Sulphur   |
16
S
32.065(5) |
The essentials
Here is a brief description of sulphur.
The spelling of sulphur is "sulfur" in the USA and now that IUPAC has decided it has jurisdiction over the British English language (as distinct from American English) as well as nomenclature, so we in the UK are expected to use the f word.
Sulphur is found in meteorites, volcanoes, hot springs, and as galena, gypsum, Epsom salts, and barite. It is recovered commercially from "salt domes" along the Gulf Coast of the USA. Jupiter's moon Io owes its colours to various forms of sulphur. A dark area near the crater Aristarchus on the moon may be a sulphur deposit.
The picture above shows the result from burning a mixture of zinc metal powder and sulphur. Do not attempt this reaction unless are a professionally qualified chemist and you have carried out a legally satisfactory hazard assessment.
Sulphur is a pale yellow, odourless, brittle solid, which is insoluble in water but soluble in carbon disulphide. Sulphur is essential to life. It is a minor constituent of fats, body fluids, and skeletal minerals.
Carbon disulphide, hydrogen sulphide, and sulphur dioxide should be handled extremely carefully. Hydrogen sulphide in very small concentrations can be metabolized, but in higher concentrations it can cause death quickly by respiratory paralysis. It is insidious in that it quickly deadens the sense of smell. Sulphur dioxide is a dangerous component in atmospheric air pollution and is one of the factors responsible for acid rain.
IsolationHere is a brief summary of the isolation of sulphur.
It is not normally necessary to make sulphur in the laboratory as it is so readily available. It is found as the native element in nature and extracted by the Frasch process. This is an interesting process since it means that sulphur can be extracted from underground without mining it. In the Frasch process underground deposits of sulphur are forced to the surface using superheated water and steam (160°C, 16 atmospheres, to melt the sulphur) and compressed air (25 atmospheres). This gives molten sulphur which is allowed to cool in large basins. Purity can reach 99.5%.
The process in energy intensive. Commercial success for this operation depends upon suitable geological conditions as well as access to cheap water and energy.
Hydrogen sulphide, H2S, is an important impurrity in natural gas which must be removed before the gas is used. This is done by an absorption and regeneration process to concentrate the H2S, followed by a catalytic oxidation (Claus process) using porous catalysts such as Al2O3 or Fe2O3.
8H2S + 4O2  S8 + 8H2O
Over the years the Claus process has been improved and a modified process can yield 98% recovery.
In the laboratory, sulphur can be purified by recrystallisation from solutions in carbon disulphide, CS2. However the resulting crystals are contaminated with solvent, H2S, and SO2. One good way to purify sulphur is to use a quartz heater (700°C) immersed in liquid sulphur. Carbon impurities decompose to form volatile materials of solid carbon, which coat the heater. After a week or so, finishing with a distillation under vacuum, the result is sulphur with a carbon content of about 0.0009%.
Sulphur |
16
S
32.065(5) |
Chemical reactions of the elements
Reaction of sulphur with air
Sulphur burns in air to form the gaseous dioxide sulphur(IV) oxide, SO2.
S8(s) + 8O2(g) 8SO2(s)
Reaction of sulphur with water
Sulphur does not react with water under normal conditions.
Reaction of sulphur with the halogens
Sulphur racts with all the halogens upon heating. Molten sulphur reacts with molten sulphur to form disulphur dichloride, S2Cl2. This apparently smells dreadfully. With excess chlorine and in the presence of a catalyst, such as FeCl3, Snl4, etc., it is possible to make a mixture containing an equilibrium mixture of red sulphur(II) chloride, SCl2, and disulphur dichloride, S2Cl2
S8 + 4Cl2 4S2Cl2(l) [orange]
S2Cl2(l) + Cl2  2SCl2(l) [dark red]
Reaction of sulphur with acids
Sulphur does not react with dilute non-oxidizing acids.
Reaction of sulphur with bases
Sulphur reacts with hot aqueous potassium hydroxide, KOH, to form sulphide and thiosulphate species.
S8(s) + 6KOH(aq) 2K2S3 + K2S2O3 + 3H2O(l) | 
