Mixture Separation Methods

In chemistry, a mixture consists of joining two substances or components, in a single mixture, but each component retains its individual properties.

Depending on the characteristics of the components, they can produce homogeneous or heterogeneous mixtures.

In homogeneous mixtures, the components are similar in some of their characteristics, so taking any one serving, we find that they are combined more or less evenly. In heterogeneous mixtures, the components have different characteristics that make the mixture not uniform, so we can find parts in which a component dominates, or even that the same components tend to break away.

Mixtures can be more or less easy to separate. When it is necessary to separate the components of a mixture, we can use various methods, which are will decide according to the substance that we want to separate mainly and its physical characteristics and Chemicals.

Main methods of separating mixtures

There are several methods of separating mixtures, which, as we have already said, will be used according to the characteristics of the components of the mixture. These are some of the main separating mixtures:

Separation of mixtures by decantation: By this method, a liquid that is mixed with a solid is dislodged. It is also used to separate two liquids of different densities, as one will float on top of the other.

Example: When we mix water with oil and let it rest, the oil, being less dense, will accumulate on top of the water; If we tilt the glass that contains them, we can separate the oil that will begin to flow to the container where we are collecting it.

Separation of mixtures by sublimation: When two solids are mixed, and one of them has the characteristic that when heated it evaporates, this characteristic allows the substance to be purified by sublimation.

Example. In some solid mixtures that contain iodine, this element can be purified by heating it and putting a lid on the container, where iodine crystals begin to accumulate.

Separation of mixtures by filtration: When we have a substance in a liquid that does not dissolve, we can filter it. Filtering consists of passing through a porous body (cloth, paper and certain stones, the liquid with the particles that are in the liquid. Solid particles will be retained by the filter, while the water will pass to the other side of the filter.

Example: The most common example of this is coffee makers. Once the water with the coffee beans has boiled, it passes through a filter that allows the infusion to pass through, and retains the ground coffee.

Separation of mixtures by evaporation: When a substance dissolves in a liquid and cannot be filtered, the dissolved substance can be recovered by boiling the liquid until it evaporates, leaving the substance with which it had been combined.

ExampleThis is the method used in the salt flats, where the sea water is spread in evaporators where the rays of the sun give it; once the water has evaporated, the dissolved salt remains on the evaporator.

Separation of mixtures by distillation: Distillation is similar to evaporation. In the case of distillation, the vapor obtained from heating the liquid passes through a coil, where it is cooled and condensed; the condensed liquid collects in a container on the other side of the alembic. It is also used to separate liquids of similar densities, but different boiling points.

Example. This is used, for example, to separate water from alcohol. Water boils at 100 ° C, while alcohol evaporates at 79 ° C. If the mixture is heated to this temperature, without reaching 100 ° C, the alcohol will evaporate and the water will remain. The evaporated alcohol passes through the coil and, once cooled and condensed, falls into the container that will contain it.

Separation of mixtures by sieving: It is to separate solids, in which the mixture is passed through a strainer or sieve, which retains particles larger than the size of the hole in the net or mesh that is used as a sieve.

Example. When we want to remove the leftovers after flouring some food, we pass the flour through a strainer (a sieve), which will retain large residues, and we will have the flour without particles as residue large.

Separation of mixtures by solution: This system is used when one substance is soluble in a liquid and the other is not. The liquid is added to the mixture, and the soluble substance will disappear little by little, leaving only the substance that is not soluble.

Example. If we have salt or sugar mixed with sand, as both components are very small particles, the easiest way to separate them is by adding water. We shake the resulting mixture and we will realize that the salt has dissolved and only the sand remains.

Separation of mixtures by sedimentation: Sedimentation is the phenomenon that occurs when a solid substance is in suspension in a liquid, and the mixture is allowed to settle: as time passes, the more solid particles will settle to the bottom of the container.

Example. This happens when we have land turned into water. As soon as the mixture is made, all the liquid is cloudy; once it is put to rest, the earth will settle to the bottom and the water will regain its transparency.

Separation of mixtures by centrifugation: Centrifugation is similar to sedimentation, except that in this case a circular movement intervenes, which, by force centrifugal, it causes the heavier particles to crowd on the farthest walls of the circular path, separating from the liquid.

Example. Centrifugation is used in the milk process to obtain butter. The milk container is centrifuged, and the water, which is heavier than the fat, is separated, while the fat remains in the upper part of the container.

Separation of mixtures by levigation: It is also similar to sedimentation. In this case, there is a stream of water that passes over a mixture, which carries the lighter particles, while the heavier ones remain at the bottom. It is a kind of wash.

Example. This technique is used in metal mines, especially iron, which are subjected to jets of water, which carry away the earth and light materials, leaving the heavier particles that contain the metal.

Separation of mixtures by magnetization: Also called magnetization, it is separating magnetic materials from other non-magnetic solids.

Example. We can verify this when we mix iron filings and sand, and then we pass the mixture through a magnet. The iron sticks to the magnet and the sand falls off.

Example of Mixture Separation Methods

Let's take as a basis some of the examples mentioned.

We begin by considering that we have a mixture of sand with salt.

The first step is separation by solution. We add water and stir, dissolving the salt and we get saline solution and sand.

As a next step we will allow the sedimentation, allowing the sand to settle to the bottom of the container.

Below follows the decantation: we tilt the glass towards another container, and we will have separated the saline solution on one side and the sand on the other.

Then, we take the container that contains the sand, which is still wet, and heat it over the fire, with which we apply the evaporation so that we only have sand.

On the other hand, we heat the saline solution until it boils, and we pass the resulting steam through an alembic for the distillation. Thus, leaving the coil, we will have pure water, and an increasingly concentrated saline solution will remain in the container, until the evaporation only the salt that was dissolved remains at the bottom of the container.