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Recrystallization is a method used to purify chemicals by dissolving a mixture of a compound and its impurities, in an appropriate solvent, prior to heating the solution. [1] Following the dissolution of crude product, the mixture will passively cool, yielding a crystallized compound and its impurities as separate entities. The newly formed crystals can then be subjected to x-ray anaylsis for purity assessment. [2]
The solvent utilized in single-solvent recrystallization must dissolve the crude reaction mixture only when it is heated to reflux. [3] The heated solution is then passively cooled, yielding a crystallized product absent of impurities. [3] The solid crystals are then collected utilizing a filtration apparatus and the filtrate is discarded. [4] Product purity can then be assessed via NMR spectroscopy. [5]
Multi-solvent recrystallization relies on the crude product being soluble in one solvent, when it is heated to reflux, while being insoluble in a secondary solvent, regardless of the solvent's temperature. [6] The volume ratio between the first and second solvent is critical. A higher ratio of first to second solvent will lead to permanent dissolution of the desired product, while a low ratio will lead to minimal pure crystal recovery. The terms first and second are in reference to crude product soluble and crude product insoluble solvents respectively. Typically, the second solvent, following the dissolution of the impure solid in the first solvent, is added slowly until the desired product begins to crystallize from solution. The solution is then cooled to further induce recrystallization. [6]
Hot filtration recrystallization can be used to separate a pure compound from both impurities and some insoluble matter, which may be anything from a third party impurity to fragments of broken glass. [7] The technique makes use of the single solvent system, outlined above, by dissolving a crude reaction mixture, in a minimum amount of hot solvent, before gravity filtering the saturated solution to remove insoluble matter. The saturated solution will then passively cool, yielding pure crystals. [7]
Recrystallized products are often subject to X-ray crystallography for purity assessment. [8] The technique requires crystalized products to be singular, and absent of clumps. [8] Several approaches to this phenomena are listed below.
An alloy is a mixture of chemical elements of which in most cases at least one is a metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Most alloys are metallic and show good electrical conductivity, ductility, opacity, and luster, and may have properties that differ from those of the pure elements such as increased strength or hardness. In some cases, an alloy may reduce the overall cost of the material while preserving important properties. In other cases, the mixture imparts synergistic properties such as corrosion resistance or mechanical strength.
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.
In chemistry, a solution is defined by IUPAC as "A liquid or solid phase containing more than one substance, when for convenience one substance, which is called the solvent, is treated differently from the other substances, which are called solutes. When, as is often but not necessarily the case, the sum of the mole fractions of solutes is small compared with unity, the solution is called a dilute solution. A superscript attached to the ∞ symbol for a property of a solution denotes the property in the limit of infinite dilution." One important parameter of a solution is the concentration, which is a measure of the amount of solute in a given amount of solution or solvent. The term "aqueous solution" is used when one of the solvents is water.
A solvent is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for polar molecules, and the most common solvent used by living things; all the ions and proteins in a cell are dissolved in water within the cell.
In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution.
Solubility equilibrium is a type of dynamic equilibrium that exists when a chemical compound in the solid state is in chemical equilibrium with a solution of that compound. The solid may dissolve unchanged, with dissociation, or with chemical reaction with another constituent of the solution, such as acid or alkali. Each solubility equilibrium is characterized by a temperature-dependent solubility product which functions like an equilibrium constant. Solubility equilibria are important in pharmaceutical, environmental and many other scenarios.
In physical chemistry, supersaturation occurs with a solution when the concentration of a solute exceeds the concentration specified by the value of solubility at equilibrium. Most commonly the term is applied to a solution of a solid in a liquid, but it can also be applied to liquids and gases dissolved in a liquid. A supersaturated solution is in a metastable state; it may return to equilibrium by separation of the excess of solute from the solution, by dilution of the solution by adding solvent, or by increasing the solubility of the solute in the solvent.
In an aqueous solution, precipitation is the "sedimentation of a solid material from a liquid solution". The solid formed is called the precipitate. In case of an inorganic chemical reaction leading to precipitation, the chemical reagent causing the solid to form is called the precipitant.
Crystallization is the process by which solids form, where the atoms or molecules are highly organized into a structure known as a crystal. Some ways by which crystals form are precipitating from a solution, freezing, or more rarely deposition directly from a gas. Attributes of the resulting crystal depend largely on factors such as temperature, air pressure, cooling rate, and in the case of liquid crystals, time of fluid evaporation.
A separatory funnel, also known as a separation funnel, separating funnel, or colloquially sep funnel, is a piece of laboratory glassware used in liquid-liquid extractions to separate (partition) the components of a mixture into two immiscible solvent phases of different densities. Typically, one of the phases will be aqueous, and the other a lipophilic organic solvent such as ether, MTBE, dichloromethane, chloroform, or ethyl acetate. All of these solvents form a clear delineation between the two liquids. The more dense liquid, typically the aqueous phase unless the organic phase is halogenated, sinks to the bottom of the funnel and can be drained out through a valve away from the less dense liquid, which remains in the separatory funnel.
Trituration is the name of several different methods used to process materials. In one sense, it is a form of comminution. In another sense, it is the production of a homogeneous powdered material by mixing and grinding component materials thoroughly. For example, a dental amalgam is formed by combining particles of a metal, usually gold or silver, with mercury.
In chemistry, fractional crystallization is a stage-wise separation technique that relies on the liquid-solid phase change. fractional crystallisation. This is an old established method which is nevertheless capable of excellent results and a description is available in "The practical Methods of organic Chemistry" by Ludwig Gattermann in 1898 and a translation was available in English by WILLIAM B. SHOBER who was a Lehigh University, USA.
The flux method is a crystal growth method where starting materials are dissolved in a solvent (flux), and are precipitated out to form crystals of a desired compound. The flux lowers the melting point of the desired compound, analogous to a wet chemistry recrystallization. The flux is molten in a highly stable crucible that does not react with the flux. Metal crucibles, such as platinum, titanium, and niobium are used for the growth of oxide crystals. Ceramic crucibles, such as alumina, zirconia, and boron nitride are used for the growth of metallic crystals. For air-sensitive growths, contents are sealed in ampoules or placed in atmosphere controlled furnaces.
Acid–base extraction is a subclass of liquid–liquid extractions and involves the separation of chemical species from other acidic or basic compounds. It is typically performed during the work-up step following a chemical synthesis to purify crude compounds and results in the product being largely free of acidic or basic impurities. A separatory funnel is commonly used to perform an acid-base extraction.
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:
A sugar cane mill is a factory that processes sugar cane to produce raw sugar or plantation white sugar. Some sugar mills are situated next to a back-end refinery, that turns raw sugar into (refined) white sugar.
A separation process is a method that converts a mixture or a solution of chemical substances into two or more distinct product mixtures, a scientific process of separating two or more substances in order to obtain purity. At least one product mixture from the separation is enriched in one or more of the source mixture's constituents. In some cases, a separation may fully divide the mixture into pure constituents. Separations exploit differences in chemical properties or physical properties between the constituents of a mixture.
Fulminating gold is a light- and shock-sensitive yellow to yellow-orange amorphous heterogeneous mixture of different polymeric compounds of predominantly gold(III), ammonia, and chlorine that cannot be described by a chemical formula. Here, "fulminating" has its oldest meaning, "explosive" ; the material contains no fulminate ions. The best approximate description is that it is the product of partial hydrolysis of . Upon combustion, it produces a purple vapor. The complex has a square planar molecular geometry with a low spin state.
Instant tea is a powdered mix in which water is added, in order to reconstitute it into a cup of tea. The earliest form of instant tea was developed in the United Kingdom in 1885. A patent was granted for a paste made of concentrated tea extract, sugar, and evaporated milk, which became tea when hot water was added. However, no notable developments were made until spray drying technology allowed for drying the tea concentrates at a temperature which did not damage the flavors of the product.
