Industrial grade Potassium bromide CAS 7758-02-3

What is Potassium bromide?

Potassium bromide (KBr) is an inorganic salt formed from bromine and potassium. It is one of the most widely used bromides in infrared spectroscopy and photosensitive materials. Its chemical formula is usually written as:

KBr (CAS No.: 7758-02-3, EINECS No.: 231-830-3, molecular weight approximately 119.00)

It is a colorless or white crystalline powder at room temperature, odorless, with a salty and slightly bitter taste. Its melting point is approximately 734℃, boiling point approximately 1435℃, and relative density approximately 2.75. It is extremely soluble in water (approximately 65.5 g/100 mL at 20℃) and slightly soluble in ethanol. Potassium bromide crystals are transparent from near-ultraviolet to long-wave infrared, and have almost no absorption in the mid-infrared region—this is the physical basis for its use as a standard material for infrared spectroscopy.

From a molecular structure perspective, potassium bromide is a typical ionic crystal, composed of potassium ions (K+) and bromide ions (Br-) bonded together by ionic bonds. The large radius and high polarizability of bromide ions give potassium bromide crystals excellent transmittance in the infrared region without absorbing infrared radiation. When a solid sample is mixed with potassium bromide powder and pressed into a pellet, infrared light is absorbed only by the sample and not interfered with by potassium bromide, resulting in a pure sample spectrum. This "optically transparent carrier" characteristic is the structural basis for the KBr pellet method becoming the standard method for preparing solid samples for infrared spectroscopy; while the photosensitivity of bromide ions makes it an important component of silver halide photographic emulsions.

Chemically, potassium bromide is readily soluble in water and hygroscopic, absorbing moisture from the air and deliquescing over long periods. It is stable and has low toxicity, but long-term, high-dose ingestion of bromides can lead to bromine poisoning. Spectrum-grade products must be stored in a dry, sealed, and light-protected environment.

Potassium bromide is classified into industrial grade, spectral grade, and reagent grade according to its application. The key indicators that are important for each grade are different:

Bromate content

Bromate is an oxidizing impurity that affects infrared transmittance and photosensitivity, and is a key quality indicator for both spectral and photosensitive products.

Water-insoluble matter

Low water-insoluble matter content is required to ensure clear solution and uniform tablet compression.

chloride

Chloride is a common process impurity. Excessive chloride content can affect optical and photosensitive properties and must be controlled within standard limits.

Iron and heavy metal limits

Iron and heavy metal impurities affect light transmittance and safety.

What are the uses of Potassium bromide?

Potassium bromide, with its properties of infrared transparency, photosensitivity, easy solubility, and physiological effects, has applications spanning optics, detection, photosensitive materials, and energy.

1. Infrared spectroscopy materials (core application )

Potassium bromide is a standard sample preparation material for Fourier transform infrared (FTIR) analysis. It is used to prepare solid samples by the KBr pellet method, and pure sample spectra are obtained due to its non-absorption characteristics in the mid-infrared region. High-purity potassium bromide crystals are also used as infrared windows, lenses and prisms, and are a basic material in the infrared optics industry.

2. Photosensitive materials (silver halide photography)

Potassium bromide is an important component of silver halide photosensitive emulsions and is used in the preparation of photosensitive films, photographic paper, developing agents, and negatives. It helps control the crystallization and photosensitivity of silver halides and is a basic raw material in the traditional photography industry.

3. Drilling and completion fluid (high-density brine)

Potassium bromide is used as a component of completion and workover fluids in oilfield drilling. It is also used to prepare high-density brine to help balance formation pressure and protect reservoirs. It is an important chemical raw material for oil and gas extraction.

4. Analytical chemical reagents (spectral grade)

Spectroscopically pure potassium bromide is a standard reagent for infrared spectroscopy analysis, and is also used as a reagent for ion analysis and the preparation of standard solutions. It is a basic material in analytical laboratories.

5. Optical crystals (windows, lenses, prisms)

Potassium bromide single crystals are used as windows, lenses, prisms, and beam splitters in infrared optical instruments, serving spectrometers, infrared thermometers, and laser systems due to their wide-band transmittance.

6. Standard Reagents and Quality Control Analysis

High-purity potassium bromide is used as a calibration material for infrared spectrometers and a standard reagent for ion analysis. It is used for method calibration and quality control and is a commonly used standard in quality control laboratories.

7. Other Applications

With the development of spectral analysis and optical technology, the application scope of potassium bromide continues to expand, including in areas such as lithographic inks, specialty soaps, catalysts, and water treatment.

It should be noted that although potassium bromide has low toxicity, industrial-grade products are strictly prohibited from being consumed, and long-term intake of large amounts of bromide carries the risk of bromine poisoning; potassium bromide is hygroscopic, and spectral-grade products must be stored in a dry, sealed, and light-proof manner to avoid moisture absorption that could affect optical performance.

Summarize

Potassium bromide (KBr, CAS No. 7758-02-3) is a white crystalline powder with a melting point of approximately 734°C. It is highly soluble in water, and the crystals are transparent in the near-ultraviolet to long-wave infrared region and have no absorption in the mid-infrared region. It is a standard material for infrared spectroscopy analysis and an important component of silver halide photosensitive emulsions and drilling completion fluids. In daily life, we indirectly come into contact with it through infrared detection and quality inspection, old photos and photography, oil and gas, optical instruments, and daily chemical products. Potassium bromide has applications covering infrared spectroscopy tablets and window materials, silver halide photosensitive emulsions, drilling completion fluids , spectral analysis reagents, optical crystals, and inks and soaps. It is an important bromide that connects "bromine chemistry" with "optics, detection, photosensitivity, and energy."