Chemical name: Phosphorous acid (98.5% & 99%)
Synonyms: orthophosphorous acid, phosphonic Acid
CAS: 13598-36-2
Molecular formula: H3PO3
Molecular weight: 82
98.5% Specification：
| Item | Standard |
| Appearance | White crystalline |
| H3PO3 | 98.5% min |
| P2O5 | 85% min |
| PO4 | 0.2% max |
| S | 0.008% max |
| Cl | 0.01% max |
| Fe | 0.002% max |
Packing: 25kg bag, customized packing is available.
Usage:
In agriculture, phosphorous acid is used mainly as a fungicide. It is effective against fungal diseases like downy mildew and Phytophthora, which affect various crops. This application is crucial for plant protection and maintaining healthy crop yields.
Key Applications of Phosphorous Acid
- Crop protection: Controls Phytophthora, downy mildew, and other oomycete diseases in grapes, avocados, potatoes, and leafy vegetables.
- Phosphite fertilization: Systemic absorption by plants provides phosphorus nutrition and activates natural defense (SAR).
- Industrial use: Intermediate in the synthesis of phosphonate compounds, flame retardants, and water treatment agents.
- pH regulator: Used to adjust pH in fertilizer blends and nutrient solutions for hydroponics and fertigation.
Unifarm Chemical offers phosphorous acid in 98.5% and 99% purity grades, packaged in 25 kg bags or 250 kg IBC drums. As a leading China exporter, we supply to customers in 30+ countries with reliable lead times and competitive pricing. Request a quotation today.
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Applications
Phosphorous acid has several important applications beyond basic chemical synthesis. In agriculture, phosphite salts derived from phosphorous acid are used as systemic fungicides and plant disease suppressants, particularly against Phytophthora and downy mildew pathogens. Phosphite acts as a plant defence activator rather than a direct fungicide, stimulating the plant’s own SAR (systemic acquired resistance) pathway. Industrial applications include its use as an antioxidant and reducing agent in polymer stabilisation, and as a buffering agent in chemical synthesis. In water treatment, phosphorous acid derivatives inhibit scale formation in cooling tower and boiler systems. It is also used as a precursor in the synthesis of glyphosate herbicide and other organophosphorus compounds. Following the 2026 US executive order classifying elemental phosphorus as a strategic material, global phosphorous acid prices have risen significantly, making supply chain planning critical for downstream users.