EXPERIMENT STATION BULLETINS. 517 



should be noted, viz. that a iiuich greater force was used and applied dif- 

 ferently by the above men than that used in our experiments. It must 

 be noted that the moisture equivalent will vary according to the force 

 applied. 



If we consider Tables III and IV together, we will find that those 

 soils with the finer particles and also those with more organic matter 

 have a tendency to hold back the water very tenaciously. This is very 

 noticeable in the soils of the sandy loam, silt loam, clays, muck and 

 peat types. Even in the centrifuge method, those containing a larger 

 percentage of the finer grain and organic matter retained a larger per- 

 centage of the moisture. 



PROPERTIES OF SOIL SOLUTION. 



The study of certain of the physical, chemical and biological factors 

 of that solution ought to give some information in respect to the soil 

 problems. 



Physical. 



The specific gravity of the solution gives an index of its concentra- 

 tion. It is necessary for the calculations of viscosity and surface ten- 

 sion and is determined by the pycnometer at 18° C. 



The color of the solution may give some indication as to the presence 

 of organic matter, perhaps something as to the nature of that organic 

 matter. The author has noticed in some box experiments where the soil 

 was treated with a large amount of dried blood, tankage or cotton seed 

 meal, a distinct coloration of the solution. However any information 

 gained in this connection must be very indefinite. 



Other things being equal turbidity shows something as to the fineness 

 of the soil, — the finer it is, the more turbid the solution. The larger and 

 heavier particles can be separated after a few minutes centrifuging. 

 Some of the remainder will settle out after long standing. The turbidity 

 is determined by making a comparison with a known mixture of BaSOj 

 and water by means of Schreiner's colormeter. The above mixture is 

 made by mixing 1 cc. each of N/10 BaClo. and N/10 KoSO^ and diluting 

 to the desired strength. As in the case of color, data collected in con- 

 nection with turbidity are of questionable value at the present stage of 

 our studies. 



Surface tension and viscosity are very important in that they have 

 much to do with the capillary movement of the soil water. The greater 

 the surface tension, the thicker will be the capillary film and the harder 

 it will be to remove this film. The more viscous the liquid is, the less 

 will be the movement due to capillary action. The surface tension is 

 determined by the drop method, that is, comparing the size of a drop of 

 the solution with that of distilled water at a given temperature. Traube's 

 Viscostagonometer^ is considered the best instrument for this work in 

 that it could be used both for the determination of surface tension and 

 viscosity. With a little care both could be run at the same time. The 

 apparatus consisted of a long graduated tube Avhich is joined at the 

 lower end to a narrow capillary tube ending in a polished dropping sur- 

 face. The tube is graduated into 50 divisions and holds 2 or 3 cc. of 

 liquid. The liquid is drawn up by suction through a rubber tube at- 

 tached to the top of the glass tube either by a pump or the mouth. The 



^E. Abderhalden, "KapiUaranalyllsch Methoden von J. Traube," Handb. Biochem. Arbt. 

 Meth. B. v., pt. 2, p. 1358 and Seq. 



