What is a centrifuge?

A centrifuge is any device that applies a sustained centrifugal force, which is a force due to rotation. In effect, a centrifuge substitutes a similar, stronger force for that of gravity. Every centrifuge has a spinning vessel, with many configurations depending on its use. For example, perforated rotating drums are used to throw off excess water from clothes in laundry or to separate fluids from solid matter after crushing in industry. Centrifuges are widely used to concentrate and purify materials in suspension or dissolved in fluids. Suspended particles that are denser than the suspending liquid tend to migrate toward the periphery, while those less dense move toward the center. Bottle centrifuges are standard equipment in biological, chemical, and medical laboratories. They separate solid materials in suspension or clarify liquids when precipitation will not take place in a reasonable time in the gravitational field g.

What is a centrifuge used for?

A centrifuge is a device that applies a strong rotational force, stronger than gravity, to separate components of different densities in a liquid mixture. Centrifuges have a spinning vessel, with configurations that vary depending on use. For example, perforated rotating drums are used to remove excess water from clothes. Solid-wall centrifuges, perforated-wall centrifuges, or a combination of the two may also be used. Vacuum-type centrifuges can purify biological materials, determine molecular weights of proteins, and separate gases. They are used in medicine, biology, and the pharmaceutical industry.

What parts make up a basic centrifuge?

A basic centrifuge applies a strong rotational force, substituting for gravity to separate materials. It consists of a spinning vessel, which may be a solid-wall bowl, a perforated wall, or a combination. Key parts include: * A rotor, bowl, or drum, which is the rotating element, driven by an electric motor or air turbine. * An internal structure that contains radial vanes to regulate the flow of material. For optimal performance, a well-balanced load is essential to minimize vibration and strain.

Why does spinning separate substances in a centrifuge?

A centrifuge applies a strong rotational force, stronger than gravity, to separate substances. This force, known as centrifugal force , causes denser particles in a suspension to move towards the periphery, while less dense particles move toward the center. The rate of separation depends on factors such as the intensity of the centrifugal field, the densities of the particles and liquid, the liquid's viscosity, and the size and shape of the particles. The greater the difference in density between the substance and the suspending liquid, the faster the separation.

What are some common uses of centrifuges in science and medicine?

Centrifuges use centrifugal force to separate substances, with applications spanning science and medicine. Common uses: * Purification Centrifuges purify vaccines by removing harmful materials, and can also purify lubricating and industrial oils. * Separation They separate substances of differing densities, such as separating isotopes of an element. * Analysis Centrifuges determine molecular weights of proteins and other substances through sedimentation rate and equilibrium methods. * Medical and biological applications They purify materials important in biochemistry, biophysics, medicine, and the pharmaceutical industry. * Clarification Centrifuges clarify and purify food products like essential oils, extracts, and fruit juices.

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Top Questions

What is a centrifuge?
A centrifuge is any device that applies a sustained centrifugal force, which is a force due to rotation. In effect, a centrifuge substitutes a similar, stronger force for that of gravity.

Every centrifuge has a spinning vessel, with many configurations depending on its use. For example, perforated rotating drums are used to throw off excess water from clothes in laundry or to separate fluids from solid matter after crushing in industry.

Centrifuges are widely used to concentrate and purify materials in suspension or dissolved in fluids. Suspended particles that are denser than the suspending liquid tend to migrate toward the periphery, while those less dense move toward the center. Bottle centrifuges are standard equipment in biological, chemical, and medical laboratories. They separate solid materials in suspension or clarify liquids when precipitation will not take place in a reasonable time in the gravitational field g.
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1. centrifuge
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What is a centrifuge used for?
A centrifuge is a device that applies a strong rotational force, stronger than gravity, to separate components of different densities in a liquid mixture.

Centrifuges have a spinning vessel, with configurations that vary depending on use. For example, perforated rotating drums are used to remove excess water from clothes. Solid-wall centrifuges, perforated-wall centrifuges, or a combination of the two may also be used.

Vacuum-type centrifuges can purify biological materials, determine molecular weights of proteins, and separate gases. They are used in medicine, biology, and the pharmaceutical industry.
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1. centrifuge
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How does a centrifuge work?
A centrifuge is a device that applies a strong, sustained rotational force. It replaces gravity with a similar, stronger force. Every centrifuge has a spinning vessel, with configurations that vary depending on its use.

As an object revolves in a circle, it exerts force away from the center of rotation. The amount of force can be increased by increasing either the angular velocity of rotation, the mass of the object, or the radius of the circle through which the object moves.

Centrifuges are used widely to concentrate and purify materials in suspension or dissolved in fluids. Suspended particles denser than the suspending liquid migrate toward the periphery, while those less dense move toward the center. At the end of a washing machine cycle, it becomes a weak and simple centrifuge as it whirls the water out of clothes.
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2. centrifugal and Science
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What parts make up a basic centrifuge?
A basic centrifuge applies a strong rotational force, substituting for gravity to separate materials. It consists of a spinning vessel, which may be a solid-wall bowl, a perforated wall, or a combination.

Key parts include:
* A rotor, bowl, or drum, which is the rotating element, driven by an electric motor or air turbine.
* An internal structure that contains radial vanes to regulate the flow of material.

For optimal performance, a well-balanced load is essential to minimize vibration and strain.
2 Britannica Sources
1. centrifuge
2. centrifugal and Science
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Why does spinning separate substances in a centrifuge?
A centrifuge applies a strong rotational force, stronger than gravity, to separate substances. This force, known as centrifugal force, causes denser particles in a suspension to move towards the periphery, while less dense particles move toward the center.

The rate of separation depends on factors such as the intensity of the centrifugal field, the densities of the particles and liquid, the liquid's viscosity, and the size and shape of the particles. The greater the difference in density between the substance and the suspending liquid, the faster the separation.
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Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What are some common uses of centrifuges in science and medicine?
Centrifuges use centrifugal force to separate substances, with applications spanning science and medicine.

Common uses:
* Purification Centrifuges purify vaccines by removing harmful materials, and can also purify lubricating and industrial oils.
* Separation They separate substances of differing densities, such as separating isotopes of an element.
* Analysis Centrifuges determine molecular weights of proteins and other substances through sedimentation rate and equilibrium methods.
* Medical and biological applications They purify materials important in biochemistry, biophysics, medicine, and the pharmaceutical industry.
* Clarification Centrifuges clarify and purify food products like essential oils, extracts, and fruit juices.
1 Britannica Source
1. centrifuge
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

centrifuge, any device that applies a sustained centrifugal force—that is, a force due to rotation. Effectively, the centrifuge substitutes a similar, stronger, force for that of gravity. Every centrifuge contains a spinning vessel; there are many configurations, depending on use. A perforated rotating drum in a laundry that throws off excess water from clothes, for example, is a type of centrifuge. A similar type is used in industry to separate fluids from solid matter after crushing.

As enunciated by Sir Isaac Newton in his first law of motion, a freely moving body (such as a ball) tends to travel in a straight line, and, if directed along a curved path by some restraining force (such as would result were a hand-held string tied to it), it will exert a force against the directing or restraining force in its continual effort to fly off onto a straight tangential course. It is a familiar observation that an object revolving in a circle exerts a force away from the centre of rotation. This force, which is the outward pull of the ball on its string, is the centrifugal force. Also, there is general appreciation of the fact that the amount of this force can be increased by increasing either the angular velocity of rotation, the mass of the object, or the radius of the circle through which the object moves. Perhaps not so generally appreciated is the fact that, whereas the centrifugal force is directly proportional to the radius and to the mass, it is proportional to the square of the angular velocity. For example, doubling the mass of the rotating object will increase the centrifugal force by a factor of 2, but doubling the number of revolutions per minute (rpm) will increase the centrifugal force by a factor of 4 (equals 2 times 2); similarly, increasing the speed by a factor of 10 will increase the force by a factor of 100 (equals 10 times 10). Centrifugal force is expressed by the basic relation F = mν² / R = 4π²mn²R; F is the centrifugal force, m the mass, R the radius, v the speed, and n the number of revolutions per second.

The centrifugal force is often compared directly with the weight (pull of gravity) of the object, and the amount of force is stated as so many “times gravity” or so many “g.” Through the use of special research apparatus, forces greater than 5,000,000 times gravity have been produced by spinning small metal rotors of about pea size at speeds exceeding 1,000,000 revolutions per minute.

The rotating element of a centrifuge is usually driven about a fixed axis by an electric motor, or by an air turbine in some high-speed machines, and is known as a rotor, bowl, or drum. For the minimizing of vibration and strain on the shaft and bearings, it is essential that a loaded rotor be well balanced—i.e., that its total mass be so distributed about the axis of rotation that the resultant of all the elemental forces is zero. If the bearings are suited to high speeds and if ample power is available to overcome the frictional resistance of the bearings, the only limitation to the speed of a well-balanced rotor is the strength against rupture of the material from which it is made.

For example, a rotor with a 15-cm (6-inch) diameter used in certain biological studies and designed especially for high speeds has a limiting speed for routine operation of about 60,000 revolutions per minute. In a rotor of given design, the maximum angular velocity obtainable before rupture is to a close approximation inversely proportional to the rotor’s diameter. Thus, a small rotor having only one-half the diameter of a larger one can be as safely rotated at twice the angular velocity and with the production at the periphery of twice the centrifugal force.

The widest use of centrifuges is for the concentration and purification of materials in suspension or dissolved in fluids. Suspended particles denser than the suspending liquid tend to migrate toward the periphery, while those less dense move toward the centre. The rapidity with which the migration proceeds is dependent on the intensity of the centrifugal field, the difference between the density of the particle and that of the suspending liquid, the viscosity of the liquid, the size and shape of the particle, and to some extent the concentration of the particles and the degree to which they are electrically charged. The net motivating force exerted on the particle is the difference between the centrifugal field acting on it and the opposing buoyancy of the liquid. All other things being equal for two particles, one with a diameter 10 times that of the other will require only 1/100 as much average centrifugal field to move a given distance in a given time as the smaller.

From the foregoing discussion, it is clear that a practically complete separation of the suspending medium and the suspended particles can be produced if the centrifugation is allowed to continue until all particles have collected against the outer wall of the spinning vessel or centrifuge. It should also be noted that a partial separation of two groups of suspended particles of different size can be effected by allowing centrifugation to continue only long enough for all of the larger particles to be completely packed into the sediment, since then many of the small particles will still be suspended in the fluid. If separation of the larger as well as the smaller particles is desired, the surface fluid can be drawn off and the sediment resuspended in some suitable liquid and subsequently centrifuged again to effect further separation.

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Centrifuges may be classified in three general categories depending on whether the spinning centrifuge bowl that contains the material to be separated has a solid wall, a perforated wall, or some combination of the two. Also, they may be characterized according to whether the material is treated in a continuous flow process, a batch process, or a combination of the above processes.

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