chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

, a condenser is laboratory apparatus used to

condense Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor ...

vapor In physics, a vapor (American English) or vapour (Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is a substance in the gas phase at a temperature lower than its critical temperature,R ...

sthat is, turn them into liquidsby cooling them down. Condensers are routinely used in laboratory operations such as

distillation 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 mixt ...

reflux Reflux is a technique involving the condensation of vapors and the return of this condensate to the system from which it originated. It is used in industrial and laboratory distillations. It is also used in chemistry to supply energy to Chemical ...

, and extraction. In distillation, a mixture is heated until the more volatile components boil off, the vapors are condensed, and collected in a separate container. In reflux, a reaction involving volatile liquids is carried out at their boiling point, to speed it up; and the vapors that inevitably come off are condensed and returned to the reaction vessel. In Soxhlet extraction, a hot solvent is infused onto some powdered material, such as ground seeds, to leach out some poorly soluble component; the solvent is then automatically distilled out of the resulting solution, condensed, and infused again. Many different types of condensers have been developed for different applications and processing volumes. The simplest and oldest condenser is just a long tube through which the vapors are directed, with the outside air providing the cooling. More commonly, a condenser has a separate tube or outer chamber through which water (or some other fluid) is circulated, to provide a more effective cooling. Laboratory condensers are usually made of

glass Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window pane ...

for chemical resistance, for ease of cleaning, and to allow visual monitoring of the operation; specifically,

borosilicate glass Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), ma ...

to resist

thermal shock Thermal shock is a phenomenon characterized by a rapid change in temperature that results in a transient mechanical load on an object. The load is caused by the differential expansion of different parts of the object due to the temperature chang ...

and uneven heating by the condensing vapor. Some condensers for dedicated operations (like water distillation) may be made of metal. In professional laboratories, condensers usually have

ground glass joint Ground glass joints are used in laboratories to quickly and easily fit leak-tight apparatus together from interchangeable commonly available parts. For example, a round bottom flask, Liebig condenser, and oil bubbler with ground glass joints may ...

s for airtight connection to the vapor source and the liquid receptacle; however, flexible tubing of an appropriate material is often used instead. The condenser may also be fused to a boiling flask as a single glassware item, as in the old

retort In a chemistry laboratory, a retort is a device used for distillation or dry distillation of substances. It consists of a sphere, spherical vessel with a long downward-pointing neck. The liquid to be distilled is placed in the vessel and heat ...

and in devices for microscale distillation.

History

The water-cooled condenser, which was popularized by

Justus von Liebig Justus ''Freiherr'' von Liebig (12 May 1803 – 18 April 1873) was a Germans, German scientist who made major contributions to the theory, practice, and pedagogy of chemistry, as well as to agricultural and biology, biological chemistry; he is ...

, was invented by

Weigel Weigel is a German language, German surname. Notable people with this name include: *Alicia Roth Weigel, American intersex activist and writer *Beverly Weigel (born 1940), New Zealand Olympic athlete *Christian Ehrenfried Weigel (1748–1831), Germ ...

, Poisonnier, and Gadolin, and perfected by Göttling, all in the late 18th century. Several designs that are still in common use were developed and became popular in the 19th century, when chemistry became a widely practiced scientific discipline.

General principles

Designing and maintaining systems and processes using condensers requires that the heat of the entering vapor never overwhelm the ability of the chosen condenser and cooling mechanism; as well, the thermal gradients and material flows established are critical aspects, and as processes scale from laboratory to pilot plant and beyond, the design of condenser systems becomes a precise engineering science.

Temperature

In order for a substance to condense from a pure vapor, the

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and eve ...

of the latter must be higher than the

vapor pressure Vapor pressure or equilibrium vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. The equilibrium vapor pressure is an indicat ...

of the adjacent liquid; that is, the liquid must be below its

boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envi ...

at that pressure. In most designs, the liquid is only a thin film on the inner surface of the condenser, so its temperature is essentially the same as of that surface. Therefore, the primary consideration in the design or choice of a condenser is to ensure that its inner surface is below the liquid's boiling point.

Heat flow

As the vapor condenses, it releases the corresponding

heat of vaporization In thermodynamics, the enthalpy of vaporization (symbol ), also known as the (latent) heat of vaporization or heat of evaporation, is the amount of energy (enthalpy) that must be added to a liquid substance to Phase transition, transform a qua ...

, that tends to raise the temperature of the condenser's inner surface. Therefore, a condenser must be able to remove that heat energy quickly enough to keep the temperature low enough, at the maximum rate of condensation that is expected to occur. This concern can be addressed by increasing the

area Area is the measure of a region's size on a surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while '' surface area'' refers to the area of an open surface or the boundary of a three-di ...

of the condensation surface, by making the wall thinner, and/or by providing a sufficiently effective heat sink (such as circulating water) on the other side of it.

Material flow

The condenser must also be dimensioned so that the condensed liquid can flow out at the maximum rate (mass over time) that the vapor is expected to enter it. Care must also be taken to prevent the boiling liquid to enter the condenser as splattering from explosive boiling, or droplets created as bubbles pop.

Carrier gases

Additional considerations apply if the gas inside the condenser is not pure vapor of the desired liquid, but a mixture with gases that have a much lower boiling point (as may occur in

dry distillation Dry distillation is the heating of solid materials to produce gaseous products (which may condense into liquids or solids). The method may involve pyrolysis or thermolysis, or it may not (for instance, a simple mixture of ice and glass could be ...

, for example). Then the

partial pressure In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal g ...

of its vapor must be considered when obtaining its condensation temperature. For example, if the gas entering the condenser is a mixture of 25%

ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...

vapor and 75%

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

(by moles) at 100

kPa The pascal (symbol: Pa) is the unit of pressure in the International System of Units (SI). It is also used to quantify internal pressure, stress, Young's modulus, and ultimate tensile strength. The unit, named after Blaise Pascal, is an SI ...

(typical atmospheric pressure), the condensation surface must be kept below 48 °C, the boiling point of ethanol at 25 kPa. Moreover, if the gas is not pure vapor, condensation will create a layer of gas with even lower vapor contents right next to the condensing surface, further lowering the boiling point. Therefore, the condenser's design must be such that the gas is well-mixed and/or that all of it is forced to pass very close to the condensation surface.

Liquid mixtures

Finally, if the input to the condenser is a mixture of two or more miscible liquids (as is the case in

fractional distillation Fractional distillation is the separation of a mixture into its component parts, or fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize. It uses distillation ...

), one must consider the vapor pressure and the percentage of the gas for each component, which depends on the composition of the liquid as well as its temperature; and all these parameters typically vary along the condenser.

Coolant flow direction

Most condensers can be divided in two broad classes. The concurrent condensers receive the vapor through one port and deliver the liquid through another port, as required in simple distillation. They are usually mounted vertically or tilted, with the vapor input at the top and the liquid output at the bottom. The countercurrent condensers are intended to return the liquid toward the source of the vapor, as required in reflux and fractional distillation. They are usually mounted vertically, above the source of the vapor, that enters them from the bottom. In both cases, the condensed liquid is allowed to flow back to the source by its own weight. The classification is not exclusive, since several types can be used in both modes.

Historical condensers

Straight tube

The simplest type of condenser is a straight tube, cooled only by the surrounding air. The tube is held in a vertical or oblique position, and the vapor is fed through the upper end. The heat of condensation is carried away by

convection Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...

. The neck of the retort is a classical example of a straight tube condenser. However, this kind of condenser may also be a separate piece of equipment. Straight tube condensers are no longer widely used in research laboratories, but may be used in special applications and simple school demonstrations.

Still head

The still head is another ancient type of air-cooled condenser. It consists of a roughly globular vessel with an opening at the bottom, through which the vapor is introduced. The vapor condenses on the inner wall of the vessel, and drips along it, collecting at the bottom of the head and then draining through a tube to a collecting vessel below. A raised lip around the input opening prevents the liquid from spilling through it. As in the tube condenser, the heat of condensation is carried away by natural convection. Any vapor that does not condense in the head may still condense in the neck. Still head type condensers are now rarely used in laboratories, and are usually topped by some other type of reflux condenser where most of the condensation takes place.

Modern condensers

Liebig

The Liebig condenser is the simplest design with circulating coolant, easy to build and inexpensive. It is named after Justus von Liebig, who perfected an earlier design by

and Göttling and popularized it. It consists of two concentric straight glass tubes, the inner one being longer and protruding at both extremities. The ends of the outer tube are sealed (usually by a blown glass ring seal), forming a water jacket, and is fitted with side ports near the ends for cooling fluid inflow and outflow. The ends of the inner tube, that carries the vapor and condensed liquid, are open. Compared to the simple air-cooled tube, the Liebig condenser is more efficient at removing the heat of condensation and at maintaining the inner surface a stable low temperature.

West

The West condenser is variant of the Liebig type, with a more slender design, with cone and socket. The fused-on narrower coolant jacket may render more efficient cooling with respect to coolant consumption.

Allihn

The Allihn condenser or bulb condenser is named after Felix Richard Allihn (1854–1915). The Allihn condenser consists of a long glass tube with a water jacket. A series of bulbs on the tube increases the surface area upon which the vapor constituents may condense. Ideally suited for laboratory-scale refluxing; indeed, the term reflux condenser often means this type specifically.

Davies

A Davies condenser, also known as a double surface condenser, is similar to the Liebig condenser, but with three concentric glass tubes instead of two. The coolant circulates in both the outer jacket and the central tube. This increases the cooling surface, so that the condenser can be shorter than an equivalent Liebig condenser. According to Alan Gall, archivist of the Institute of Science and Technology, Sheffield, England, the 1981 catalog of Adolf Gallenkamp & Co. of London (makers of scientific apparatus) states that the Davies condenser was invented by James Davies, a director of the Gallenkamp company. In 1904, Gallenkamp was offering "Davies' Condensers" for sale:. In 1920, Gallenkamp listed "J. Davies" as a director of the company.

Graham

A Graham or Grahams condenser has a coolant-jacketed spiral coil running the length of the condenser serving as the vapor–condensate path. This is not to be confused with the coil condenser. The coiled condenser tubes inside will provide more surface area for cooling and for this reason it is most favorable to use but the drawback of this condenser is that as the vapors get condensed, it tends to move them up in the tube to evaporate which will also lead to the flooding of solution mixture. It may also be called Inland Revenue condenser due to the application for which it was developed.

Coil

A coil condenser is essentially a Graham condenser with an inverted coolant–vapor configuration. It has a spiral coil running the length of the condenser through which coolant flows, and this coolant coil is jacketed by the vapor–condensate path.

Dimroth

A Dimroth condenser, also known as a spiral condenser, named after Otto Dimroth, is somewhat similar to the coil condenser; it has an internal double spiral through which coolant flows such that the coolant inlet and outlet are both at the top. The vapors travel through the jacket from bottom to top. Dimroth condensers are more effective than conventional coil condensers. They are often found in rotary evaporators which may use a more elaborate arrangement with several spirals. There also exists a version of Dimroth condenser with an external jacket, like in a Davies condenser, to further increase the cooling surface.

Cold finger

A cold finger is a cooling device in the form of a vertical tube that is cooled from the inside, that is to be immersed in the vapor while supported at the upper end only. This may be either flow-cooled, with both coolant ports at the top, or open-topped where liquid or solid coolant is simply placed inside. The vapor is meant to condense on the rod and drip down from the free end, and eventually reach the collecting vessel. A cold finger may be a separate piece of equipment, or may be only a part of a condenser of another type. Cold fingers are also used to condense vapors produced by sublimation in which case the result is a solid that adheres to the finger and must be scraped off, or as a cold-trap, where the liquid or solid condensate is not intended to return to the source of the vapor (often used to protect vacuum pumps and/or prevent venting of harmful gasses).

Friedrichs

The Friedrichs condenser (sometimes incorrectly spelled Friedrich's) was invented by Fritz Walter Paul Friedrichs, who published a design for this type of condenser in 1912. It consists of a large water-cooled finger tightly fitted inside a wide cylindrical housing. The finger has a helical ridge along its length, so as to leave a narrow helical path for the vapor. This arrangement forces the vapor to spend a long time in contact with the finger.

Refluxing and fractional distillation columns

Vigreux

The Vigreux column, named after the French glass blower (1869–1951) who invented it in 1904, consists of a wide glass tube with multiple internal glass "fingers" that point downwards. Each "finger" is created by melting a small section of the wall and pushing the soft glass inwards. The vapor that enters from the lower opening condenses on the fingers and drips down from them.Vigreux, Henri (1904
"Excelsior-Kühler und Excelsior-Destillationaufsatz"
("Excelsior condenser and Excelsior distillation attachment"). ''Chemiker-Zeitung'', volume 28, issue 58, page 686.A. McK. (1904
"Excelsior condenser and Excelsior distillation column,"
''Journal of the Chemical Society'', volume 86, page 611. It is usually air-cooled, but may have an outer glass jacket for forced fluid cooling.

Snyder

The Snyder column is a wide glass tube divided into sections (usually 3 to 6) by horizontal glass partitions or constrictions. Each partition has a hole, into which seats a hollow glass bead with an inverted "teardrop" shape. Vigreux-like glass "fingers" limit the vertical motion of each bead.. These floating glass stoppers act as check valves, closing and opening with vapor flow, and enhancing vapor-condensate mixing. A Snyder column can be used with a Kuderna-Danish concentrator to efficiently separate a low boiling extraction solvent such as

methylene chloride Dichloromethane (DCM, methylene chloride, or methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odor is widely used as a solvent. Although it is not miscible with ...

from volatile but higher boiling extract components (e.g., after the extraction of organic contaminants in soil).

Widmer

The Widmer column was developed as a doctoral research project by student Gustav Widmer at

ETH Zurich ETH Zurich (; ) is a public university in Zurich, Switzerland. Founded in 1854 with the stated mission to educate engineers and scientists, the university focuses primarily on science, technology, engineering, and mathematics. ETH Zurich ran ...

in the early 1920s, combining a Golodetz-type arrangement of concentric tubes and the Dufton-type rod-with-spiral core. It consists of four concentric glass tubes and a central glass rod, with a thinner glass rod coiled around it to increase the surface area. The two outer tubes (#3 and #4) form an insulating dead air chamber (shaded). Vapor rises from a boiling flask into space (1), proceeds up through the space between tubes #2 and #3, then down the space between tubes #1 and #2, and finally up between tube #1 and the central rod. Arriving at space (3), vapor is then directed via a distillation head (glass branching adapter) to cooling and collection. A so-called modified Widmer column design was reported as being in wide use, but undocumented, by L. P. Kyrides in 1940.

Packed

A packed column is a condenser used in

. Its main component is a tube filled with small objects to increase the surface area and the number of theoretical plates. The tube can be the inner conduit of some other type, such as Liebig or Allhin. pp 1-229 (Ch. 8) and 230-415 (Ch. 9), ''esp. pp. 255, 277''ff'', 247''f'', 230''ff'', 1-14''. These columns can achieve theoretical plate counts of 1–2 per 5 cm of packed length. A large variety of packing materials and object shapes has been used, including beads, rings, or helices (such as Fenske rings Raschig or Lessing rings) of glass,

porcelain Porcelain (), also called china, is a ceramic material made by heating Industrial mineral, raw materials, generally including kaolinite, in a kiln to temperatures between . The greater strength and translucence of porcelain, relative to oth ...

aluminum Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...

, or

stainless steel Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chromi ...

;

nichrome Nichrome (also known as NiCr, nickel-chromium or chromium-nickel) is a family of alloys of nickel and chromium (and occasionally iron) commonly used as resistance wire, heating elements in devices like toasters, electrical kettles and space he ...

and

inconel Inconel is a nickel-chromium-based superalloy often utilized in extreme environments where components are subjected to high temperature, pressure or Mechanical load, mechanical loads. Inconel alloys are oxidation- and corrosion-resistant. When he ...

wires (akin to Podbielniak columns), stainless steel gauze ( Dixon rings), etc. Specific combinations are known as Hempel, Todd, and Stedman columns.

Other

* Spinning band distillation uses a spinning helical band (spun by a motor) inside a straight tube to increase the mixing of the upgoing vapor and downcoming reflux liquid. * Oldershaw columns have the same theory of operation as industrial plate columns. They are highly efficient for fractionating but they have significant holdup (the amount of liquid in the column during use) and their complexity makes them one of the more expensive types of glass column. * Straight tube, or air condensers, which are just a straight tube, can be used as a crude reflux column. * Pear columns consist of multiple bulbous segments shaped like inverted pears.

Alternative coolants

Condensers with forced-circulation cooling usually employ water as the cooling fluid. The flow may be open, from a tap to a sink, and driven only by the water pressure in the tap. Alternatively, a closed system may be used, in which the water is drawn by a pump from a tank, possibly refrigerated, and returned to it. Water-cooled condensers are suitable for liquids with boiling points well above 0 °C, and can easily condense vapours with boiling points much higher than that of the water. Other cooling fluids may be used instead of water. Air with forced circulation can be effective enough for situations with high boiling point and low condensation rate. Conversely, low-temperature coolants, such as

acetone Acetone (2-propanone or dimethyl ketone) is an organic compound with the chemical formula, formula . It is the simplest and smallest ketone (). It is a colorless, highly Volatile organic compound, volatile, and flammable liquid with a charact ...

cooled by

dry ice Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and Sublimation (phase transition), sublimes directly from the solid state to the gas ...

or chilled water with

antifreeze An antifreeze is an additive which lowers the freezing point of a water-based liquid. An antifreeze mixture is used to achieve freezing-point depression for cold environments. Common antifreezes also increase the boiling point of the liquid, allow ...

additives, can be used for liquids with low boiling point (like

dimethyl ether Dimethyl ether (DME; also known as methoxymethane) is the organic compound with the formula CH3OCH3, (sometimes ambiguously simplified to C2H6O as it is an isomer of ethanol). The simplest ether, it is a colorless gas that is a useful precursor ...

, −23.6 °C). Open-topped cold fingers can use a wider variety of coolants since they allow solids to be inserted, and can be used with water ice, dry ice, and

liquid nitrogen Liquid nitrogen (LN2) is nitrogen in a liquid state at cryogenics, low temperature. Liquid nitrogen has a boiling point of about . It is produced industrially by fractional distillation of liquid air. It is a colorless, mobile liquid whose vis ...

References

{{Laboratory equipment Laboratory glassware