Calcium cyanide

• Cyancalcium
• Blue Acid Calcium
• Calcid
• Aero Brand cyanide
• Black Cyanide

White, hygroscopic, rhombohedral crystals

Fixed

1.853 g · cm -3

> 300 ° C ( decomposition)

Slightly soluble in water and ethanol

Risk

39 mg · kg -1 ( LD50, rat, oral)

-184.5 KJ / mol

Template: Infobox chemical / molecular formula search available

Calcium cyanide is a chemical compound from the group of cyanides.

Production and representation

Calcium cyanide can be produced by exothermic Azotierung of calcium carbide at 1000 ° C. The result here as an intermediate in the production of calcium cyanamide.

In aqueous solution, calcium cyanide is also produced by the reaction of hydrogen cyanide with calcium hydroxide:

Isolation of the solid is not possible due to the low stability of the solution.

Pure calcium cyanide can be obtained by reaction of calcium carbonate with hydrogen cyanide.

Properties

Calcium cyanide is a white, non-flammable solid which is readily soluble in water with decomposition. On exposure to moist air at temperatures above 300 ° C, the compound decomposed to hydrogen cyanide and nitrogen oxides. It has a hexagonal crystal structure (a = 3.67, c = 14.85 Å).

Due to the poor stability against humid air calcium cyanide is usually a mixture with 45 - 50 % sodium cyanide used as so-called Black Cyanide. This name is due to the staining by a contamination with 1-2 % carbon. Commercial solutions also with less than 17% calcium cyanide are available as highly concentrated solutions are very prone to hydrolysis.

Use

Calcium cyanide is used in the extraction of gold and silver from their ores. Worldwide it is exclusively produced in South Africa. It also serves as a rodenticide.