Physical Chemistry Third Edition

226 5 Phase Equilibrium

h h

(a) (b) (c)

h

Figure 5.17 Capillary Rise or Depression of a Liquid in a Tube.(a) A liquid that wets

the solid surface. (b) A liquid that partially wets the solid surface. (c) Capillary depression

of mercury in a glass capillary.

EXAMPLE5.11

Find the height to which water at 20◦C will rise in a glass capillary tube of diameter 0.60 mm.

Solution

From Table A.10,γ 0 .07275 J m−^2.

h

2 γ

ρgr



2(0.07275 J m−^2 )

(1000 kg m−^3 )(9.80 m s−^2 )(0. 30 × 10 −^3 m)

 0 .049 m 4 .9cm

Exercise 5.14

Find the height to which the surface of water will rise in a glass tube with a diameter equal to

6 .0 cm.

If the contact angleθis not equal to zero, the surface tension force is exerted at an

angle ofθfrom the vertical. Its upward component is equal to 2πrγcos(θ), and the

height to which the liquid rises is

h

2 γcos(θ)

ρgh

(5.5-9)

Mercury atoms are attracted so weakly to glass compared with their attractions for each

other that mercury forms a contact angle with glass nearly equal to 180◦. The surface