I

Isotonic

π₁ = π₂
Quick Reference
Formula / Notationπ₁ = π₂
Also Known AsIsotonic solution, iso-osmotic solution, normal saline, physiological saline (isotonic)

What is Isotonic?

Isotonic solutions are solutions that have the same osmotic pressure as another reference solution. In biology and medicine, isotonic solutions have the same osmotic concentration as blood plasma (~308 mOsm/kg) or intracellular fluid. Cells placed in an isotonic solution neither gain nor lose water by osmosis. Normal saline (0.9% NaCl) and 5% glucose solution are common isotonic solutions.

Formula & Notation

π₁ = π₂

Other Names / Synonyms: Isotonic solution, iso-osmotic solution, normal saline, physiological saline (isotonic)

Properties & Characteristics

Osmotic pressure: π = MRT (van't Hoff equation). Isotonic: same osmotic pressure on both sides of membrane. Red blood cells: isotonic with ~0.9% NaCl or ~5% glucose. Hypertonic: higher osmotic pressure → cells shrink. Hypotonic: lower osmotic pressure → cells swell/lyse. Normal saline: 0.9% NaCl = 308 mOsm/L.

Uses & Applications

Intravenous (IV) fluid therapy (normal saline, lactated Ringer's). Eye drops and contact lens solutions. Blood cell storage and preservation. Tissue culture media. Pharmaceutical formulations for injection. Wound irrigation. Oral rehydration solutions.

Safety Information

Isotonic solutions for IV use must be sterile and pyrogen-free. Incorrect osmolarity in IV solutions causes red blood cell hemolysis (hypotonic) or crenation (hypertonic) — potentially fatal. Preparation of IV fluids requires strict pharmaceutical standards.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Isotonic
Formula π₁ = π₂
Synonyms Isotonic solution, iso-osmotic solution, normal saline, physiological saline (isotonic)

Frequently Asked Questions

Isotonic solutions are solutions that have the same osmotic pressure as another reference solution. In biology and medicine, isotonic solutions have the same osmotic concentration as blood plasma (~308 mOsm/kg) or intracellular fluid. Cells placed in an isotonic solution neither gain nor lose water by osmosis. Normal saline (0.9% NaCl) and 5% glucose solution are common isotonic solutions.

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