Suspension: Sedigmentation And Calculation

Experiment 4

Suspension-sedimentation

Objective

To obtain a good formulation in controlling the rate of flocculation and sedimentation.

Introduction

In colloid chemistry, suspension is a heterogeneous mixture containing solid particles which are large enough to settle out from the liquid through sedimentation. The internal phase (solid) is dispersed throughout the external phase (fluid) through mechanical agitation, with the use of certain excipients or suspending agents and it will eventually settle. Suspension is considered as thermodynamically unstable because the properties of suspension is always changing with time as they will undergo sedimentation. Suspension may be flocculated or deflocculated.

Sedimentation is the tendency for particles

First, bismuth subnitrate was added into the graduated cylinder. Bismuth subnitrate is a white powder which soluble in water. The purpose of adding bismuth subnitrate is to mix the solute (bismuth subnitrate) and solvent together. Methylcellulose is a hydrophilic white powder in pure form and dissolves in only cold water, forming a clear viscous solution or gel.

In the first boiling tube, the solution consists of 2 g of bismuth nitrate and water. Based on the results, the height of sediments was the same over time which the value kept constant at 0.4cm. This is because flocculating agent was absent in the boiling tube hence cannot undergo flocculation process.

For the second boiling tube, the solution consists of 2g of bismuth subnitate, 10 mL of flocculating agent and water. The height of sediments was the same as time goes on which the value kept constant at 1.1 cm. But supposingly, the height of sediments should increase over time due to the presence of flocculating agent. With flocculating agent, Zeta potential between the particles decrease and cause the van der waals forces become