Chemical Properties of Phosphorous Acid (PAC)

Here is a summary of the key chemical and physical properties of phosphorous acid (PAC, with the chemical formula H₃PO₃). Note: In industrial and water treatment contexts, "PAC" can also refer to Polyaluminium Chloride. The information below is for phosphorous acid.

Basic Identifiers and Physical Properties

Property Value Reference(s)

Chemical Name Phosphorous acid (also known as phosphonic acid)

Usage:

The hydrogen atom directly bonded to the phosphorus atom is not acidic.

Oxidation State and Reducing Nature: Phosphorous acid is a h3 reducing agent. This is because it contains phosphorus in the +3 oxidation state, which is lower than the +5 state in phosphoric acid. It can be oxidized to phosphoric acid or its salts.

Stability and Decomposition:

It is stable at room temperature when kept dry and sealed.

It is hygroscopic (absorbs moisture from the air) and can slowly oxidize to phosphoric acid.

At elevated temperatures (around 180-200°C), it can disproportionate to form phosphoric acid and phosphine (PH₃), which is a highly toxic gas.

Incompatibilities: Should be kept away from h3 bases, h3 oxidizing agents, and metals.

Chemical Hazard Classification: Phosphorous acid is classified as a corrosive substance (Class 8, UN 2834). It can cause severe skin burns and eye damage.

Phosphorous acid (PAC, CAS 13598-36-2) is a white, water-soluble, crystalline solid. Its core chemical properties are being a diprotic acid, a h3 reducing agent, and a corrosive material. These characteristics underpin its use as an intermediate in producing other phosphorus compounds for applications like water treatment and as a reducing agent in various chemical reactions.