What are the common product specifications for HEDP?

The common product specifications for HEDP (1-Hydroxy Ethylidene-1,1-Diphosphonic Acid) are crucial for ensuring its quality and performance in water treatment applications.

These specifications are typically divided into two main grades: Industrial Grade (the most common) and High-Purity / Electronic Grade.

1. Industrial Grade HEDP (as a 50% or 60% Aqueous Solution)

This is the standard form used in cooling water, boiler water, and other industrial systems. The specifications focus on the active component content and key impurity limits.

Here is a typical specification table for industrial-grade HEDP (50%):

Specification Parameter Typical Value / Range Importance & Reason

Active Content (as HEDP) 50.0% min. (or 60% min. for concentrated grade) The primary performance indicator. Ensures the product has the advertised concentration of the active molecule.

Phosphite (as PO₃³⁻) 1.5% max. A critical quality indicator. Phosphite is the main oxidation product and a process impurity. High levels indicate poor production control or aged/degraded product and can reduce effectiveness.

Orthophosphate (as PO₄³⁻) 0.5% max. Another key impurity. High phosphate can indicate hydrolysis (breakdown) of HEDP and may contribute to calcium phosphate scaling.

pH (1% Aqueous Solution) ~2.0 A characteristic property. Confirms the acidic nature of the product and helps verify its identity and concentration.

Density (20°C) ~1.34 - 1.38 g/cm³ Used for quality control and for converting volumetric dosing to mass-based dosing.

Chloride (as Cl⁻) ~0.3% max. An impurity from the production process. High chloride can increase the corrosivity of the water.

Iron (as Fe) ~0.002% (20 ppm) max. An impurity that can cause discoloration and may interfere with certain applications.

Appearance Colorless to light yellow clear liquid A visual check for purity and the absence of suspended matter or severe degradation.

2. High-Purity / Electronic Grade HEDP

This grade is used in demanding applications where even trace impurities can cause major problems, such as in microelectronics manufacturing for wafer cleaning and ultra-pure water systems.

The specifications for this grade are much stricter, focusing on ultra-low levels of metallic ions.

Specification Parameter Typical Value / Range

Active Content (as HEDP) ≥ 60% or often supplied as a solid (≥ 95%)

Metallic Impurities Extremely Low (in parts-per-billion, ppb)

- Sodium (Na) < 100 ppb

- Iron (Fe) < 50 ppb

- Calcium (Ca) < 50 ppb

- Heavy Metals (e.g., Cu, Ni, Cr) < 10 ppb each

Chloride (Cl⁻) < 1 ppm

Phosphite (PO₃³⁻) < 0.5%

Key Points for Users:

Always Request the SDS and Technical Data Sheet (TDS): Reputable suppliers will provide these documents, which list the exact specifications for their product.

Focus on Active Content and Phosphite: For most industrial applications, the "Active Content" ensures you are getting what you pay for, and the "Phosphite" level is the best indicator of product freshness and quality.

Understand the Trade-Off: High-purity grades command a significantly higher price due to the intensive purification processes required. Use industrial grade for standard water treatment and reserve high-purity grades for critical applications like electronics or pharmaceuticals.

In summary, when procuring HEDP, the common specifications revolve around its active content, the levels of critical impurities like phosphite and orthophosphate, and its physical properties like pH and density.