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A sodium nitrate solution can retain its chemical properties for weeks to months, assuming it's kept sealed, cool, and uncontaminated. Sodium nitrate is very stable in water.

Conditions for Long-Term Stability:
Condition Effect on Stability
Sealed container Prevents contamination or evaporation
Cool temperature Reduces microbial growth and degradation
Dark storage Avoids light-induced reactions (minimal for SN)
Sterile water Avoids bacteria or algae that might reduce nitrate
Neutral pH Keeps the solution chemically inert
Under these ideal conditions, sodium nitrate remains stable for months without breaking down.

When It Might Degrade or Lose Potency:
Bacterial contamination: Certain bacteria (e.g., denitrifying bacteria) can convert nitrate (NO₃⁻) into nitrite (NO₂⁻) or nitrogen gas, especially under low-oxygen conditions.
Exposure to air and light: Generally doesn't degrade sodium nitrate directly, but might cause indirect contamination.
Organic contaminants: Sugars, proteins, or other materials can promote microbial growth and reduce nitrate over time.

Practical Storage Tip:
If you're making a sodium nitrate "drink" (e.g., for fertilizer, laboratory, or performance supplement purposes):
Use distilled water.
Store in a glass or high-quality plastic container.
Keep it refrigerated and sealed.
Label with concentration and date mixed.

Shelf Life Estimate:
Storage Condition Estimated Stability
Room temp, open bottle ~1–3 days (risk of contamination)
Sealed, room temp, clean ~1–2 weeks
Sealed, refrigerated 1–3+ months