77 



The gain in weight by immersion in H~SO^ is greater 

 than by immersion in HCl. 



In experiments 1 — 4 the gain per cent is : 



For immersion in HCl = -010659 



Dittoin H-SO' = -025126 



or almost as 2 to 5, more accurately as 1 : 2*357. 



In experiments 5 — 7 the gain per cent for 



HCl =-02918 



H^SO^ = -037U 



as 1 : 1-284. 



Experiments 9 — 13 show how rapidly steeping in water 

 removes what the iron has taken np by immersion in acid ; 

 the loss in weight on subsequent heating being only about 

 1-1 0th of that in previous experiments where the iron had 

 not been immersed in water any length of time. 



III. — Effect on the Breaking Strain and 

 Elongation. 



The effect of immersion in acid on the breakino- strain 

 and elongation of ii'on wire naturally suggested itself as an 

 interesting subject for inquiry. Accordingly a number of 

 pieces of iron wire were immersed in hydrochloric acid for 

 one or more hours, and then carefully tested for elongation 

 and breaking strain. The pieces were then heated on a hot 

 plate for some hours and again tested with the following 

 general results. 



1. That immersion in acid diminishes the breaking strain 

 of iron wire from ^ to 3 per cent, and steel wire about 4-76 

 per cent. 



2. That immersion in acid appears in some cases to 

 diminish, in others slightly to augment, the elongation of 

 iron wire; and to augment the elongation of steel wire about 

 30 per cent. 



