AS INDICATED BY OSMOMETERS. 67 



such periods of time as are here considered, and, in comparison with the 

 great changes induced in the viscosity of such solutions by tempera- 

 ture variation, this minor effect may safely be neglected. Powell 1 

 states that the viscosity of a 40 per cent cane-sugar solution (40 grams 

 in 100 c.c. of water) decreases about 3 per cent with each degree of 

 temperature rise. In a 50 per cent solution the corresponding decre- 

 ment is 3.5 per cent. The concentration of the solutions here used, 

 computed upon the same basis as the above, is about 117 per cent. 

 Some rough observations with an Ostwald viscosimeter indicate that 

 the viscosity decrement of our solution, per degree rise in temperature, 

 may be well above 7 per cent, and table 2 shows that the increase in 

 water intake of our osmometers per degree rise in temperature was about 

 3 per cent. Powell's observation that the viscosity decrement in- 

 creases by 0.5 per cent between solution concentrations of 40 and 50 

 per cent supports our own rough observation upon the higher concen- 

 trations used. These considerations make it reasonable to conclude 

 that the decrease in viscosity of the sugar solution, with higher tempera- 

 ture, is alone sufficient to account for the observed variations in the 

 water intake of our osmometers. 



On account of the preliminary nature of the present studies, and 

 because of the inadequacy of the experimental data for such treatment, 

 we shall here make no attempt to utilize the temperature increments just 

 mentioned, as in attempting to approximate by calculation the absorp- 

 tion rates from water with other temperature ranges. The range of 

 temperatures for the soil tests to be presented below was generally not 

 far from that employed for the first and second water tests. Thus, 

 the mean data from these two tests should be roughly applicable for 

 comparison of the rates of absorption from water with those from soil. 



SOIL TESTS WITH OSMOMETER A. 



Osmometer A was operated in soil mixtures containing 25, 20, 15, 

 10, and 5 per cent of water, on the basis of dry volume, unpacked. 

 After thorough mixing by hand, the soil sample to be studied was 

 placed in the jar with as uniform (usually medium) firming as possible, 

 the surface was smoothed, and the osmometer was placed. The 

 cotton packing above the soil and around the instrument was applied 

 immediately and the device for constant pressure upon the osmometer 

 was then attached. Readings were obtained at 15-minute intervals, 

 as in the water tests. 



The data to be presented below refer to a test with each one of the 

 five soil mixtures just mentioned, to a second test with the 20 per cent 

 soil (much more firmly packed than usual), and to a duplicate test with 

 the 10 per cent soil. 



iPowell, C. W. R. Viscosity of sugar solutions. Jour. Chem. Soc. 105: 1-23. 1914. 



