12 julio, 2024

Levigation: what it is, levigating agents, uses, examples

What is levigation?

The levigation It is a technique of separating mixtures that consists of grinding or crushing an insoluble substance to a fine powder, while it is wet. The material is fed into the mill or mortar together with water, the powdered substance remains suspended and flows from the mill as a cloudy liquid or fine paste, depending on the amount of water used.

A mortar and pestle is commonly used in the process, and it is completed by letting the coarser particles settle in water, then decanting, letting it settle until the fine powder has fallen to the bottom, and finally pouring out the water.

In the chemical analysis of minerals this process is repeated until the mineral has been reduced to a sufficient degree of fineness, the coarsest part being subjected to further pulverization after each separation with the aid of water.

There is no loss of material such as dust, or injury or discomfort to workers. Furthermore, any soluble impurities in the substance are dissolved and the product is purified.

The greatest advantage of this process is the ease it provides for the subsequent separation of the product into various degrees of fineness, due to the slower decay of the finer particles from the suspension.

The cloudy liquid flows into the first of a series of tanks, and is allowed to settle for some time. The coarser and heavier particles quickly disappear, leaving the finer material suspended in the water, which is drawn above the sediment to the next tank.

The liquid passes from tank to tank, staying in each one for a longer time than it did in the previous one, since the finer and lighter the particles, the more time is necessary for their deposition.

In some cases a dozen or more tanks may be used, and the process then becomes extremely slow, as very fine sludge or sludge may require several weeks for final settling. But as a rule, three to five days is enough.

The term “levigation” is often applied to mere sedimentation, a substance that is simply agitated in water, without prior wet grinding, in order to separate the finer particles from the coarser ones.

lifting agents

A levating agent is a material used to moisten a solid before reducing it to a powder. The liquid, also called a levigating agent, is somewhat viscous and has a low surface tension to improve the ease of wetting the solid.

Levitating agents act as lubricants. They make incorporating solids easier, and generally give smoother preparations.

Generally, a levitating agent is not added when the incorporated solid has very fine particles. The amount of solid to be incorporated is small, the ointment base is soft, and the final preparation is intended to be a stiff paste.

Levitating agents must be added in equal proportion to the solid material. Apart from water, examples of levating agents are glycerin and mineral oils for the separation of polar substances.

Uses of levigation

The levigation technique is not common in laboratories, it is used mostly in industry.

– Examples of uses of this technique are in the mining industry, where it is used to separate a gangue from a mineral, which is the material that is discarded from the minerals, with water.

In gold mining, the levigation technique is often used. The auriferous sand contained in the gold deposits is separated with water, leaving the gold deposited at the bottom, while the lighter sand is washed away with the water.

Generally, in gold deposits, mercury is used, which forms an amalgam with gold, which makes it easier to separate, but mercury is a highly toxic and polluting element for the environment, so this practice It is prohibited in some countries.

– To avoid explosions, when preparing gunpowder, the ingredients are ground while they are wet and then the impurities are separated.

– In the pharmaceutical industry, the levigation process is used to incorporate solids into ophthalmological and dermatological ointments or suspensions.

It is also used in the preparation of creams or balms and in the purification of drugs.

Practical examples of levigation

– There are times when we are lazy to wash the dishes properly with soap, and we simply put them under running water to separate the dirt. By doing so, we are unconsciously using the levigation process.

– Another fairly common example of levigation is the preparation of rice. When rice is washed in a colander under running water, the water will separate the rice from the starch, which will be washed away.

– Also when vegetables are washed before cooking, the water separates them from the soil and the insects that can be found on them.

– Levigation is also used in the preparation of clays. When dissolving the clay in the water, the heavier particles fall to the bottom of the container, while the finer particles remain in suspension.

This process is repeated until the clay has the desired consistency. Archaeologists can determine the age of a clay vessel by its levigation process.

References

Lenntech BV (SF). levigation. Retrieved from lenntech.com.
Levitation (SF). Recovered from finedictionary.com.
Levitating Agent. Retrieved from drtedwilliams.net.

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