Green hexagonal crystal; density 4.10 g/cm3; decomposes to NiO on heating at 230°C; insoluble in water; KSP 5.47x10-16; monohydrate is insoluble in water but soluble in dilute acids and ammonia.
Nickel hydroxide is prepared by various methods, mostly involving reaction of caustic soda or caustic potash with a soluble nickel salt. Thus, treating nickel sulfate solution with sodium hydroxide forms a voluminous green gel. The gel crystallizes on prolonged storage. Alternatively, the solution on neutralization forms a fine precipitate of nickel hydroxide. Nickel nitrate also is used as starting material to prepare nickel hydroxide. Its aqueous solution, on treatment with sodium or potassium hydroxide, yields a gelatinous precipitate of nickel hydroxide which may be extracted with hot alcohol to form high purity product.
Nickel hydroxide in high purity is prepared by an electrolytic process using metallic nickel as the anode and nickel nitrate solution as the electrolyte. Nickel hydroxide is electrodeposited at an inert cathode.
Nickel hydroxide is a light, apple-green powder.
Nickel hydroxide was used as a reference material in a study where the influence of stacking faults on the electrochemical activity of Ni(OH)2 electrodes was studied.
Due to its redox behavior, it finds use in rechargeable battery electrodes. It is useful for the storage of electrochemical energy, with potential applications in car batteries. It is a potential material for several biological applications, for example in chromosomal DNA quantification assay.
This is precipitated as finely divided green powder when an alkali
metal hydroxide solution is added to an aqueous solution of a nickel(II) salt. It is frequently
difficult to filter at first but becomes more crystalline upon prolonged standing. If the nickel
salt is incompletely precipitated, especially if very strong solutions of nickel(II) are used, then the precipitate may be a basic salt. This is particularly true of the halides, in which case
compounds such as NiCl2?3Ni(OH)2 and NiCl2?Ni(OH)2 have been characterized.
Nickel hydroxide is obtained either by treating nickel sulfate
solution with sodium hydroxide or by hot alcohol extraction
of the precipitate formed as a result of the reaction of nickel
nitrate with potassium hydroxide. Nickel hydroxide is
used for the manufacture of nickel–cadmium electric
cells, and as an intermediate product during the manufacture
of nickel catalysts.
Flammability and Explosibility
Non flammable
Confirmed carcinogen
with experimental carcinogenic and
tumorigenic data. Poison by subcutaneous
route. See also NICKEL COMPOUNDS.
It may be found in the workplace as a
dust, liquid, or acid solution. This compound may be used
in nickel plating operations.
UN3077 Environmentally hazardous substances,
solid, n.o.s., Hazard Class: 9; Labels: 9-Miscellaneous hazardous
material, Technical Name Required.
Incompatible with strong acids. Aqueous
solution may be acidic.
Recover and recycle where
possible or dispose of in a chemical waste landfill.
