Soluble in acetone, alcohol, and dilute aqueous alkali. Soluble in water.
1-(2-Pyridylazo)-2-resorcinol (PAR), an orange colored dye, is commonly used as an acid-base indicator. It can form chelates with metal ions, which makes it a valuable indicator in complexometric titrations. 1-(2-Pyridylazo)-2-resorcinol is an indicator in complexometry and a reagent for the extraction and spectrophotometric determination of many transition metals.
4-(2-Pyridylazo)resorcinol monosodium salt is a useful indicator in complexometry, as well as a reagent for the extraction and spectrophotometric determination of many transition compounds. It is a highly selective and sensitive reagent for cobalt and iron. 4-(2-Pyridylazo)resorcinol monosodium salt is also a useful reagent for selective determination of trace level chrome(III) by ion-pair reversed-phase high-performance liquid chromatography.