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Solubility equilibrium is a type of
dynamic equilibrium In chemistry, a dynamic equilibrium exists once a reversible reaction occurs. Substances transition between the reactants and products at equal rates, meaning there is no net change. Reactants and products are formed at such a rate that the co ...
that exists when a
chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
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 The equilibrium constant of a chemical reaction is the value of its reaction quotient at chemical equilibrium, a state approached by a dynamic chemical system after sufficient time has elapsed at which its composition has no measurable tendency ...
. Solubility equilibria are important in pharmaceutical, environmental and many other scenarios.


Definitions

A solubility equilibrium exists when a
chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
in the solid state is in chemical equilibrium with a solution containing the compound. This type of equilibrium is an example of
dynamic equilibrium In chemistry, a dynamic equilibrium exists once a reversible reaction occurs. Substances transition between the reactants and products at equal rates, meaning there is no net change. Reactants and products are formed at such a rate that the co ...
in that some individual molecules migrate between the solid and solution phases such that the rates of dissolution and
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
are equal to one another. When equilibrium is established and the solid has not all dissolved, the solution is said to be saturated. The
concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', '' molar concentration'', '' number concentration'', ...
of the solute in a saturated solution is known as the
solubility 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. The extent of the solubil ...
. Units of solubility may be molar (mol dm−3) or expressed as mass per unit volume, such as μg mL−1. Solubility is temperature dependent. A solution containing a higher concentration of solute than the solubility is said to be
supersaturated 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 ...
. A supersaturated solution may be induced to come to equilibrium by the addition of a "seed" which may be a tiny crystal of the solute, or a tiny solid particle, which initiates precipitation. There are three main types of solubility equilibria. # Simple dissolution. # Dissolution with dissociation reaction. This is characteristic of
salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively cha ...
. The equilibrium constant is known in this case as a solubility product. # Dissolution with ionization reaction. This is characteristic of the dissolution of
weak acid Acid strength is the tendency of an acid, symbolised by the chemical formula HA, to dissociate into a proton, H+, and an anion, A-. The dissociation of a strong acid in solution is effectively complete, except in its most concentrated solutio ...
s or
weak base A weak base is a base that, upon dissolution in water, does not dissociate completely, so that the resulting aqueous solution contains only a small proportion of hydroxide ions and the concerned basic radical, and a large proportion of undissociat ...
s in aqueous media of varying pH. In each case an
equilibrium constant The equilibrium constant of a chemical reaction is the value of its reaction quotient at chemical equilibrium, a state approached by a dynamic chemical system after sufficient time has elapsed at which its composition has no measurable tendency ...
can be specified as a quotient of activities. This equilibrium constant is
dimensionless A dimensionless quantity (also known as a bare quantity, pure quantity, or scalar quantity as well as quantity of dimension one) is a quantity to which no physical dimension is assigned, with a corresponding SI unit of measurement of one (or 1) ...
as activity is a dimensionless quantity. However, use of activities is very inconvenient, so the equilibrium constant is usually divided by the quotient of activity coefficients, to become a quotient of concentrations. See Equilibrium chemistry#Equilibrium constant for details. Moreover, the activity of a solid is, by definition, equal to 1 so it is omitted from the defining expression. For a chemical equilibrium \mathrm A_p \mathrm B_q \leftrightharpoons p\mathrm A + q\mathrm B the solubility product, ''K''sp for the compound A''p''B''q'' is defined as follows K_\mathrm = mathrm Ap mathrm Bq where and are the concentrations of A and B in a
saturated solution 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. The extent of the solub ...
. A solubility product has a similar functionality to an equilibrium constant though formally ''K''sp has the
dimension In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any point within it. Thus, a line has a dimension of one (1D) because only one coordin ...
of (concentration)''p''+''q''.


Effects of conditions


Temperature effect

Solubility is sensitive to changes in
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
. For example, sugar is more soluble in hot water than cool water. It occurs because solubility products, like other types of equilibrium constants, are functions of temperature. In accordance with
Le Chatelier's Principle Le Chatelier's principle (pronounced or ), also called Chatelier's principle (or the Equilibrium Law), is a principle of chemistry used to predict the effect of a change in conditions on chemical equilibria. The principle is named after French c ...
, when the dissolution process is
endothermic In thermochemistry, an endothermic process () is any thermodynamic process with an increase in the enthalpy (or internal energy ) of the system.Oxtoby, D. W; Gillis, H.P., Butler, L. J. (2015).''Principle of Modern Chemistry'', Brooks Cole. p. ...
(heat is absorbed), solubility increases with rising temperature. This effect is the basis for the process of recrystallization, which can be used to purify a chemical compound. When dissolution is
exothermic In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity ( ...
(heat is released) solubility decreases with rising temperature. Sodium sulfate shows increasing solubility with temperature below about 32.4 °C, but a decreasing solubility at higher temperature. This is because the solid phase is the decahydrate () below the transition temperature, but a different hydrate above that temperature. The dependence on temperature of solubility for an ideal solution (achieved for low solubility substances) is given by the following expression containing the enthalpy of melting, Δ''m''''H'', and the mole fraction x_i of the solute at saturation: \left(\frac \right)_P = \frac where \bar_ is the partial molar enthalpy of the solute at infinite dilution and H_ the enthalpy per mole of the pure crystal. This differential expression for a non-electrolyte can be integrated on a temperature interval to give: \ln x_i=\frac \left(\frac 1 - \frac \right) For nonideal solutions activity of the solute at saturation appears instead of mole fraction solubility in the derivative with respect to temperature: \left(\frac \right)_P= \frac


Common-ion effect

The
common-ion effect The common-ion effect refers to the decrease in solubility of an ionic precipitate by the addition to the solution of a soluble compound with an ion in common with the precipitate. This behaviour is a consequence of Le Chatelier's principle for the ...
is the effect of decreased solubility of one salt when another salt that has an ion in common with it is also present. For example, the solubility of
silver chloride Silver chloride is a chemical compound with the chemical formula Ag Cl. This white crystalline solid is well known for its low solubility in water (this behavior being reminiscent of the chlorides of Tl+ and Pb2+). Upon illumination or heating, ...
, AgCl, is lowered when sodium chloride, a source of the common ion chloride, is added to a suspension of AgCl in water. \mathrm The solubility, ''S'', in the absence of a common ion can be calculated as follows. The concentrations g+and lare equal because one mole of AgCl would dissociate into one mole of Ag+ and one mole of Cl. Let the concentration of g+(aq)be denoted by ''x''. Then K_\mathrm=\mathrm= x^2 \text = \mathrm = x = \sqrt ''K''sp for AgCl is equal to at 25 °C, so the solubility is . Now suppose that sodium chloride is also present, at a concentration of 0.01 mol dm−3 = 0.01 M. The solubility, ignoring any possible effect of the sodium ions, is now calculated by K_\mathrm=\mathrm=x(0.01 \,\text + x) This is a quadratic equation in ''x'', which is also equal to the solubility. x^2 + 0.01 \, \text\, x - K_ = 0 In the case of silver chloride, ''x''2 is very much smaller than 0.01 M ''x'', so the first term can be ignored. Therefore \text=\mathrm = x = \frac = \mathrm a considerable reduction from . In
gravimetric analysis Gravimetric analysis describes a set of methods used in analytical chemistry for the quantitative determination of an analyte (the ion being analyzed) based on its mass. The principle of this type of analysis is that once an ion's mass has been ...
for silver, the reduction in solubility due to the common ion effect is used to ensure "complete" precipitation of AgCl.


Particle size effect

The thermodynamic solubility constant is defined for large monocrystals. Solubility will increase with decreasing size of solute particle (or droplet) because of the additional surface energy. This effect is generally small unless particles become very small, typically smaller than 1 μm. The effect of the particle size on solubility constant can be quantified as follows: \log(^*K_) = \log(^*K_) + \frac where *''KA'' is the solubility constant for the solute particles with the molar surface area ''A'', *''K''''A''→0 is the solubility constant for substance with molar surface area tending to zero (i.e., when the particles are large), ''γ'' is the
surface tension Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) to ...
of the solute particle in the solvent, ''A''m is the molar surface area of the solute (in m2/mol), ''R ''is the
universal gas constant The molar gas constant (also known as the gas constant, universal gas constant, or ideal gas constant) is denoted by the symbol or . It is the molar equivalent to the Boltzmann constant, expressed in units of energy per temperature increment pe ...
, and ''T'' is the
absolute temperature Thermodynamic temperature is a quantity defined in thermodynamics as distinct from kinetic theory or statistical mechanics. Historically, thermodynamic temperature was defined by Kelvin in terms of a macroscopic relation between thermodynamic wo ...
.


Salt effects

The salt effects (
salting in Salting in refers to the effect where increasing the ionic strength of a solution increases the solubility of a solute, such as a protein. This effect tends to be observed at lower ionic strengths. Protein solubility is a complex function of ph ...
and
salting-out Salting out (also known as salt-induced precipitation, salt fractionation, anti-solvent crystallization, precipitation crystallization, or drowning out) is a purification technique that utilizes the reduced solubility of certain molecules in a s ...
) refers to the fact that the presence of a salt which has no ion in common with the solute, has an effect on the
ionic strength The ionic strength of a solution is a measure of the concentration of ions in that solution. Ionic compounds, when dissolved in water, dissociate into ions. The total electrolyte concentration in solution will affect important properties such a ...
of the solution and hence on
activity coefficient In thermodynamics, an activity coefficient is a factor used to account for deviation of a mixture of chemical substances from ideal behaviour. In an ideal mixture, the microscopic interactions between each pair of chemical species are the same (or ...
s, so that the equilibrium constant, expressed as a concentration quotient, changes.


Phase effect

Equilibria are defined for specific crystal phases. Therefore, the solubility product is expected to be different depending on the phase of the solid. For example,
aragonite Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including prec ...
and
calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scrat ...
will have different solubility products even though they have both the same chemical identity ( calcium carbonate). Under any given conditions one phase will be thermodynamically more stable than the other; therefore, this phase will form when thermodynamic equilibrium is established. However, kinetic factors may favor the formation the unfavorable precipitate (e.g. aragonite), which is then said to be in a
metastable In chemistry and physics, metastability denotes an intermediate energetic state within a dynamical system other than the system's state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. If the ball i ...
state. In pharmacology, the metastable state is sometimes referred to as amorphous state. Amorphous drugs have higher solubility than their crystalline counterparts due to the absence of long-distance interactions inherent in crystal lattice. Thus, it takes less energy to solvate the molecules in amorphous phase. The effect of amorphous phase on solubility is widely used to make drugs more soluble.


Pressure effect

For condensed phases (solids and liquids), the pressure dependence of solubility is typically weak and usually neglected in practice. Assuming an ideal solution, the dependence can be quantified as: \left(\frac \right)_T = -\frac where x_i is the mole fraction of the i-th component in the solution, P is the pressure, T is the absolute temperature, \bar_ is the
partial molar volume In thermodynamics, a partial molar property is a quantity which describes the variation of an extensive property of a solution or mixture with changes in the molar composition of the mixture at constant temperature and pressure. It is the part ...
of the ith component in the solution, V_ is the partial molar volume of the ith component in the dissolving solid, and R is the
universal gas constant The molar gas constant (also known as the gas constant, universal gas constant, or ideal gas constant) is denoted by the symbol or . It is the molar equivalent to the Boltzmann constant, expressed in units of energy per temperature increment pe ...
. The pressure dependence of solubility does occasionally have practical significance. For example, precipitation fouling of oil fields and wells by
calcium sulfate Calcium sulfate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hydrate is better known as plaster of Paris, ...
(which decreases its solubility with decreasing pressure) can result in decreased productivity with time.


Quantitative aspects


Simple dissolution

Dissolution of an organic solid can be described as an equilibrium between the substance in its solid and dissolved forms. For example, when sucrose (table sugar) forms a saturated solution \mathrm An equilibrium expression for this reaction can be written, as for any chemical reaction (products over reactants): K^\ominus = \frac where ''K''o is called the thermodynamic solubility constant. The braces indicate activity. The activity of a pure solid is, by definition, unity. Therefore K^\ominus = \left\ The activity of a substance, A, in solution can be expressed as the product of the concentration, and an
activity coefficient In thermodynamics, an activity coefficient is a factor used to account for deviation of a mixture of chemical substances from ideal behaviour. In an ideal mixture, the microscopic interactions between each pair of chemical species are the same (or ...
, ''γ''. When ''K''o is divided by ''γ'', the solubility constant, ''K''s, K_\mathrm = \left mathrm\right/math> is obtained. This is equivalent to defining the
standard state In chemistry, the standard state of a material (pure substance, mixture or solution) is a reference point used to calculate its properties under different conditions. A superscript circle ° (degree symbol) or a Plimsoll (⦵) character is used ...
as the saturated solution so that the activity coefficient is equal to one. The solubility constant is a true constant only if the activity coefficient is not affected by the presence of any other solutes that may be present. The unit of the solubility constant is the same as the unit of the concentration of the solute. For sucrose ''K''s = 1.971 mol dm−3 at 25 °C. This shows that the solubility of sucrose at 25 °C is nearly 2 mol dm−3 (540 g/L). Sucrose is unusual in that it does not easily form a supersaturated solution at higher concentrations, as do most other
carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...
s.


Dissolution with dissociation

Ionic compounds normally dissociate into their constituent ions when they dissolve in water. For example, for
silver chloride Silver chloride is a chemical compound with the chemical formula Ag Cl. This white crystalline solid is well known for its low solubility in water (this behavior being reminiscent of the chlorides of Tl+ and Pb2+). Upon illumination or heating, ...
: \mathrm \leftrightharpoons \mathrm + \mathrm The expression for the equilibrium constant for this reaction is: K^\ominus = \frac =\left\\left\ where K^\ominus is the thermodynamic equilibrium constant and braces indicate activity. The activity of a pure solid is, by definition, equal to one. When the solubility of the salt is very low the activity coefficients of the ions in solution are nearly equal to one. By setting them to be actually equal to one this expression reduces to the solubility product expression: K_\ce = ce\ce]= ce2= ce2. For 2:2 and 3:3 salts, such as CaSO4 and FePO4, the general expression for the solubility product is the same as for a 1:1 electrolyte \mathrm \leftrightharpoons \mathrm^ + \mathrm^ :K_= \mathrm = \mathrm= \mathrm (electrical charges are omitted in general expressions, for simplicity of notation) With an unsymmetrical salt like Ca(OH)2 the solubility expression is given by \mathrm \mathrm Since the concentration of hydroxide ions is twice the concentration of calcium ions this reduces to \mathrm In general, with the chemical equilibrium \mathrm \mathrm and the following table, showing the relationship between the solubility of a compound and the value of its solubility product, can be derived. : Solubility products are often expressed in logarithmic form. Thus, for calcium sulfate, with , . The smaller the value of ''K''sp, or the more negative the log value, the lower the solubility. Some salts are not fully dissociated in solution. Examples include MgSO4, famously discovered by
Manfred Eigen Manfred Eigen (; 9 May 1927 – 6 February 2019) was a German biophysical chemist who won the 1967 Nobel Prize in Chemistry for work on measuring fast chemical reactions. Eigen's research helped solve major problems in physical chemistry and ...
to be present in
seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has app ...
as both an inner sphere complex and an outer sphere complex. The solubility of such salts is calculated by the method outlined in dissolution with reaction.


Hydroxides

The solubility product for the hydroxide of a metal ion, M''n''+, is usually defined, as follows: \mathrm K_ = \mathrm However, general-purpose computer programs are designed to use hydrogen ion concentrations with the alternative definitions. \mathrm K^*_\text = \mathrm For hydroxides, solubility products are often given in a modified form, ''K''*sp, using hydrogen ion concentration in place of hydroxide ion concentration. The two values are related by the self-ionization constant for water, ''K''w. K_\mathrm = mathrm mathrm/math> K^*_\text = \frac Lg K^*_\text = lg K_\text - n Lg K_\text For example, at ambient temperature, for calcium hydroxide, Ca(OH)2, lg ''K''sp is ca. −5 and lg ''K''*sp ≈ −5 + 2 × 14 ≈ 23.


Dissolution with reaction

A typical reaction with dissolution involves a
weak base A weak base is a base that, upon dissolution in water, does not dissociate completely, so that the resulting aqueous solution contains only a small proportion of hydroxide ions and the concerned basic radical, and a large proportion of undissociat ...
, B, dissolving in an acidic
aqueous solution An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be ...
. \mathrm \mathrm + \mathrm H^+ \mathrm \leftrightharpoons \mathrm ^+ (\mathrm This reaction is very important for pharmaceutical products. Dissolution of weak acids in alkaline media is similarly important. \mathrm The uncharged molecule usually has lower solubility than the ionic form, so solubility depends on pH and the
acid dissociation constant In chemistry, an acid dissociation constant (also known as acidity constant, or acid-ionization constant; denoted ) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction ...
of the solute. The term "intrinsic solubility" is used to describe the solubility of the un-ionized form in the absence of acid or alkali. Leaching of aluminium salts from rocks and soil by
acid rain Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but ...
is another example of dissolution with reaction: alumino-silicates are bases which react with the acid to form soluble species, such as Al3+(aq). Formation of a chemical complex may also change solubility. A well-known example is the addition of a concentrated solution of
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous w ...
to a suspension of
silver chloride Silver chloride is a chemical compound with the chemical formula Ag Cl. This white crystalline solid is well known for its low solubility in water (this behavior being reminiscent of the chlorides of Tl+ and Pb2+). Upon illumination or heating, ...
, in which dissolution is favoured by the formation of an ammine complex. \mathrm When sufficient ammonia is added to a suspension of silver chloride, the solid dissolves. The addition of
water softener Water softening is the removal of calcium, magnesium, and certain other metal cations in hard water. The resulting soft water requires less soap for the same cleaning effort, as soap is not wasted bonding with calcium ions. Soft water also ext ...
s to washing powders to inhibit the formation of
soap scum Soap scum or lime soap is the white solid composed of calcium stearate, magnesium stearate, and similar alkaline earth metal derivatives of fatty acids. These materials result from the addition of soap and other anionic surfactants to hard water. ...
provides an example of practical importance.


Experimental determination

The determination of solubility is fraught with difficulties. First and foremost is the difficulty in establishing that the system is in equilibrium at the chosen temperature. This is because both precipitation and dissolution reactions may be extremely slow. If the process is very slow solvent evaporation may be an issue. Supersaturation may occur. With very insoluble substances, the concentrations in solution are very low and difficult to determine. The methods used fall broadly into two categories, static and dynamic.


Static methods

In static methods a mixture is brought to equilibrium and the concentration of a species in the solution phase is determined by
chemical analysis Analytical chemistry studies and uses instruments and methods to separate, identify, and quantify matter. In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separati ...
. This usually requires separation of the solid and solution phases. In order to do this the equilibration and separation should be performed in a thermostatted room. Very low concentrations can be measured if a
radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
tracer is incorporated in the solid phase. A variation of the static method is to add a solution of the substance in a non-aqueous solvent, such as
dimethyl sulfoxide Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula ( CH3)2. This colorless liquid is the sulfoxide most widely used commercially. It is an important polar aprotic solvent that dissolves both polar and nonpolar compounds ...
, to an aqueous
buffer Buffer may refer to: Science * Buffer gas, an inert or nonflammable gas * Buffer solution, a solution used to prevent changes in pH * Buffering agent, the weak acid or base in a buffer solution * Lysis buffer, in cell biology * Metal ion buffe ...
mixture. Immediate precipitation may occur giving a cloudy mixture. The solubility measured for such a mixture is known as "kinetic solubility". The cloudiness is due to the fact that the precipitate particles are very small resulting in Tyndall scattering. In fact the particles are so small that the particle size effect comes into play and kinetic solubility is often greater than equilibrium solubility. Over time the cloudiness will disappear as the size of the crystallites increases, and eventually equilibrium will be reached in a process known as precipitate ageing.


Dynamic methods

Solubility values of organic acids, bases, and ampholytes of pharmaceutical interest may be obtained by a process called "Chasing equilibrium solubility". In this procedure, a quantity of substance is first dissolved at a pH where it exists predominantly in its ionized form and then a precipitate of the neutral (un-ionized) species is formed by changing the pH. Subsequently, the rate of change of pH due to precipitation or dissolution is monitored and strong acid and base titrant are added to adjust the pH to discover the equilibrium conditions when the two rates are equal. The advantage of this method is that it is relatively fast as the quantity of precipitate formed is quite small. However, the performance of the method may be affected by the formation supersaturated solutions.


See also

*
Solubility table The table below provides information on the variation of solubility of different substances (mostly inorganic compounds) in water with temperature, at one atmosphere pressure. Units of solubility are given in grams per 100 millilitres of water (g/1 ...
: A table of solubilities of mostly inorganic salts at temperatures between 0 and 100 °C. *
Solvent models In computational chemistry, a solvent model is a computational method that accounts for the behavior of solvated condensed phases. Solvent models enable simulations and thermodynamic calculations applicable to reactions and processes which take plac ...


References


External links

* Section 6.9: Solubilities of ionic salts. Includes a discussion of the thermodynamics of dissolution.
IUPAC–NIST solubility database



Solvent activity along a saturation line and solubility

Solubility challenge
Predict solubilities from a data base of 100 molecules. The database, of mostly compounds of pharmaceutical interest, is available a
One hundred molecules with solubilities (Text file, tab separated)
A number of computer programs are available to do the calculations. They include:
CHEMEQL
A comprehensive computer program for the calculation of thermodynamic equilibrium concentrations of species in homogeneous and heterogeneous systems. Many geochemical applications.
JESS
All types of chemical equilibria can be modelled including protonation, complex formation, redox, solubility and adsorption interactions. Includes an extensive database.
MINEQL+
A chemical equilibrium modeling system for aqueous systems. Handles a wide range of pH, redox, solubility and sorption scenarios.
PHREEQC
USGS The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
software designed to perform a wide variety of low-temperature aqueous geochemical calculations, including reactive transport in one dimension.
MINTEQ
A chemical equilibrium model for the calculation of metal speciation, solubility equilibria etc. for natural waters.

A Windows version of the SOLGASWATER computer program. {{DEFAULTSORT:Solubility Equilibrium Equilibrium chemistry Solutions