MF: HNaO₃Se
MW: 150.9559 g/mol
Storage temp: 2-8°C 
Chemical Properties: off-white fine powder
IUPAC Name: Sodium hydrogen selenite
Synonyms: Sodium biseleite ; Sodium biselenite ; Sodium acid selenite ; Sodium hydrogen selenite ; Sodium hydroselenite ; Hydrogensodiumselenite ; Hydrogensodiumseleniumoxide ; Seleniousacid,monosodiumsalt
Following is the molecular structure of Selenious acid, monosodium salt (7782-82-3):

Selenious acid, monosodium salt (7782-82-3) is used as a general analytical reagent, but also for the preparation of bacterial culture medium.
 

Experimental reproductive effects. When heated to decomposition it emits toxic vapors of Se.
Safety Information of Selenious acid, monosodium salt (7782-82-3):
Hazard Codes: T,N
T: Toxic N: Dangerous for the environment
Risk Statements: 23/25-33-50/53
23/25: Toxic by inhalation and if swallowed
33: Danger of cumulative effects 
50/53: Very Toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment    
Safety Statements: 20/21-28-45-60-61
20/21:  When using, do not eat, drink or smoke 
28: After contact with skin, wash immediately with plenty of ... (to be specified by the manufacturer) 
45: In case of accident or if you feel unwell, seek medical advice immediately (show label where possible) 
60: This material and/or its container must be disposed of as hazardous waste 
61: Avoid release to the environment. Refer to special instructions safety data sheet 
RIDADR: UN 2630 6.1/PG 1
WGK Germany: 3
RTECS: VS7500000
HazardClass: 6.1
PackingGroup: I