A TRIAZOLE DERIVATIVE AS A NEW ACID-BASE INDICATOR

摘要

In this study a new pH indicator, 3-benzyl-4-p-nitrobenzylidenamino-4,5-dihydro-1,2,4-triazole5-on (BPNBAT), soluble in acetonitrile:water (1:4), was developed. The estimation of pH is possible either from the position of the absorption maxima or from the absorbance intensity at a constant wavelength, This feature allowed us to determine the basic transition range of the medium because BPNBAT is colorless at pH lower than 8.5 and showed strong yellow-green color with high extinction coefficient in the pH range of 8.5-10.1. pK,, pH at equivalent point and the molar absorptivity (in the aqueous medium at 380 nm) of BPNBAT are determined as 9.3, 8.3 and 8.8 x 10~3 L.mol~(-1)cm~(-1), respectively. The color change at the transition range can be attributed to the resonance structures of BPNBAT. The triazole compound was compared with thymolplithalein for accuracy test.