Cadmium hydroxide

Crystal structure
	__ Cd 2+ __ OH -
General
Surname	Cadmium hydroxide
other names	Cadmium dihydroxide
Ratio formula	Cd (OH) 2
Brief description	white solid
External identifiers / databases
EC number	244-168-5
ECHA InfoCard	100.040.137
PubChem	10313210
ChemSpider	8488675
Wikidata	Q420717
properties
Molar mass	146.43 g · mol -1
Physical state	firmly
density	4.79 g cm −1
Melting point	300 ° C
solubility	almost insoluble in water
safety instructions
H and P phrases	H: 302-312-330-340-350-361fd-372-410
	P: 201-260-273-304 + 340 + 310-308 + 313-403 + 233-501
Authorization procedure under REACH	particularly worrying : carcinogenic, mutagenic ( CMR ), serious effects on human health are considered likely
MAK	repealed because it is carcinogenic
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Cadmium hydroxide is a chemical compound of cadmium from the group of hydroxides . It is a solid, white substance that decomposes at around 300 ° C.

Extraction and presentation

Cadmium hydroxide is formed by the reaction of bases with cadmium salt solutions and precipitation. Fine crystalline cadmium hydroxide can only be obtained by reacting cadmium nitrate solutions with sodium hydroxide .

{\ displaystyle \ mathrm {Cd (NO_ {3}) _ {2} +2 \ NaOH \ rightarrow Cd (OH) _ {2} +2 \ NaNO_ {3}}}

High concentrations of halide ions prevent the formation of cadmium hydroxide, as the [CdX ₄ ] ²⁻ ion (X = F, Cl, Br, I) is formed.

properties

Cadmium hydroxide crystallizes in the trigonal crystal system with the space group P 3 m 1 (space group no. 164) with the lattice parameters a = 349.9 pm and c = 470.1 pm as well as one formula unit per unit cell . The structure thus corresponds to the brucite structure and the polytype 2H of the cadmium iodide structure . Template: room group / 164

Cadmium hydroxide is more basic than zinc hydroxide and therefore only dissolves in strong bases. It is soluble in ammonia with the formation of hexaammine ions [Cd (NH ₃ ) ₆ ] ²⁺ .

use

Cadmium hydroxide is used as the anode material for discharged nickel-cadmium accumulators . In anode production, it is generated by the oxidation of metallic cadmium by hydrogen peroxide on the carrier material. It also arises during the discharge process of these accumulators, while charging it is reduced to cadmium.

It more often replaces cadmium oxide in the production of other cadmium compounds .

safety instructions

At the proposal of the Swedish Chemicals Agency, the chemical classification of cadmium hydroxide was revised in 2015. The Committee for Risk Assessment (RAC) of the European Chemicals Agency (ECHA) changed the classification for cadmium hydroxide as follows on December 4th: Cadmium hydroxide is classified as carcinogenic Carc 1B, mutagenic Muta 1B and STOT RE 1, the additional warnings have been set to H340, H350 and H372 (kidney, bone). This classification of the RAC has yet to be implemented by the EU Commission into applicable law, but with the publication it represents the state of knowledge that must be taken into account by companies and authorities.

Individual evidence

↑ ^a ^b ^c ^d ^e data sheet cadmium hydroxide from AlfaAesar, accessed on September 1, 2010 ( PDF )(JavaScript required) .
↑ ^a ^b Entry on cadmium hydroxide in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
↑ Entry on cadmium hydroxide in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on November 22, 2019. Manufacturers or distributors can expand the harmonized classification and labeling .
↑ Entry in the SVHC list of the European Chemicals Agency , accessed on January 19, 2018.
^ ^A ^b ^c Karl-Heinz Schulte-Schrepping, Magnus Piscator: Cadmium and Cadmium compounds . In: Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim 2002, doi : 10.1002 / 14356007.a04_499 .
↑ Jean D'Ans, Ellen Lax: Taschenbuch fur chemists and physicists: Volume 3: elements, inorganic compounds and materials, minerals. 3rd edition, Springer, 1997, ISBN 978-3-5406-0035-0 , p. 1374 ( limited preview in the Google book search).
^ Gerd Blumenthal, Dietmar Linke, Siegfried Vieth: Chemistry: Basic knowledge for engineers. Vieweg + Teubner Verlag, 2006, ISBN 978-3-5190-3551-0 , p. 356 ( limited preview in the Google book search).
^ Karl-Heinz Lautenschläger, Werner Schröter: Taschenbuch der Chemie. 20th edition, Harri Deutsch Verlag, 2007, ISBN 978-3-8171-1761-1 , p. 379 ( limited preview in Google book search).
↑ RAC decision of December 4, 2015

[alfa-1] ↑ ^a ^b ^c ^d ^e data sheet cadmium hydroxide from AlfaAesar, accessed on September 1, 2010 ( PDF )(JavaScript required) .

[GESTIS-2] Entry on cadmium hydroxide in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .

[CLP_100.040.137-3] Entry on cadmium hydroxide in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on November 22, 2019. Manufacturers or distributors can expand the harmonized classification and labeling .

[SVHC-4] Entry in the SVHC list of the European Chemicals Agency , accessed on January 19, 2018.

[ullmann-5] A ^b ^c Karl-Heinz Schulte-Schrepping, Magnus Piscator: Cadmium and Cadmium compounds . In: Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim 2002, doi : 10.1002 / 14356007.a04_499 .

[6] Jean D'Ans, Ellen Lax: Taschenbuch fur chemists and physicists: Volume 3: elements, inorganic compounds and materials, minerals. 3rd edition, Springer, 1997, ISBN 978-3-5406-0035-0 , p. 1374 ( limited preview in the Google book search).

[7] Gerd Blumenthal, Dietmar Linke, Siegfried Vieth: Chemistry: Basic knowledge for engineers. Vieweg + Teubner Verlag, 2006, ISBN 978-3-5190-3551-0 , p. 356 ( limited preview in the Google book search).

[8] Karl-Heinz Lautenschläger, Werner Schröter: Taschenbuch der Chemie. 20th edition, Harri Deutsch Verlag, 2007, ISBN 978-3-8171-1761-1 , p. 379 ( limited preview in Google book search).

[9] RAC decision of December 4, 2015