Lead(II) Chloride
Properties
| State | Solid at room temperature |
| Color | White crystalline solid |
| Solubility | Slightly soluble in cold water (1.08 g/100 mL at 20°C), soluble in hot water (3.34 g/100 mL at 100°C) |
| Melting Point | 501°C |
| Boiling Point | 950°C |
About Lead(II) Chloride
Lead(II) chloride is a white orthorhombic salt whose entire identity in undergraduate qualitative analysis hinges on a single peculiar fact: its solubility jumps roughly threefold between cold and boiling water (1.08 g/100 mL at 20 °C versus 3.34 g/100 mL at 100 °C). That temperature dependence is what lets the Group I cation scheme separate Pb(II) from Ag(I) and Hg(I) — all three precipitate when dilute HCl is added to an unknown, but only PbCl2 redissolves when the test tube is dropped into a hot water bath, leaving AgCl and Hg2Cl2 behind on the filter. Pour the hot supernatant over potassium chromate and the canary-yellow PbCrO4 precipitate confirms the lead. The same hot-cold trick produces the recrystallization demo where a saturated solution cooled overnight grows into long, silky needle clusters sometimes called angel hair. PbCl2 also occurs as the mineral cotunnite around volcanic fumaroles on Vesuvius and Etna. Outside teaching labs and a handful of niche electrode and pigment-precursor uses, modern chemistry has largely walked away from PbCl2 because of how readily Pb(II) accumulates in bone and kidney tissue.
Where you'll encounter it
If you've ever run the classic Group I cation separation in a sophomore qual lab and watched the white precipitate melt back into solution when you set the tube in a beaker of boiling water, that's PbCl2 doing exactly what AgCl and Hg2Cl2 refuse to do. The whole separation hinges on a single endothermic dissolution: heating the white chloride mixture to 90 °C puts the lead back into solution while leaving silver and mercury chlorides on the filter, and dripping the hot supernatant onto K2CrO4 paper gives the canary-yellow PbCrO4 confirmation in seconds. Modern qual-lab instructors keep the demo alive even as schools phase out lead reagents because no other system illustrates differential solubility this cleanly. Single-crystal growers exploit the same temperature-dependent solubility to pull silky needle clusters from a slowly cooling saturated solution overnight.
Common Uses
- Group I cation separation in qualitative analysis (hot-water dissolution distinguishes from AgCl and Hg2Cl2)
- Recrystallization demonstrations producing 'angel hair' needle crystals
- Confirmatory test for Pb(II) via reaction with K2CrO4 to give yellow PbCrO4
- Historical precursor for chrome yellow and other lead-based pigments
- Substrate for PbO2 electrode preparation in lead-acid battery research
- Single-crystal growth research material for X-ray diffraction studies
- Reference material for solubility-versus-temperature lab experiments
Safety Information
Toxic. Pb(II) is a cumulative neurotoxin and reproductive toxicant — OSHA PEL is 50 µg/m3 (8-hr TWA) for inorganic lead with a blood-lead action level of 30 µg/dL. GHS classifications: H302 (harmful if swallowed), H332 (harmful if inhaled), H360Df (may damage fertility/unborn child), H373 (chronic organ damage via repeated exposure), H410 (very toxic to aquatic life with long-lasting effects). Handle in a fume hood with nitrile gloves; do not weigh on open balances. All waste must enter the hazardous-lead waste stream, never the sink.
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.