Calcium chloride 74% flakes (CAS 10035-04-8) is the dihydrate grade – CaCl2·2H2O – supplied as white flakes with a minimum CaCl2 content of 74%. That figure looks low next to a 94% grade until you recognise that it is the hydrate, not the anhydrous salt: the theoretical CaCl2 content of the dihydrate is 75.5%, so 74% is essentially pure dihydrate with a small allowance for impurities. PolyBlueChem supplies it with per-batch COA and SDS.
Specifications
| Property | Specification |
|---|---|
| Appearance | White flakes |
| Purity as CaCl2 | 74% min |
| Alkalinity as Ca(OH)2 | 0.2% max |
| Total alkali chloride (as NaCl) | 5.0% max |
| Water insoluble matter | 0.15% 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 | 10035-04-8 |
| Formula / MW | CaCl2·2H2O / 147.01 g/mol |
Why 74% and not 99%: the hydrate question
| Form | CAS | Formula | MW | Theoretical CaCl2 content |
|---|---|---|---|---|
| Dihydrate (this product) | 10035-04-8 | CaCl2·2H2O | 147.01 | 75.5% |
| Monohydrate | – | CaCl2·H2O | 128.99 | 86.0% |
| Anhydrous | 10043-52-4 | CaCl2 | 110.98 | 100% |
The 74% figure is a hydrate composition, not a purity failure. Two-thirds of what you are buying in a 74% flake is CaCl2 and the rest is water of crystallisation – water that you are paying freight on and that will be released when the material dissolves or is heated.
This leads directly to the comparison that matters: never compare a 74% grade with a 94% grade on price per tonne. Compare on cost per tonne of CaCl2 delivered, and then ask what the water in the hydrate is going to do in your process.
Where the dihydrate is the right choice
- De-icing and road salt – the traditional use. The dihydrate dissolves readily and generates heat on dissolution, which is exactly what is wanted on ice. The water content is irrelevant in this application.
- Dust suppression and unpaved road stabilisation – the hygroscopic action keeps the surface damp.
- Concrete acceleration – accelerates set, subject to the chloride restriction described below.
- Oilfield brines and drilling fluids – where density and freezing-point depression matter more than the exact hydrate form.
- Cold storage and refrigeration brines – calcium chloride brines work to lower temperatures than sodium chloride.
The chloride warning that applies to concrete
Both grades of calcium chloride contain chloride – that is the point of the material – but chloride attacks reinforcing steel. For reinforced or prestressed concrete, standards in most markets limit the total chloride ion content of the mix (commonly expressed as a percentage by mass of cement), and calcium chloride accelerator is not permitted in prestressed concrete and is restricted in reinforced concrete. Use it in plain concrete, in cold-weather acceleration of unreinforced work, or where the standard explicitly allows it – not as a general-purpose accelerator.
Separately, the 5% NaCl permitted by this specification adds chloride that is not part of the CaCl2 figure. If you are buying for a chloride-sensitive application, that allowance matters and should be checked against the total, not just the assay.
Reading the rest of the specification
| Item | Why it is on the sheet |
|---|---|
| Alkalinity as Ca(OH)2 | Free lime from the manufacturing route; high alkalinity affects pH-sensitive applications and can cause caustic attack |
| Total alkali chloride as NaCl | Carried through from the raw material and process; the largest impurity by far, and the one that matters most in chloride-sensitive uses |
| Water insoluble matter | Sludge and grit; it settles in tanks, blocks dosing lines and shows up as haze in brines |
| Iron | Colour and staining; critical in textile and paper applications, tolerable in de-icing |
| pH 7.5 – 11.0 | A wide window that reflects the alkalinity allowance – do not read it as a tight process control |
| Magnesium as MgCl2 | From the raw mineral; affects brine behaviour and the purity of any downstream calcium product |
| Sulphate as CaSO4 | Low-solubility salt that can precipitate in brines and foul equipment |
Buying notes
- Quote on CaCl2 content, not on product weight, and state the hydrate form you are comparing.
- Ask for the NaCl figure as well as the assay – it is the impurity that decides whether the material fits a chloride-sensitive application.
- Confirm the physical form: flakes, granules and pellets behave differently in dosing equipment and in dissolution rate.
- Check packaging against moisture: calcium chloride is strongly hygroscopic, so an intact moisture barrier is the difference between free-flowing flakes and a fused block.
- State the application so that the grade and the documentation match – a de-icing buyer and a food buyer need different paperwork for the same CAS.
Packaging and supply
Supplied in 25 kg PP-woven or paper bags with an inner moisture barrier, in big bags, or in bulk. The material is highly hygroscopic and deliquescent: bags should stay sealed, off damp floors and out of humid air, because a caked bag cannot be dosed and is not a warranty issue that is easy to win. Every lot ships with a COA and SDS, FOB or CIF against destination. For de-icing, dust suppression and oilfield use, the standard industrial package is appropriate; for any food-contact or regulated use, say so at enquiry stage because this grade is an industrial specification, not a food-grade one.
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 74% flakes (CAS 10035-04-8, dihydrate), alkalinity 0.2% max, NaCl 5.0% max, with per-batch COA and SDS and FOB/CIF delivery. Tell us the application and the form your handling equipment needs, and we will confirm the grade and the packaging.
