Antimony

Chemical reactions

Reaction of antimony with acids


Antimony is dissolved in hot concentrated sulphuric acid, H2SO4, or nitric acid, HNO3, forming Sb(III) solutions. The sulphuric acid reaction produces SO2. Antimony does not react with hydrochloric acid in the absence of oxygen.


Reaction of antimony with air


When heated, antimony reacts with oxygen in air forming Sb2O3. The flame is bluish white.

4 Sb(s) + 3 O2(g) 2 Sb2O3(s)


Reaction of antimony with halogens


Under controlled conditions, antimony will react with the F2, Cl2, Br2, and I2, forming the corresponding antimony(III)trihalides.

2 Sb(s) + 3 F2(g) 2 SbF3(s) [white]
2 Sb(s) + 3 Cl2(g) 2 SbCl3(s) [white]
2 Sb(s) + 3 Br2(g) 2 SbBr3(s) [white]
2 Sb(s) + 3 I2(g) 2 SbI3(s) [red]


Reaction of antimony with hydrogen peroxide


Sb(III) is oxidized to Sb(V) by hydrogen peroxide under alkaline conditions

[Sb(HO)4]−(aq) + H2O2(aq) [Sb(HO)6]−(aq)


Reaction of antimony with hydroxide ions


Sb(III) is precipitated by hydroxide ions

Sb3+(aq) + 3 OH−(aq) Sb(OH)3(s) [white]

The precipitate is amphoteric and is dissolved in excess hydroxide and strong hydrochloric acid

Sb(OH)3(s) + OH−(aq) [Sb(OH)4]−(aq)
Sb(OH)3(s) + H+(aq) SbO+(aq) + 2 H2O(l)
SbO+(aq) + 4 Cl−(aq) + 2 H+(aq) [SbCl4]−(aq) + H2O(l)


Reaction of antimony with metals/metal ions


Sb(III) is reduced by aluminum and iron

Sb3+(aq) + Al(s) Al3+(aq) + Sb(s)
2 Sb3+(aq) + 3 Fe(s) 3 Fe2+(aq) + 2 Sb(s)


Sb(V) is precipitated by sodium ions under alkaline conditions

[Sb(HO)6]−(aq) + Na+(aq) Na[Sb(HO)6](s)


Reaction of antimony with sulfide


Sb(III) is precipitated by hydrogen sulfide in 0.4M hydrochloric acid:

2 Sb3+(aq) + 2 S2−(aq) Sb2S3(s) [orange/red]

The precipitate can be dissolved in sodium hydroxide sodium sulfide and strong hydrochloric acid

Sb2S3(s) + 4 OH−(aq) [Sb(OH)4]−(aq) + [SbS3]3-(aq)
Sb2S3(s) + 3 S2−(aq) 2 [SbS3]3−(aq)
Sb2S3(s) + 8 Cl−(aq) + 6 H+(aq) 2 [SbCl4]-(aq) + 3 H2S(g)


Sb(V) is precipitated by hydrogen sulfide in 0.4 M hydrochloric acid:

2 [SbCl6]−(aq) + 5 H2S(aq) Sb2S5(s) [orange] + 12 Cl−(aq) + 10 H+(aq)

The precipitate can be dissolved by heat and strong hydrochloric acid and sodium hydroxide and -sulfide:

Sb2S5(s) + 8 Cl−(aq) + 6 H+(aq) 2 [SbCl4]−(aq) + 2 S(s) + 3 H2S(g)
4 Sb2S5(s) + 18 OH−(aq) 3 [Sb(OH)6]−(aq) + 5 [SbS4]3−(aq)
Sb2S5(s) + 3 S2−(aq) 2 [SbS4]3−(aq)


Reaction of antimony with water


At red hot, antimony reacts with water to form the trioxide antimony(III) oxide, Sb2O3.

2 Sb(s) + 3 H2O(g) Sb2O3(s) + 3 H2(g)


Sb(III) as the tetra chloro complex can react with water, forming the precipitate SbOCl

[SbCl4]−(aq) + H2O(l) SbOCl(s) [white] + 3 Cl−(aq) + 2 H+(aq)

The precipitate can be dissolved by alkali or complexing with tartaric acid

SbOCl(s) + 2 OH−(aq) + H2O(l) [Sb(OH)4]−(aq) + Cl−(aq)
2 SbOCl(s) + 2 C4H6O6(aq) [Sb2(C4H6O6)2]2−(aq) + 4 H+(aq) + 2 Cl−(aq) + 2 H2O(l)


Quantitative analysis


Method 3500-Sb C Inductively Coupled Plasma Method [6]. 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 = 0.03 mg/L
Method limit of detection in soil = 2.00 mg/kg