Molecular Formula: C₉H₆N₂O₃
Molar mass: 190.16 g/mol
EINECS: 200-281-1
Density: 1.42 g/cm³
Flash Point: 188.2 °C
Index of Refraction: 1.659
Boiling Point: 387.6 °C at 760 mmHg
Vapour Pressure: 7.25E-06 mmHg at 25°C
Melting point: 154-156 °C(lit.)
Storage temp: -20°C
Water solubility: Insoluble
Appearance: Yellowish-brown plates or needles or yellow solid
Color: Yellow to brown
Stable:Air and light sensitive. Combustible. Incompatible with oxidizing agents
Product categories: Nitroquinolines;Pharmacetical;Quinolines
Structure of 4-Nitroquinoline N-oxide (56-57-5):


XLogP3-AA: 1.1
H-Bond Donor: 0
H-Bond Acceptor: 3
Systematic Name: 4-Nitro-1-oxido-quinolin-1-ium 
SMILES: [O-][N+](=O)c2c1c(cccc1)[n+]([O-])cc2 
InChI: InChI=1/C9H6N2O3/c12-10-6-5-9(11(13)14)7-3-1-2-4-8(7)10/h1-6H 
InChIKey: YHQDZJICGQWFHK-UHFFFAOYAP 
Std. InChI: InChI=1S/C9H6N2O3/c12-10-6-5-9(11(13)14)7-3-1-2-4-8(7)10/h1-6H 
Std. InChIKey: YHQDZJICGQWFHK-UHFFFAOYSA-N

Carcinogenicity of 4-Nitroquinoline N-oxide (56-57-5) hasn't been listed as a carcinogen by NTP, IARC,ACGIH, or CA Prop 65. And its toxicological properties have not been fully investigated.You can see actual entry in RTECS for complete information.

EPA Genetic Toxicology Program.

Suspected carcinogen with experimental carcinogenic, neoplastigenic, and tumorigenic data. Poison by intraperitoneal and subcutaneous routes. An experimental teratogen. Other experimental reproductive effects. Human mutation data reported. When heated to decomposition it emits toxic fumes of NO_x.
 

Hazard Codes: T
Risk Statements:
45:  May cause cancer 
Safety Statements:
45:  In case of accident or if you feel unwell, seek medical advice immediately (show label where possible)
53:  Avoid exposure - obtain special instruction before use

 4-Nitroquinoline N-oxide (56-57-5) also can be called 4-Nitroquinoline-1-oxide ; Quinoline, 4-nitro-, 1-oxide and 4-Nitroquinoline oxide .It is hygroscopic and light sensitive.Its flash point data are not available; however, it is probably combustible.It is hazardous,so the first aid measures and others should be known.Such as: When on the skin: first,should  flush skin with plenty of water immediatelyfor at least 15 minutes while removing contaminated clothing. Secondly,Get shoesmedical aid . Or in the eyes: Flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and lower eyelids.Then get medical aid soon.While ,it's Inhaled: Remove from exposure and move to fresh air immediately.Give artificial respiration while not breathing. When breathing is difficult, give oxygen. And as soon as to get medical aid. Then you have the ingesting of the product : Wash mouth out with water,and get medical aid immediately.
In addition, 4-Nitroquinoline N-oxide (56-57-5) can be stable under normal temperature and pressure conditions.It is not compatible with strong oxidizing agents, and you must not take it with incompatible materials and not be exposured to moist air or water.And also prevent it to broken down into hazardous decomposition products: oxides of nitrogen, carbon dioxide, carbon monoxide.