LETEY, J
PARTIALLY SUPPORTED BY U.S. DEPARTMENT OF AGRICULTURE, FOREST
SERVICE, GRANT NO. 4000. IN: SYMPOSIUM ON WATER-REPELLENT SOILS,
PROCEEDINGS, MAY 6-10, 1968, UNIVERSITY OF CALIFORNIA, RIVERSIDE, P
43-47, MARCH 1969. 1 FIG, 3 REF.
THE LIQUID-SOLID CONTACT ANGLE HAS BEEN ONE METHOD OF
CHARACTERIZING WATER REPELLENCY ON PLANE SURFACES, BUT IT CANNOT BE
MEASURED WITHIN A SOIL SYSTEM. THE HEIGHT OF CAPILLARY RISE IS A
FUNCTION OF THE LIQUID-SOLID CONTACT ANGLE. IT IS ALSO A FUNCTION OF
PORE RADIUS, WHICH IS DIFFICULT TO MEASURE. HOWEVER, BY USING ETHANOL,
WHICH HAS A CONTACT ANGLE OF 0, THE PORE RADIUS CAN BE DETERMINED AND
USED TO CALCULATE THE WATER CONTACT ANGLE. THE WATER DROP PENETRATION
METHOD IS BASED ON THE ASSUMPTION THAT THE CONTACT ANGLE MUST BE
GREATER THAN 90 DEGREES ON REPELLENT SUBSTANCES. IT IS A DIFFICULT
METHOD TO USE BECAUSE THE CONTACT ANGLE CHANGES WITH TIME. THE CONTACT
ANGLE IS ALSO DEPENDENT ON THE LIQUID SURFACE TENSION AND IN GENERAL
DECREASES AS SURFACE TENSION DECREASES. CRITICAL SURFACE TENSION IS A
PROPERTY OF THE SOLID, AND THE HIGHER IT IS, THE LESS WATER REPELLENT
THE MATERIAL IS. CRITICAL SURFACE TENSION MEASUREMENTS OF SOILS MAY
LEAD TO A SIMPLE EFFICIENT REPELLENCY INDICATOR, BUT MORE RESEARCH IS
NEEDED. (CASEY-ARIZONA)
Descriptors: *WETTABILITY | *SOIL PHYSICS | *SURFACE TENSION | *CAPILLARY ACTION |
PORES | INFILTRATION | REPELLENTS | *LIQUID-SOLID CONTACT ANGLE |
*CRITICAL SURFACE TENSION | *WATER-REPELLENT SOILS | ETHANOL |
EFFECTIVE PORE RADIUS
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