Potassium Iodide

Technical Specifications

Product Description & Scientific Applications

Potassium iodide (KI) is the most commonly used soluble inorganic iodide, an ionic K+I− solid in the rock-salt structure, supplied as colourless to white crystals that are highly soluble in water (~144 g per 100 g at 20 °C), soluble in lower alcohols, and only partially soluble in acetone. Its chemistry is governed by the iodide ion — the largest, softest and most polarisable common halide — which acts as a soft, highly polarisable nucleophile and iodide-transfer reagent in SN2 halide exchange, a mild reducing agent, and a precursor to iodine/triiodide redox systems.

Applications in synthesis

• Finkelstein halide exchange: conversion of suitable primary alkyl chlorides and bromides into the corresponding alkyl iodides by SN2 displacement; in acetone, precipitation of KCl or KBr can drive the exchange toward the alkyl iodide. The aromatic variant is a distinct copper-catalysed process.
• Aryl iodides from arenediazonium salts: treatment of an arenediazonium salt with iodide gives the aryl iodide directly, without the copper catalyst required for the chloride and bromide Sandmeyer reactions.
• Metal-iodide and iodometalate synthesis: precipitation of insoluble metal iodides, including silver(I) iodide from silver nitrate, and preparation of iodide-rich complexes of soft metal cations.
• Reductant and iodine/triiodide source: iodide is oxidised to iodine by suitable oxidants and forms triiodide (I3−) in the presence of iodine.

Beyond synthesis

• Redox titrimetry: the standard iodide source in iodometric titration — excess iodide reacts with an oxidant to liberate iodine/triiodide, which is titrated against standard sodium thiosulfate — underpinning assays for peroxides, hypochlorite and copper(II), dissolved oxygen by the Winkler method, and starch-iodide indicator papers.
• Dye-sensitised solar cell electrolyte: with iodine, KI supplies the iodide/triiodide (I−/I3−) redox electrolyte used in DSSC and gel-polymer-electrolyte studies.
• Perovskite passivation additive: a potassium-halide additive used in lead-halide perovskite film research to modify surfaces and grain boundaries, reduce non-radiative losses, and suppress photoinduced ion migration.

Shipping Destinations

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• Worldwide: 7–14 business days, selected locations.