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 substance-specific occupational limit exists; treat it as a soluble lanthanide salt and control respirable dust accordingly. 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. We deliberately do not publish occupational exposure limits or other regulatory thresholds: those values are revised over time and differ between jurisdictions, so the only correct source is the current SDS and the regulations that apply where you work.