109 
Extension of the Influence of Acid beyond the part 
immersed in the liquid. 
Hitherto all the experiments have been made on iron 
totally immersed in acid solutions. It appeared to me, 
however, that very possibly the changes produced in iron 
and steel by immersion in acid might not be confined to the 
part in contact with the liquid only, but might also spread 
beyond and produce effects similar in quality but less in 
degree. With this view the following experiments were 
made. 
Pieces of carefully selected charcoal iron, mild steel (about 
*22 carbon), and hardened and tempered steel wire (about 
•65 carbon), each about 85 centimetres long and of same 
thickness, were partly immersed in 4 tubes 13*5 centimetres 
deep, filled respectively with dilute sulphuric, hydrochloric, 
and nitric acids, and a saturated solution of common salt in 
water. After 72 hours the pieces of wire were pulled out 
and examined, when considerable differences became appa- 
rent. 
1st. The pieces immersed in salt solution were freed from 
a very slight coating of rust on them before immersion, 
where they were in contact with the liquid, but above the 
surface of the liquid the rust remained as before. No 
decided alteration in toughness was apparent, and no bubbles 
were given off from the moistened fracture of the wire either 
of the part in the liquid or that out. 
2nd. The pieces in nitric acid were slightly eaten away 
on the surface, the hardened steel least and the mild steel 
most, and the surface was covered with a fine black dust in 
the case of the charcoal and hardened steel. The moistened 
fracture did not bubble, however, in any of the pieces either 
in the part in or out of the acid, and no alteration in tough- 
ness was apparent from that before immersion, except in 
that part of the hardened steel covered with acid, where a 
possible though undecided diminution seemed to exist. 
