EXPERIMENTATION. 

 GENERAL. 



Data from our osmometric tests will now be presented. Three 

 different osmometers will be considered, and the results obtained with 

 each instrument will be set forth together. The osmometers will be 

 designated as A, B, and C; these were all essentially alike, but their 

 absorbing surfaces were of different extent, which necessitates the use 

 of a different coefficient of correction in each case. 



OSMOMETER A. 

 WATER TESTS WITH OSMOMETER A. 



Osmometer A had an effective area of 12.8 sq. cm. and a coefficient 

 of correction of 0.781. It was operated against water three times, twice 

 with somewhat similar temperature ranges and once with a markedly 

 different range. Readings were obtained at intervals of 15 minutes for 

 a period of 5 hours in each of the first two operations and for one of 

 8 hours in the last. The numerical data from these tests, after appli- 

 cation of the calibration coefficient and reduction to hour rates, are 

 presented in table 1. The first column of the table shows the number 

 of the hour, beginning with the placing of the osmometer. The first 

 column under each test gives the hourly rate of water absorption for 

 each 15-minute period within each hour. The average rate for each 

 hour is then given, followed by the average temperature for each hour, 

 the latter derived as the mean of two temperature readings made at 

 the beginning and at the end of the hour, respectively. 



In the first and third tests, as shown in table 1, the initial rate for the 

 first 15 minutes is markedly higher than any succeeding rate. This 

 feature may indicate that some time needs to elapse before the mem- 

 brane comes into dynamic equilibrium with the water on one side and 

 the solution on the other. In the soil tests, as will appear, it is of pro- 

 nounced importance, but it may be neglected here; the average hourly 

 rates for the first hour are not in any case very much higher than those 

 for succeeding hours. The striking general uniformity of the average 

 rates throughout the first 5 hours for the first two tests, and throughout 

 the first 8 hours for the third, is to be noted. 



It is seen at once from table 1 that the average hourly rates obtained 

 in the third test are generally lower than the corresponding ones from 

 the first and second, and that there is no very marked, consistent differ- 

 ence to be observed between the corresponding average rates obtained 

 from the first two tests; it does appear, however, that these averages 

 are slightly lower in the second test (with the exception of the average 

 rates for the first hour). After hour 1, the mean average maintained 

 rate for the first two tests is 1.37. 



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