Mordant brown 33
Mordant brown 33 is 2,4-diamino-5- benzene sulfonic acid sodium salt.
The UV-Visible spectra of MB33 in all mixtures investigated display three absorption bands in 50% ethanol within all the pH ranges 1.5-13.3 using Thiel buffer the maximum absorption of these bands is located at 438, 453 and a double head band at 410 and 475 nm. The band at 438 nm corresponds to absorption attributed to the cationic form of MB33 and disappears at pH > 3.0. The band at 453 nm corresponds to the absorption of the neutral form of the reagent. The double head bands at 410 and 475 nm correspond to the di-anionic of MB33.