The act of centrifuging is called centrifugation : using centrifugal force to achieve the separation of the components of a mixture or the drying of certain materials.
A centrifugal force is one manifested in bodies that develop a curved path. This force is equal but opposite to the centripetal force , which is directed radially towards the center.
Centrifugation, in short, consists of using centrifugal force to separate elements according to density or to dry something. The machine that supplies centrifugal force is called a centrifuge .
What a centrifuge does is accelerate the process of sedimentation or decantation of the phases of a mixture. This is possible thanks to the different densities of the components. Through centrifugation, in this way, serum can be separated from plasma in the blood or the pulp of a fruit juice, to name two possibilities.
The solids that can be separated by using centrifugation are insoluble, that is, they do not form a solution with a liquid. When a liquid is mixed with an insoluble solid, a heterogeneous system is produced in which it is possible to notice solid particles suspended within the other substance. Centrifugation is just one of the unit operations for separating this class of solids; The other four are: filtration , elutriation, sedimentation and flotation.
When a considerable centrifugal field is applied to said duo (liquid and insoluble solids), the particles tend to move through the fluid due to acceleration ( angular velocity squared times radius).
The centrifugal force writes a movement in a rotating reference system or, equivalently, the apparent force that a non-inertial observer notices (that is, one that does not comply with Newton's laws of motion; in this particular case, the observer should present an accelerated movement with respect to the rotating reference system).
Types of centrifugation:
* differential : it is based on the difference in densities of the molecules, which must be considerable so that it can be observed during centrifugation. Particles with similar densities settle together. It is worth mentioning that this method is considered "nonspecific", and therefore it is used as a preparation to separate the components of the mixture but not for the separation of molecules. For example, it serves to separate membrane mitochondria and nuclei;
* isopycnic : it is based on the fact that if different density media are used it is possible to separate particles with the same sedimentation coefficient. Its use is very common to separate DNA ;
* zonal : with this type of centrifugation, the difference in the sedimentation speed results in the separation of the particles, since they all have different masses. The sample must be placed on a density gradient through which the centrifugal force causes sedimentation to occur at different speeds , depending on the mass. If the centrifugation time is excessive, particles may settle at the base of the tube.
It is common for washing machines (also known as washing machines ) to have a spin option. These machines used to wash clothes have an electric motor and a drum where dirty clothes are placed. This drum is filled with water and soap and moves quickly thanks to the motor, washing the clothes. To dry the clothes, the machine performs a centrifugation process.
The spin stage reduces the humidity of the clothing, as the centrifugal force causes water to separate from the fabrics. In this way, the centrifuge dries the clothes.