74 
" On the Influence of Acids on Iron and Steel,” by 
William H. Johnson, B.Sc. 
L — 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 sulphuric 
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 restored 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. 
% The fracture of a piece of iron or steel immersed for 
