IUPAC Name: 3-Phenyldiazenylpyridine-2,6-diamine
Molecular Formula: C₁₁H₁₂ClN₅
Molecular Weight: 249.70 g/mol
Canonical SMILES: c1(c(nc(N)cc1)N)\N=N/c1ccccc1.Cl
InChI: InChI=1/C11H11N5.ClH/c12-10-7-6-9(11(13)14-10)16-15-8-4-2-1-3-5-8;/h1-7H,(H4,12,13,14);1H/b16-15-; 
EINECS: 205-243-8
Classification Code: Analgesic; Drug / Therapeutic Agent; Human Data; Mutation data; Tumor data
Product Categories: Intermediates & Fine Chemicals; Pharmaceuticals
H-Bond Donor: 3
H-Bond Acceptor: 5
Rotatable Bond Count: 2
Tautomer Count: 12
Exact Mass: 249.078123
MonoIsotopic Mass: 249.078123
Topological Polar Surface Area: 89.6
Heavy Atom Count: 17 
Complexity: 237
Flash Point: 221.3 °C 
Enthalpy of Vaporization: 69.97 kJ/mol 
Boiling Point: 442.3 °C at 760 mmHg 
Melting Point: 139 °C
Water Solubility: 0.01-0.1 g/100 mL at 20 °C
Vapour Pressure of Phenazopyridine hydrochloride (CAS NO.136-40-3): 5.1E-08 mmHg at 25 °C

  Phenazopyridine hydrochloride (CAS NO.136-40-3) is used as a local anesthetic that has been used in urinary tract disorders. Its use is limited by problems with toxicity (primarily blood disorders) and potential carcinogenicity.

Confirmed carcinogen with experimental carcinogenic and tumorigenic data. A poison by intraperitoneal and intravenous routes. Moderately toxic by ingestion. Human systemic effects by ingestion: somnolence, cyanosis, diarrhea, nausea or vomiting, anuria or decreased urine volume, normocytic anemia, methemoglobinemia-carboxyhemoglobinemia, dehydration, changes in blood sodium levels. Mutation data reported. When heated to decomposition it emits very toxic fumes of NO_x and HCl.
Hazard Codes: Xn,C
Risk Statements: 22-36/37/38-40-34
R22: Harmful if swallowed. 
R36/37/38: Irritating to eyes, respiratory system and skin. 
R34: Causes burns. 
R40: Limited evidence of a carcinogenic effect.
Safety Statements of Phenazopyridine hydrochloride (CAS NO.136-40-3): 26-36/37-45-36/37/39-27 
S26: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. 
S36/37: Wear suitable protective clothing and gloves. 
S36/37/39: Wear suitable protective clothing, gloves and eye/face protection. 
S45: In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.)
S27: Take off immediately all contaminated clothing.

 Phenazopyridine hydrochloride (CAS NO.136-40-3), its Synonyms are 2,6-Diamino-3-(phenylazo)pyridine monohydrochloride ; 2,6-Diamino-3-phenylazopyridine hydrochloride ; 2,6-Pyridinediamine, 3-(phenylazo)-, monohydrochloride ; 3-(Phenylazo)-2,6-pyridinediamine, hydrochloride ; 3-Phenylazo-2,6-diaminopyridine hydrochloride ; Azo-Standard ; Azodyne ; Azomine ; Azosulfisox ; Bisteril ; Phenazodine ; Phenazopyridine HCl ; Phenazopyridinium chloride ; Phenyl-idium ; Pyridine, 2,6-diamino-3-(phenylazo)-, hydrochloride and so on. It is brick-red crystals.