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Last updated date: 29th May 2024
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Introduction to Dialysis

It is one of the most common laboratory techniques that is used to remove molecules from solutions. This principle is also used to artificially purify blood in case of kidney dysfunction. This article delves into what dialysis is, the procedure and its importance. 

Dialysis - Chemical Separation

To define the scientific term, ‘dialysis’ is a process of separating molecules in particular solutions with the help of a membrane that is semipermeable known as a dialysis tube. It is a separation of dissolved ions and molecules from solid solutions. The separation of molecules takes place because there is a difference in the rate of diffusion of certain molecules in the solution. 


The application of dialysis is used for the elimination of small and unwanted molecules such as salt, and large unwanted molecules such as dyes in particular solutions. It is also used in the studies of drugs and electrophoresis. 


History of Dialysis

The chemical procedure of dialysis was discovered and introduced by a Scottish chemist namely Thomas Graham in the year 1868. 


Graham used this technique in the separation of small molecules and large molecules in an aqueous solution. The name that he has given to those diffusible substances as crystalloids and those that would get stuck in the membrane or dialysis tube is called colloids. This process of separation is also called Graham’s Law in chemistry. 


This chemical separation is an extremely rapid and spontaneous process of separating with the help of the semipermeable membrane, and the most types of membranes used in the process of dialysis are cellulose and synthetic polymer. 


The Procedure of Dialysis Separation

To separate molecules, dialysis is one of the most straightforward and fast-paced chemical procedures. There is particular equipment that is required for the process of dialysis such as: 

  1. A container to keep the molecules.

  2. A dialysis tube

  3. Control of temperature


The Steps Involved in the Procedure of Dialysis are as Follow:

  1. Preparation of membrane according to the instructions.

  2. Loading the molecules into a tube or any instrument.

  3. Placing the sample solution into the dialysis tube

  4. Dialyzation of the sample at room temperature for around 2-3 hours.

  5. Changing of buffer and again placing the sample for the process of dialyzation for approx 2 hours.


Importance of Dialysis

It is used for two reasons (i) for introducing new molecules in a sample solution or (ii) to remove small molecules from a sample solution because it flows smoothly in any direction of the membrane. These two reasons make dialysis an extremely important chemical procedure for various applications and scientists prefer this procedure as well. 


It is also one of the chemical procedures to change the size and matrix of molecules in particular samples with the help of differentiating the sizes of molecules present inside the solution. During the process of dialysis, equilibrium is obtained in between the solution and celluloid as only small molecules can pass through the membrane or dialysis tube. Dialysis chemical separation is also used in the procedure of eliminating salt.


Osmosis helps in the smooth functioning of dialysis as the fluid moves from high to low water concentration which makes it easy to pass through the semipermeable membrane or the dialysis tube. 


Ultrafiltration also helps in dialysis as it easily removes the excess fluid and small molecules in the sample solution which makes the procedure of dialysis extremely easy and fast to perform. 


Types of Dialysis Chemical Separation

  1. Diffusion Dialysis 

The spontaneous and rapid type of dialysis chemical separation process. It is preferred by many scientists. Diffusion Dialysis uses AEM (Anion exchange membranes) and CEM (cation exchange membrane) which is dependent on the compounds and molecules that are to be separated.

  1. Electrodialysis

It uses the electrical potential for the procedure of dialysis chemical separation and uses the ion-membrane as a driving force. Electrodialysis is extremely important when it comes to removing molecules from aqueous solutions.

Three other kinds of electrodialysis are commonly and widely used by scientists in laboratories worldwide. They are as follow:

  • Reverse Dialysis

  • Electro-electrodialysis

  • Donnan dialysis


Uses of Dialysis Chemical Separation

The Application of This Chemical Separation are as Follows:

  • Desalting soy sauces.

  • The dealcoholization of beer

  • Alkali waste

  • Aqueous solutions

  • Acid

  • Caustic soda solution

  • De-acidification of fruits and vegetables

  • Food industry for desalination

  • Amino acids.

  • Neutral and basic element groups. 


Fact About Dialysis Chemical Separation

Here is the List of Facts About the Dialysis Chemical Separation. They are as Follow:

  • Low consumption of heat

  • Operates under room temperature

  • No operating, installing, and other costs.

  • Flexible and stable

  • Good for the environment as it doesn’t pollute it. 



Dialysis separation is a slow procedure that is slowed by differences in particle size and diffusion rates between colloidal and crystalloid materials. But it is one of the most appreciable methods when it comes to change of solvent, analytes and chemical buffers without disrupting the nature of molecules due to any sudden change of chemical environment and hence in that regard the most beneficial.

FAQs on Dialysis

1. Is Chemical Dialysis and Biological Dialysis the Same Thing?

There are various terms used in the medical field that make it difficult for people to gain a better idea about a specific concept. People often get confused with this scientific term which is ‘DIALYSIS’, which is often used in the medical or biological field for kidney dialysis.

Both procedures of dialysis chemical and biological are almost the same as it is the process of separation of small molecules from a sample solution into a dialysate buffer in the zone of chemistry while in the biological area the same process of separation is used to remove the toxins from the blood dialysate. 

2. What are the Most Common and Widely Used Dialysate Buffers for the Process of Dialysis Chemical Separation?

There are various processes used in the medical industry to treat diverse and unique diseases. To handle the molecules in a dialysate buffer, pH is essential for the stabilisation and the separation of the molecular properties in the sample solutions. The range of typical pH rate in any dialysate or dialysis buffer is approximately around 4 to 5. There several types of buffers available but the most common dialysate buffer that is used and found in the biochemical solutions are as follow:

  • Water

  • Amino acid

  • HEPES 

  • Buffered Tris Saline (TBS)

  • Phosphate buffered saline (PBS)