442 Philippine Journal of Science 1920 
As in the experiments recorded with 0.5 N acid, the corrosion 
of iron with increasing potassium dichromate concentration in 
normal sulphuric acid first increased, then decreased, and finally 
was entirely inhibited. A much greater salt concentration was 
necessary, however, to effect passivity than was required in the 
case of the more dilute acid. These first experiments indicated 
a maximum corrosion rate with a concentration between 25 and 
50 grams of salt per liter, and passivity beyond 50 grams of 
potassium dichromate per liter of acid. To locate these points 
more closely, the experiments explained in Table 3 were per- 
formed. 
TABLE 3—Effect of addition of potassium dichromate on the corrosion of 
iron in normal sulphuric acid. 
Exp i. ‘ssciie tine 
. sium di- eig! ter 24 
teen chromate} of iron. pe 
added. 
Grams 
per liter.| Grams. Grams. 
Ope Ee ee o| ws) 018 
ee eee eos gitttesrecieti-- rit 0} 14.755 | 0.125 
Serre atria et eases sae eae go| 16.119; 4 331 
x ‘IS RS URS ce SSS 30 15.031 | 4-278 
a Se Oe g5| 14.692 | 3-715 
ssa ST BG Sie ag RR can ahah ae aS 36.| 15.526) 8 820 
pergtitde Woe t ts sant 6 a7 sei Se 4o| 15.217: 3.659 
SS eee 40 | 15.770| 8.6% 
ee eee 45 | 18.883 3. 633 
erectile: taceroncitie: fenietdc sts rt 45| 13.798} 3.518 
Be in ecldat as 50 | 15.040 | 0.002 | 
i. 50 | 15.328 | 8-429 | 
Gees Gh oe cs a 65 | 14.577 0.005 
PE SETS 453 -| 
GS Sane ioe Sent wenger na ee 65 | 15-201 3. 
ae a oie 3.517 | 
es of 
As in the preceding experiments, increasing quantiti 
potassium dichromate decreased the amount of corrosion. 
additions above 45 grams of salt per liter results became &¥ 
ceedingly irregular, and no definite passivifying concentratio® 
was determined, though passivity was effected in individual cases 
for concentrations as low as 50 grams of salt per liter. 
_ With 2 N sulphuric acid, the addition of potassium dichromate 
induced no passivity, as shown in Table 4, even when 
solution was saturated with the salt. 
