Main Difference – Peptization vs Coagulation
Peptization and coagulation are two chemical processes that can be mainly observed in colloidal dispersions. Peptization is the formation of a colloidal dispersion from a precipitation. Coagulation is the formation of aggregates from oppositely charged particles which are then settled down under gravity. Coagulation is one of the various properties exhibited by colloidal solutions. The main difference between peptization and coagulation is that peptization involves the breakdown of a precipitate in order to form colloids whereas coagulation includes the formation of aggregates in a colloidal dispersion.
Key Areas Covered
1. What is Peptization
– Definition, Process, Examples
2. What is Coagulation
– Definition, Process
3. What is the Difference Between Peptization and Coagulation
– Comparison of Key Differences
Key Terms: Coagulation, Colloid, Colloidal Dispersion, Electrolyte, Peptization, Peptizing Agent
What is Peptization
Peptization is the formation of stable colloids in a dispersion medium. This results in a colloidal dispersion. A colloidal dispersion is a heterogeneous system which is made up of a dispersed phase and a dispersion medium. The dispersed phase is a phase in a two-phased system. It includes colloidal particles. The dispersion medium is the other phase in the two-phased system. It is the liquid or gaseous medium in which the dispersed phase is distributed.
Peptization process involves a peptizing agent. It is an electrolyte which is used to pass a precipitate into colloidal particles. This is done by shaking the precipitate with dispersion medium or the peptizing agent. This peptization happens since the electrolyte can attract the particles of the precipitate (charged particles) and then the particles can get separated from each other due to electrostatic repulsions. If these particles have the dimensions in colloidal range, this forms a colloidal dispersion. The process is called peptization.
Figure 1: Iron(III) chloride solution with iron(III) hydroxide precipitate. By shaking this mixture we can obtain a colloidal dispersion.
A precipitate of silver iodide can be peptized by shaking it with a dilute KI solution. The final solution is a colloidal dispersion. Peptization is also used in the production of nanoparticles. Here, the electrolyte can separate large precipitates into smaller colloidal particles which can be further separated into nanoparticles via other advanced methods.
What is Coagulation
Coagulation is the gelling or clumping of particles. Typically, coagulation takes place in colloidal suspensions. Coagulation happens when unstable particles are present in a mixture.
The stability of a colloidal dispersion is dependent on the electrical charges that the particles carry with them. An imbalance of these charged particles can cause the coagulation of particles in order to stabilize the system by balancing the charges. Here, the particles get accumulated to form aggregates. Then these aggregates settle down in the container under gravity. This process is known as coagulation.
Figure 2: Coagulation of Milk Forms Yoghurt
The coagulation can be observed via several techniques. For example, electrophoresis can be used. Here, the charged particles are forced to move towards the oppositely charged particles. Then those particles form aggregates that can settle down under gravity. If not, this can be simply done by mixing two sols having oppositely charged particles. Another easy method is boiling. When boiled, particles colloid with each other due to increased kinetic energy inside the system. This causes the formation of aggregates.
Difference Between Peptization and Coagulation
Definition
Peptization: Peptization is the formation of stable colloids in a dispersion medium.
Coagulation: Coagulation is the gelling or clumping of particles.
Process
Peptization: In peptization, a precipitate is passed to a colloidal phase using an electrolyte.
Coagulation: In coagulation, oppositely charged particles form aggregates which then settle down under gravity.
Examples
Peptization: Peptization of silver iodide using a KI solution.
Coagulation: Particles in milk can get coagulated to form yogurt.
Conclusion
Peptization and coagulation are chemical processes that take place in colloidal dispersions. A colloidal dispersion is a heterogeneous mixture of two or more substances having particles of 1-100nm dispersed in a dispersion medium. The main difference between peptization and coagulation is that peptization involves the breakdown of a precipitate in order to form colloids whereas coagulation includes the formation of aggregates in a colloidal dispersion.
References:
1. Helmenstine, Anne Marie, Ph.D. “Coagulation Definition.” ThoughtCo, Mar. 8, 2014, Available here.
2. “Coagulation Of Colloidal Solutions | Coagulation Techniques | Chemistry | Byju’s.” Chemistry, Byjus Classes, 27 Oct. 2017, Available here.
Image Courtesy:
1. “Iron(III) hydroxide and iron(III) chloride” By Chemicalinterest – Own work (Public Domain) via Commons Wikimedia
2. “yoghurt-3” by Jules (CC BY 2.0) via Flickr
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