erbium(III) Chloride
Properties
| State | Solid (hygroscopic; commonly hydrated) |
| Color | pink |
| Solubility | Very soluble in water; soluble in alcohols |
| Melting Point | 807 °C (anhydrous) |
About erbium(III) Chloride
Erbium(III) chloride is the soluble Er entry point — that distinctive deep-pink hexahydrate ErCl3·6H2O is what you actually pull off the shelf, because the anhydrous chloride is a hygroscopic nightmare to keep dry. The pink color is f-f electronic transitions of Er3+ around 522, 540, and 654 nm; it's intense enough that a centimolar aqueous solution looks like dilute cranberry juice. As with the rest of the heavy lanthanide chlorides, simple thermal dehydration in air goes the wrong way — you lose HCl preferentially over H2O above 200 °C and end up with ErOCl, not anhydrous ErCl3. The clean preparations are the same as for DyCl3: NH4Cl-assisted dehydration at 300 °C under inert gas, vacuum sublimation around 800 °C, or direct synthesis from Er metal turnings plus dry HCl. The crystallographic punchline is the same too — anhydrous ErCl3 takes the AlCl3 layered structure with 6-coordinate Er3+, while in aqueous solution the [Er(H2O)8]3+ aqua ion (8-coordinate, square antiprism) dominates because Er3+ is small enough to start losing one inner-sphere water relative to the lighter lanthanides. The chemistry that makes Er3+ commercially indispensable is its 4I13/2 → 4I15/2 transition at 1530 nm, which sits exactly in the C-band telecom window and made the entire modern optical-fiber backbone possible. ErCl3 is the typical wet-chemistry starting point for Er-doped phosphors, Er:YAG laser crystal precursors, and Er-doped optical-fiber preforms.
Where you'll encounter it
If you've ever fed an Er-doped sol-gel synthesis or made a precursor solution for an Er-doped fluoride fiber preform, you started by dissolving ErCl3·6H2O in deionized water or methanol — the pink color tells you immediately whether you've hit the right concentration. In a dental or dermatology clinic, the practical product downstream of ErCl3 is the Er:YAG laser at 2.94 µm — the wavelength sits on the OH-stretch absorption peak of water, so the laser ablates enamel or skin in 5 µm slices with almost no thermal collateral. In a research telecom lab, ErCl3 is the precursor for MCVD (modified chemical vapor deposition) Er-doped fiber preforms that get drawn into the EDFA gain fibers used in every undersea cable repeater.
Common Uses
- Precursor for Er-doped silica and ZBLAN fluoride glass fiber amplifiers (EDFAs)
- Wet-chemistry starting material for Er:YAG laser crystal feedstock preparation
- Dopant source for green and red upconversion phosphors in Er/Yb systems
- Feedstock for Er metal production by molten chloride electrolysis
- Lewis acid catalyst for selected aldol and Mannich reactions
- Reagent for Er3+ separations from Ho and Tm via solvent extraction
- NMR shift reagent precursor for paramagnetic chemical shift work
- Pink colorant in specialty optical glass and ceramic glaze formulations
Safety Information
GHS H315/H319 (skin and eye irritation, Category 2/2A). The hexahydrate is mildly acidic in solution (pH ~4 for 0.1 M) and releases small amounts of HCl as it deliquesces in humid air — handle in a fume hood with nitrile gloves. Acute toxicity is moderate (LD50 ~3-5 g/kg). No specific OSHA PEL; treat as a soluble lanthanide salt with respirable dust limit of 5 mg/m3. As with all rare-earth chlorides, chronic occupational inhalation has been linked to pulmonary fibrosis in refinery cohorts.
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.