What are the differences between dihydrate and anhydrous calcium chloride?
Calcium chloride (CaCl₂) is a versatile inorganic salt widely used in de-icing, dust control, refrigeration brines, concrete acceleration, and more. It is sold in two primary forms:
| Property | Dihydrate (CaCl₂·2H₂O) | Anhydrous (CaCl₂) |
|---|---|---|
| Chemical Formula | CaCl₂·2H₂O | CaCl₂ |
| CAS No. | 10035-04-8 | 10043-52-4 |
| Molecular Weight | 147.01 g/mol | 110.98 g/mol |
| Active CaCl₂ Content (theoretical) | ~75.5 % | 100 % |
| Typical Purity Range | 74 – 80 % | 90 – 98 % |
| Water of Crystallization | 20 % (two H₂O molecules) | 0 % |
| Appearance | White, deliquescent flakes/pellets | White, granular/powder |
| Hygroscopicity | Moderately hygroscopic | Extremely hygroscopic |
| Bulk Density | ~0.8 – 1.0 g/cm³ | ~0.9 – 1.2 g/cm³ |
Water Content
Dihydrate contains two molecules of water for each CaCl₂ unit (≈20 % by weight).
Anhydrous contains no crystallization water, giving a higher active-ingredient concentration.
Purity & Strength
Dihydrate grades typically deliver 74 – 80 % CaCl₂ when measured by mass.
Anhydrous grades deliver 90 – 98 % CaCl₂, making them ideal where maximum chloride ion availability is required.
Handling & Storage
Both forms are hygroscopic, but anhydrous absorbs moisture more rapidly—pack and store in airtight, moisture-barrier bags or silos.
Dihydrate is slightly more stable in open air, but still benefits from dry, cool storage.
| Aspect | Dihydrate | Anhydrous |
|---|---|---|
| Cost per kg of CaCl₂ | Lower (contains inert water weight) | Higher (more active material per kg) |
| Transportation Efficiency | Heavier (water content ↑ shipping weight) | Lighter (shipping more CaCl₂ per tonne) |
| Dissolution Rate | Slower (water of crystallization must release) | Faster (pure salt dissolves readily) |
| Ideal Applications | Dust suppression, medium-strength brines | High-strength brines, desiccants, cement accelerator |
Economic Tip: Although dihydrate is cheaper per tonne, anhydrous delivers more active CaCl₂ per shipment—choose based on your application’s cost-vs. performance balance.
| Application | Dihydrate | Anhydrous |
|---|---|---|
| Road De-icing & Anti-icing | ✔ (widely used) | ✔ (more aggressive melting) |
| Dust Control & Soil Stabilization | ✔ | ✔ (faster uptake, longer persistence) |
| Refrigeration Brines | ✔ (lower freezing point) | ✔ (stronger freezing point depression) |
| Concrete Acceleration | ✔ | ✔ (often preferred for precast, rapid-set) |
| Desiccant & Drying Agent | ✘ | ✔ (industrial-grade drying) |
| Industrial Water Treatment | ✔ | ✔ (pH adjustment, hardness control) |
Factory Direct Supply
We manufacture both Calcium Chloride Dihydrate and Anhydrous grades in our ISO-certified facility—guaranteed purity, competitive pricing.
Custom Packaging & Delivery
Options from 25 kg moisture-barrier bags to bulk tankers or ISO-silos, tailored to your operation’s scale.
Technical Support
Dedicated specialists to help you select the right grade, optimize dosage, and troubleshoot end-use performance.