LYNDE-DUPREj 



ON OSMOSIS IN SOILS 



71 



The soil mud from one shaker bottle was poured into two tubes, 

 1-4 cm. inside diameter and 15-20 cm. long, closed at the lower end 

 with one layer of cotton cloth. The tubes were placed in cups of the 

 centrifuge and the cups were filled with water to the level of the mud 

 in the tubes. The centrifuge was run at top speed for about one- 

 half hour to settle the soil. The liquid was decanted and more 

 mud was added and settled. This was continued until the desired 

 depth of soil was obtained. 



The centrifuge made 1,300 revolutions per minute and the middle 

 of the soil columns when settled was 25 cms. from the axis. 



The liquid left in the tubes after the last settling was used as 

 the soil solution. The tubes were fitted with measuring tubes, -5-1 «0 

 m.m. inside diameter and 45 cms. long, and were then rinsed in dis- 

 tilled water and placed in wide mouth bottles filled with distilled 

 water. The water in the bottles was changed daily. 



When the apparatus was arranged as in Fig. 1, the bottles were 

 kept full to the brim, and the liquid in the measuring tubes was, 

 at the start, made to coincide with the water level in the bottle. 



Thermomefer 

 ^/ Meosurn^'J Tube. . 



Fig 2 



When the apparatus was arranged as shown in Fig. 2, the water 

 level in the bottles was kept at all times 1 -5-2 cm. below the horizontal 

 part of the measuring tubes. This distance (marked "h" on Fig. 2) 

 was made greater than the capillary lift of the measuring tubes. 

 This was done to eliminate the flow which might be produced by the 

 capillary lift of the tubes. 



