 |
| Angle of Contact and Shape of Meniscus |
|
 |
| |
| The above figure shows two liquids, one liquid which wets the glass and the other (i.e. diagram 'b') which does not wet the glass. In the first case, the force of adhesion (i.e. force of attraction between unlike molecules) is more than the force of cohesion (i.e. force of attraction between like molecules). The force of adhesion in the first case, is the force of attraction between glass molecules and water molecules. The force of cohesion is between the molecules of water. In the second case, the force of cohesion is more than the force of adhesion. We find that in the first case, the angle q is acute and in the second case, it is obtuse. This angle is called the angle of contact. It is the angle enclosed between the tangents to the liquid surface and the solid surface inside the liquid, both tangents being drawn at the point of contact of the liquid with the solid. |
| |
| The value of angle of contact |
| |
 depends on the nature of the liquid and solid in contact |
| |
 depends on the medium that exists above the free surface of liquid |
| |
 is independent of the inclination of solid to liquid surface. |
| |
 is fixed for a given pair of solid and liquid and surrounding medium. |
| |
