398 C. E. FAWSITT AND A. A. PAIN, 
or active, is tested against platinum in nitric acid. 
This is shown in Table I. 
Table I. 
Time after Rontaee of iron with acid. Potential 
1 Minute 1 * 2 volts 
8 99 1 = 1 99 
lentes 0:95 ,, 
30 as Oats) 
65 OFT, 
99 
After 65 minutes insertion in the acid, the iron was 
touched with a piece of tin, when the potential rose only 
to 0°68 volts. The iron was then scratched vigorously with 
tin, when the potential rose to 0°79 volts. The potential 
however started to fall again immediately. On bringing 
the iron now into the air for one minute, and again intro- 
ducing into the sulphuric acid, the potential was found to 
have risen to 0°95 volt. The voltage immediately began 
to decrease slowly again as before. Whenever the iron 
was lifted into the air for one minute, the potential rose 
considerably, and in some cases as much as 0°4 volt. 
III.—Passive iron (made passive by 1°4 sp. gr. nitric acid) 
was put into concentrated sulphuric acid (96%). 
In the concentrated sulphuric acid the potential of the cell 
—Passive Iron [concentrated sulphuric acid] Platinum— 
was found to be from 0 to 0°2 volt. When the passive iron . 
was brought into the air for a minute, and then replaced 
in the sulphuric acid, the potential was not noticeably 
affected. On touching the passive iron (while in the sul- 
phuric acid) with a piece of copper, the potential rose 
suddenly to 1 . 15 volts. 
It will be seen from these experiments that wrought iron 
made passive by 1°4 nitric acid, bears no simple relation 
to ordinary (active) iron which has been lying io pure con- 
centrated sulphuric acid for.some time. 
