In an experiment to determine how well benzene wets glass, benzene was found to rise to 1.71 mm in a certain capillary tube at 20.0 C. In the same tube, water rose 4.90 mm at 20.0 C. Calculate the contact angle for benzene, give that at 20.0 C, benzene = 0.879 gcm^-3, pwater = 0.998 gcm^-3, benzene = 2.89 * 10^-2 Nm^-1 and ywater = 7.28 * 10^-2 Nm^-1. The contact angle for water is assumed to be theta = 0.
y1 = cosθ + y1,2 - y2 = 0
The Attempt at a Solution
I don't know where to start. I know y1 can be found by finding the capillary radius of water and using that for benzene. But how do you find y1,2 and y2? Aren't they surface tensions of the solid glass surface which is not given?