Solubility

In <a href="/facts/Chemistry/SrNqkGVm">chemistry</a>, solubility is the ability of a <a href="/facts/Chemical_substance/EWcXU41d">substance</a>, the <a href="/facts/Solute/MGchhMQV">solute</a>, to form a <a href="/facts/Solution_(chemistry)/MGchhMQV">solution</a> with another substance, the <a href="/facts/Solvent/LoMPMz8S">solvent</a>. Insolubility is the opposite property, the inability of the solute to form such a solution.
The extent of the solubility of a substance in a specific solvent is generally measured as the <a href="/facts/Concentration/wqBmz5od">concentration</a> of the solute in a saturated solution, one in which no more solute can be dissolved. At this point, the two substances are said to be at the <a href="/facts/Solubility_equilibrium/MNBoGyJb">solubility equilibrium</a>. For some solutes and solvents, there may be no such limit, in which case the two substances are said to be "<a href="/facts/Miscibility/HwQaolbQ">miscible</a> in all proportions" (or just "miscible").
The solute can be a <a href="/facts/Solid/hj5UsXno">solid</a>, a <a href="/facts/Liquid/t9GkLWzt">liquid</a>, or a <a href="/facts/Gas/hVVAoodV">gas</a>, while the solvent is usually solid or liquid. Both may be pure substances, or may themselves be solutions. Gases are always miscible in all proportions, except in very extreme situations, and a solid or liquid can be "dissolved" in a gas only by passing into the gaseous state first.
The solubility mainly depends on the composition of solute and solvent (including their <a href="/facts/PH/RnSv8D7y">pH</a> and the presence of other dissolved substances) as well as on temperature and pressure. The dependency can often be explained in terms of interactions between the particles (<a href="/facts/Atom/FoQ4kGN5">atoms</a>, <a href="/facts/Molecule/N9ljSfFq">molecules</a>, or <a href="/facts/Ion/3bePpDna">ions</a>) of the two substances, and of <a href="/facts/Thermodynamics/q4hIx3yP">thermodynamic</a> concepts such as <a href="/facts/Enthalpy/bBou8lCE">enthalpy</a> and <a href="/facts/Entropy/s52IXeFz">entropy</a>.
Under certain conditions, the concentration of the solute can exceed its usual solubility limit. The result is a <a href="/facts/Supersaturation/YaTN0D1L">supersaturated solution</a>, which is <a href="/facts/Metastability/H72SMWof">metastable</a> and will rapidly exclude the excess solute if a suitable <a href="/facts/Nucleation/efUVLsLR">nucleation</a> site appears.
The concept of solubility does not apply when there is an irreversible <a href="/facts/Chemical_reaction/GpqWlKrz">chemical reaction</a> between the two substances, such as the reaction of <a href="/facts/Calcium_hydroxide/Kz2KzRd8">calcium hydroxide</a> with <a href="/facts/Hydrochloric_acid/HqItJlUT">hydrochloric acid</a>; even though one might say, informally, that one "dissolved" the other. The solubility is also not the same as the <a href="/facts/Rate_of_solution/kLE9h3Jb">rate of solution</a>, which is how fast a solid solute dissolves in a liquid solvent. This property depends on many other variables, such as the physical form of the two substances and the manner and intensity of mixing.
The concept and measure of solubility are extremely important in many sciences besides chemistry, such as <a href="/facts/Geology/WGvVRIYF">geology</a>, <a href="/facts/Biology/1M1ee3pB">biology</a>, <a href="/facts/Physics/a7aH2y08">physics</a>, and <a href="/facts/Oceanography/LtrG6peD">oceanography</a>, as well as in <a href="/facts/Engineering/RFVg8H3I">engineering</a>, <a href="/facts/Medicine/2fnp90Je">medicine</a>, <a href="/facts/Agriculture/TGztqzJs">agriculture</a>, and even in non-technical activities like <a href="/facts/Painting/ygQ47K3b">painting</a>, <a href="/facts/Cleaning/DVzmMbl9">cleaning</a>, <a href="/facts/Cooking/YWVfGWD1">cooking</a>, and <a href="/facts/Brewing/aKCgJVyJ">brewing</a>. Most chemical reactions of scientific, industrial, or practical interest only happen after the <a href="/facts/Reagent/c3GLInCu">reagents</a> have been dissolved in a suitable solvent. <a href="/facts/Water/0lkXnJPK">Water</a> is by far the most common such solvent.
The term "soluble" is sometimes used for materials that can form <a href="/facts/Colloid/9EVucqND">colloidal suspensions</a> of very fine solid particles in a liquid. The quantitative solubility of such substances is generally not well-defined, however.

Solubility open-in-new

Solubility