Tin

Under normal conditions tin does not react with air. When heated, tin reacts with oxygen, O₂, forming tin dioxide, SnO₂.

Sn(s) + O₂(g) SnO₂(s)

Tin reacts with Cl₂ forming tin(IV)chloride [6].

Sn(s) + 2 Cl₂(g) SnCl₄(s)

Sn(II) is precipitated by hydroxide ions as a white gelatinous precipitate [6]:

Sn²⁺(aq) + 2 OH⁻(aq) Sn(OH)₂(s) [white]

The precipitate is dissolved in excess alkali [6]:

Sn(OH)₂(s) + 2 OH⁻(aq) [Sn(OH)₄]²⁻(aq)

Sn(II) is oxidized by Hg₂²⁺. This reaction is used for qualitative analysis for Sn(II):

Hg₂²⁺(aq) + Sn²⁺(aq) 2 Hg(l) + Sn⁴⁺(aq)

Under acidic conditions and in the presence of chloride ions, Hg(II) is reduced to Hg(I) by Sn(II), forming Hg₂Cl₂:

Hg²⁺(aq) + Sn²⁺(aq) + 2 Cl⁻(aq) Hg₂Cl₂(s) + Sn⁴⁺(aq)

In excess Sn(IV), Hg(I) is reduced to Hg:

Hg₂Cl₂(s) + Sn²⁺(aq) 2 Hg(l) + Sn⁴⁺(aq) + 2 Cl⁻(aq)


Sn(IV) is reduced by Fe to Sn(II) in HCl(aq)

[SnCl₆]²⁻(aq) + Fe(s) [SnCl₃]⁻(aq) + Fe²⁺(aq) + 3 Cl⁻(aq)


Manganese with oxidation steps >2 will be reduced to Mn(II) by Sn(II) under acidic conditions under the formation of Sn(IV), e.g.

MnO₂(s) + Sn²⁺(aq) + 4 H⁺(aq) Mn²⁺(aq) + Sn⁴⁺(aq) + 2 H₂O(l)

Sn(II) is easily oxidized to Sn(IV) by hydrogen peroxide under acidic conditions

[SnCl₃]⁻(aq) + H₂O₂(aq) + 2 H⁺(aq) [SnCl₆]²⁻(aq) + 2 H₂O(l)

Sn(II) is precipitated by hydrogensulfide in 0.4M HCl(aq):

Sn²⁺(aq) + H₂S(aq) SnS(s) [brown/black] + 2 H⁺(aq)

In strong acid, the precipitate is dissolved:

SnS(s) + 2 H⁺(aq) + 3 Cl⁻(aq) [SnCl₃]⁻(aq) + H₂S(g)

The precipitate is also dissolved in Na₂S₂ but not in Na₂S:

SnS(s) + S₂²⁻(aq) [SnS₃]²⁻(aq)


Sn(IV) is precipitated by hydrogensulfide in moderately acidic solutions [6]:

[SnCl₆]²⁻(aq) + H₂S(aq) SnS₂(s) [yellow] + 4 H⁺(aq) + 6 Cl⁻(aq)

The precipitate is dissolved in alkali metal sulfides, forming thiostannate ions, and concentrated hydrochloric acid [6]:

SnS₂(s) + S²⁻(aq) [SnS₃]²⁻(aq)
SnS₂(s) + 4 H⁺(aq) + 6 Cl⁻(aq) [SnCl₆]²⁻(aq) + H₂S(aq)

When an alkali metal hydroxide is added, a white precipitate is formed. The precipitate is not Sn(OH)₄, as could be expected. It may be orthostannic acid H₂[Sn(OH)₆] [6]

Tin does not react with water under normal conditions. When exposed to steam, tin dioxide, SnO₂ and hydrogen are formed.

Sn(s) + 2 H₂O(g) SnO₂(s) + 2 H₂(g)


Sn(IV) is precipitated as α-tin acid upon hydrolysis of Sn(IV) solutions:

[SnCl₆]²⁻(aq) + 6 H₂O(l) H₂[Sn(OH)₆](s) + 4 H⁺(aq) + 6 Cl⁻(aq)

The precipitate is amphoteric and is dissolved in acids and strong alkali:

H₂[Sn(OH)₆](s) + 2 OH⁻(aq) [Sn(OH)₆]²⁻(aq) + 2 H₂O(l)
H₂[Sn(OH)₆](s) + 4 H⁺(aq) + 6 Cl⁻(aq) [SnCl₆]²⁻(aq) + 6 H₂O(l)

Method 3500-Sn B Atomic Absorption Spectrometric Method [2]. A portion of the sample is digested in a combination of acids. The digest is atomized in a graphite tube and resulting absorption of light is measured at 235.5 nm.

Method limit of detection in water = 0.002 mg/L
Method limit of detection in soil = 0.50 mg/kg