What Is Hypophosphorous Acid?
Hypophosphorous acid, with the molecular formula H3PO2, is known for its potent corrosive properties, capable of causing blindness and skin irritation upon contact. Its CAS registration number is 6303-21-5.
Uses of Hypophosphorous Acid
Valued for its reducing power, hypophosphorous acid’s primary applications include roles as a reducing agent in electroless plating, a catalyst in organic synthesis, a surface treatment agent, an antioxidant, and a thermal change inhibitor. It also serves as a bleaching and decolorizing agent for synthetic fibers and plastics and as a precursor for phosphinic acid salts and various substances used as dispersants, emulsifiers, and wet antistatic agents.
Properties of Hypophosphorous Acid
This inorganic acid has a molecular weight of 66.00, melts at 26.5°C, and boils at 130°C. Appearing as a clear, colorless oily liquid or solid at room temperature, its density is 1.493 g/mL and an acid dissociation constant (pKa) of 1.2. Hypophosphorous acid is soluble in water, alcohols, and ethers, and decomposes into phosphoric acid and phosphine when heated.
Types of Hypophosphorous Acid
Available as an industrial chemical and R&D reagent, hypophosphorous acid is sold in 30% or 50% solutions. Industrial grades often come in 25 kg polyethylene cans or 200 L drums, catering to various applications. For research purposes, smaller quantities such as 25g, 100g, and 500g solutions are common, with storage recommendations at room temperature.
Other Information on Hypophosphorous Acid
1. Synthesis of Hypophosphorous Acid
The synthesis involves boiling phosphorus in an alkaline solution to form a hypophosphorous acid solution. Precipitation of phosphorous acid salts as calcium salts removes them, followed by treatment with a non-oxidizing strong acid (e.g., sulfuric acid) to yield hypophosphorous acid.
2. Chemical Reaction of Hypophosphorous Acid
Hypophosphorous acid, favoring the HP(O)(OH)2 tautomeric form for its stability, showcases its reducing power by converting chromium(III) oxide to chromium(II) oxide. Upon heating to about 110°C, it decomposes into phosphorous acid and phosphine. It reacts violently with alkaline substances and metals, necessitating careful storage away from high temperatures, sunlight, and moisture.
3. Hazardousness of Hypophosphorous Acid and Regulatory Information
Identified as hazardous, hypophosphorous acid can cause metal corrosion, serious skin burns, and eye damage. While not classified under specific laws, it is regulated as a corrosive substance for transportation and storage. Appropriate handling measures, including personal protective equipment, are essential to prevent skin, eye, and clothing contact.