The application of hydroxytriazenes as analytical reagents has been reviewed after 1997 , i.e. from 1998. The literature on the recent work done on hydroxytriazenes has been reviewed and it is found that, apart from being useful analytical reagents for spectrophotometric and complexometric determination of transition metal ions, they have also found application as bioactive compounds. The details of λ," 3Χ or working wavelength with pH conditions etc. have been given in this review. Ressalan et al. 121 have reported the use of 3-hydroxy-3-m-tolyl-l-mnitrophenyltriazene as a metallochromic indicator for the complexometric determination of trace amounts of chromium (III). Using this reagent as an indicator the selective complexometric determination of Cr (III) in binary and ternary metal ion mixtures has also been done. The end point of the titration is marked by change of colour from violet to yellow at a pH between 5.2 to 6.0 using hexamine. It is reported that the presence of 20 fold excess of eleven diverse cations and anions did not interfere with the determination of 5.2 mg of Cr (III). It has been further reported that the amount of metal ions found was in good agreement with the amount of metal ions actually present, indicating that the determinations are quite accurate. For the sake of comparison parallel titrations have been carried out using xylenol orange as indicator. Thus a useful method for the complexometric determination of chromium (III) has been developed. Ressalan et al. 13/ have reported the use of 3-hydroxy-3-p-tolyl-l-onitrophenyltriazene at 60-65°C in hexamine buffer (pH 5.2 to 6.0). The colour reaction results in the formation of a stable dark grassy green chromium complex. The chromium (III): reagent ratio in this complex is 1:2

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