2 nitroresorcinol has been used as an acid-base indicator. In acid it is yellow while in basic form it changes to red colour. The pH range of the indicator is 5.4 to 7.4. The pK, is 6.4±0.1and pT value is 6.2. As pK4 6.4 is reasonably near-to 7.0, which is the equivalence point pH 8f strong acids versus strong bases, therefore, it is more suitable than the commonly employed indicators, phenolphthlein and methyl orange which have pK in 8.3 and 4.2 1.4irectivly.