Calcium cyanide

Structural formula
${\displaystyle \mathrm {\ {\Biggl [}} }$ ${\displaystyle \mathrm {\ \!\ {\Biggr ]}_{2}} }$
General
Surname	Calcium cyanide
other names	Cyan calcium Hydrocyanic calcium Calcid Aero-fire cyanide Black cyanide
Molecular formula	Ca (CN) 2
Brief description	white, hygroscopic, rhombohedral crystals
External identifiers / databases
CAS number 592-01-8 EC number 209-740-0 ECHA InfoCard 100,008,856 PubChem 11590 Wikidata Q420491
properties
Molar mass	92.11 g mol −1
Physical state	firmly
density	1.853 g cm −3
Melting point	> 300 ° C (decomposition)
solubility	Easily soluble in water and ethanol
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 300-410 EUH: 032 P: ?
Toxicological data	39 mg kg −1 ( LD 50 ,  rat ,  oral )
Thermodynamic properties
ΔH f 0	−184.5 kJ / mol
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

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

Extraction and presentation

Calcium cyanide can be produced by exothermic azotization of calcium carbide at 1000 ° C. It is created as an intermediate product in the manufacture of calcium cyanamide .

${\displaystyle \mathrm {CaC_{2}+N_{2}\longrightarrow \ Ca(CN)_{2}} }$

Calcium cyanide in aqueous solution is also prepared by reacting prussic acid with calcium hydroxide prepared:

${\displaystyle \mathrm {Ca(OH)_{2}+2\ HCN\longrightarrow \ Ca(CN)_{2}+2\ H_{2}O} }$

Isolation of the solid from the solution is not possible due to its poor stability.

properties

Calcium cyanide is a white, non-flammable solid that is easily soluble in water when it decomposes. When exposed to moist air and at temperatures above 300 ° C, the compound decomposes, producing hydrogen cyanide and nitrogen oxides .

Due to its poor stability against moist air, calcium cyanide is usually used as a mixture with 45-50% sodium cyanide as so-called black cyanide . This name can be traced back to the coloring due to contamination with approx. 1–2% carbon . Solutions with less than 17% calcium cyanide are also commercially available, since more highly concentrated solutions have a strong tendency to hydrolysis .

use

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

Individual evidence

1. ↑ ^{a b c d e f g} Entry for CAS no. 592-01-8 in the GESTIS substance database of the IFA , accessed on November 30, 2011(JavaScript required) .
2. ↑ ^{a b} David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. CRC Press, 2009, ISBN 978-1-4200-9084-0 .
3. ↑ Entry on Calcium cyanide in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
4. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-20.
5. ↑ ^{a b} entry on calcium cyanamide. In: Römpp Online . Georg Thieme Verlag, accessed on November 11, 2014.
6. ↑ ^{a b c} Gail, E., Gos, S., Kulzer, R., Lorösch, J., Rubo, A., Sauer, M., Kellens, R., Reddy, J., Steier, N. and Hasenpusch , W: Cyano Compounds, Inorganic . In: Ullmann's Encyclopedia of Industrial Chemistry . October 2011. doi : 10.1002 / 14356007.a08_159 .
7. ^ Use of Cyanide in the Gold Industry . International Cyanide Management Institute . Retrieved July 30, 2011.
8. ↑ Pradyot Patnaik: A Comprehensive Guide to the Hazardous Properties of Chemical Substances . Wiley, 2008, ISBN 978-0-470-13494-8 ( page 325 in the Google book search).