The chemical reduction of azo dyes was carried out
using sodium dithionite. The process for the reduction
of DB 38 and CR dyes was as follows: 0.06 g of dye
sample was heated to boiling point with 1 M NaOH for
1 h; 0.6 g sodium dithionite was added after 30 min.
Hundred milligram per litre of dye was reduced according
to the method mentioned by Pielesz