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

What is monopotassium phosphite? How does it work? What are its uses?

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 agriculture, horticulture, fine chemicals, and scientific research. 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.

In terms of grading system, potassium dihydrogen phosphite is classified according to its use into industrial grade (agricultural formulation processing, fine chemicals, water treatment), agricultural grade (fertilizer and pesticide formulation), and reagent grade (scientific research experiments), etc.

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 in different applications are as follows:

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

Potassium dihydrogen phosphite provides both phosphorus (phosphite form) 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. 2.Disease resistance induction mechanism (inducing acquired systemic resistance)

3. 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.

4. 3.Direct antibacterial mechanism (inhibition of oomycete pathogens)

5. Phosphite directly inhibits oomycete pathogens such as downy mildew, Phytophthora, and Pythium by interfering with their growth and reproduction. Together with its effect of inducing disease resistance it becomes a powerful component for the control of oomycete diseases.

6. 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.

7. 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 fine phosphite 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 the synthesis of organic phosphorus. It is one of the most widely used phosphite varieties in agriculture, industry, and scientific research.

II. What are all the uses of Monopotassium phosphite?

1. Raw materials for integrated liquid foliar fertiliser and disease resistant nutrient formula (core application of fertiliser industry)

Areas of Application: Fertiliser processing sector.

Related Products: Liquid foliar fertiliser, formulations for field crops, fruit trees and vegetables, integrated disease-resistant and nutrient-rich foliar formulations, high-phosphorus and potash foliar nutrient solutions.

Why it works: Potassium dihydrogen phosphite is very soluble in water and provides both phosphorus and potassium, which can be quickly formulated into high-concentration liquid foliar fertilisers. It is applied by spraying and is easily absorbed by leaves, supplementing crops with phosphorus and potassium nutrients. At the same time, the phosphorus in the phosphite form, after being absorbed by the leaves, can trigger the plant’s disease resistance, so that an integrated approach of “fertilization + disease prevention” is achieved. It is a valuable raw material in foliar fertiliser formulations.

2. Raw materials for water-soluble fertilisers and fertigation fertilisers of drip irrigation (main application in facility agriculture).

Application Fields: Facility agriculture, fertigation.

Related Products: Fertigation Fertiliser, Water Soluble Fertiliser for Drip Irrigation, fertigation nutrient solutions for greenhouses, nutrient solution formulations for soilless cultivation.

Why it works for this purpose: Potassium dihydrogen phosphite is completely soluble in water and does not cause any precipitation or clogging of the drip irrigation system. It can be stably mixed into fertigation nutrient solutions, and supplied directly to the roots for absorption during drip/fertigation. It provides phosphorus and potassium nutrition for greenhouse vegetables, fruits and flowers and also delivers disease resistance. It is a good source of phosphorus and potassium for water-soluble fertilisers and for use in fertigation systems.

3. Seed treatment agents and raw materials for seed coating agents (seed treatment sector)

Areas of application: Seed Coating and Seed Treatment Agent Industry.

Product types: Seed treatment suspensions, seed coating agent components for disease prevention, seed nutrient coating formulations.

Why it works for this use case: Seed coating attaches potassium dihydrogen phosphite to the seed surface. It enters the seedling using water absorbed by the seed after sowing, establishing disease resistance and providing nutrition in the early growth stage. It helps seedlings resist oomycete diseases such as damping-off and seedling blight. It is one of the seed treatment agents that combine nutritional and disease-preventing functions.

4. Industrial reducing agents (fine chemical industry)

Application domains: 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.

5. Raw materials for organophosphorus fine chemicals (fine chemicals industry)

Application Domains: 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. The potassium salt form is useful for metering and control of the reaction. It is one of the phosphorus-source raw materials for synthesis of phosphite flame retardants, organophosphonate water treatment agents and other products.

6. Raw materials for water treatment agents and scale and corrosion inhibitors (water treatment industry)

Uses: 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. Potassium dihydrogen phosphite is widely used in the industrial circulating cooling water treatment and participates in the production chain as a phosphite source.

7. Plant nutrition research

Application fields: Agricultural science research, plant physiology and plant pathology.

Corresponding products: Reagents for the preparation of plant nutrient solutions, reagents for the study of phosphite mechanism of action, reagents for disease resistance induction experiments, and nutrient formulas for greenhouse experiments.

How it is appropriate for this purpose: Pure potassium dihydrogen phosphite has a well-defined composition. It is a standard reagent for studies on phosphite effects on plant nutrition, induction of disease resistance (SAR mechanism) and inhibition of oomycetes. It is also a common raw material for preparation of phosphite treatment solutions in greenhouse and field trials.

In summary,potassium dihydrogen phosphite (CAS 13977-65-6) is a monopotassium salt of phosphoric acid. It has mature applications in eight sectors: agriculture (liquid foliar fertiliser, drip irrigation water-soluble fertiliser, fungicide, seed treatment agent), industry (reducing agent, organophosphorus synthesis raw material, water treatment agent raw material), and scientific research (reagent for plant nutrition and disease resistance research) with five major mechanisms of action: phosphorus and potassium nutrition, disease resistance induction, direct antibacterial activity, reducing properties, and synthetic raw materials. Its phosphorus form has special properties, and is a representative variety of phosphorus and potassium in the integrated agricultural disease resistance fertilisation technology and industrial applications of phosphites.