Calcium chloride 94% (CAS 10043-52-4) is the near-anhydrous grade – the same salt as the 74% flakes but without most of the water of crystallisation. That difference of twenty percentage points is not a purity claim: it is a different hydrate form, with different freight economics, different dissolution behaviour and one serious handling consequence – the anhydrous material is strongly hygroscopic and will absorb its way back towards the dihydrate if it is left open.
Specifications
| Property | Specification |
|---|---|
| Appearance | White |
| Purity as CaCl2 | 94% min |
| Alkalinity as Ca(OH)2 | 0.25% max |
| Total alkali chloride (as NaCl) | 5.0% max |
| Water insoluble matter | 0.25% max |
| Iron (Fe) | 0.006% max |
| pH | 7.5 – 11.0 |
| Total magnesium (as MgCl2) | 0.5% max |
| Sulphate (as CaSO4) | 0.05% max |
| CAS number | 10043-52-4 |
| Formula / MW | CaCl2 / 110.98 g/mol |
94% is not “pure”, and it is not 100% either
| Form | CAS | Theoretical CaCl2 | What the commercial figure means |
|---|---|---|---|
| Dihydrate | 10035-04-8 | 75.5% | Sold as 74% min – essentially the pure hydrate |
| Monohydrate | – | 86.0% | Rarely traded as a distinct product |
| Near-anhydrous (this product) | 10043-52-4 | 100% | Sold as 94% min – the balance is residual water, NaCl, MgCl2, Ca(OH)2 and insolubles |
So a 94% figure means “close to anhydrous, with the usual industrial impurities”. A laboratory-grade anhydrous calcium chloride assays far higher; this is a technical grade and should be read that way. The 5% NaCl allowance is the largest single impurity and is the same in both grades – if chloride is a problem in your application, the difference between the two products does not help you.
The handling consequence: it rehydrates
Anhydrous calcium chloride is one of the strongest common desiccants, which is useful when you want it to dry something and awkward when you do not:
| Behaviour | Practical effect |
|---|---|
| Absorbs atmospheric moisture rapidly | An open bag absorbs water until it can become the dihydrate – at which point the CaCl2 content has fallen towards 75%, and the assay on the label no longer describes the material in the drum |
| Deliquesces above about 30% relative humidity | Fused lumps, blocked feeders, and a product that cannot be weighed accurately |
| Releases heat on dissolution | Dissolving anhydrous CaCl2 is strongly exothermic – hotter than the dihydrate. Add it to water slowly, never the reverse, and expect the solution to get hot |
| Releases heat on hydration | Even absorbing moisture generates heat, which is a real consideration in bulk storage |
This is the single most important difference in day-to-day use: the 94% grade demands better packaging discipline than the 74% grade, and a partially used bag is a genuine problem rather than an inconvenience.
Where the near-anhydrous grade is the right choice
- Desiccation and gas dehydration – where the water capacity per kilogram of product is what you are buying, and the 25% water in the dihydrate would be dead weight.
- Long-distance freight – you are not paying to ship water of crystallisation, which can make the 94% grade cheaper per tonne of CaCl2 delivered despite a higher unit price.
- Oilfield completion and workover fluids – high-density brines where the water balance is calculated precisely.
- Concentrated solution preparation – where a plant makes up brine on site and wants maximum salt per bag.
- De-icing in premium or blended products – where a higher active content reduces storage footprint.
Two restrictions that apply to both grades
- Chloride and reinforcing steel. Calcium chloride accelerates set but attacks rebar. Standards in most markets limit chloride ion in concrete, and the material is not permitted in prestressed concrete. Use it in plain concrete or where the standard explicitly allows.
- It is an industrial specification, not a food grade. Food-grade calcium chloride (E509) has tighter limits on heavy metals and on the NaCl allowance than the 5% permitted here. If the application is food, say so – the same CAS is available to a food specification, but this sheet is not it.
Buying notes
- Compare on delivered CaCl2, including freight. A 94% grade at a higher price per tonne can still be cheaper once the water in the 74% grade stops being shipped for free.
- Insist on intact moisture-barrier packaging and check it on arrival; a split bag of anhydrous material is not a small defect.
- Confirm the physical form (flake, prill, powder) – dissolution rate and feeding behaviour differ.
- Ask whether the assay is on an as-received or dried basis, because for a hygroscopic material that distinction decides what the number means.
- Plan consumption against pack size; half-used bags are the most common source of “the product went lumpy”.
Packaging and supply
Supplied in 25 kg PP-woven or paper bags with an inner moisture barrier, in big bags, or in bulk tankers for large users. Storage must be dry and sealed: this grade is deliquescent and will draw moisture from humid air. Every lot ships with a COA and SDS, FOB or CIF against destination. For desiccant, oilfield or food applications, state the end use at enquiry stage so the specification and the documentation package match.
Further reading
- Calcium chloride 74% vs 94%: hydrate form, assay and which one to buy
- Calcium chloride applications by grade: de-icing, drying, oilfield and concrete
- Reading a calcium chloride specification: NaCl, alkalinity and insolubles
PolyBlueChem supplies calcium chloride 94% (CAS 10043-52-4), alkalinity 0.25% max, NaCl 5.0% max, with per-batch COA and SDS and FOB/CIF delivery. Tell us whether you are buying for desiccation, brine preparation or de-icing, and we will confirm the form, the packaging and the delivered cost per tonne of CaCl2.
