Soda lime (also known as sodium lime or indicating soda lime) is a granular mixture of calcium hydroxide (Ca(OH)₂) and sodium hydroxide (NaOH) or potassium hydroxide (KOH). It appears as white to off-white, porous granules with a uniform particle size distribution. Soda lime is chemically formulated to provide efficient and reliable carbon dioxide (CO₂) removal through a controlled chemical reaction, converting CO₂ into stable carbonate compounds. It is non-toxic, odorless, and partially soluble in water.
As the most widely used CO₂ absorbent in medical, industrial, and safety applications, soda lime is the preferred choice for closed-circuit anesthesia systems, respiratory therapy, diving rebreathers, mine refuge chambers, and industrial gas purification.
Parameter | Typical Value | Reference Standard |
Appearance | White to off-white granules | Visual |
CO₂ Absorption Capacity | >25% – 35% (by weight) | USP-NF |
CO₂ Activity | >35% | USP-NF |
CO₂ Absorption Rate | >140 L/kg | USP-NF |
Moisture Content (H₂O) | 12% – 19% | USP-NF |
Moisture Absorption | <7.5% | USP-NF |
Loss on Drying | ≤7.0% – 7.5% | USP-NF |
Particle Hardness | ≥80% | USP-NF |
Particle Size | 2.5 – 5.0 mm (irregular D-shaped) | USP-NF |
Fines Content | ≤1.0% | USP-NF |
Bulk Density | ~2.0 g/cm³ | USP-NF |
Color Change (Indicating Grade) | White → Purple | Visual |
pH (Before Use) | 12 – 14 | USP-NF |
pH (After Use) | ~10 | USP-NF |
With a CO₂ absorption capacity exceeding 140 L/kg and CO₂ activity greater than 35%, our soda lime delivers dependable and efficient CO₂ removal in critical applications. The porous, loose structure maximizes surface area for rapid chemical reaction.
Medical-grade soda lime contains a pH-sensitive indicator dye (ethyl violet) that provides a visual indication of exhaustion. As CO₂ is absorbed, the granules change distinctly from white to purple. When the deep purple color has penetrated to approximately half the depth of the absorber, the material should be replaced.
Our soda lime is processed to minimize dust formation (fines ≤1.0%). The high particle hardness (≥80%) ensures minimal attrition during handling, transportation, and operation.
Medical-grade formulations are KOH-free, minimizing anesthetic agent degradation (such as sevoflurane to Compound A) and reducing the risk of harmful byproduct formation.
In closed anesthesia circuits, each kilogram provides approximately 10 hours of effective CO₂ absorption under normal operating conditions. Low moisture absorption (<7.5%) helps maintain stable performance during storage.
Soda lime removes carbon dioxide through a controlled two-step chemical reaction.
Step 1 – CO₂ Absorption
Carbon dioxide reacts with calcium hydroxide to produce calcium carbonate and water.
Reaction: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O
Step 2 – Hydroxide Regeneration
Sodium hydroxide acts as a catalyst, regenerating calcium hydroxide.
Reaction: CaCO₃ + 2NaOH → Na₂CO₃ + Ca(OH)₂
Overall Reaction: 2NaOH + CO₂ → Na₂CO₃ + H₂O
The color indicator changes because the granule pH gradually decreases as hydroxide is consumed. The ethyl violet indicator changes from white to purple, providing a clear visual signal that the absorbent is exhausted.
Application Area | Specific Use | Recommended Grade |
Medical / Anesthesia | CO₂ removal in closed-circuit anesthesia systems and respiratory therapy equipment | Medical Grade (KOH-free) |
Diving / Rebreather | CO₂ scrubbing in closed-circuit scuba rebreathers | Medical or Industrial Grade |
Mine Refuge Chambers | CO₂ removal in emergency shelter environments | Industrial Grade |
Laboratory | CO₂ absorption for gas analysis and carbon determination | Analytical Grade |
Industrial Gas Purification | Drying neutral gases (oxygen, ammonia) and absorbing acidic gases (CO₂, SO₂) | Industrial Grade |
Soda lime is a non-regenerable adsorbent.
Although exhausted soda lime may partially return to its original white color due to unreacted hydroxide inside the granules, this does not indicate restored adsorption capacity. The material has very little remaining CO₂ absorption capability and should never be reused. Absorber canisters should be emptied and refilled with fresh soda lime after use.
Spent soda lime should be disposed of according to local environmental regulations. Since the material remains mildly alkaline (pH approximately 10 after use), neutralization may be required before disposal where applicable.
Available Grades:
– Medical Grade (KOH-free): For anesthesia and respiratory therapy; low dust, high hardness, sensitive color indication
– Analytical Grade (AR/CP): For laboratory CO₂ absorption and carbon determination
– Industrial Grade: For diving, mining, and industrial gas purification
Available Sizes: 2.5 – 5.0 mm irregular D-shaped granules (standard); other sizes available upon request
Packaging Options: – 500g, 1kg, 4.5kg, 5kg containers, – 16kg drums , – Custom packaging available upon request
Shelf Life: 3 years when stored in sealed, airtight containers under dry, cool conditions
Storage Conditions: Store in a tightly sealed container, protected from light, in a cool, dry, well-ventilated area. Keep away from acids and ammonia salts. Do not open packaging before use to prevent moisture absorption and premature CO₂ exposure.
Our soda lime meets or exceeds United States Pharmacopoeia – National Formulary (USP-NF) specifications and is manufactured in accordance with Good Manufacturing Practices (GMP) and ISO Quality Management Systems. Products are available with CE and ISO certifications.
HENTEKCAT provides comprehensive technical support, including:
HENTEKCAT – Adsorption Technologies, Engineered for Performance.
