 | This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations .(August 2013) |
Vacuum filtration is a fast filtration technique used to separate solids from liquids.
| This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations .(August 2013) |
Vacuum filtration is a fast filtration technique used to separate solids from liquids.
By flowing through the aspirator, water will suck out the air contained in the vacuum flask and the Büchner flask. There is therefore a difference in pressure between the exterior and the interior of the flasks : the contents of the Büchner funnel are sucked towards the vacuum flask. The filter, which is placed at the bottom of the Büchner funnel, separates the solids from the liquids.
The solid residue, which remains at the top of the Büchner funnel, is therefore recovered more efficiently: it is much drier than it would be with a simple filtration.
The rubber conical seal ensures the apparatus is hermetically closed, preventing the passage of air between the Büchner funnel and the vacuum flask. It maintains the vacuum in the apparatus and also avoids physical points of stress (glass against glass.)
Filtration is a unit operation that is commonly used both in laboratory and production conditions. This apparatus, adapted for laboratory work, is often used to isolate the product of synthesis of a reaction when the product is a solid in suspension. The product of synthesis is then recovered faster, and the solid is drier than in the case of a simple filtration. Other than isolating a solid, filtration is also a stage of purification: the soluble impurities in the solvent are eliminated in the filtrate (liquid).
This apparatus is often used to purify a liquid. When a synthesised product is filtered, the insolubles (catalysers, impurities, sub-products of the reaction, salts, ...) remain in the filter. In this case, vacuum filtration is also more efficient that a simple filtration: there is more liquid recovered, and the yield is therefore better.
It is often necessary to maintain the Büchner flask and, incidentally, the vacuum flask. The rigidity of the vacuum pipes and the difference in height between the different parts of the apparatus (as visible in the diagram) make such an apparatus relatively unstable.
Therefore, a three-pronged clamp should be used to maintain the Büchner flask. This clamp should be placed such that the two prongs surround the part of the flask connected to the vacuum tube, the lasting prong resting on the other side.
If it is also necessary to maintain the vacuum flask we use either a mandible clamp, or a three-pronged clamp, depending on the apparatus and its stability. The clamp to use is left to the judgement of the operator.
Before closing the tap, it is necessary to "break the vacuum" (letting in the air in through any area in the apparatus, by removing the funnel for example), otherwise water goes up the apparatus from the aspirator. The vacuum flask prevents the water from going up the Büchner flask.
Vacuum Filtration , retrieved 2017-01-14
Distillation, also classical distillation, is the process of separating the component substances of a liquid mixture of two or more chemically discrete substances; the separation process is realized by way of the selective boiling of the mixture and the condensation of the vapors in a still.
Filtration is a physical separation process that separates solid matter and fluid from a mixture using a filter medium that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter medium are described as oversize and the fluid that passes through is called the filtrate. Oversize particles may form a filter cake on top of the filter and may also block the filter lattice, preventing the fluid phase from crossing the filter, known as blinding. The size of the largest particles that can successfully pass through a filter is called the effective pore size of that filter. The separation of solid and fluid is imperfect; solids will be contaminated with some fluid and filtrate will contain fine particles. Filtration occurs both in nature and in engineered systems; there are biological, geological, and industrial forms.
An Erlenmeyer flask, also known as a conical flask or a titration flask, is a type of laboratory flask which features a flat bottom, a conical body, and a cylindrical neck. It is most often used in a laboratory. It is named after the German chemist Emil Erlenmeyer (1825–1909), who created it in 1860.
A funnel is a tube or pipe that is wide at the top and narrow at the bottom, used for guiding liquid or powder into a small opening.
A rotary evaporator (rotavap) is a device used in chemical laboratories for the efficient and gentle removal of solvents from samples by evaporation. When referenced in the chemistry research literature, description of the use of this technique and equipment may include the phrase "rotary evaporator", though use is often rather signaled by other language.
A Büchner funnel is a piece of laboratory equipment used in filtration. It is traditionally made of porcelain, but glass and plastic funnels are also available. On top of the funnel-shaped part there is a cylinder with a fritted glass disc/perforated plate separating it from the funnel. The Hirsch funnel has a similar design; it is used similarly, but for smaller quantities of material. The main difference is that the plate of a Hirsch funnel is much smaller, and the walls of the funnel angle outward instead of being vertical.
Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the general subject of organic synthesis, there are many different types of synthetic routes that can be completed including total synthesis, stereoselective synthesis, automated synthesis, and many more. Additionally, in understanding organic synthesis it is necessary to be familiar with the methodology, techniques, and applications of the subject.
Laboratory flasks are vessels or containers that fall into the category of laboratory equipment known as glassware. In laboratory and other scientific settings, they are usually referred to simply as flasks. Flasks come in a number of shapes and a wide range of sizes, but a common distinguishing aspect in their shapes is a wider vessel "body" and one narrower tubular sections at the top called necks which have an opening at the top. Laboratory flask sizes are specified by the volume they can hold, typically in metric units such as milliliters or liters. Laboratory flasks have traditionally been made of glass, but can also be made of plastic.
A Büchner flask, also known as a vacuum flask, filter flask, suction flask, side-arm flask, Kitasato flask or Bunsen flask, is a thick-walled Erlenmeyer flask with a short glass tube and hose barb protruding about an inch from its neck. The short tube and hose barb effectively act as an adapter over which the end of a thick-walled flexible hose (tubing) can be fitted to form a connection to the flask. The other end of the hose can be connected to source of vacuum such as an aspirator, vacuum pump, or house vacuum. Preferably this is done through a trap, which is designed to prevent the sucking back of water from the aspirator into the Büchner flask. The purpose of applying a vacuum is to speed the filtration by providing a pressure differential across the filter medium that is greater than that produced by gravity alone.
A Rotary Vacuum Filter Drum consists of a cylindrical filter membrane that is partly sub-merged in a slurry to be filtered. The inside of the drum is held lower than the ambient pressure. As the drum rotates through the slurry, the liquid is sucked through the membrane, leaving solids to cake on the membrane surface while the drum is submerged. A knife or blade is positioned to scrape the product from the surface.
The Schlenk line is a commonly used chemistry apparatus developed by Wilhelm Schlenk. It consists of a dual manifold with several ports. One manifold is connected to a source of purified inert gas, while the other is connected to a vacuum pump. The inert-gas line is vented through an oil bubbler, while solvent vapors and gaseous reaction products are prevented from contaminating the vacuum pump by a liquid-nitrogen or dry-ice/acetone cold trap. Special stopcocks or Teflon taps allow vacuum or inert gas to be selected without the need for placing the sample on a separate line.
In chemistry, work-up refers to the series of manipulations required to isolate and purify the product(s) of a chemical reaction. The term is used colloquially to refer to these manipulations, which may include:
Air-free techniques refer to a range of manipulations in the chemistry laboratory for the handling of compounds that are air-sensitive. These techniques prevent the compounds from reacting with components of air, usually water and oxygen; less commonly carbon dioxide and nitrogen. A common theme among these techniques is the use of a fine (100–10−3 Torr) or high (10−3–10−6 Torr) vacuum to remove air, and the use of an inert gas: preferably argon, but often nitrogen.
A vacuum ceramic filter is designed to separate liquids from solids for dewatering of ore concentrates purposes. The device consists of a rotator, slurry tank, ceramic filter plate, distributor, discharge scraper, cleaning device, frame, agitating device, pipe system, vacuum system, automatic acid dosing system, automatic lubricating system, valve and discharge chute. The operation and construction principle of vacuum ceramic filter resemble those of a conventional disc filter, but the filter medium is replaced by a finely porous ceramic disc. The disc material is inert, has a long operational life and is resistant to almost all chemicals. Performance can be optimized by taking into account all those factors which affect the overall efficiency of the separation process. Some of the variables affecting the performance of a vacuum ceramic filter include the solid concentration, speed rotation of the disc, slurry level in the feed basin, temperature of the feed slurry, and the pressure during dewatering stages and filter cake formation.
In chemistry, recrystallization is a technique used to purify chemicals. By dissolving a mixture of a compound and impurities in an appropriate solvent, either the desired compound or impurities can be removed from the solution, leaving the other behind. It is named for the crystals often formed when the compound precipitates out. Alternatively, recrystallization can refer to the natural growth of larger ice crystals at the expense of smaller ones.
Laboratory funnels are funnels that have been made for use in the chemical laboratory. There are many different kinds of funnels that have been adapted for these specialized applications. Filter funnels, thistle funnels, and dropping funnels have stopcocks which allow the fluids to be added to a flask slowly. For solids, a powder funnel with a short and wide neck/stem is more appropriate as it prevents clogging.
A filter drier is a piece of process equipment used during the filtration and drying phase of a pharmaceutical, bio pharmaceutical or chemical process for an active pharmaceutical ingredient (API) or other compounds production. Filter dryers are designed for washing and isolating solids with or without integrated containment systems.
A pusher centrifuge is a type of filtration technique that offers continuous operation to de-water and wash materials such as relatively in-compressible feed solids, free-draining crystalline, polymers and fibrous substances. It consists of a constant speed rotor and is fixed to one of several baskets. This assembly is applied with centrifugal force that is generated mechanically for smaller units and hydraulically for larger units to enable separation.
Gravity filtration is a method of filtering impurities from solutions by using gravity to pull liquid through a filter. The two main kinds of filtration used in laboratories are gravity and vacuum/suction. Gravity filtration is often used in chemical laboratories to filter precipitates from precipitation reactions as well as drying agents, inadmissible side items, or remaining reactants. While it can also be used to separate out strong products, vacuum filtration is more commonly used for this purpose.