68 CHE MIS TR V FOR A GRIC UL TURA L STUDENTS 



It has been noticed that there are metals which, when placed 

 in dilute sulphuric acid, cause the evolution of hydrogen gas. 

 It is possible that if the sulphides of these metals were placed 

 in dilute acid, the sulphide of hydrogen would be produced. 

 Try the sulphide of iron just obtained. Note that the escaping 

 gas is distinguished from hydrogen by its foul smell. Ignite it. 

 What are the two products of combustion, and what evidence 

 do these yield that the gas is indeed the sulphide of hydrogen, 

 or sulphuretted hydrogen'^ The percentage composition is 

 found by analysis to be : — Sulphur = 94. 1 1 %, hydrogen = 5.88%. 

 What is the simplest formula that would represent the com- 

 pound ? 



When organic matter containing sulphur decays, the sulphur is set free 

 combined with hydrogen. This accounts for the smell of rotten eggs, the 

 white of egg consisting of sulphur compounds. Rotting cabbages afnd 

 turnips have a similar odour, these being also rich in sulphur compounds. 

 The water of many springs is impregnated with sulphuretted hydrogen, 

 notably the Harrogate waters. 



The composition of sulphuretted hydrogen shows that, like 

 oxygen, a single combining weight of sulphur combines with 

 two of hydrogen. In other words, sulphur is able to replace 

 oxygen, and this is true, not only of the compound with hydro- 

 gen, but also of compounds with other elements. Thus, the 

 formula for ferrous oxide was found to be FeO ; that for the 

 ferrous sulphide just prepared is FeS. 



Burn some sulphur in a jar of air or oxygen. Shake the 

 gaseous sulphurous anhydride produced with water in order to 

 form a solution of sulphurous acid. Preserve a portion of the 

 solution in a corked test-tube, and expose the remainder in a 

 shallow dish to the air, or allow air slowly to bubble through it. 

 Note that after some time the smell of sulphurous acid 

 disappears from the liquid in the open dish, yet it still remains 

 acid to litmus, while in the closed tube the sulphurous acid 

 is unchanged. The sulphurous acid has apparently become 

 oxidised by the air to an acid which is odourless. What is the 



