Potassium bitartrate, also known as potassium hydrogen tartrate, with formula
K C4 H5 O6, is a byproduct of
winemaking
Winemaking or vinification is the production of wine, starting with the selection of the fruit, its fermentation into alcohol, and the bottling of the finished liquid. The history of wine-making stretches over millennia. The science of wine and ...
. In cooking, it is known as cream of tartar. It is processed from the
potassium
Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosph ...
acid salt Acid salts are a class of salts that produce an acidic solution after being dissolved in a solvent. Its formation as a substance has a greater electrical conductivity than that of the pure solvent. An acidic solution formed by acid salt is made dur ...
of
tartaric acid
Tartaric acid is a white, crystalline organic acid that occurs naturally in many fruits, most notably in grapes, but also in bananas, tamarinds, and citrus. Its salt, potassium bitartrate, commonly known as cream of tartar, develops naturally ...
(a
carboxylic acid). The resulting powdery base can be used in baking or as a cleaning solution (when mixed with an acidic solution such as
lemon juice
The lemon (''Citrus limon'') is a species of small evergreen trees in the flowering plant family Rutaceae, native to Asia, primarily Northeast India (Assam), Northern Myanmar or China.
The tree's ellipsoidal yellow fruit is used for culina ...
or
white vinegar
Vinegar is an aqueous solution of acetic acid and trace compounds that may include flavorings. Vinegar typically contains 5–8% acetic acid by volume. Usually, the acetic acid is produced by a double fermentation, converting simple sugars to eth ...
).
History
Potassium bitartrate was first discovered by Swedish chemist Karl Wilhelm Scheele (1742-1786). This was a result of Scheele's work studying
fluorite
Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon.
The Mohs sca ...
and
hydrofluoric acid.
Scheele may have been the first scientist to publish work on potassium bitartrate, but use of potassium bitartrate has been reported to date back 7000 years to an ancient village in northern Iran.
Modern applications of cream of tartar started in 1768 after it gained popularity when the French started using it regularly in their cuisine.
Occurrence
Potassium bitartrate is naturally formed in grapes from the acid dissociation of tartaric acid into bitartrate and tartrate ions.
Potassium bitartrate has a low solubility in water. It
crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...
lizes in wine casks during the
fermentation of
grape
A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus '' Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters.
The cultivation of grapes began perhaps 8,000 years a ...
juice
Juice is a drink made from the extraction or pressing of the natural liquid contained in fruit and vegetables. It can also refer to liquids that are flavored with concentrate or other biological food sources, such as meat or seafood, such as ...
, and can precipitate out of wine in bottles. The rate of potassium bitartrate precipitation depends on the rates of nuclei formation and
crystal growth
A crystal is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. Crystal growth is a major stage of a crystallization process, and consists of the ...
, which varies based on a wine's alcohol, sugar, and extract content.
The crystals (
wine diamonds) will often form on the underside of a cork in wine-filled bottles that have been stored at temperatures below , and will seldom, if ever, dissolve naturally into the wine. Over time, crystal formation is less likely to occur due to the decreasing
supersaturation of potassium bitartrate, with the greatest amount of precipitation occurring in the initial few days of cooling.
Historically, it was known as beeswing for its resemblance to the sheen of bees' wings. It was collected and purified to produce the white, odorless,
acidic
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a ...
powder used for many culinary and other household purposes.
These crystals also precipitate out of fresh grape juice that has been chilled or allowed to stand for some time. To prevent crystals from forming in homemade grape
jam or jelly, the prerequisite fresh grape juice should be chilled overnight to promote crystallization. The potassium bitartrate crystals are removed by filtering through two layers of
cheesecloth
Cheesecloth is a loose-woven gauze-like carded cotton cloth used primarily in cheesemaking and cooking.
Grades
Cheesecloth is available in at least seven different grades, from open to extra-fine weave. Grades are distinguished by the nu ...
. The filtered juice may then be made into jam or jelly. In some cases they adhere to the side of the chilled container, making filtering unnecessary.
The presence of crystals is less prevalent in red wines than in white wines. This is because red wines have a higher amount of
tannin
Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids.
The term ''tannin'' (from Anglo-Norman ''tanner'' ...
and colouring matter present as well as a higher sugar and extract content than white wines.
Various methods such as promoting crystallization and filtering, removing the active species required for potassium bitartrate precipitation, and adding additives have been implemented to reduce the presence of potassium bitartrate crystals in wine.
Applications
In food
In food, potassium bitartrate is used for:
* Stabilizing
egg whites, increasing their warmth, tolerance, and volume
* Stabilizing
whipped cream
Whipped cream is liquid heavy cream that is whipped by a whisk or mixer until it is light and fluffy and holds its shape, or by the expansion of dissolved gas, forming a firm colloid. It is often sweetened, typically with white sugar, an ...
, maintaining its texture and volume
*
Anti-caking and
thickening
A thickening agent or thickener is a substance which can increase the viscosity of a liquid without substantially changing its other properties. Edible thickeners are commonly used to thicken sauces, soups, and puddings without altering thei ...
* Preventing
sugar syrup
Inverted sugar syrup, also called invert syrup, invert sugar, simple syrup, sugar syrup, sugar water, bar syrup, syrup USP, or sucrose inversion, is a syrup mixture of the monosaccharides glucose and fructose, that is made by hydrolytic sacc ...
s from
crystallizing by causing some of the
sucrose to break down into
glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
and
fructose
* Reducing discoloration of boiled
vegetable
Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still commonly used and is applied to plants collectively to refer to all edible plant matter, including the flowers, fruits, stems, ...
s
Additionally, it is used as a component of:
*
Baking powder
Baking powder is a dry chemical leavening agent, a mixture of a carbonate or bicarbonate and a weak acid. The base and acid are prevented from reacting prematurely by the inclusion of a buffer such as cornstarch. Baking powder is used to increas ...
, as an acid ingredient to activate
baking soda
Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3� ...
*
Sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
-free
salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
substitutes, in combination with
potassium chloride
A similar acid salt,
sodium acid pyrophosphate
Disodium pyrophosphate or sodium acid pyrophosphate (SAPP) is an inorganic compound consisting of sodium cations and pyrophosphate anion. It is a white, water-soluble solid that serves as a buffering and chelating agent, with many applications ...
, can be confused with cream of tartar because of its common function as a component of baking powder.
Baking
Adding cream of tartar to egg whites gives volume to cakes, and makes them more tender.
As cream of tartar is added, the pH decreases to around the isoelectric point of the foaming proteins in egg whites. Foaming properties of egg whites are optimal at this pH due to increased protein-protein interactions. The low pH also results in a whiter crumb in cakes due to flour pigments that respond to these pH changes.
However, adding too much cream of tartar (>2.4% weight of egg white) can affect the texture and taste of cakes.
The optimal cream of tartar concentration to increase volume and the whiteness of interior crumbs without making the cake too tender, is about 1/4 tsp per egg white.
As an acid, cream of tartar with heat reduces sugar crystallization in
invert syrups by helping to break down
sucrose into its monomer components -
fructose and
glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
in equal parts.
Preventing the formation of sugar crystals makes the syrup have a non-grainy texture, shinier and less prone to break and dry. However, a downside of relying on cream of tartar to thin out crystalline sugar confections (like fudge) is that it can be hard to add the right amount of acid to get the desired consistency.
Cream of tartar is used as a type of
acid salt Acid salts are a class of salts that produce an acidic solution after being dissolved in a solvent. Its formation as a substance has a greater electrical conductivity than that of the pure solvent. An acidic solution formed by acid salt is made dur ...
that is crucial in
baking powder
Baking powder is a dry chemical leavening agent, a mixture of a carbonate or bicarbonate and a weak acid. The base and acid are prevented from reacting prematurely by the inclusion of a buffer such as cornstarch. Baking powder is used to increas ...
.
Upon dissolving in batter or dough, the
tartaric acid
Tartaric acid is a white, crystalline organic acid that occurs naturally in many fruits, most notably in grapes, but also in bananas, tamarinds, and citrus. Its salt, potassium bitartrate, commonly known as cream of tartar, develops naturally ...
that is released reacts with
baking soda
Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3� ...
to form
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
that is used for
leavening
In cooking, a leavening agent () or raising agent, also called a leaven () or leavener, is any one of a number of substances used in doughs and batters that cause a foaming action (gas bubbles) that lightens and softens the mixture. An altern ...
. Since cream of tartar is fast-acting, it releases over 70 percent of carbon dioxide gas during mixing.
Household use
Potassium bitartrate can be mixed with an acidic liquid such as lemon juice or white vinegar to make a paste-like cleaning agent for metals such as
brass
Brass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other wit ...
,
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
, or
copper
Copper is a chemical element with the symbol Cu (from la, cuprum) 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 pinkis ...
, or with water for other cleaning applications such as removing light stains from
porcelain
Porcelain () is a ceramic material made by heating substances, generally including materials such as kaolinite, in a kiln to temperatures between . The strength and translucence of porcelain, relative to other types of pottery, arises main ...
.
This mixture is sometimes mistakenly made with vinegar and
sodium bicarbonate (baking soda), which actually
react to
neutralize each other, creating
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
and a
sodium acetate
Sodium acetate, CH3COONa, also abbreviated Na O Ac, is the sodium salt of acetic acid. This colorless deliquescent salt has a wide range of uses.
Applications
Biotechnological
Sodium acetate is used as the carbon source for culturing bacteria ...
solution.
Cream of tartar was often used in traditional
dyeing
Dyeing is the application of dyes or pigments on textile materials such as fibers, yarns, and fabrics with the goal of achieving color with desired color fastness. Dyeing is normally done in a special solution containing dyes and particular c ...
where the
complexing action of the tartrate ions was used to adjust the solubility and
hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolys ...
of
mordant
A mordant or dye fixative is a substance used to set (i.e. bind) dyes on fabrics by forming a coordination complex with the dye, which then attaches to the fabric (or tissue). It may be used for dyeing fabrics or for intensifying stains in ...
salts such as
tin chloride and
alum.
Cream of tartar, when mixed into a paste with
hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...
, can be used to clean
rust
Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO( ...
from some
hand tools, notably hand
files. The paste is applied and allowed to set for a few hours and then washed off with a baking soda/water solution. After another rinse with water and thorough drying, a thin application of oil will protect the file from further rusting.
Slowing the set time of
plaster of Paris
Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "re ...
products (most widely used in
gypsum plaster
Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "re ...
wall work and artwork casting) is typically achieved by the simple introduction of almost any acid diluted into the mixing water. A commercial retardant premix additive sold by USG to trade interior plasterers includes at least 40% potassium bitartrate. The remaining ingredients are the same plaster of Paris and
quartz
Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...
-silica
aggregate already prominent in the main product. This means that the only active ingredient is the cream of tartar.
Cosmetics
For dyeing hair, potassium bitartrate can be mixed with
henna as the mild acid needed to activate the henna.
Medicinal use
Cream of tartar has been used internally as a
purgative
Laxatives, purgatives, or aperients are substances that loosen stools and increase bowel movements. They are used to treat and prevent constipation.
Laxatives vary as to how they work and the side effects they may have. Certain stimulant, lubri ...
, but this is dangerous because an excess of potassium, or
hyperkalemia
Hyperkalemia is an elevated level of potassium (K+) in the blood. Normal potassium levels are between 3.5 and 5.0mmol/L (3.5 and 5.0mEq/L) with levels above 5.5mmol/L defined as hyperkalemia. Typically hyperkalemia does not cause symptoms. Occasi ...
, may occur.
Chemistry
Potassium bitartrate is the United States'
National Institute of Standards and Technology
The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ...
's primary reference standard for a
pH buffer. Using an excess of the salt in water, a
saturated solution is created with a
pH of 3.557 at . Upon dissolution in water, potassium bitartrate will
dissociate
Dissociation in chemistry is a general process in which molecules (or ionic compounds such as salts, or complexes) separate or split into other things such as atoms, ions, or radicals, usually in a reversible manner. For instance, when an acid ...
into acid tartrate, tartrate, and potassium
ions
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
. Thus, a saturated solution creates a buffer with standard pH. Before use as a standard, it is recommended that the solution be filtered or
decanted between and .
Potassium carbonate
Potassium carbonate is the inorganic compound with the formula K2 CO3. It is a white salt, which is soluble in water. It is deliquescent, often appearing as a damp or wet solid. Potassium carbonate is mainly used in the production of soap and gl ...
can be made by burning cream of tartar, which produces "
pearl ash
Potash () includes various mined and manufactured salts that contain potassium in water-soluble form. ". This process is now obsolete but produced a higher quality (reasonable purity) than "
potash
Potash () includes various mined and manufactured salts that contain potassium in water-soluble form. " extracted from wood or other plant ashes.
Production
See also
*
Tartrate
A tartrate is a salt or ester of the organic compound tartaric acid, a dicarboxylic acid. The formula of the tartrate dianion is O−OC-CH(OH)-CH(OH)-COO− or C4H4O62−.
The main forms of tartrates used commercially are pure crystalline ta ...
*
Tartaric acid
Tartaric acid is a white, crystalline organic acid that occurs naturally in many fruits, most notably in grapes, but also in bananas, tamarinds, and citrus. Its salt, potassium bitartrate, commonly known as cream of tartar, develops naturally ...
*
Potassium tartrate (K
2C
4H
4O
6)
References
External links
Description of Potassium Bitartrate at Monash ScientificMaterial Safety Data Sheet (MSDS) for Potassium Bitartrate at Fisher Scientific
{{DEFAULTSORT:Potassium Bitartrate
Acid salts
Potassium compounds
Tartrates
Leavening agents
Edible thickening agents