Prepare a Colloidal Solution of Sulphur


To prepare a colloidal solution of sulphur and differentiate it from a true solution or from a suspension on the basis of transparency and filtration. 



True solution 

A true solution is formed when a solute and a solvent are combined. It has a 1nm particle size. It is a homogeneous solute-solvent combination.  The solute and the solvent pass through the filter paper in a true solution. A true solution does not scatter light or exhibit the Tyndall effect. Filtration is incapable of separating the particles. As a result, it is a consistent solution throughout. Because of the uniformity, the solute particles do not settle.  

Properties of the true solution 

  • A homogenous mixture is a true solution.
  • The particles are invisible to the human eye or a microscope.
  • The particles in the solution readily flow through the filter paper, making separation difficult.
  • It just has one phase.
  • When other substances are introduced to a real solution, their physical and chemical characteristics, such as melting and boiling point, change. 

Colloidal Solution 

Colloids are solutions in which the size of the solute particles is intermediate between real solution and suspension. E.g., soap solution, starch solution, milk, blood, ink, and so forth.  A colloid's suspended particles can range in size from 1 to 1000 nanometers meters (10-9 meters). To be categorised as a colloid, a mixture's suspended particles must not settle so that the particles of suspensions settle at the bottom of the container if left undisturbed.  

Properties of colloidal solution 

  • When examined under a microscope, they look homogenous but are heterogeneous.
  • They are not entirely transparent; they are translucent.
  • The particles are invisible to the human eye or a microscope.
  • Filtration cannot separate the particles.
  • The particles are large enough that they scatter light.
  • The particle size is larger than that of the real solution but smaller than that of the suspension. 

The different types of colloidal solutions are

  • Aerosols: Solid or liquid mixed with gas; for Example, fog (liquid in gas).
  • Sols: Solid mixed with liquid; Example: Paint.
  • Emulsion: Liquid with liquid; Example: oil and water.
  • Gel: liquid in solid; Example: Fruit jelly.


A homogeneous mixture of particles visible to the human eye and a diameter bigger than 1000 nm is called a suspension. All the components in this combination are thoroughly combined, and all the particles are visible under a microscope. A heterogeneous mixture that contains solid particles large enough for sedimentation is called a suspension. 

Properties of Suspension 

  • A heterogeneous mixture is a suspension.
  • A suspension contains large-sized solute particles.
  • It has a diameter greater than 100 mm.
  • A suspension's constituent particles are readily visible.
  • Filter paper does not allow suspended particles to flow through it.
  • Filtration can therefore be used to separate a suspension.
  • Due to the enormous particle size of a suspension, a light beam travelling through it will be scattered. 

Tyndall Effect, colloidal, and suspension 

The phenomenon by which colloidal particles scatter light is called the Tyndall effect. The particles of colloidal solution scatter a beam of light passing through it and making its path visible. True solutions do not show the Tyndall effect. Scattering of light or Tyndall Effect is exhibited by Colloidal and Suspension particles. 


Learning Outcomes 

  • Students understand the terms: true solution, suspension, colloid, transparency, filterability, stability, etc.
  • Students classify the mixtures given to them as true solutions, suspensions and colloids based on the information from the experiment.
  • Students acquire skills to perform experiments.
  • Students learn the concept of the Tyndall effect.