, each 

 precipitation being followed by a washing of the crystals upon the filter with 

 both ethyl and methyl alcohols. The Bureau of Standards at Washington 

 has kindly undertaken for us a polariscopic examination of the original mate- 

 rial and of the products of the diflferent recrystallizations. 



The results of series 3, 4, and 5, which have not been published elsewhere, 

 are given below in the form of ratios of osmotic to calculated gas pressures. 

 It will be seen, on comparing the figures for any one concentration at differ- 

 ent temperatures, that the ratios are practically identical, differing from the 

 mean value at most by only 2 units in the third decimal place, showing that 

 the temperature increment of osmotic pressure from 0° to 10° is identical 

 with that of gases; in other words, that the osmotic pressure of cane-sugar 

 solutions, within this range of temperatures, obeys the law of Gay-Lussac 

 for gases. 



Two blank spaces occur in the table, owing to the fact that the work in the 

 regions in question is still incomplete. 



Ratios 0/ osmotic to calculated gas pressures. 



In the work here reported, the writer has had the continuous assistance of 

 Drs. W. W. Holland and B. B. Turner, and of Messrs. E. E. Gill and E. G. 

 Zies. Messrs. G. Cash, W. M. Clark, and C. N. Meyers have also rendered 

 valuable service. 



