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Views: 0 Author: Site Editor Publish Time: 2026-08-05 Origin: Site
Calcium chloride dihydrate (CaCl2·2H2O, CAS Number: 10035-04-8) is an inorganic salt composed of calcium, chlorine, and two water molecules of crystallization. It is the most common hydrated form of calcium chloride, typically appearing as white flakes, granules, or crystalline powder.
As a member of the calcium chloride family, the dihydrate form contains approximately 24.5% water of crystallization by weight, giving it a molecular weight of 147.01 g/mol. In nature, it occurs as the rare evaporite mineral sinjarite, first discovered in the Sinjar Mountains of Iraq.
Key characteristics that make calcium chloride dihydrate indispensable across industries:
Highly hygroscopic
● — aggressively absorbs moisture from the air
Deliquescent
● — eventually dissolves in the water it absorbs
Exothermic dissolution
● — releases significant heat when dissolved in water
High water solubility
● — dissolves readily in water at most temperatures
Freezing point depression
● — lowers the freezing point of water substantially
Understanding the physical and chemical profile of calcium chloride dihydrate is essential for proper application and handling.
Property | Value |
Chemical Formula | CaCl2·2H2O |
CAS Number | 10035-04-8 |
Molecular Weight | 147.01 g/mol |
Appearance | White flakes, granules, or crystalline powder |
Odor | Odorless |
Purity (Industrial Grade) | ≥ 74% (as CaCl2) / ≥ 77% (high-purity) |
Purity (Food Grade) | ≥ 99% |
Melting Point | ~175°C (decomposes, loses water of crystallization) |
Solubility in Water (20°C) | 74.5 g/100 mL |
Solubility in Water (60°C) | 134.5 g/100 mL |
pH (5% Solution) | 8.0–10.0 |
Bulk Density | 0.8–1.0 g/cm³ (flakes) |
Heat of Solution | −72.8 kJ/mol (exothermic) |
Choosing between dihydrate and anhydrous forms is one of the most common decisions facing procurement and engineering teams. Here is a side-by-side comparison.
Feature | Calcium Chloride Dihydrate | Anhydrous Calcium Chloride |
Chemical Formula | CaCl2·2H2O | CaCl2 |
CAS Number | 10035-04-8 | 10043-52-4 |
Water Content | ~24.5% (2 H2O molecules) | 0% |
Typical Purity | ≥ 74% (as CaCl2) | ≥ 94% (as CaCl2) |
Physical Form | White flakes (1–2 mm thick) | White beads/prills (2–6 mm diameter) |
Melting Point | ~175°C (decomposes) | 772–775°C |
Heat Stability | Poor above 175°C | Excellent up to 775°C |
Hygroscopicity | High | Very high (stronger desiccant) |
Caking Tendency | Moderate to high | Low |
Shelf Life | 12–24 months | 24+ months (properly sealed) |
Relative Cost | Lower | Higher |
Best For | De-icing, dust control, food processing, concrete, water treatment, oil drilling fluids | Desiccants, high-temperature processes, moisture-sensitive reactions, laboratory use |
● Budget-sensitive large-volume applications
● Processes where the water content is not detrimental
● De-icing, dust control, and concrete acceleration
● Food-grade applications (as firming agent E509)
● Oil & gas drilling fluid formulation
● Applications requiring water exclusion
● High-temperature industrial processes
● Laboratory desiccation and drying tubes
● Moisture-sensitive chemical synthesis
Calcium chloride dihydrate serves as a workhorse chemical across more than a dozen industries. Below are its most significant applications, organized by sector.
De-icing is the single largest end-use application for calcium chloride dihydrate globally.
How it works:
● When spread on icy surfaces, CaCl2·2H2O dissolves and depresses the freezing point of water to as low as
−51°C (−60°F)
. The exothermic dissolution additionally generates heat that accelerates ice melting.
Advantages over NaCl (rock salt):
● Calcium chloride works at much lower temperatures, is less corrosive to concrete when used properly, and acts faster.
Application rate:
● Typically 0.3–0.5 kg/m² for road de-icing, adjusted by temperature and precipitation.
Dust control on unpaved roads, construction sites, and mining haul roads:
● The hygroscopic property keeps surfaces continuously moist by absorbing atmospheric humidity
● Reduces water truck frequency by up to
50%
compared to water-only treatment
● Typical application: 0.5–1.5 L/m² of a 30–38% CaCl2 solution
Calcium chloride dihydrate is a critical component in drilling, completion, and workover fluids.
Drilling fluid density control:
● Added to water-based drilling muds to increase density, helping control formation pressure and prevent blowouts
Shale stabilization:
● The calcium ions inhibit clay swelling and shale dispersion, maintaining wellbore stability
Completion brines:
● Used as a clear, solids-free brine for well completion and workover operations at densities up to 1.40 g/cm³ (11.7 lb/gal)
Cement acceleration:
● Added to oil well cement slurries to reduce WOC (waiting-on-cement) time, especially in low-temperature formations
Typical dosage in oilfield cementing: 2–4% by weight of cement (BWOC).
In the construction industry, calcium chloride dihydrate is the most widely used non-reinforced concrete set accelerator.
Benefit | Detail |
Faster setting time | Can reduce initial set time by up to 50% |
Early strength development | Achieves 7-day strength in 2–3 days |
Cold-weather concreting | Enables concrete placement at temperatures as low as −5°C |
Economic benefit | Faster formwork stripping → shorter project cycle |
Critical note: Calcium chloride should not be used in reinforced concrete due to the risk of chloride-induced rebar corrosion. It is suitable for non-reinforced applications such as:
● Roof tiles
● Pavement stones and paving bricks
● Concrete blocks
● Precast non-structural elements
Typical dosage: 0.5–2.0% by weight of cement.
Calcium chloride dihydrate plays multiple roles in industrial and municipal water treatment.
Fluoride Removal
● Reacts with fluoride ions to form insoluble calcium fluoride (CaF2) precipitate
● Used in treatment of effluent from aluminum smelters, semiconductor fabs, and petroleum refineries
● Helps meet increasingly stringent fluoride discharge limits
Phosphate Reduction
● Precipitates phosphates from agricultural runoff and industrial wastewater as calcium phosphate
● Mitigates eutrophication (excessive algae growth) in receiving water bodies
● The captured phosphate solids can sometimes be repurposed or sold as fertilizer
Sulfate Removal
● Forms gypsum (CaSO4·2H2O) precipitate when reacted with sulfate-bearing effluent
● Applicable to acid mine drainage, demolition wastewater, and mineral processing streams
● Prevents acidification of surface water and soil
Coagulation & Colloid Destabilization
● Acts as an effective coagulant for destabilizing colloidal suspensions
● Used in oil & gas produced water treatment and food & beverage process water
Ballast for Ion Exchange Resins
● Provides calcium ions for water softening regeneration cycles
In the food industry, calcium chloride dihydrate is recognized as a safe food additive (E509 in the EU) with multiple functional roles.
Function | Application Examples |
Firming agent | Canned fruits and vegetables — maintains texture and crispness |
Sequestrant | Prevents undesirable metal-catalyzed reactions in processed foods |
Coagulant | Tofu production — precipitates soy protein to form curds |
Mineral enrichment | Calcium fortification in beverages and sports drinks |
Pickling & brining | Maintains firmness in pickled cucumbers and olives |
Cheese making | Restores calcium balance in pasteurized milk for proper curd formation |
Beer brewing | Adjusts water mineral profile for specific beer styles |
Food grade specifications require ≥ 99% purity and compliance with FCC (Food Chemicals Codex) or equivalent national standards.
Leveraging its exceptional hygroscopicity, calcium chloride dihydrate is a cost-effective desiccant for numerous scenarios.
Shipping container desiccants:
● Calcium chloride-based desiccant packs protect cargo from moisture damage during ocean freight — a single container pole can absorb 2–3 liters of water
Industrial dehumidification:
● Used in warehouse and basement dehumidifier units
Gas drying:
● Dries industrial gases (air, nitrogen, CO2) in drying towers
Moisture-proof packaging:
● Integrated into desiccant sachets for electronics, machinery, and sensitive goods
In synthetic rubber and polymer production, calcium chloride dihydrate serves as a coagulating agent:
● Precipitates polymer from emulsion (latex) by breaking the emulsion
● Used in SBR (styrene-butadiene rubber) and NBR (nitrile rubber) production
● Also applied in the manufacture of acrylic impact modifiers and ABS resins
Coagulant enhancer:
● Improves the performance of organic polymer retention aids
Printability improvement:
● Increases surface electrical conductivity for sharper, more uniform ink transfer
De-inking:
● Facilitates ink removal in paper recycling processes
Web strength:
● Enhances the wet and dry strength of corrugating medium
Calcium chloride dihydrate is commercially available in several grades, each tailored to different end-use requirements.
Parameter | Typical Value |
Purity (as CaCl2) | ≥ 74% (standard); ≥ 77% (high-grade) |
Appearance | White to off-white flakes |
Alkalinity (as Ca(OH)2) | ≤ 0.25% |
Water Insoluble Matter | ≤ 0.15% |
Sulfate (as CaSO4) | ≤ 0.10% |
pH (1% Solution) | 7.0–10.0 |
Parameter | Typical Value |
Purity (as CaCl2·2H2O) | ≥ 99.0% |
Heavy Metals (as Pb) | ≤ 10 ppm |
Arsenic (As) | ≤ 3 ppm |
Fluoride (F) | ≤ 40 ppm |
Lead (Pb) | ≤ 2 ppm |
Magnesium & Alkali Salts | ≤ 4.0% |
