50
The Main Subgroup of Group Six
-> S 2 -^S . At from 800 to 1400 °C, sulphur vapour coi&ists mainly of diatomic molecules, at 1700 °C of atoms. Sulphur is a typical non-metal. It combines directly with many metals such as copper, iron, and zinc with the evolution of a great amount of heat. It also combines with almost all non-metals, but not so readily and vigor6 usly as with metals. Sulphur is widely used in the national economy. It is employed in the rubber industry to cure crude rubber. The latter acquires its valuable properties only after being mixed with sulphur and heated to a definite temperature. This process is called vulcanization of rubber (p. 173). Rubber having a very large sulphur content is known as ebonite, it is a good electrical insulator. Flowers of sulphur are used to combat certain plant pests. Sulphur is also employed for the production of matches, ultramarine (a blue pigment), carbon disulphide, and a number of other substances. In countries having rich sulphur deposits, it is used as the starting material in sulphuric acid production. 14. Hydrogen Sulphide. Sulphides
At a high temperature, sulphur combines with hydrogen to form the gas hydrogen sulphide. Hydrogen sulphide is generally prepared in practice by reacting dilute acids with metal sulphides, for example with irori^II) sul phide: -o FeS + 2HC1 = FeC l2 + H 2S |
, : V‘
k
Hydrogen sulphide is a colourless gas with the ^hi;acteristic odour of rotten eggs. It is slightly heavier than air, liquefies at —60.3 °C, and solidifies at —85.6 °C. It burns in air with a bluish flame and forms sulphur dioxide and water: 2 H 2S + 3 0 2 = 2 H 20 + 2 S 0 2
If we introduce an object such as a porcelain cup into a hydrogen sulphide flame, the temperature of the latter will lower appreciably, and the hydrogen sulphide will be oxidized only to free sulphur that forms a yellow deposit on the cup: 2 H 2S + 0 2 = 2 H 20 + 2S
Hydrogen sulphide readily ignites; a mixture of it with air ex plodes. Hydrogen sulphide is a strong poison. The prolonged inhala tion of air containing even small amounts of this gas causes serious poisoning. At 20 °C, one volume of water dissolves 2.5 volumes of hydrogen sulphide. A solution of the latter in water is known asvhydrogen sul phide water. When left standing in the air, especially in the light, hydrogen sulphide water soon becomes turbid because of the sulphur