1-(2-Pyridylazo)-2-naphthol(85-85-8) is used as indicator for metal titration.

The IUPAC name of 1-(2-Pyridylazo)-2-naphthol is 1-(pyridin-2-ylhydrazinylidene)naphthalen-2-one. With the CAS registry number 85-85-8, it is also named as 2-Hydroxy-1-(2-pyridylazo)naphthalene. The product's categories are pyridylazo compounds; analytical chemistry; azo compounds; chelating reagents; naphthylazo compounds. It is orange crystals which is soluble in methanol, ethanol, benzene, ether, chloroform and hot dilute alkali, and insoluble in water. In addition, it is stable and incompatible with strong oxidizing agents, strong bases. Furthermore, 1-(2-Pyridylazo)-2-naphthol is used as complexometric indicator. And it must be stored in a cool, dry place.

The other characteristics of this product can be summarized as: (1)ACD/LogP: 2.74; (2)# of Rule of 5 Violations: 0; (3)ACD/LogD (pH 5.5): 2.74; (4)ACD/LogD (pH 7.4): 2.56; (5)ACD/BCF (pH 5.5): 71.1; (6)ACD/BCF (pH 7.4): 46.85; (7)ACD/KOC (pH 5.5): 735.06; (8)ACD/KOC (pH 7.4): 484.37; (9)#H bond acceptors: 4; (10)#H bond donors: 1; (11)#Freely Rotating Bonds: 3; (12)Index of Refraction: 1.662; (13)Molar Refractivity: 74.04 cm³; (14)Molar Volume: 199.9 cm³; (15)Polarizability: 29.35×10^-24 cm³; (16)Surface Tension: 50.8 dyne/cm; (17)Enthalpy of Vaporization: 76 kJ/mol; (18)Vapour Pressure: 1.92E-09 mmHg at 25°C; (19)Rotatable Bond Count: 2; (20)Tautomer Count: 5; (21)Exact Mass: 249.090212; (22)MonoIsotopic Mass: 249.090212; (23)Topological Polar Surface Area: 54.4; (24)Heavy Atom Count: 19.

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.

When you are using this chemical, please be cautious about it as the following:
It is irritating to eyes, respiratory system and skin. In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. If you want to contact this product, you must wear suitable protective clothing, gloves and eye/face protection.

People can use the following data to convert to the molecule structure. 
1. SMILES: Oc2ccc3ccccc3c2/N=N/c1ccccn1;
2. InChI: InChI=1/C15H11N3O/c19-13-9-8-11-5-1-2-6-12(11)15(13)18-17-14-7-3-4-10-16-14/h1-10,19H.