`ast` `text(Allotropic forms of Sulphur :)`

(i) `text(Rhombic octahedral or)` `alpha` `text(-sulphur :)`

(ii) `text(Monoclinic Prismatic or)` `beta` `text(-sulphur :)`

(a) These two sulphur are called as enantiatropic substances.

`alpha` - sulphur ⇋ `beta`- sulphur.

(b) `alpha` and `beta` sulphur are crystalline and rest being amorphous and exist as `S_8` cyclic molecule.

(iii) `text(Plastic or) gamma-text(sulphur :)` It is obtained by quenching of boiling sulphur in a thin stream to cold water.

(iv) `text(Milk of sulphur :)` It is obtained by boiling milk of lime with sulphur and decomposing the products with HCl.

`=> 3Ca(OH)_3 + 12S -> 2CaS_5 + CaS_2O_3 + 3H_2O`

`=> 2CaS_5 + CaS_2O_3 + 6HCl -> 3CaCl_2 + 3H_2O + 12S`

Milk of sulphur is soluble in `CS_2` and is mainly used in medicine.

(v) `text(Colloidal or)` `delta` `text(-sulphur :)` It is prepared by passing `H_2S` through a solution of an oxidising agent

Eg. `HNO_3 + H_2S -> 2NO_2 + 2H_2O + S`

`SO_2 + 2H_2S -> 2H_2O + 3S`