The concentration of chromium oxide was determined colorime trically by its reaction with s-diphenyl carbazide
according Marino et al.
Remaining chromium concentration was measured time to time by 1-5 diphenyle carbazide
method as described below.
The concentration of free Cr (VI) ions in the effluent was determined with 1, 5-diphenyl carbazide
(DPC) in acidic solution spectrophotometrically (Elico SL 171) at l max 535 nm.
For the case of Cr(VI) on the above spiked samples 1 mL of prepared diphenyl carbazide
solution was added and a red violet color was immediately developed.
The reaction mixture was centrifuged and the concentration of the residual Cr(VI) was determined using the diphenyl carbazide
spectrophotometry method [29, 30] at the wavelength of 540 nm.
To the above 15 mL solution is added 3 M sufficient [H.sub.2]S[O.sub.4] in a 25 mL standard flask and to this is added 1mL of 1,5 diphenyl carbazide
reagent and made up to 25 mL using deionized water to get a pink coloured complex.
Quantification of LPS was done by the semi- carbazide
method of Batley et al.
Inhibition of corrosion of zinc in hydrochloric acid by some carbazide
derivatives has also been reported.
The treating solutions were analyzed for pH by meter and initial hexavalent chromium concentration by the diphenyl carbazide
method (Coggins and Hiscocks 1987) using a Shimatzu UV 160 spectrophotometer.
In each flask, 2ml of diphenyl carbazide
was then added and the flasks were kept for half an hour in dark.
The 1,5-diphenyl carbazide
from Merck were directly used for chromium detection.