Zirconium(IV) hydroxide

Zirconium(IV) hydroxide

Identifiers
CAS Number	14475-63-9 Y
ChemSpider	76194 Y
Jmol 3D model	Interactive image
PubChem	84465
InChI InChI=1S/4H2O.Zr/h4*1H2;/q;;;;+4/p-4 Y Key: HAIMOVORXAUUQK-UHFFFAOYSA-J Y InChI=1/4H2O.Zr/h4*1H2;/q;;;;+4/p-4 Key: HAIMOVORXAUUQK-XBHQNQODAM
SMILES [Zr+4].[OH-].[OH-].[OH-].[OH-]
Properties
Chemical formula	Zr(OH)4
Molar mass	159.253 g/mol
Appearance	white filter cake
Density	3.25 g/cm3, solid
Melting point	550 °C (1,022 °F; 823 K) decomposes
Solubility in water	0.02 g/100 mL (20 °C)
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Zirconium (IV) hydroxide is often called hydrous zirconia. It has an indeterminate chemical formula often described as ZrO₂.nH₂O. The formula ZrO₂.2H₂O being written as Zr(OH)₄ gives rise to its description as a hydroxide. The compound is a toxic, amorphous white powder which is insoluble in water, but is soluble in dilute mineral acids.

Uses

It is primarily used as in intermediate for the manufacture of zirconium compounds. It is also used in pigments, glass and dyes.

Preparation

Zirconium nitrate is prepared by reacting nitric acid with zirconium oxide:

ZrO₂ + 4HNO₃ → Zr(NO₃)₄ + 2H₂O

The compound is crystallized as pentahydrate following evaporation to dryness.

Upon remembering the intended goal is not zirconium nitrate, but actually zirconium (IV) hydroxide, the wayward preparation may be salvaged as follows: begin by undoing the just-completed dehydration, reconstituting aqueous zirconium nitrate. Now the addition of ammonium hydroxide will cause precipitation of Zirconium (IV) hydroxide, which may be filtered and washed.

If zirconium oxide is not conveniently at hand, (making the meandering reaction path above low in utility) Zirconium (IV) hydroxide can be made from the commercially available mineral, zircon sand (zirconium silicate: ZrSiO₄).

Zirconium silicate with an excess of sodium hydroxide is heated to around 650 C and held for several hours, yielding sodium silicate and sodium zirconate. Adding water hydrolyzes sodium zirconate to precipitate Zirconium (IV) hydroxide which may be filtered and then further washed with water to remove the sodium hydroxide and sodium silicate.