Copper (II) hydroxide

Crystal structure
__ Cu 2+      __ O 2−      __ H +
General
Surname	Copper (II) hydroxide
other names	Copper hydroxide Copper dihydroxide Blue copper Hydrate of copper oxide
Ratio formula	Cu (OH) 2
Brief description	odorless light blue powder
External identifiers / databases
CAS number 20427-59-2 EC number 243-815-9 ECHA InfoCard 100,039,817 PubChem 164826 Wikidata Q186357
properties
Molar mass	97.56 g mol −1
Physical state	firmly
density	3.37 g cm −3
Melting point	229 ° C (decomposition)
solubility	almost insoluble in water (2.9 mg l −1 )
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 302-330-318-410 P: 260-273-280-284-305 + 351 + 338-310
MAK	0.1 mg m −3
Toxicological data	1000 mg kg −1 ( LD 50 ,  rat ,  oral ) > 3160 mg kg −1 ( LD 50 ,  rabbit ,  transdermal )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Copper (II) hydroxide is a hydroxide - salt of copper . It is a blue solid that, alone or in combination, forms the color pigment Bremer Blau (also called lime blue ).

Occurrence

Of course, copper (II) hydroxide occurs as part of the green patina of copper, which consists of basic copper carbonate . A rare pure copper (II) hydroxide mineral is spertiniite .

${\displaystyle \mathrm {2\ Cu+H_{2}O+CO_{2}+O_{2}\longrightarrow Cu(OH)_{2}+CuCO_{3}} }$

Extraction and presentation

Copper hydroxide can be produced by reacting copper salts with alkaline solutions . Typically, copper sulfate pentahydrate is dissolved in water and converted to copper hydroxide and sodium sulfate by adding sodium hydroxide while cooling .

${\displaystyle \mathrm {CuSO_{4}+2\ NaOH\longrightarrow Cu(OH)_{2}+Na_{2}SO_{4}} }$

Alternatively, copper hydroxide can also be produced by the electrochemical conversion of copper into water.

properties

Copper (II) hydroxide

technical copper (II) hydroxide with a light green color

Copper (II) hydroxide is insoluble in cold water. The compound is soluble in concentrated alkaline solutions. Hydroxo complexes such as the deep blue [Cu (OH) ₄ ] ^{2− are formed} . Freshly precipitated copper (II) hydroxide is also soluble in ammonia solution with the formation of the complex compound tetraammine copper (II) hydroxide. The reaction with mineral acids leads to the corresponding copper (II) salts.

${\displaystyle \mathrm {Cu(OH)_{2}+2\ HCl\longrightarrow CuCl_{2}+2\ H_{2}O} }$

${\displaystyle \mathrm {Cu(OH)_{2}+2\ HNO_{3}\longrightarrow Cu(NO_{3})_{2}+2\ H_{2}O} }$

${\displaystyle \mathrm {Cu(OH)_{2}+H_{2}SO_{4}\longrightarrow CuSO_{4}+2\ H_{2}O} }$

When heated, (freshly precipitated) copper (II) hydroxide breaks down into copper (II) oxide and water .

${\displaystyle \mathrm {Cu(OH)_{2}\longrightarrow CuO+H_{2}O} }$

With careful drying (100 ° C.), almost anhydrous copper (II) hydroxide is obtained in crystallized form.

use

Copper (II) hydroxide is used as

• Pesticides ( fungicide with special approval in organic fruit, wine, hops, vegetable and banana cultivation)
• for the production of pigments (e.g. Peligot blue , which is lightfast in artificial light)
• for the preparation of the ammoniacal solution known as Schweizer's reagent , which is used as a reagent and for dissolving rayon .
• for the production of copper silk
• for the production of mordants , ship floor paints, catalysts

Admission

Copper (II) hydroxide is approved as a pesticide (trade names Cuprozin , Kocide etc.) in pesticides in many EU countries, including Germany and Austria, as well as Switzerland.

See also

• Fehling's sample (without the addition of potassium sodium tartrate , copper hydroxide would precipitate)
• Copper (I) hydroxide , CuOH

literature

• Georg Brauer: Handbook of preparative inorganic chemistry. ISBN 3-432-26081-4 .
• Pradyot Patnaik: Handbook of Inorganic Chemicals . McGraw-Hill, New York 2002, ISBN 0-07-049439-8 (English)

Individual evidence

1. ↑ ^{a b c d e f g h i j} Entry on copper (II) hydroxide in the GESTIS substance database of the IFA , accessed on December 30, 2019(JavaScript required) .
2. ↑ Entry on Copper dihydroxide in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on December 30, 2019. Manufacturers or distributors can expand the harmonized classification and labeling .
3. ↑ uni-bayreuth.de: The color of complex compounds using the example of copper salts , accessed on June 17, 2017.
4. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , p. 1335.
5. ↑ Remy: Textbook of Inorganic Chemistry Volume II. 10th Edition. Akademische Verlagsgesellschaft, Leipzig 1961, p. 455.
6. ↑ The Copper Silk Process - Chemical Basics ( Memento from April 20, 2009 in the Internet Archive )
7. ↑ General Directorate Health and Food Safety of the European Commission: Entry on Copper hydroxide in the EU pesticide database; Entry in the national registers of plant protection products in Switzerland , Austria and Germany ; accessed on March 13, 2016.