Here is a detailed overview of the physical properties of GLDA·Na₄ (Tetrasodium Glutamate Diacetate).
GLDA·Na₄ is the tetrasodium salt of GLDA, which is the most common commercial form due to its high solubility and stability. It is a next-generation, readily biodegradable chelating agent derived from a natural, renewable feedstock (fermented sugar).
Its physical properties are typically described for its aqueous solution form, as it is rarely isolated as a dry solid for commercial use.
Key Physical Properties of GLDA·Na₄ (Typically as a Solution)
| Property | Description & Typical Value for a ~40% Solution |
|---|---|
| Chemical Name | Tetrasodium Glutamate Diacetate |
| Molecular Formula | C₉H₇NNa₄O₈ |
| Appearance | Clear, light yellow to amber liquid. |
| Odor | Faint, characteristic odor. Often described as mild and slightly sweet or odorless. |
| Solubility | Miscible with water in all proportions. Very high solubility. Practically insoluble in non-polar organic solvents (e.g., ethanol, acetone, toluene). |
| Density | Approximately 1.25 – 1.35 g/cm³ at 20°C (for a ~40% active solution). This is higher than water. |
| pH | Strongly alkaline. Typically between 11.0 – 12.5 for a concentrated solution (e.g., 38-40% active matter). This is due to it being a tetrasodium salt. |
| Viscosity | Low to medium viscosity liquid, similar to a thin syrup. Viscosity increases with concentration and decreases with temperature. |
| Boiling Point/Freezing Point | The solution’s boiling point is slightly above that of water (~101-103°C). The freezing point is depressed well below 0°C. Exact values depend on concentration. |
| Stability | Excellent thermal and chemical stability. Stable in alkaline conditions and under high temperatures. Stable in the presence of oxidants and reducing agents. |
| Hygroscopicity | The solid form (if isolated) is highly hygroscopic, meaning it readily absorbs moisture from the air. This is a key reason it is sold as a solution. |
Detailed Explanation of Properties:
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Appearance and Solubility:
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The clear, amber-yellow color is typical and results from its manufacturing process from natural feedstocks.
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Its extremely high water solubility is a critical property, driven by its four sodium ions (-Na⁺) and multiple polar carboxylate groups (-COO⁻), which form extensive hydrogen bonds with water molecules. This allows for easy handling, dosing, and rapid action in aqueous systems.
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pH (Alkaline Nature):
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The high pH (strongly alkaline) is a direct result of it being the tetrasodium salt. In water, it fully dissociates into the GLDA⁴⁻ anion and Na⁺ ions, creating a basic solution.
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Handling Implication: This high pH requires appropriate safety precautions (safety glasses, gloves) as it can cause skin and eye irritation. It is chemically the opposite of acidic chelants like HEDP.
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Viscosity and Density:
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The density is greater than water due to the high concentration of dissolved salts and organic molecules.
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The viscosity is manageable for pumping and pouring, though it is more viscous than water.
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Stability:
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Thermal Stability: GLDA exhibits excellent stability across a wide temperature range, making it suitable for hot process applications like cleaning-in-place (CIP) in food and dairy industries, and textile processing.
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Stability to Hydrolysis: Unlike some esters or amides, the molecular backbone of GLDA is very stable and does not hydrolyze (break down with water) under normal conditions, ensuring long-term performance.
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Oxidative Stability: It maintains its chelating power even in the presence of oxidants like hydrogen peroxide or peracetic acid, which is why it’s a key component in “bleach-containing” detergents and cleaners.
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Biodegradability (A Crucial “Functional” Property):
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While not a classic “physical” property, its ready biodegradability is a defining characteristic. Derived from natural amino acids, microorganisms in the environment can completely break it down via the glutamate pathway, minimizing environmental persistence. This is a major advantage over non-biodegradable chelants like EDTA.
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Physical Form in Commerce:
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GLDA·Na₄ is almost exclusively available as a liquid solution with active matter concentrations typically around 38-40% or sometimes higher (~50%). It is not commonly found as a powder due to its hygroscopic nature.
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Summary Table for Quick Reference
| Property | Value / Description for GLDA·Na₄ (~40% Solution) | Significance |
|---|---|---|
| Form | Low viscosity Liquid | Ease of handling, pumping, and dosing. |
| Color | Clear, Light Yellow to Amber | Visual identification. |
| Solubility | Completely Miscible with Water | Rapid dissolution and effectiveness. |
| pH | 11.0 – 12.5 (Strongly Alkaline) | Defines its applications; requires safe handling. |
| Density | ~1.3 g/mL | Important for calculating dosage by weight or volume. |
| Key Differentiator | High Chelating Strength + Ready Biodegradability | Powerful performance with an excellent environmental profile. |
Comparison with Common Chelants:
| Property | GLDA·Na₄ | EDTA·Na₄ | NTA·Na₃ | Citric Acid |
|---|---|---|---|---|
| Typical Form | Liquid (~40%) | Powder / Solution | Powder | Powder / Solution |
| pH (1% sol.) | ~11.5 | ~11.3 | ~10.5 | ~2.2 |
| Biodegradability | Readily Biodegradable | Not Readily Biodegradable | Readily Biodegradable | Readily Biodegradable |
| Solubility | Very High | High | High | High |
In conclusion, the physical properties of GLDA·Na₄—particularly its high water solubility, alkaline pH, liquid form, and stability—make it an easy-to-use and effective chelating agent for a wide range of applications, from cleaning and personal care to water treatment and agriculture, all while supporting a strong green and sustainable profile.