Physical world and mathematics

Posterior probability

A posterior probability, also called the posterior distribution, is the probability assigned to a hypothesis after data are observed, produced by combining a prior with the likelihood through Bayes' theorem.

Sep 29, 2026

Posterior sampling

Posterior sampling is the task of drawing representative samples from a Bayesian posterior distribution, usually by Markov chain Monte Carlo, to estimate moments and intervals.

Postsynthetic exchange

Postsynthetic exchange is a chemistry strategy in which building blocks of an already-formed porous solid, usually a metal–organic framework, are swapped while the lattice is preserved.

Postsynthetic metal exchange in MOFs

Postsynthetic metal exchange is a MOF modification in which metal ions forming the framework's nodes are replaced after synthesis by soaking in another metal salt solution.

Postsynthetic modification

Postsynthetic modification (PSM) is the chemical alteration of a porous framework, such as a metal–organic framework, after it has been assembled, enabling gas sorption, catalysis, and drug delivery.

Potash

Potash, also called pearl ash, is the common name for water-soluble potassium salts mined as fertilizer, one of the three primary plant nutrients alongside nitrogen and phosphorus.

Potassium

Potassium, symbol K, is a soft, silvery alkali metal isolated by Humphry Davy in 1807; about 94% of its chloride is used in fertilizer, and it is vital to human physiology.

Potassium alum

Potassium alum, also known as potash alum or potassium aluminum sulfate, is a double sulfate of potassium and aluminum that forms large octahedral crystals and purifies water.

Potassium amyl xanthate

Potassium amyl xanthate (PAX) is the potassium salt of O-pentyl dithiocarbonic acid, a strong, unselective froth flotation collector for copper, nickel, zinc, and gold sulfide ores.

Potassium bicarbonate

Potassium bicarbonate (KHCO₃), also called potassium hydrogen carbonate, is a white crystalline, slightly alkaline salt used as a food ingredient, antacid, fungicide for powdery mildew, and fire-extinguishing agent.

Oct 21, 2026

Potassium bisulfate

Potassium bisulfate (KHSO4, potassium hydrogen sulfate), an acid salt used as a pH control, leavening, and processing agent; GRAS Notice 60 (Jones-Hamilton, 2000) covered cake mixes at 0.1-1.0%. Distinct from potassium bisulfite.

Potassium bitartrate

Potassium bitartrate, also called cream of tartar or potassium hydrogen tartrate, is the potassium acid salt of tartaric acid, a byproduct of wine manufacture used in baking powder.

Potassium bromate

Potassium bromate (E 924) is the potassium salt of bromic acid, used as a dough conditioner in bread-making and classified by IARC as possibly carcinogenic.

Potassium bromide

Potassium bromide (KBr) is a white crystalline ionic salt, best known as the raw material for photographic silver bromide emulsions and as a long-standing antiseizure drug.

Potassium carbonate

Potassium carbonate (K2CO3), also known as salt of tartar or pearlash, is a white, hygroscopic inorganic salt that forms strongly alkaline solutions and has long been used in glassmaking and baking.

Oct 21, 2026

Potassium Channels

Potassium channels: tetrameric, potassium-selective membrane pores in four families (Kv, KCa, Kir, K2P) with a conserved TVGYG selectivity filter; they set resting potential, shape cardiac and neuronal action potentials, and underlie channelopathies.

Potassium chlorate

Potassium chlorate (KClO3), or chlorate of potash, is a white crystalline salt used as a strong oxidizing agent in matches, fireworks, explosives, and oxygen candles.

Potassium chloride

Potassium chloride (KCl), sold in agriculture as muriate of potash, is an ionic salt used as the dominant potassium fertilizer, a low-sodium table-salt substitute, and a medication for potassium deficiency.

Potassium chromate

Potassium chromate, also called dipotassium chromate, is a yellow, water-soluble inorganic salt of chromic acid used as a strong oxidizing agent and analytical reagent, notably as an indicator for chloride ions.

Potassium cyanide

Potassium cyanide (KCN) is a highly toxic white crystalline inorganic salt that releases hydrogen cyanide gas and is rapidly fatal, used in gold mining, electroplating, and fumigation.

Potassium dichromate

Potassium dichromate (K₂Cr₂O₇), also known as kali bichromicum, is an inorganic chromium salt forming orange-red crystals, used as a strong oxidizing agent and primary analytical standard, and restricted in the EU as carcinogenic.

Potassium ferricyanide

Potassium ferricyanide, also known as red prussiate, is a red crystalline salt with formula K3[Fe(CN)6], used in cyanotype blueprint photography, Prussian blue pigment, and electroplating.

Potassium ferrocyanide

Potassium ferrocyanide, also known as yellow prussiate of potash, is a lemon-yellow potassium salt used as the food additive E 536 and for making Prussian blue pigment.

Potassium fluoride

Potassium fluoride (KF) is an inorganic salt of potassium and fluoride, a white toxic powder used in insecticides, solder flux, and glass etching, and as a base catalyst in organic synthesis.

Potassium hydrogen phthalate

Potassium hydrogen phthalate, also known as potassium biphthalate or KHP, is the monopotassium salt of phthalic acid, used as a primary standard for acid–base titrations and pH calibration.

Potassium hydroxide

Potassium hydroxide, also known as caustic potash or potassium lye, is a strongly alkaline inorganic compound used to make soaps, fertilizers, potassium carbonate, and alkaline battery electrolytes.

Potassium iodide

Potassium iodide (KI), the potassium salt of iodide, is a stable-iodine thyroid blocking agent used in nuclear emergencies to block radioactive iodine uptake, plus table salt iodization and goiter treatment; not a general radiation antidote.

Potassium iron selenide

Potassium iron selenide (KxFe2−ySe2) is an iron-based superconductor formed by intercalating potassium between FeSe layers, discovered by the end of 2010 with a transition temperature above 30 K.

Potassium nitrate

Potassium nitrate (KNO₃), historically known as saltpeter or nitre, is a colorless crystalline salt used as a fertilizer, meat-curing agent, toothpaste ingredient, and the oxidizer in black powder.