Cyanogen Bromide - Toxicity, Storage, and Deactivation

Toxicity, Storage, and Deactivation

Cyanogen bromide is moisture-sensitive but can be stored under dry conditions at 2 to 8 °C for extended periods of time.

Cyanogen bromide is volatile, and readily absorbed through the skin or gastrointestinal tract. Therefore, toxic exposure may occur by inhalation, physical contact, or ingestion. It is acutely toxic, causing a variety of nonspecific symptoms. Exposure to even small amounts may cause convulsions or death. LD₅₀ orally in rats is reported as 25–50 mg/kg.

To deactivate CNBr in a solution not exceeding 60 g/L of CNBr (dilute if necessary), the recommended method is to add 1 mol/L NaOH and 1 mol/L NaOCl in volumes of ratio 1:1:2 (CNBr solution:NaOH:NaOCl). The aqueous alkali hydroxide instantly hydrolyzes CNBr to alkali cyanide and bromide. The cyanide can then be oxidized by sodium or calcium hypochlorite to the less toxic cyanate ion. Note that deactivation is extremely exothermic and may be explosive.