404 C. E. FAWSITT AND A. A. PAIN. 
M 
in the case of most of the concentrations given in Table I, 
a determination was also made by titrating the acid with 
alkali. 
In Table II the gas evolved has been calewinted to ce. 
of gas evolved per sq. decimetre per hour, on the assump- 
tion that the whole of the surface of the steel used (143 
sq. cm.) was freely exposed to the action of the acid. This 
is only approximately true, as the small pieces of steel 
touched each other in places. 
SERIES ‘‘B.”’ 
Samples of steel of the same kind as in series *‘A’’ but. 
only 5 grams in weight (the surface being 35 sq. centi- 
metres) were exposed to the action of concentrated sul- 
phuric acid in large test tubes, and the tubes were then 
placed in a thermostat at 30° O. and shaken from side to 
side by a mechanical shaker worked by a motor. In this 
case the gas evolved was not measured, but the weight of 
the iron was taken before action, and after 28 days of action; 
the iron on being taken out of the sulphuric acid was washed 
with alcohol, then with water, then with alcohol and dried 
before the final weighing. The results obtained are as 
follows :-— 
Table IIT. 
Concentrated acid. | Weight of iron lost in 28 days. 
97°4 0:0993 
94-0 0°8605 
90:0 1°2223 
89°3 0:°1401 
89°3 0°1331 
87:9 0°5230 
85:0 0:5264 
80-0 2°9145 | 
The experiments with 89°3% concentrated acid show 
distinctly less action than those with 94°0% acid, thus con- 
firming the results obtained in the unstirred experiments. 
