Industrial grade 98% Monopotassium phosphite CAS 13977-65-6

What is monopotassium phosphite? How does it work? What are all the industrial applications?

1. What is Monopotassium phosphite? How does it work?

Monopotassium phosphite, also known as potassium dihydrogen phosphite (or simply potassium phosphite), is a monopotassium salt of phosphorous acid (H3PO3, CAS 13598-36-2). It is one of the most widely used phosphite varieties in agricultural formulations and fine chemicals. Its molecular formula is:

KH2PO3 (molecular weight approximately 120.09; CAS No.: 13977-65-6)

It is a white crystalline powder at room temperature, readily soluble in water, and its aqueous solution is weakly acidic. Chemically, it belongs to the phosphite family (phosphorus has a +3 oxidation state), exhibiting strong reducing properties and can be oxidized to phosphate (phosphorus has a +5 oxidation state). It oxidizes slowly in air and decomposes easily upon heating. Phosphorous acid is a dicarboxylic acid (pKa 1.3 and 6.7, only the two hydroxyl hydrogens can ionize, the hydrogen on the PH bond is not ionized), therefore its potassium salt is divided into two types: potassium dihydrogen phosphite (KH2PO3) and potassium hydrogen phosphite (K2HPO3). This article describes the former. Industrially, it is produced by neutralizing phosphorous acid with potassium hydroxide/potassium carbonate to form a salt, followed by crystallization and drying. It should be stored in a sealed, moisture-proof, and light-protected environment.

From the perspective of its mechanism of action, potassium dihydrogen phosphate exerts its effects through its unique properties of "phosphorus and potassium nutrition + disease resistance induction + direct antibacterial effect + reducing properties + synthetic raw material". The mechanisms of action for the different applications are:

1.Phosphorus and potassium nutrition mechanism (dual-element nutrients)

Potassium dihydrogen phosphite provides phosphorus (as phosphite) and potassium, two essential plant nutrients. It is very soluble in water, and is readily taken up and used by plants. Potassium is involved in osmotic regulation and photosynthesis. Phosphorus in phosphite form can be converted into a usable form within the plant, providing a nutritional basis for its use as a water-soluble fertiliser and foliar fertiliser.

2.Disease resistance induction mechanism (inducing acquired systemic resistance)

Phosphate ions entering the plant can also induce plant’s defence response (systemically acquired resistance, SAR) by stimulating the plant to synthesise disease-resistant substances such as phytoalexins and defence enzymes (such as peroxidase and chitinase) so that the plant can develop broad spectrum resistance to a variety of diseases. This is the basic mechanism which sets phosphate apart from common phosphate fertilisers.

3.Direct antibacterial mechanism (inhibition of oomycete pathogens)

Phosphite directly inhibits oomycete pathogens like downy mildew, phytomyces and pythium, interfering with their growth and reproduction. Combined with the induced effect of disease resistance, it is an effective ingredient for the prevention and control of oomycete diseases (corresponding preparations are widely registered and used around the world).

4.Reduction mechanism (phosphite reducing property)

The phosphorus in potassium dihydrogen phosphite has a +3 oxidation state and strong reducing ability. It can be oxidized to +5 phosphate and can reduce oxidizing substances such as noble metal ions, which is the chemical basis for its use as an industrial reducing agent.

5.Synthesis raw material mechanism (phosphite source)

Potassium dihydrogen phosphite can be used as a source of phosphite ions to participate in the synthesis of phosphorus-based fine chemicals such as phosphite esters and organophosphonates, and is a phosphorus source raw material in the fine chemical industry chain.

In summary, potassium dihydrogen phosphite is a multi-functional phosphite fine chemical: as a fertilizer raw material, it provides phosphorus and potassium nutrition to crops; as a fungicide raw material, it induces plant disease resistance and directly inhibits oomycetes; as a reducing agent, it participates in chemical reduction; and as a phosphorus source, it participates in organophosphorus synthesis. It is one of the most widely used phosphite varieties in agricultural formulations and fine chemicals.

What are all the uses of industrial-grade Monopotassium Phosphite?

1. Raw materials for liquid foliar fertilisers and water soluble fertilisers (fertiliser industry, core application)

Areas of Application: Fertiliser manufacturing industry.

Related Products: liquid foliar fertiliser, drip irrigation water soluble fertiliser, fertigation fertiliser, water soluble phosphorus and potassium fertiliser raw material, compound fertiliser synergist components.

Why it works for this purpose: Potassium dihydrogen phosphite has excellent water solubility and contains phosphorus and potassium, so it can be quickly formulated into high concentration liquid fertilisers. It is rapidly absorbed by crops after spraying or drip irrigation to supplement phosphorus and potassium nutrients. Its phosphite form also delivers disease-resistant and synergistic effects, making it a high-value phosphorus and potassium raw material for water-soluble fertiliser and foliar fertiliser formulations.

2. Fine chemicals industry (industrial reducing agents)

Application areas: Hydrometallurgy and fine chemicals.

Related products: Reducing agents for precious metal ions, Reducing agents for chemical reduction processes, Auxiliary reducing agents for metal surface treatment.

Why this is good for this application: The trivalent phosphorus in potassium dihydrogen phosphite has strong reducing properties. It can be oxidised to pentavalent phosphate, which can reduce oxidising species such as precious metal ions (e.g. silver, mercury). Thus it can be used in precious metal recovery and chemical reduction processes. This is an industrial application of the reducing properties of phosphite.

3. Raw materials for synthesis of organophosphorus fine chemicals (fine chemical industry)

Application Fields: Organic Chemistry.

Matching Products: Phosphonates, phosphites and raw materials for synthesising organophosphonate scale and corrosion inhibitors.

Why it is appropriate for this application: Potassium dihydrogen phosphite can be used as a source of phosphite (phosphonate) for the synthesis of phosphorus-based fine chemicals. It exists as a potassium salt, which is easy to meter and control during reactions. It is one of the phosphorus-source raw materials for synthesising phosphite flame retardants, organophosphonate water treatment agents and other products.

4. Water treatment agents & raw materials for scale and corrosion inhibitors (water treatment industry)

Applications: Industrial water treatment.

Related Products: Raw materials for synthesis of cooling tower scale and corrosion inhibitor (ATMP and HEDP type organophosphonic acid water treatment agents) and components of circulating water treatment formulations.

How it helps: Phosphites can be used to prepare organophosphonic acid scale and corrosion inhibitors such as aminotrimethylene phosphonic acid (ATMP) and hydroxyethylidene diphosphonic acid (HEDP). The scale and corrosion inhibition effects of these water treatment agents are realised by chelating calcium and magnesium ions and adsorbing them on metal surfaces. They are widely used in the treatment of industrial circulating cooling water, where potassium dihydrogen phosphite participates in the production chain as a source of phosphite.

In summary, the Monopotassium salt of phosphorous acid (CAS 13977-65-6) is known as Potassium dihydrogen phosphite. It has five major mechanisms of action: phosphorus and potassium nutrition, induction of disease resistance, direct antibacterial activity, reducing property and synthetic raw material. It has mature applications in five major sectors: fertiliser industry (liquid foliar fertiliser, water-soluble fertiliser), pesticide formulation industry (fungicides, disease resistance inducers), fine chemicals (reducing agents, organophosphorus synthesis raw materials), and water treatment industry (organophosphonic acid scale and corrosion inhibitor raw materials). Because of the special properties of the phosphorus phosphorus form, it is a typical phosphorus and potassium raw material in the comprehensive agricultural disease-resistant fertilisation technology.