Hessian crucible
The Hessian crucible is a type of crucible manufactured in the Hesse region of Germany from the late Middle Ages and during the Renaissance period, that were renowned for their ability to withstand very high temperatures, rapid changes in temperature, and strong reagents. They were highly soughtafter for these properties, and their use in alchemy and premodern metallurgy became widespread, with many millions of these mixing vessels being exported throughout Europe, Scandinavia, and the new colonies in the Americas.An alembic is an alchemical still consisting of two retorts connected by a tube. Technically, the alembic is only the upper part the capital or stillhead, while the lower part is the cucurbit, but the word was often used to refer to the entire distillation apparatus. The alembic was developed circa AD by the Persian alchemist Jabir ibn Hayyan its modern descendant used to produce alcohol is the pot still.The word alembic has taken on a metaphorical meaning anything that refines or transmutes, as if by distillation as in the alembic of creative thought.The word, as most alchemical terminology, comes from the Arabic alambiq, still ultimately from the Greek ambix, cup.
The French spelling alambic is also commonly used, especially as the apparatus is often associated with Cognac where it is known as alambic charentaise. Charente is the area where the grapes must be grown and the brandy itself produced in order to be rightfully called Cognac.In the Netherlands, at Twente University in Enschede, a study association is named after the Alembic.A pot still is a type of still used in distilling spirits such as whisky or brandy. Heat is applied directly to the pot in which the mash in the case of whisky or wine in the case of Cognac is contained. This is called a batch distillation, as opposed to a continuous distillation.At sea level, water boils at degrees Celsius but alcohol boils at degrees Celsius . Therefore, in the distilling process, while there is still alcohol in the mash, the vapour is richer in alcohol than the liquid itself. When this vapour is condensed, the resulting liquid therefore contains more alcohol. In the pot still, the alcohol and water vapour, combined with vapours of the multitude of aroma components such as esters, alcohols that give the mash or wine its aroma, evaporate and flow from the still through the condensing coil. There they condense to the first distillation liquid, the socalled low wines, with a strength of about alcohol by volume, which then flows into a second still below. It is then distilled a second time to produce the colourless spirit, collected at about alcohol by volume. Maturation in an oak aging barrel typically causes the brown color to develop over time.The modern pot still is a descendant of the alembic, a distillation device invented around the eighth century AD for use in alchemy.
chemical substances
Distillation is a method of separating chemical substances based on differences in their volatilities in a boiling liquid mixture. Distillation usually forms part of a larger chemical process, and is thus referred to as a unit operation.Commercially, distillation has a number of uses. It is used to separate crude oil into more fractions for specific uses such as transport, power generation and heating. Water is distilled to remove impurities, such as salt from sea water. Air is distilled to separate its components notably oxygen, nitrogen and argon for industrial use. Distillation of fermented solutions has been used since ancient times to produce distilled beverages with a higher alcohol content.The first pure distillation procedures for producing fully purified chemical substances were carried out by Muslim chemists for industrial purposes such as isolating natural esters perfumes and producing pure alcohol. However, early forms of distillation were known to Babylonian alchemists in Mesopotamia in what is now Iraq from at least the nd millennium BC. Distillation was later known to Greek alchemists from the st century AD, and the later development of largescale distillation apparatus occurred in response to demands for spirits. Hypathia of Alexandria is credited with having invented an early distillation apparatus, and the first exact description of apparatus for distillation is given by Zosimos of Alexandria in the fourth century.
Later, copper alembics were invented. Riveted joints were often kept tight by using various mixtures, for instance a dough made of rye flour. These alembics often featured a cooling system around the beak, using cold water for instance, which made condensation of alcohol more efficient. These were called pot stills.Today, the retorts and pot stills have been largely supplanted by more efficient distillation methods in most industrial processes. However, the pot still is still widely used for the elaboration of some fine alcohols such as cognac, Scotch whisky and some vodkas. Pot stills made of various materials wood, clay, stainless steel are also used by bootleggers in various countries. Small pot stills are also sold for the domestic production of flower water or essential oils.The main difference between laboratory scale distillation and industrial distillation is that laboratory scale distillation is often performed batchwise, whereas industrial distillation often occurs continuously. In batch distillation, the composition of the source material, the vapors of the distilling compounds and the distillate change during the distillation. In batch distillation, a still is charged supplied with a batch of feed mixture, which is then separated into its component fractions which are collected sequentially from most volatile to less volatile, with the bottoms remaining least or nonvolatile fraction removed at the end. The still can then be recharged and the process repeated.
Volatility context
Volatility in the context of chemistry, physics and thermodynamics is a measure of the tendency of a substance to vaporize. It has also been defined as a measure of how readily a substance vaporizes. At a given temperature, substances with higher vapor pressures will vaporize more readily than substances with a lower vapor pressure.Although usually applying to liquids, volatility can apply to solid materials such as dry ice solid carbon dioxide and ammonium chloride, which can change directly from solid to vapor without becoming liquid. The direct transition of a solid to a vapor is called sublimation.Vapor pressure is the pressure of a vapor which is in equilibrium with its nonvapor phases i.e., liquid or solid. Most often the term is used to describe a liquids tendency to evaporate. It is a measure of the tendency of molecules and atoms to escape from a liquid or a solid. A liquids atmospheric pressure boiling point corresponds to the temperature at which its vapor pressure is equal to the surrounding atmospheric pressure and it is often called the normal boiling point.The higher is the vapor pressure of a liquid at a given temperature, the higher is the volatility and the lower is the normal boiling point of the liquid.
The higher is the vapor pressure of a liquid at a given temperature, the higher is the volatility and the lower is the normal boiling point of the liquid.The vapor pressure chart to the right has graphs of the vapor pressures versus temperatures for a variety of liquids. As can be seen in the chart, the liquids with the highest vapor pressures have the lowest normal boiling points.For example, at any given temperature, propane has the highest vapor pressure of any of the liquids in the chart. It also has the lowest normal boiling point. °C, which is where the vapor pressure curve of propane the purple line intersects the horizontal pressure line of one atmosphere atm of absolute vapor pressure.During operation after charging the pot and starting up the system the high boiling constituents are primarily separated from the charge mixture. The liquid in the pot is depleted in the high boiling constituents, and enriched in low boiling ones. The high boiling product is routed into the bottom product receivers. The residual low boiling product is withdrawn from the charge pot. This mode of batch distillation is very seldom applied in industrial processes.A third feasible batch column configuration is the middle vessel column. The middle vessel column consists of both a rectifying and a stripping section and the charge pot is located at the middle of the column.
Partial pressure
In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture.In chemistry, the partial pressure of a gas in a mixture of gases is defined as above. The partial pressure of a gas dissolved in a liquid is the partial pressure of that gas which would be generated in a gas phase in equilibrium with the liquid at the same temperature. The partial pressure of a gas is a measure of thermodynamic activity of the gass molecules. Gases will always flow from a region of higher partial pressure to one of lower pressure the larger this difference, the faster the flow. Gases dissolve, diffuse, and react according to their partial pressures, and not necessarily according to their concentrations in a gas mixture.The partial pressure of an ideal gas in a mixture is equal to the pressure it would exert if it occupied the same volume alone at the same temperature. This is because ideal gas molecules are so far apart that they dont interfere with each other at all. Actual realworld gases come very close to this ideal.
Vapor pressure is the pressure of a vapor in equilibrium with its nonvapor phases i.e., liquid or solid. Most often the term is used to describe a liquids tendency to evaporate. It is a measure of the tendency of molecules and atoms to escape from a liquid or a solid. A liquids atmospheric pressure boiling point corresponds to the temperature at which its vapor pressure is equal to the surrounding atmospheric pressure and it is often called the normal boiling point.The higher is the vapor pressure of a liquid at a given temperature, the lower is the normal boiling point of the liquid.The vapor pressure chart to the right has graphs of the vapor pressures versus temperatures for a variety of liquids. As can be seen in the chart, the liquids with the highest vapor pressures have the lowest normal boiling points.For reversible reactions, changes in the total pressure, temperature or reactant concentrations will shift the equilibrium so as to favor either the right or left side of the reaction in accordance with Le Chateliers Principle. However, the reaction kinetics may either oppose or enhance the equilibrium shift. In some cases, the reaction kinetics may be the overriding factor to consider.
Fractional distillation
Fractional distillation is the separation of a mixture into its component parts, or fractions, such as in separating chemical compounds by their boiling point by heating them to a temperature at which several fractions of the compound will evaporate. It is a special type of distillation. Generally the component parts boil at less than °C from each other under a pressure of one atmosphere ATM. If the difference in boiling points is greater than °C, a simple distillation is used.Fractional distillation in a laboratory makes use of common laboratory glassware, as well as some singlepurpose items like a fractionating column.As an example, consider the distillation of a mixture of water and ethanol. Ethanol boils at . °C while water boils at . So, by gently heating the mixture, the most volatile component will concentrate to a greater degree in the vapor leaving the liquid. Some mixtures form azeotropes, where the mixture boils at a lower temperature than either component. In this example, a mixture of ethanol and water boils at , being more volatile than pure ethanol. For this reason, ethanol cannot be completely purified by direct fractional distillation of ethanolwater mixtures. Fractional distillation is also used in air separation, producing liquid oxygen, liquid nitrogen, and high purity argon. Distillation of chlorosilanes also enable the production of highpurity silicon for use as a semiconductor.
In industrial uses, sometimes a packing material is used in the column instead of trays, especially when low pressure drops across the column are required, as when operating under vacuum. This packing material can either be random dumped packing wide such as Raschig rings or structured sheet metal. Typical manufacturers are Koch, Sulzer and other companies. Liquids tend to wet the surface of the packing and the vapors pass across this wetted surface, where mass transfer takes place. Unlike conventional tray distillation in which every tray represents a separate point of vapor liquid equilibrium the vapor liquid equilibrium curve in a packed column is continuous. However, when modeling packed columns it is useful to compute a number of theoretical plates to denote the separation efficiency of the packed column with respect to more traditional trays. Differently shaped packings have different surface areas and void space between packings. Both of these factors affect packing performance.Design and operation of a distillation column depends on the feed and desired products. Given a simple, binary component feed, analytical methods such as the McCabeThiele method or the Fenske equation can be used. For a multicomponent feed, simulation models are used both for design and operation.
Extractive distillation
Extractive distillation is defined as distillation in the presence of a miscible, high boiling, relatively nonvolatile component, the solvent, that forms no azeotrope with the other components in the mixture. The method is used for mixtures having a low value of relative volatility, nearing unity. Such mixtures cannot be separated by simple distillation, because the volatility of the two components in the mixture is nearly the same, causing them to evaporate at nearly the same temperature at a similar rate, making normal distillation impractical.The method of extractive distillation uses a separation solvent, which is generally nonvolatile, has a high boiling point and is miscible with the mixture, but doesnt form an azeotropic mixture. The solvent interacts differently with the components of the mixture thereby causing their relative volatilities to change. This enables the new threepart mixture to be separated by normal distillation. The original component with the greatest volatility separates out as the top product. The bottom product consists of a mixture of the solvent and the other component, which can again be separated easily because the solvent doesnt form an azeotrope with it. The bottom product can be separated by any of the methods available.
It is important to select a suitable separation solvent for this type of distillation. The solvent must alter the relative volatility by a wide enough margin for a successful result. The quantity, cost and availability of the solvent should be considered. The solvent should be easily separable from the bottom product, and should not react chemically with the components or the mixture, or cause corrosion in the equipment. A classic example to be cited here is the separation of an azeotropic mixture of benzene and cyclohexane, where aniline is one suitable solvent.f two solvents can form a negative azeotrope, then distillation of any mixture of those constituents will result in the residue being closer in composition to the azeotrope than the original mixture. For example, if a hydrochloric acid solution contains less than . hydrogen chloride, boiling the mixture will leave behind a solution that is richer in hydrogen chloride than the original. If the solution initially contains more than . hydrogen chloride, then boiling will leave behind a solution that is poorer in hydrogen chloride than the original. Boiling of any hydrochloric acid solution long enough will cause the solution left behind to approach the azeotropic ratio.
Heteroazeotrope
Heterogeneous distillation means that during the distillation the liquid phase of the mixture is immiscibility. In this case on the plates can be two liquid phases and the top vapour condesated splits two liquid phases, which can be separeted in a decanter. The simplest case of continuous heteroazeotropic distillation is the separation of a binary heterogeneous azeotropic mixture. In this case the system contains two columns and a decanter. The fresh feed AB be added into the first column. The feed may also be added into the decanter directly or the into the second column depending on the composition of the mixture. From the decanter the Arich phase is withdrawn as reflux into the first column while the Brich phase is withdrawn as reflux into the second column. This mean the first column produces A and the second column produces B as a bottoms product. In the industrial the butanolwater mixture is separeted with this technique.Batch heteroazeotropic distillation is an efficient method for the separation of azeotropic and low relative volatility low a mixtures. A third component entrainer, E is added to the binary AB mixture, which makes the separation of A and B possible. The entrainer forms a heteroazeotrope with at least one and preferably with only one selective entrainer of the original components. The main parts of the conventional batch distillation columns are the followings pot inlude reboiler column condenser to condesate the top vapour product receivers entrianer fed In case of the heteroazeotropic distillation the equipment is completed with a decanter, where the two liquid phases are splitted.
Mixed Addition of the Entrainer The combination of the batch addition and continuous feeding of the entrainer. We added one part of the entrainer to the charge before the start of the distillation and the other part continuously during distillation.At the previously case the binary system forms already heterogeneous azeotrope. The other application of the heteroazeotropic distillation, when binary system AB forms homogeneous azeotrope and an entrainer or solvent is added to the mixture in order to form an heteroazeotrope with one or both of the components in order to help the separation of the original AB mixture. The system became then ternary.Batch distillation refers to the use of distillation in batches, meaning that a mixture is distilled to separate it into its component fractions before the distillation still is again charged with more mixture and the process is repeated. This is in contrast with continuous distillation where the feedstock is added and the distillate drawn off without interruption.Batch distillation has always been an important part of the production of seasonal, or low capacity and highpurity chemicals. It is a very frequent separation process in the pharmaceutical industry and in wastewater treatment units.