This document discusses surface tension and viscosity. Surface tension is the tendency of liquid surfaces to shrink into the minimum surface area possible. It can be reduced by substances like soaps, detergents, and bile salts. Viscosity is the resistance of a liquid to flow, and is measured using devices like an Ostwald viscometer. Viscosity increases with factors like lower temperatures, additional chemical components, and suspended particles in the liquid.

1. SURFACE
TENSION
&
VISCOSITY
Source : Medical
Biochemistry by
Mushtaq Ahmed
(Vol. 1)
Maryam Fida
(o-1827)

2. SurfaceTension
■ Surface tension is a phenomenon in which the surface of a liquid,
where the liquid is in contact with gas, acts like a thin elastic sheet
■ Units are erg/cm2 or dynes/cm
■ Soaps, detergents ,bile salts and proteins reduce the surface
tension.
■ NaCl increases the surface tension.
■ Bile salts facilitate the emulsification and digestion of fats in the
small intestine.
■ Surface tension is decreased by an increase in temperature.

3. Stalagmometer

4. Meaurement of surface tension
■ Two methods are given below:
1)Drop method
By using stalagmometer
ϒoil= no. of drops of water x Specific gravity of oil
no. of drops of oil
2)Using torsion balance or tensiometer
(Du Nouy,s)
By using light metal ring

5. Viscosity
■ The resistance of a liquid in its flow is
called viscosity
■ Water is less viscous than honey.
■ The rate of flow of a liquid is inversely
proportional to its viscosity.
■ Higher the viscosity, lesser will be the
flow.
■ Meaurement by Ostwalds viscometer.

7. Relative viscosity of unknown solution=
Density of the unknown solutionxT2
Density of waterxT1

8. Factors affecting viscosity
1)Temperature
2)Chemical composition
3)Colloidal particle/suspended material
Hyperviscosity syndrome
■ Abnormal levels of proteins
■ Serum viscosity may rise upto 12 to 15 times
that of water.