Chemical reactions

Reaction of nickel with acids

Nickel metal dissolves slowly in dilute sulphuric acid to form the aquated Ni(II) ion and hydrogen, H2. In aqueous solution, Ni(II) is present as the complex ion [Ni(H2O)6]2+.

Ni(s) + H2SO4(aq) Ni2+(aq) + SO42−(aq) + H2(g)

The strongly oxidizing concentrated nitric acid, HNO3, reacts on the surface of iron and passivates the surface.

Reaction of nickel with air

Nickel does not react with oxygen, O2 at room temperature, under normal conditions. Finely divided nickel can burn, forming nickel(II) oxide, NiO.

2 Ni(s) + O2(g) 2 NiO(s)

Reaction of nickel with ammonia

Nickel(II)-ions are precipitated by ammonia as a green gelatinous precipitate of nickel(II)hydroxide which dissolves forming a deep blue hexaaminenickel(II) hydroxide at excess ammonia [4]

Ni2+(aq) + 2 OH(aq) 2 Ni(OH)2(s) [light green]
Ni(OH)2(s) + 6 NH3(aq) [Ni(NH3)6]2+(aq) + 2 OH(aq) [deep blue]

Reaction of nickel with dimethylglyoxim

Nickel(II) ions are precipitated by dimethylglyoxime under slightly alkaline conditions as a raspberry colored complex.

Reaction of nickel with halogens

Nickel reacts slowly with halogens, forming the corresponding dihalides.

Ni(s) + Cl2(g) NiCl2(s) [yellow]
Ni(s) + Br2(g) NiBr2(s) [yellow]
Ni(s) + I2(g) NiI2(s) [black]

Nickel(II) can be oxidized to nickel(III) using Br2 under alkaline conditions

2 Ni(OH)2(s) + Br2(aq) + 2 OH(aq) 2 Ni(OH)3(s) + 2 Br(aq)

Reaction of nickel with hydroxide ions

Metallic nickel does not react with aqueous sodium hydroxide [4].

Nickel(II)-ions are precipitated by hydroxide ions forming a green gelatinous precipitate [4]

Ni2+(aq) + 2 OH(aq) 2 Ni(OH)2(s) [light green]

Reaction of nickel with sulfide

Nickel(II)-ions are precipitated by sulfide either using H2S and acetic acid (HCl can't be used) or Na2S under neutral to alkaline conditions forming the black NiS

Ni2+(aq) + S2−(aq) NiS(s) [black]

Reaction of nickel with water

Nickel metal does not react with water under normal conditions.

Nickel(II) ions complexes with water under acidic and neutral conditions forming a light green hexaqua nickel ion [4].

Quantitative analysis

Method 3500-Ni C Inductively Coupled Plasma Method [2]. A portion of the sample is digested in a combination of acids. The digest is aspirated into an 8,000 K argon plasma where resulting light emission is quantified for 30 elements simultaneously.

Method limit of detection in water = 0.005 mg/L
Method limit of detection in soil = 1.00 mg/kg