Potassium bromide

Potassium bromide is an inorganic substance with the chemical formula KBr and a relative molecular weight of 119.00. Colorless crystals or white powder, with a strong salty taste, turning yellow when exposed to light. Slightly hygroscopic. 1g dissolved in 1.5ml of water, the aqueous solution is neutral. The relative density is 2.75 (25 ℃). Melting point 730 ℃. Boiling point 1435 ℃. It is stimulating. Mainly used for spectral analysis, droplet analysis to determine copper and silver, polarographic analysis of indium, cadmium, and arsenic, and as a developer.

Physical property

Molar mass: 119.01g/mol

Appearance: White powder

Density: 2.75g/cm3 (solid)

Melting point: 734 ℃ (1007K)

Boiling point: 1435 ℃ (1708K)

Solubility in water: 53.5g/100ml (0 ℃).

Colorless cubic crystals. Odorless, with a salty and slightly bitter taste. Easy to turn yellow when exposed to light, slightly hygroscopic. Soluble in water (with a solubility of 102g/100ml water at 100 ℃) and glycerol, slightly soluble in ethanol and ether. The aqueous solution is neutral. Its bromine ions can be replaced by fluorine and chlorine. Reacting with sulfuric acid can generate hydrogen bromide. React with silver nitrate to form yellow silver bromide precipitate.

Chemical reaction

Potassium bromide is a typical ionic compound that is completely ionized and neutral when dissolved in water. Commonly used to provide bromine ions - the following important reactions can generate silver bromide for photography:

KBr (aq)+AgNO3 (aq) → AgBr (s)+KNO3 (aq)

Bromine ion Br - in aqueous solution can form complexes with some metal halides, such as:

2 KBr (aq)+CuBr2 (aq) → K2 [CuBr4] (aq)

The traditional method is the iron bromine method: first, excess bromine is used to react with iron filings in water to generate hexahydrate octabromo triferric oxide (Fe3Br8 · 16H2O). Then, it reacts with boiling potassium carbonate solution, filters out the precipitate of ferric oxide, and concentrates and crystallizes to obtain:

4 K2CO3+Fe3Br8 → 8 KBr+Fe3O4+4 CO2 ↑

Application area

1. The photosensitive materials industry is used to manufacture photosensitive films, developing agents, film thickeners, toners, and color photo bleaching agents;

2. Used as a sedative in medicine (tribromide tablets);

3. In addition, it is also used for chemical analysis reagents, spectral and infrared transmission, making special soaps, as well as carving, lithography, and other aspects;

4. Also used as an analytical reagent.

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