What is Levigation?

The levigation is a mixture separation technique that consists of grinding or grinding an insoluble substance into a fine powder, while it is wet. The material is introduced into the mill or mortar together with water, the powder remains suspended and flows from the mill as a cloudy liquid or fine paste, according to the amount of water used..

A mortar and pistil are commonly used in the process, and it is completed by letting the coarser particles settle in water, then decanting the water, letting it sit until the fine powder has fallen to the bottom, and finally pouring 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 thickest part being subjected to additional pulverization after each separation with the help of water..

There is no loss of material such as dust, no injury or annoyance to workers. In addition, 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 decrease, 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 a certain time. The coarser and heavier particles disappear quickly, 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, remaining in each one longer than it was 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 sludge or very fine sludge may require several weeks for final sedimentation. But as a general rule, three to five days is enough.

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

Levigating agents

A leavening agent is material used to wet 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..

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

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

The leavening agents must be added in equal proportion to the solid material. Apart from water, examples of leavening 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 is 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 gold sand contained in the gold deposits is separated by water, leaving the gold deposited on the bottom while the sand that is lighter is dragged 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 is prohibited in some countries.

To avoid explosions, in the preparation of gunpowder the ingredients are ground while 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 the stream of water to separate the dirt. In doing so, we are unconsciously using the levigation process.

Another fairly common example of levigation is in the preparation of rice. When rice is washed in a colander under running water. This 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 may be found in them..

Levigation is also used in the preparation of clays. By dissolving the clay in 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 is of the desired consistency. Archaeologists can determine the age of a clay pot by the levigating process of the pot..

References

1. wings 3. (2016, February 15). levigation. Recovered from youtube.com.
2. David B. Troy, P. B. (2006). Remington: The Science and Practice of Pharmacy. Philadelphia: Lippincott Williams & Wilkins.
3. Gad, S. C. (2008). Pharmaceutical Manufacturing Handbook: Production and Processes. Hoboken n.j .: Wiley-interscience.
4. Lenntech B.V… (S.F.). Levigation. Recovered from lenntech.com.
5. Levigation. (S.F.). Recovered from finedictionary.com.
6. Paul T. Nicholson, I. S. (2000). Ancient Egyptian Materials and Technology. Cambridge University Press.
7. Williams, T. (2006, June 6). Levigating Agent. Recovered from drtedwilliams.net.