There are mixtures that cannot be separated by traditional methods, so it is necessary to use special methods. Let's look at some:
Levitation: When a mixture is formed by solid substances of different densities, a stream of water can be used to separate them. This is the case of gold, which is usually found near a piece of earth or sand. To separate these substances, the mixture is crushed in a proper container and a stream of water is passed through it. The less dense part (sand or earth) is carried by water, while the denser part (gold) is deposited on the bottom. This process separates the denser elements from the less dense.
Flotation: To separate a mixture of sand and saw dust, for example, just place the mixture in a bowl and add water. The less dense part of the mixture (the sawdust) floats, while the denser part (the sand) is at the bottom of the bowl. Flotation is often used in mining to separate ores from their impurities. In this case, proceed as follows: crush the rock and add oil. The ore particles will settle in the oil. Adding water to the set, the particles fixed in the oil go to the surface and the impurities stay at the bottom of the container.
Decanting is a traditional method of separating heterogeneous mixtures, it consists of draining one mixed liquid into another, but it is often not very effective. There are alternative methods such as centrifugation and siphoning:
Centrifugation: If we want to quickly separate the solid from a liquid, we can "accelerate" the decantation. For this, the mixture is placed in a device called a centrifuge, which rotates at high speed, depositing solid particles, which are denser, at the bottom. Today, this process can be observed in our own home. Clothes washing machines, for example, have a device to spin, which is activated when you want to "twist" the clothes. Spinning at high speed, the clothes are thrown against the walls of the machine, extracting much of the water.
Another example is the centrifuge that is used in clinical analysis laboratories to separate the blood components, with it the sedimentation of white and red blood cells and platelets can be done. of the blood. When shaken, the solid part (globules, platelets) of the blood is separated from the liquid part, which is the plasma.
Siphonation: After decanting, if it is not possible to overturn the container and empty the liquid, we can siphon it off. This method can be performed more accurately if a decanting funnel, which consists of a glass vessel, is used. If we place, for example, a mixture of water and oil in this container and let it settle for a moment, when we open the tap at the bottom of the funnel, the water runs out, we close the tap and we get the separation.
By Líria Alves
Graduated in Chemistry
Source: Brazil School - https://brasilescola.uol.com.br/quimica/metodos-especiais-para-separar-misturas-heterogeneas.htm
