Editing Solubility (section)

==Quantification of solubility==
The solubility of a specific solute in a specific solvent is generally expressed as the concentration of a saturated solution of the two.<ref name=iupac>{{GoldBookRef|title=Solubility|file=S05740}}</ref> Any of the several ways of expressing concentration of solutions can be used, such as the [[mass]], [[volume]], or [[mole (unit)|amount in moles]] of the solute for a specific mass, volume, or mole amount of the solvent or of the solution.

===Per quantity of solvent===

In particular, chemical [[handbook]]s often express the solubility as [[gram]]s of solute per 100 [[millilitres]] of solvent (g/(100 mL), often written as g/100 ml), or as grams of solute per [[decilitre]] of solvent (g/dL); or, less commonly, as grams of solute per [[litre]] of solvent (g/L). The quantity of solvent can instead be expressed in mass, as grams of solute per 100 grams of solvent (g/(100 g), often written as g/100 g), or as grams of solute per [[kilogram]] of solvent (g/kg). The number may be expressed as a percentage in this case, and the abbreviation "w/w" may be used to indicate "weight per weight".<ref name=abler2021>Abler (2021): "[https://help.abler.com/ww-weightweight/ W/W (Weight/Weight)]". Online page at Abler Help Center. Accessed on 2021-11-26.</ref> (The values in g/L and g/kg are similar for water, but that may not be the case for other solvents.)

Alternatively, the solubility of a solute can be expressed in moles instead of mass. For example, if the quantity of solvent is given in [[kilograms]], the value is the [[molality]] of the solution (mol/kg).

===Per quantity of solution===

The solubility of a substance in a liquid may also be expressed as the quantity of solute per quantity of ''solution'', rather than of solvent. For example, following the common practice in [[titration]], it may be expressed as moles of solute per litre of solution (mol/L), the [[molarity]] of the latter.

In more specialized contexts the solubility may be given by the [[mole fraction]] (moles of solute per total moles of solute plus solvent) or by the [[mass fraction (chemistry)|mass fraction]] at equilibrium (mass of solute per mass of solute plus solvent). Both are [[Dimensionless quantity|dimensionless]] numbers between 0 and 1 which may be expressed as [[percentages]] (%).

===Liquid and gaseous solutes===

For solutions of liquids or gases in liquids, the quantities of both substances may be given volume rather than mass or mole amount; such as litre of solute per litre of solvent, or litre of solute per litre of solution. The value may be given as a percentage, and the abbreviation "v/v" for "volume per volume" may be used to indicate this choice.

===Conversion of solubility values===

Conversion between these various ways of measuring solubility may not be trivial, since it may require knowing the density of the solution — which is often not measured, and cannot be predicted. While the total mass is conserved by dissolution, the final volume may be different from both the volume of the solvent and the sum of the two volumes.<ref name=lee2012>I. Lee and J. Lee (2012): "Measurement of mixing ratio and volume change of ethanol-water binary mixtures using suspended microchannel resonators". ''SENSORS'', volume 2012, pages 1-3. {{doi|10.1109/ICSENS.2012.6411272}}.</ref>

Moreover, many solids (such as [[acid]]s and [[salt (chemistry)|salts]]) will [[dissociation (chemistry)|dissociate]] in non-trivial ways when dissolved; conversely, the solvent may form [[coordination complex]]es with the molecules or ions of the solute. In those cases, the sum of the moles of molecules of solute and solvent is not really the total moles of independent particles solution. To sidestep that problem, the solubility per mole of solution is usually computed and quoted as if the solute does not dissociate or form complexes—that is, by pretending that the mole amount of solution is the sum of the mole amounts of the two substances.