Removal of Chromates from Pickling Liquors
621
TO
2 0 Time Imin)
0
io
20 Time (min)
Fig. 6.
Settling rate of Fe(0H>3 sludge precipitated at pH = 6 resp. with
NaOH (left) and Ca(OH) 2 (right) in 100 ml measuring-cylinders
at variable amounts of conditioning agent (Praestol 2700). The initial Cr^I
concentration was 1.92 mmol/1, the initial FeHtyCrVI ratio was 4.65.