70% ethanol recipe
70% ethanol for disinfecting surfaces and washing DNA pellets. It disinfects better than 100%.
🧮 Volume calculator
| Component | Amount | Final concentration (1X) |
|---|---|---|
| Absolute ethanol (≥99.5%) | 350 mL | 70% (v/v) |
| Water (distilled) | to final volume |
Steps
- Measure the absolute ethanol (with 95% ethanol use 737 mL/L).
- Bring to the final volume with water (the mixture contracts slightly, so top up to the mark).
- Store tightly capped at room temperature.
Good to know
- For DNA work, make it with nuclease-free water and keep it separate.
⚠ Safety Flammable — keep away from flames and burners.
FAQ
Why does 70% disinfect better than 100%?
Water helps ethanol penetrate and denature proteins; 100% coagulates the surface and kills less effectively.
This is a widely used standard composition. Amounts depend on the hydrate form and purity of your reagents — check the formula weight (FW) on the bottle and follow your institution's safety rules and the manufacturers' instructions.