Sodium Hydroxide, ≥ 98% (Caustic Soda)
Strong inorganic base for pH adjustment, standard solutions and analytical work
Sodium hydroxide (NaOH) is the most widely used strong base in the laboratory, supplied as white solid with an assay of at least 98%. It is used to prepare alkaline and standard solutions, adjust the pH of buffers and culture media, and in titration, digestion and cleaning procedures. It is corrosive and must be handled with eye and skin protection.
Also known as: Caustic soda, lye, soda lye, NaOH.
Overview
Sodium hydroxide dissociates completely in water to sodium and hydroxide ions, giving strongly alkaline solutions (a 0.1 M solution has a pH of about 13). It dissolves with strong heat release and absorbs moisture and carbon dioxide from the air, slowly forming sodium carbonate. In microbiology laboratories it is the standard reagent for adjusting the pH of culture media.
Applications
| Application | How NaOH is used |
|---|---|
| pH adjustment | 1 M NaOH to raise the pH of culture media, buffers and reagents |
| Titration | Standard alkaline solutions (0.1 M, 1 M) for acid–base titration |
| Sample digestion | Alkaline digestion and decontamination procedures |
| Molecular biology | Alkaline lysis in plasmid preparation; DNA denaturation |
| Cleaning | Removal of protein and organic residues from equipment |
| Organic chemistry | Base for saponification and neutralisation reactions |
Preparing a NaOH Solution
Always add NaOH to water, never water to NaOH. Add the solid slowly to cold purified water in a heat-resistant vessel while stirring, and allow the solution to cool before making up to volume.
Example: 1 M NaOH — dissolve 40.0 g in water and make up to 1 L. Store in a tightly closed plastic bottle; standardise by titration when an exact concentration is needed.
Frequently Asked Questions
What is sodium hydroxide used for in the laboratory?
Sodium hydroxide is a strong base used to adjust the pH of culture media and buffers, prepare standard solutions for titration, digest samples, clean equipment and perform alkaline lysis in molecular biology.
How do I make 1 M sodium hydroxide?
Dissolve 40.0 g of NaOH in about 800 mL of cold purified water while stirring, let it cool, then make up to 1 litre. Always add the solid to water, never water to the solid.
Why should NaOH solutions be stored in plastic?
Concentrated NaOH slowly attacks glass, and ground-glass stoppers can seize. Store solutions in tightly closed polyethylene or polypropylene bottles.
Is sodium hydroxide a dangerous good?
Yes. It is UN1823, Sodium hydroxide, solid, Class 8 (corrosive), Packing Group II. It is also a Schedule 6 poison in Australia.
How should sodium hydroxide be stored?
Store in a tightly closed plastic container in a cool, dry place, away from acids, aluminium, zinc and tin. Keep closed, because the solid absorbs moisture and carbon dioxide.
What is the difference between sodium hydroxide and potassium hydroxide?
Both are strong bases. Sodium hydroxide (40.00 g/mol) is the standard choice for pH adjustment and titration. Potassium hydroxide (56.11 g/mol) forms more soluble salts and soaps and is used for the microbiological string test.
Product Identification
Specifications
Storage and Shelf Life
Store at 15–25 °C in the original tightly closed plastic container, in a dry place away from acids, aluminium, zinc and tin. Keep closed: the solid absorbs moisture and carbon dioxide. Store locked up. Use before the expiry date on the label.
Hazard Identification
| Signal word | Danger |
|---|---|
| GHS classification | Corrosive to metals 1; Skin corrosion 1A; Serious eye damage 1 |
| Hazard statements | H290 May be corrosive to metals. H314 Causes severe skin burns and eye damage. |
| Key precautions | P260 Do not breathe dust. P280 Wear protective gloves, protective clothing, eye and face protection. P301+P330+P331 IF SWALLOWED: Rinse mouth. Do NOT induce vomiting. P305+P351+P338 IF IN EYES: Rinse cautiously with water for several minutes. P310 Immediately call a POISON CENTER or doctor. P405 Store locked up. |
| Poisons Schedule | Schedule 6 |
First Aid
| Eyes | Rinse immediately with running water for at least 15 minutes, holding eyelids apart. Get medical help without delay. |
|---|---|
| Skin | Remove contaminated clothing. Rinse with plenty of water until advised to stop by the Poisons Information Centre. |
| Ingestion | Rinse mouth. Do NOT induce vomiting. Call 13 11 26 immediately. |
| Inhalation | Move to fresh air. Seek medical advice. |
Transport
| UN number | UN1823 |
|---|---|
| Proper shipping name | SODIUM HYDROXIDE, SOLID |
| Class / Packing group | 8 / II |
| Hazchem | 2W |
| Limited quantity (ADG) | 1 kg per inner packaging (the 5 kg pack ships as full Dangerous Goods) |
The full 16-section Safety Data Sheet is supplied with every order and is available from support@ausamics.com.