ACTION OF CONCENTRATED SULPHURIC ACID ON IRON. 



67 



In Experiment III, 20*97 grams of iron were immersed 

 in about 70 c. cms. of concentrated sulphuric acid. 



Analysis of Gas evolved from a Mild Steel and Commercial 

 Sulphuric Acid. 



This mild steel contained 0*5% of nickel, and the com- 

 mercial acid contained 95% H 2 S0 4 — being somewhat less 

 pure than that used in the above three experiments. The 

 reaction was allowed to proceed for some time before the 

 initial analysis was made, and in the following table sub- 

 sequent analyses are timed from the initial analysis. The 

 amount of air in the gases was determined as before, and 

 sulphur dioxide and hydrogen are again expressed as per- 

 centages of total gases evolved. 



Gases evolved, using Mild Steel. 



Time in days. 



S0 2 



H 





_ 



2-1 



97-9 



100-0 



4 



1-2 



98-8 



100-0 



11 



•8 



99-2 



100-0 



15 



1-0 



99-0 



100-0 



39 



•8 



99-2 



100-0 



This series of experiments was carried out at atmospheric 

 temperature, which for the 39 days over which the analyses 

 extended was generally 25-27° C. In the above table the 

 ratio of S0 2 to hydrogen is somewhat smaller than that 

 obtained in the experiments with steel wire. But the 

 main facts are still the same, namely, that concentrated 

 sulphuric acid has a definite action on iron in the cold (25 

 - 30° 0.), and in no case was hydrogen gas liberated with- 

 out sulphur dioxide gas being formed at the same time. 



Prom this it would seem to be the case that two actions 

 are proceeding simultaneously, one producing hydrogen 

 and ferrous sulphate, and the other sulphur dioxide, ferrous 

 sulphate and water according to the equations : — 



1. Fe + H 2 S0 4 = FeS0 4 + H 2 . 



2. Fe + 2H 2 SQ 4 = FeSQ 4 + S0 2 + 2H a O. 



