Hydrides of sulphur

The hydrogen sulphide collected over hot water .The prepared hydrogen

sulphide always contains hydrogen generated by the action of the acid on

the free metallic iron which is present in ferrous sulphide. The hydrogen

does not interfere with the use of hydrogen sulphide as an analytical

reagent. Hydrogen sulphide free from hydrogen may be prepared by the

action of hot concentrated hydrochloric acid on antimony sulphide:

The pure hydrogen sulphide is prepared by passing a mixture of sulphur

vapour and hydrogen over finely divided nickel heated to 450? . The

hydrogen sulphide is condensed by cooling with solid carbon dioxide. It

may be dried with fused calcium chloride.

Hydrogen sulphide is a colorless gas, B. Pt. -60.4? , M. Pt.-85.6?. The

liquid is colorless and the solid transparent. The gas has a sweet offensive

smell (the odour of rotten egg is due to the presence of hydrogen

sulphide), and it is very poisonous at concentration above 0.1% .

Hydrogen sulphide is soluble in water 1 volume of water dissolves 4.7

volumes of the gas at 0? .

Hydrogen sulphide is completely expelled from its aqueous solution on

boiling.

Hydrogen sulphide burns in excess of air or oxygen with a blue flame to

yield sulphur dioxide and water:

But if the supply of oxygen is limited ,sulphur is deposited.

Hydrogen sulphide is a reducing agent :

Hydrogen sulphide in solution is a weak acid reacts with potassium

hydroxide to form potassium sulphide and potassium hydrosulphide.

The hydrogen persulphides are yellow oils. They spontaneously

decompose into sulphur and hydrogen sulphide. And they dissolve one

another and also sulphur. For these reasons the determination of their

formula is difficult , and the results are uncertain.