Methdos of preparation colloids

1. Methdos of preparation colloids DISPERSION METHOD

2. Dispersion Methods In dispersion methods, colloidal particles are obtained by breaking large particles of a substance in the presence of a dispersion medium. Since the solsformed are unstable, they are stabilized by adding mechanical energy input . Dispersion method in the preparation of colloids can be done by crushing the large suspension’s particles into small in size.

3. Dispersion Method In these methods, the bigger particles of a substances are broken down to form smaller particles of colloidal dimensions thus obtained are stabilized by the addition of certain stabilizing agents. Some important dispersion methods are as follows: 

4. Mechanical Dispersion Method In this method, the dispersion of the coarse material (whose colloidal solution is to be prepared) is carried out in a machine called colloid mill. Colloid mill - It consists of two heavy steel discs separated by a little gap. The gap may be adjusted according to the particle size desired. The two discs rotate at high speed (about 8000 revolutions per minute) in the opposite direction.

5. Mechanical Dispersion Method A suspension of the substance in water is introduced into the mill. The coarse particles present in the suspension are grinded to the particles of colloidal dimensions and get dispersed in water to form a sol. Finer dispersion can be obtained by adding an inert diluents which prevents the colloidal particles to grow in size.

6. I. Mechanical Dispersion Method Mechanical dispersion is also called direct dispersion. It is a method of making a colloid by crushing or milling a given solid and the powder produced is dispersed into a given dispersing medium. Examples : Making of sulphur sol with the use of glucose as diluents.

7. Mechanical Dispersion Method The diagram shows the mechanical dispersion method.

8. Electrical Dispersion Method Also known as “ Bredig arch method “ I s a method of preparing colloids, especially metallic sols. In this method, two metallic wires functioning as electrodes are immersed into water, then on both ends of wires is given a strong enough electric current to be evaporated and then it is dispersed into water to form a metallic sol.

9. Electrical Dispersion Method In this method, an electric are is struck between the two electrodes of the metal (whose colloidal solution is to be prepared) immersed in the dispersion medium (say water). The dispersion medium is cooled by surrounding it with a freezing mixture. High temperature of the arc vaporizes some of the metal. The vapour condenses to the particles of colloidal size on cooling. The colloidal particles thus formed get dispersed in the medium to form a sol. of the metal.

10. Electrical Dispersion Method This method is used for the preparation of sols metals such as gold, silver, platinum etc . Electtrical Dispersion Method

11. Peptization Dispersion T he process of converting aprecipitate into a colloidalsol by shaking it with thedispersion medium, in thepresence of a small amountof electrolyte Electrolyte = Peptizing agent This method is used to convert a freshly prepared precipitate into a colloidal sol

12. Peptization dispersion In this method, a freshly prepared precipitate of the substance is made to pass into the colloidal state by the addition of a suitable electrolyte. The process of dispersing a freshly prepared precipitate into colloidal form by using a suitable electrolyte is called peptization. The electrolyte added is called peptizing agent. 

13. Peptization Dispersion  In peptization, the larger particles is dispersed into smaller particles in a colloidal size by adding a particular electrolyte which acts as a dispersing agent . For example, sediment of Al(OH)3 will change into a colloid by adding a solution of AlCl3 ; NiS will charge into sol when it is added into H2S; and sediment of AgCl will charge into a colloid by adding a solution of ammonia.

14. Homogenization Homogenization is a process for preparing something to become homogeneous. In this preparation, a particular emulsifier is usually added to emulsify the fat particles in milk or cream so that the milk or cream form a stable colloid. In this process, skim milk powder is often used and it is conducted in a homogenization device.

15. Summary of Dispersion Method Dispersion method - larger particles of a substance (suspensions) are broken into smaller particles. The following methods are employed. There are 4 ways using dispersion method : Mechanical Dispersion Method -  the substance is first ground to coarse particles. Electical Dispersion Method - is used to prepare sols of platinum, silver, copper or gold. Peptization Dispersion - The process of converting a freshly prepared precipitate into colloidal form by the addition of suitable electrolyte  Homogenization - is any of several processes used to make a chemical  mixture the same throughout.