Potassium Chloride
Properties
| State | Solid (white crystalline) |
| Color | White (colorless crystals) |
| Solubility | Soluble in water (344 g/L at 25 °C) |
| Melting Point | 770 °C |
| Boiling Point | 1420 °C |
About Potassium Chloride
Potassium chloride (KCl, 74.548 g/mol) is the face-centered cubic alkali halide that is to potassium what NaCl is to sodium — same rock-salt structure, similar appearance, very different biological role. Roughly 95 percent of mined KCl goes to fertilizer (the K in N-P-K, sold as muriate of potash), with Saskatchewan, Belarus, and Russia accounting for most of the world's ~70 million tonnes of annual production. The mineral form is sylvite, mined from evaporite basins by either conventional shaft mining or solution mining of the deep Devonian Prairie evaporite in western Canada. Outside of agriculture, KCl is the active ingredient in low-sodium salt substitutes (Morton Lite Salt, NoSalt) for hypertensive diets — it gives a salty taste with a faint metallic bitter note that some palates pick up at concentrations above 30 percent of NaCl replacement. In the clinical lab and ICU it is the source for potassium replacement in hypokalemia, dosed orally as slow-release tablets or intravenously as dilute KCl in saline at no faster than 10-20 mEq/hour with cardiac monitoring. The same compound at very different concentration is what executions by lethal injection use for cardiac arrest in the third-drug protocol; this is why concentrated KCl is one of the most carefully controlled medications on any hospital floor. KCl is also the IUPAC reference electrolyte for conductivity measurement (a 0.1 M KCl solution at 25 °C has a precisely defined conductivity of 12.856 mS/cm) and the salt-bridge electrolyte in saturated calomel and Ag/AgCl reference electrodes.
Where you'll encounter it
If you've ever calibrated a conductivity meter, you've made up a 0.1 M or 1 M KCl standard from a NIST-traceable bottle and used the precisely defined conductivity values as your reference points — KCl is the IUPAC primary standard for this measurement specifically because its dissociation is essentially complete and its temperature coefficient is well characterized. If you're a clinical pharmacist or ICU nurse, the bright purple cap on a vial of concentrated KCl is the visual cue that the drug must be diluted before infusion — a bolus of concentrated KCl will stop a heart in seconds, which is also why hospitals removed concentrated KCl from floor stock after a run of fatal medication errors in the 1990s. If you garden, the orange-red granules in a 0-0-60 fertilizer bag are KCl, mined as sylvite ore in Saskatchewan or Russia and shipped by the millions of tonnes per year to growers who need to replace the potassium their crops pull out of the soil.
Common Uses
- Muriate of potash fertilizer (~95 percent of global KCl tonnage; the K in N-P-K)
- Active ingredient in low-sodium salt substitutes (Morton Lite Salt, NoSalt, LoSalt)
- Oral and IV potassium replacement for hypokalemia (dosed at <=10-20 mEq/hour IV with cardiac monitoring)
- IUPAC primary standard for conductivity meter calibration (0.1 M = 12.856 mS/cm at 25 °C)
- Salt-bridge electrolyte in saturated calomel and Ag/AgCl reference electrodes
- Lethal injection third-drug for induced cardiac arrest in capital punishment protocols
- Component of LiCl/KCl eutectic molten salts for pyroprocessing nuclear fuel
- Feedstock for KOH manufacture by chlor-alkali electrolysis
Safety Information
Non-toxic in dietary amounts (oral LD50 rat 2600 mg/kg). Excessive oral intake causes nausea, vomiting, and gastric ulceration. IV administration must be controlled — a concentrated KCl bolus causes fatal cardiac arrest, which is why clinical use requires dilution, a controlled infusion rate and continuous ECG monitoring. No substance-specific occupational exposure limit; treated as a nuisance dust. Not flammable, not carcinogenic, not environmentally hazardous. Concentrated KCl vials are stored as a high-alert medication with double-check protocols on every U.S. hospital floor.
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.