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Separation of Mixtures of Two or More Liquids

  • Last Updated : 23 Jan, 2022

Most of the time, the substances we encounter are not in their purest form. They are essentially a chemical synthesis of two or more substances. Surprisingly, mixtures can take on a number of forms. As a result, many types of separation processes are used to separate a mixture of substances. When it comes to separation, it is normally done to eliminate all of the undesirable ingredients and acquire usable components.

Some Methods of Separating Mixtures

Centrifugation

Solid particles in a liquid can sometimes be so minute that they can pass through a filter paper. The filtration technique cannot be utilised to separate such particles. Centrifugation is used to separate such mixes. Centrifugation is the technique of separating insoluble components from a liquid when regular filtering fails. The size, shape, and density of the particles, the viscosity of the medium, and the speed of rotation all influence centrifugation. When the particles are spun quickly, the denser particles are driven to the bottom and the lighter particles remain at the top. A centrifuge is an apparatus used for centrifugation. The centrifuge is made up of a centrifuge tube holder known as a rotor. The rotor contains equal volumes of the solid-liquid combination in balanced centrifugal tubes. The centrifuge tubes revolve horizontally as the rotor rapidly rotates, and the denser insoluble particles separate from the liquid due to centrifugal force. When the rotation stops, the solid particles fall to the bottom of the centrifuge tube, while the liquid rises to the top.

Handpicking

This process is simply plucking out all of the undesirable compounds by hand and separating them from the beneficial ones. The separated substances may be an impurity that must be discarded, or both separated substances may be valuable. For instance, suppose you distinguish black grapes from green grapes from a mixture of the two.

Threshing

This method is usually used during agricultural harvesting. When wheat stalks are harvested, they are typically dried. By beating the dry stalks to shake off the dried grains, the grain is separated from the stalks and crushed into the floor.

Winnowing

When the grains are recovered from the threshing process, they must be cleaned of husks and chaffs before being ground into flour. Normally, the separation of the mixture is accomplished with the assistance of wind or blowing air. When farmers drop the combination from a given height to the ground, the husk and chaff are blown away by the powerful wind. The heavier grains are gathered in one location.

Sieving

It is used to separate mixtures containing largely different sizes of components. The mixture is filtered via the sieve’s pores. All of the tiny compounds pass through easily, but the mixture’s larger components are trapped.

Evaporation

Evaporation is a technique for separating a mixture, most commonly a solution of a solvent and a soluble substance. In this technique, the solution is heated until the organic solvent evaporates, converting it into a gas and predominantly leaving behind the solid residue.

Distillation

Distillation is done when a mixture consists of two or more pure liquids. The constituents of a liquid mixture are evaporated, condensed, and isolated here. When the combination is heated, the volatile component vaporises first. The vapour is collected in a liquid state after passing through a condenser.

Filtration or Sedimentation

Filtration is the most common method of separating a liquid from an insoluble material. Take, for example, a sand-water mixture. Filtration is employed to remove solid particles from the liquid in this case. Various filtering agents, such as filtering paper or other materials, are commonly utilised. Sedimentation is the process through which heavier contaminants in a liquid, often water, settle to the bottom of the container carrying the mixture. It takes some time to complete the process.

Magnetic Separation

When one of the substances in the mixture has magnetic properties, this approach is quite useful. To separate magnetic elements, strong magnets are usually utilised.

Separation of a Mixture of two or more liquids

Separating Funnel

A separating funnel is primarily used to separate two immiscible liquids. The mechanism works by exploiting the uneven density of the particles in the mixture. Using this procedure, oil and water may be easily separated. 

A separating funnel is used to separate the components of a combination that has two immiscible liquid phases. The aqueous phase is one phase, and the organic solvent phase is the other. The differences in the densities of the liquids are used to separate them. The lower layer is formed by the liquid with the highest density, while the top layer is formed by the liquid with the lowest density.

Chromatography

Chromatography is a method of separating the constituents of a liquid mixture. It was first proposed by Michael Tswett, a Russian scientist. Chromatography requires that the sample be dissolved in a specific solvent known as the mobile phase. 

The mobile phase might be either a gas or a liquid. The mobile phase is subsequently passed through a second phase known as the stationary phase. A substance placed in a glass plate or a piece of chromatography paper can be used as the stationary phase. 

The mixture’s various components travel at different rates, causing them to separate. There are various chromatographic techniques available, including column chromatography, TLC, paper chromatography, and gas chromatography. One of the most important chromatographic procedures is paper chromatography. In paper chromatography, the stationary phase is paper, and the mobile phase is a liquid solvent. The sample is placed on a spot on the paper, and the paper is carefully dipped into a solvent in paper chromatography. Because of capillary action, the solvent rises up the paper, and the components of the mixture rise up at different speeds, separating them from one another.

Simple distillation

Simple distillation is a process for separating components of a combination including two miscible liquids that boil without decomposition and have a large enough difference in boiling points. 

Distillation entails heating a liquid to its boiling point, moving the vapours to the cool portion of the device, condensing the vapours, and collecting the condensed liquid in a container. When the temperature of a liquid rises in this process, the vapour pressure of the liquid rises as well. When the vapour pressure of the liquid and the air pressure equalises, the liquid enters the vapour state. The vapours move through the heated portion of the apparatus until they come into touch with the cold surface of the water-cooled condenser. When the vapour cools, it condenses and flows down the condenser, where it is collected by the vacuum adapter.

Fractional distillation

Fractional distillation is used to separate a mixture of two or more miscible liquids with boiling points that differ by less than 25K. The apparatus for fractional distillation is similar to that used for simple distillation, with the exception of a fractionating column installed between the distillation flask and the condenser. 

A simple fractionating column is a glass bead-filled tube. The beads provide a surface for the vapours to repeatedly cool and condense. When vapours of a mixture pass through the fractionating column, the vapours of the liquid with the lower boiling point first flow out of the fractionating column, condense and are collected in the receiver flask due to repeated condensation and evaporation. The other liquid, which has a little higher boiling point, can be collected in a similar manner in a different receiver flask.

Sample Questions

Question 1: What are chemical methods of separation?

Answer: 

The typical chemical engineering processes of separation and purification are distillation, crystallisation, adsorption, membrane operations, absorption and stripping, and oxidation.

Question 2: How can you separate sand and salt?

Answer:

It either stays in the bath as sand is added to it or develops a film on the bottom of the bottle. As a result, sand is insoluble in water and does not dissolve in it. It is simple to separate sand and water from a mixture by separating it. Evaporation can be used to separate salt from a solution.

Question 3: Is Coca Cola a mixture?

Answer:

Despite the fact that the sugar and water are mixed equally in the solution, Coca-Cola is a homogeneous combination. In a homogeneous mixture, such as Coca-Cola, you can see the essential ingredients, but in a heterogeneous mixture, such as a salad, you cannot.

Question 4: Can homogeneous mixtures be separated?

Answer:

“Typically, components in homogeneous mixes may be recognised by taking into account the varied qualities of the distinct components.” During the distillation process, a mixture can be heated “until the component that boils at the lowest temperature produces a vapour and can be differentiated.”

Question 5: What is fractional distillation?

Answer:

Fractional distillation is used to separate a mixture of two or more miscible liquids with boiling points that differ by less than 25K.


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