Oxygen can be prepared by heating oxides of Hg, Pb,Ag, Mn and Ba.

2HgO \(\overset{\Delta }{\rightarrow}\) ₂2Hg + O₂

PbO₂ is a powerful oxidizing agent and liberate O₂ when treated with acids.

\(\underset{Thiosulphat}{2S_{2}O_{3}^{-2}}+I_{2}\rightarrow \underset{Tetrathionate}{S_{4}O_{6}^{-2}}+2I^{-}\)

In the manufacture of bromine from sea water, the mother liquor which contains bromides is treated with chlorine which oxidies bromide ion to bromine

2KBr + Cl₂ + 2KCl + Br₂

2KMnO₄ + 5H₂S + 3H₂SO₄ → K₂SO₄ + 2MnSO₄ + 5S +8H₂O.

Thus in this reaction S^2–is oxidised to S.

Caro’s acid is H₂SO₅ which contains one S – O –OH peroxy linkage. It is also known as permonosulphuric acid.

Due to greater tendency forcatenation, sulphur shows property of polyanion formation to a greater extent.For example, in polysulphides such as \(S_{3}^{2-},S_{4}^{2-},S_{5}^{2-}\)

Solubility depends upon temperature. In most cases it increases with rise in temperature but in those cases where the process of dissolution is exothermic,solubility decreases with rise in temperature.

Alkaline solution of pyrogallol absorbs oxygen quickly.

Air is liquified by making use of the joule-Thompson effect (cooling by expansion of the gas) Water vapour and CO₂ are removed by solidification. The remaining major constituents of liquid air i.e., liquid oxygen and liquid nitrogen are separated by means of fractional distillation (b.p. of O₂= –183°C :b. P. of N₂ = – 195.8°C)