dysprosium(III) Chloride
Properties
| State | Solid (hygroscopic; commonly hydrated) |
| Color | white to pale yellow |
| Solubility | Very soluble in water; soluble in alcohols |
| Melting Point | 774 °C (anhydrous) |
About dysprosium(III) Chloride
Dysprosium(III) chloride is the workhorse soluble Dy salt — pale yellow, viciously hygroscopic, and almost always sold as the hexahydrate because the anhydrous form is a genuine pain to obtain cleanly. Try to dehydrate DyCl3·6H2O by simple heating in air and you get DyOCl plus HCl rather than anhydrous DyCl3, a problem shared by the entire heavy-lanthanide chloride series. The standard workarounds are the NH4Cl method (heat the hydrate with a 6:1 excess of NH4Cl, which sublimes off the water as HCl·NH3 and leaves anhydrous DyCl3 behind) or vacuum sublimation at 800 °C under dynamic vacuum. Crystallographically the anhydrous chloride takes the AlCl3 layered structure with 6-coordinate Dy3+, while in aqueous solution the [Dy(H2O)9]3+ aqua ion is the dominant species — that 9-coordination tricapped trigonal prism is characteristic of the larger trivalent lanthanides. The most photogenic application of DyCl3 is in the strontium aluminate phosphor SrAl2O4:Eu2+,Dy3+, the bright green afterglow material in modern emergency exit signs. The Dy3+ acts as a charge-trap dopant: UV light pumps Eu2+, some carriers get caught in Dy3+ trap states, and they leak back out over hours to give the long persistent glow that ZnS:Cu (the old radium-replacement phosphor) couldn't match.
Where you'll encounter it
If you've ever opened a bottle of DyCl3·6H2O on the bench, you've seen it deliquesce into a pale-yellow puddle within minutes — that's not a mistake, it's a hexahydrate that wants to be a heptahydrate or just a solution. In a phosphor synthesis lab, you'd weigh DyCl3 alongside SrCO3, Al2O3, Eu2O3, and a bit of B2O3 flux, then fire under reducing atmosphere (5% H2/N2) at 1200-1400 °C to make the SrAl2O4:Eu,Dy that ends up in glow-in-the-dark watch dials and emergency signage. In a Schlenk-line organolanthanide lab, anhydrous DyCl3 is the entry point to Dy(Cp)3, Dy(Cp*)3, and the single-molecule magnets that have driven the magnetic-anisotropy literature for the past decade.
Common Uses
- Starting material for anhydrous Dy organometallics (cyclopentadienyl, amide complexes)
- Dopant precursor for SrAl2O4:Eu2+,Dy3+ long-afterglow phosphors in safety signage
- Co-dopant source in single-molecule magnet research (Dy3+ has the highest single-ion anisotropy)
- Feedstock for electrolytic production of dysprosium metal in molten chloride baths
- Lewis acid catalyst for selected acetalization and Diels-Alder reactions
- Reagent for Dy3+ separations via solvent extraction with organophosphorus extractants
- Precursor for Dy-doped scintillator and laser host crystal synthesis
- NMR shift reagent precursor for paramagnetic relaxation studies
Safety Information
GHS H315 (skin irritation) and H319 (eye irritation), Category 2/2A. Acute oral toxicity is moderate (LD50 ~3-5 g/kg in rat). The real workplace hazard is HCl evolution when the hydrate contacts skin moisture or warm humid air — wear nitrile gloves and weigh in a hood. No OSHA PEL specifically for Dy compounds, but treat as a respirable nuisance dust at 5 mg/m3. Repeated lanthanide dust inhalation has been linked to pulmonary granulomas in occupational studies of rare-earth refinery workers.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.