74 



" On the Influence of Acids on Iron and Steel," by 

 William H. Johnson, B.Sc. 



I. — General Effects of Acid. 



Pieces of iron and steel wire of various qualities were 

 immersed in sulphuric or hydrochloric acids for spaces of 

 time varying from 10 minutes to 12 hours, and then well 

 washed with water and dried, and the following experiments 

 made : 



1. On breaking one of the pieces of wire and moistening 

 the fracture, still warm from the effort of breaking it, 

 bubbles were seen to rise through the water from the whole 

 surface of the fracture, even when the piece was -412 inch 

 diameter. Further, pieces of wire that had been immersed 

 in acid, washed, coated with lime, dried, and drawn to a 

 smaller diameter, thus removing any trace of acid on the 

 surface, gave bubbles in the same manner. The bubbles 

 are most abundant if the iron has been immersed in sulj)huric 

 acid, and may be seen several days after the iron has been 

 removed from the acid. If steeped in hydrochloric acid the 

 bubbles are seen with difficulty and only after long immer- 

 sion. 



Bubbles are not apparent with steel, even after prolonged 

 immersion, except the steel be very mild. 



Test paper was not sensibly altered in colour by the 

 water on the fractures. 



By exposure to the atmosphere, or more quickly by steep- 

 ing in water, the above phenomena, as well as those to be 

 mentioned later on, decrease in intensity until at length 

 they are no longer visible, and the iron is quite restoi:ed to 

 its original state. Gentle heat greatly aids this. They also 

 cease to be visible sooner if hydrochloric acid be employed 

 than if sulphuric acid is used, doubtless because the latter is 

 less volatile. 



2. The fracture of a piece of iron or steel immersed for 



