| Abstract from DBPedia | 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 solubility of a substance in a specific solvent is generally measured as the concentration 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 solubility equilibrium. For some solutes and solvents, there may be no such limit, in which case the two substances are said to be "miscible in all proportions" (or just "miscible"). The solute can be a solid, a liquid, or a gas, 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 pH 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 (atoms, molecules, or ions) of the two substances, and of thermodynamic concepts such as enthalpy and entropy. Under certain conditions, the concentration of the solute can exceed its usual solubility limit. The result is a supersaturated solution, which is metastable and will rapidly exclude the excess solute if a suitable nucleation site appears. The concept of solubility does not apply when there is an irreversible chemical reaction between the two substances, such as the reaction of calcium hydroxide with hydrochloric acid; even though one might say, informally, that one "dissolved" the other. The solubility is also not the same as the rate of solution, 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 geology, biology, physics, and oceanography, as well as in engineering, medicine, agriculture, and even in non-technical activities like painting, cleaning, cooking, and brewing. Most chemical reactions of scientific, industrial, or practical interest only happen after the reagents have been dissolved in a suitable solvent. Water is by far the most common such solvent. The term "soluble" is sometimes used for materials that can form colloidal suspensions of very fine solid particles in a liquid. The quantitative solubility of such substances is generally not well-defined, however.溶解度（ようかいど、solubility）とはある溶質が一定の量の溶媒に溶ける限界量をいう。飽和溶液の濃度である。通常、Sという記号で表される。 固体の溶解度は、一定温度で、溶媒100 gに溶ける溶質の質量[g]や、飽和溶液100 gに溶けている溶質の質量[g]などで表す。本来は無名数であるが、一般に[g/100g-溶媒の化学式]等の単位を付して表す。この場合、溶媒が水なら[g/100g-H2O]となる。溶解度は温度によって変化し、固体に関しては、例外もあるが、温度が上がると溶解度が上がるものが多い。 気体の溶解度は一定温度で、1 atm（1気圧）の気体が溶媒1 mlに溶ける体積を標準状態（STP）に換算して表す。この溶解度は温度によって変化する。 化学の金言として「似たものは似たものを溶かす」と言われる。これが意味するところは、極性分子は極性分子（水）に溶解し、非極性分子は非極性溶媒（例えば油）に溶解するという傾向のことである。このため溶媒同士でも水と油は溶けあわず分離し、水とエタノールではよく混和する。 (Source: http://dbpedia.org/resource/Solubility) |
