Orange crystals. Insoluble in water. Soluble in ethanol, methanol, benzene, ether and chloroform, and hot dilute alkaline solution.
2.Structured data is divided
Molar refractive index: 74.04
Molar volume (cm3/mol): 199.9
Isotropic volume (cm3/mol): 199.9
Surface tension (dyne/cm): 50.8
Polarizability (10-24cm3): 29.35
Preparation of 1-(2-Pyridylazo)-2-naphthol: After the diazotization of 2-aminopyridine, coupling with the 2-naphthol. Anhydrous ethanol reacts with metal sodium to get caustic alcohol, and then adding 2-aminopyridine in ethanol and passing ethyl nitrite vapor to react at 45-50 °C. Completed the reaction, heating 8 hours, filtering out the diazonium salt and washed with ether. The diazonium salt was added in 2-naphthol in ethanol solution, then passing carbon dioxide at 45-50 °C to carry on coupling reaction. After 6 hours, filtering out the crystals, washed with distilled water and recrystallized with ethanol, then we can get the product by drying.
1-(2-Pyridylazo)-2-naphthol is a complexometric indicator. The solution is pink at pH 12 and above, orange-red in weak acids and purple in concentrated sulphuric acid. Its metal complexes are pink or red in color. It is also used as a metal indicator and reagent for the spectroscopic analysis of transition metals. Specifically, it is used as a color developer of some metal ions including Al3+, Sb3+, Cd2+, Zn2+, Co2+, Cu2+, Ga3+, In3+, Fe3+, Pd 2+ in spectrophotometry, extraction spectrophotometry and fluorospectrophotometry. Besides, it is also used as a precipitating agent for trace metals such as titanium, vanadium, manganese, iron, cobalt, nickel, copper, zinc and lead.
Molecular formula: C15H11N3O
Relative molecular mass: 249.27
Melting point: 138-141 °C
In certain ph solutions, it can form red or other colored complexes with most metal ions; the complexes are insoluble in water.