Nickel (II) hydroxide

Crystal structure
__ Ni 2+      __ OH -
General
Surname	Nickel (II) hydroxide
other names	Nickel dihydroxide
Ratio formula	Ni (OH) 2
Brief description	apple green powder
External identifiers / databases
CAS number 12054-48-7 EC number 235-008-5 ECHA InfoCard 100,031,813 PubChem 61534 ChemSpider 55452 Wikidata Q414637
properties
Molar mass	92.71 g mol −1
Physical state	firmly
density	4.1 g cm −3
Melting point	230 ° C (decomposes to nickel (II) oxide)
solubility	practically insoluble in water (0.13 g l −1 at 20 ° C)
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 302-332-315-317-334-341-350i-360D-372-410 P: 201-261-273-280-308 + 313-501
Toxicological data	1515 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Nickel (II) hydroxide is a chemical compound of the metal nickel that belongs to the group of hydroxides .

Occurrence

Of course, nickel (II) hydroxide occurs in the form of the very rare mineral theophrastite .

Extraction and presentation

Precipitation of nickel (II) hydroxide from a nickel (II) sulfate solution

Nickel (II) hydroxide is formed when nickel ions are detected from nickel salt solutions with sodium hydroxide solution as a precipitate with a clear green color:

${\displaystyle \mathrm {Ni^{2+}+2\ NaOH\longrightarrow Ni(OH)_{2}\downarrow +2\ Na^{+}} }$

Nickel (II) ions from nickel salt solutions (such as nickel (II) chloride dissolved in water ) react with caustic soda to form green, water-insoluble nickel (II) hydroxide and sodium ions.

If there is an excess of ammonia , the nickel (II) hydroxide dissolves again as a hexaammine complex , turning blue :

${\displaystyle \mathrm {Ni(OH)_{2}+6\ NH_{3}\longrightarrow [Ni(NH_{3})_{6}]^{2+}+2\ OH^{-}} }$

Nickel (II) ions react with excess ammonia to form blue, water-soluble hexaammine nickel (II) ions and hydroxide ions.

Chemical properties

By adding strong oxidizing agents such as chlorine or bromine , but not with hydrogen peroxide , nickel (II) hydroxide is converted into black nickel (IV) oxide :

${\displaystyle \mathrm {Ni(OH)_{2}+Br_{2}\longrightarrow NiO_{2}\downarrow +2\ HBr} }$

Green nickel (II) hydroxide reacts with bromine to form black, water-insoluble nickel (IV) oxide and hydrogen bromide .

Electrolytic oxidation turns nickel (II) hydroxide into nickel (III) oxide or nickel (III) oxide hydroxide. This reversible process is important for the nickel-cadmium accumulator and the nickel-iron accumulator .

${\displaystyle \mathrm {2\ Ni(OH)_{2}+2\ OH^{-}\rightleftarrows 2\ NiO(OH)+2\ H_{2}O+2\ e^{-}} }$

With 3Ni (OH) ₂ 2H ₂ O there is also a green hydrate that is stable in the dry state.

use

Nickel (II) hydroxide is used for electroplating, as the main component for plates of alkaline accumulators (see nickel-iron accumulator , nickel-cadmium accumulator , nickel-hydrogen accumulator and nickel-metal hydride accumulator ) and for the production of nickel catalysts.

safety instructions

Like many nickel compounds, nickel (II) hydroxide is classified as carcinogenic (Category 1A), toxic to reproduction (Category 1B) and germ cell mutagenic (Category 2). In addition, nickel (II) hydroxide has a sensitizing effect.

Individual evidence

1. ↑ ^{a b c d e f} Entry on nickel (II) hydroxide in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
2. ↑ Entry on nickel dihydroxide 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 .
3. ↑ Data sheet nickel (II) hydroxide (PDF) from Fisher Scientific , accessed on February 13, 2014.
4. ^ Mineralienatlas.de: Theophrastit
5. ↑ Georg Brauer (ed.) U. a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume III, Ferdinand Enke, Stuttgart 1981, ISBN 3-432-87823-0 , p. 1691.
6. ↑ Swiss Confederation: Products of the chemical industry or related industries ( Memento of the original of February 6, 2012 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.