Molecular Structure:

Molecular Formula: H₃O₂P
Molecular Weight: 65.9964
IUPAC Name: Phosphenous acid
Synonyms of Hypophosphorous acid (CAS NO.6303-21-5): EINECS 228-601-5 ; Hypophosphorous acid (VAN) ; Hypophosphorus acid ; NSC 41904 ; Phosphine oxide, hydroxy- ; Phosphonous acid (VAN) ; Phosphinic acid
CAS NO: 6303-21-5
Classification Code: Pharmaceutic aid [antioxidant]
Product Categories:  Buffer
Melting Point: -25 °C 
H bond acceptors: 2
H bond donors: 1
Polar Surface Area: 37.3 Å² 
Boiling Point: 108 °C 
Density: 1.206 g/mL at 20 °C
Water Solubility: SOLUBLE
Merck: 13,4894
Stability: Stable:. Incompatible with strong bases. Reacts violently with oxidizing agents, strong bases, mercury (II) nitrate and mercury (II) oxide. Do not heat above 100 C.
SMILES: O=PO 
InChI: InChI=1/H3O2P/c1-3-2/h3H2,(H,1,2) 
InChIKey: ACVYVLVWPXVTIT-UHFFFAOYAQ
Std. InChI: InChI=1S/H3O2P/c1-3-2/h3H2,(H,1,2) 
Std. InChIKey: ACVYVLVWPXVTIT-UHFFFAOYSA-N

 Hypophosphorous acid (CAS NO.6303-21-5) is used in the formulation of pharmaceuticals, discoloration of polymers, water treatment, retrieval of precious or non-ferrous metals. Its main use is for electroless plating. In organic chemistry, It is used in the reduction of arenediazonium salts.

 Hypophosphorous acid (CAS NO.6303-21-5) is prepared industrially via a two step process. Hypophosphite salts of the alkali and alkaline earth metals result from treatment of white phosphorus with hot aqueous solution of the appropriate hydroxide
P₄ + 3OH+ 3H₂O → 3H₂PO ₂ + PH₃
The free acid may be prepared by the action of a strong acid on these hypophosphite salts.
H₂PO₂ + H⁺ → H₃PO₂
Alternatively, H₃PO₂ arises by the oxidation of phosphine with iodine in water.
PH₃ + 2I₂ + 2H₂O → H₃PO₂ + 4I + 4H⁺
HPA is usually supplied as a 50% aqueous solution.

Safety Information of Hypophosphorous acid (CAS NO.6303-21-5):
Hazard Codes:C
Risk Statements:34
34:Causes burns
Safety Statements:26-36/37/39-45
26:In case of contact with eyes, rinse immediately with plenty of water and seek medical advice
36/37/39:Wear suitable protective clothing, gloves and eye/face protection
45:In case of accident or if you feel unwell, seek medical advice immediately (show the label where possible)
RIDADR:UN 3264 8/PG 3
WGK Germany:1
RTECS:SZ6400000
HazardClass:8
PackingGroup:II
Reaction with mercury(II) oxide is explosive. Violent reaction with mercury(II) nitrate. When heated to decomposition it emits toxic fumes of PO_x.

First Aid Measures of Hypophosphorous acid(6303-21-5):
Eyes:Immediately flush eyes with plenty of water for at least 15 minutes, occasionally lifting the upper and lower eyelids. Get medical aid immediately.
Skin:Get medical aid immediately. Immediately flush skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes.
Ingestion:Do not induce vomiting. If victim is conscious and alert, give 2-4 cupfuls of milk or water. Get medical aid immediately.
Inhalation:Get medical aid immediately. Remove from exposure and move to fresh air immediately. If not breathing, give artificial respiration. If breathing is difficult, give oxygen.

Storage of Hypophosphorous acid(6303-21-5):
Store in a cool, dry place. Store in a tightly closed container. Corrosives area.