Cadmium Chloride
Properties
| State | Solid (white to colorless hygroscopic crystals) |
| Color | White to colorless |
| Solubility | Very soluble in water (1190 g/L at 20°C); soluble in ethanol and acetone |
| Melting Point | 568°C |
| Boiling Point | 960°C |
About Cadmium Chloride
Cadmium chloride is the structural archetype that gives an entire family of layered transition-metal dihalides their name — the "CdCl2 structure type." Cubic close-packed chloride layers stack ABCABC, and Cd²⁺ ions occupy every octahedral hole in alternating layers, leaving the others empty. The result is electrically neutral Cl–Cd–Cl slabs separated by van-der-Waals gaps with no ions between them, the same kind of two-dimensional motif that makes graphite cleave or MoS₂ a good lubricant. NiCl2, MgCl2, CoCl2, and FeCl2 all crystallize this way; the closely related CdI2 structure differs only in the stacking of the halide layers (hexagonal close packing instead of cubic). The compound itself is a colorless, hygroscopic, water-soluble solid with a molar mass of 183.317 g/mol, melting at 568 °C and boiling at 960 °C. In the lab, CdCl2 is the standard precursor for cadmium-chalcogenide semiconductor synthesis: cadmium oleate or CdCl2 in coordinating solvents reacts with TOP-S or TOP-Se to give CdS and CdSe quantum dots with size-tunable photoluminescence — the chemistry that earned the 2023 Nobel Prize in Chemistry. Historically, CdCl2 was the source for the brilliant cadmium yellow, orange, and red pigments that Monet and Van Gogh used in their late paintings; modern restorers track the gradual oxidative degradation of those pigments to CdSO4 and CdCO3 as part of the pigment-stability story. The toxicity caveat is real and immediate — cadmium is an IARC Group 1 carcinogen, water-soluble forms like CdCl2 are absorbed efficiently in the gut and lung, and the biological half-life in human kidney cortex is 10–30 years.
Where you'll encounter it
If you've ever made CdSe quantum dots in a hot-injection synthesis — TOP-Se rapidly injected into a 300 °C cadmium-oleate solution — the cadmium source was probably either CdO or CdCl2 dissolved in oleic acid. In a teaching solid-state course, CdCl2 is the worked example for layered structures with octahedral cation coordination, paired with CdI2 to show how cation–anion radius ratio and polarizability change the stacking sequence. Outside the chemistry lab, CdCl2 historically appeared in electroplating baths for cadmium coatings on aircraft fasteners, where the self-lubricating, corrosion-resistant deposit is irreplaceable in high-strength steel applications even though most consumer plating has switched to zinc-nickel.
Common Uses
- Cadmium source for CdS, CdSe, and CdTe quantum-dot synthesis
- Electrolyte salt in cadmium electroplating for aerospace fasteners
- Reference structure type for layered transition-metal dihalides
- Mordant in textile dyeing and toning bath in historical photography
- Trace cadmium reagent for atomic absorption spectroscopy calibration
Safety Information
Acutely toxic and a confirmed human carcinogen. GHS classifications: H330 (fatal if inhaled), H340 (mutagenic), H350 (carcinogen, IARC Group 1), H360 (reproductive toxicity), H410 (very toxic to aquatic life with long-lasting effects). OSHA PEL 5 µg/m³ as Cd, ACGIH TLV 10 µg/m³ TWA. The biological half-life in renal cortex is 10–30 years, and chronic exposure produces proximal-tubule damage, β2-microglobulinuria, and the bone-demineralization syndrome (itai-itai disease) documented in the Jinzu River basin in the 1950s. Handle only in a fume hood with nitrile gloves; dispose as RCRA-listed hazardous waste (D006).
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.