- What it is. This potassium hydroxide is a concentrated 45% (w/w) aqueous solution, supplied in a 1 pint size. It is a clear, colorless, strongly alkaline liquid used for etching, cleaning, saponification, electrolyte preparation, and pH control.
- How concentrated it is. Every 100 g of solution contains 45 g of KOH. With a specific gravity of about 1.45, that equals roughly 650 g of KOH per liter, about 11.7 M (calculated). It boils near 132 °C and stays liquid down to about -29 °C.
- Chemical identity. Potassium hydroxide (caustic potash, CAS 1310-58-3, KOH, 56.11 g/mol) is a strong base that dissociates completely in water. Its potassium salts are generally more soluble than sodium salts, which matters in soaps, electrolytes, and organic chemistry.
- Why a liquid concentrate. Dissolving solid KOH releases a great deal of heat and creates caustic dust and spatter. A ready-made 45% solution avoids that step, is easier to meter accurately, and gives consistent strength for dilution.
- Silicon etching. Hot KOH solutions etch crystalline silicon anisotropically, attacking some crystal planes much faster than others. That property is used in MEMS and semiconductor processing to form V-grooves, cavities, and membranes in silicon wafers.
- Other uses. Potassium hydroxide is used to make soft and liquid soaps, as the electrolyte in alkaline batteries and fuel cells, for biodiesel catalyst preparation, for heavy-duty cleaning and degreasing, and to adjust pH in water treatment and chemical processing.
- Handling at a glance. Forty-five percent KOH causes severe skin burns and eye damage, and it is harmful if swallowed and corrosive to metals such as aluminum and zinc. Wear chemical splash goggles, a face shield, and alkali-resistant gloves, and always add base slowly to water when diluting.
- Carbon dioxide absorption. Like all hydroxide solutions, KOH absorbs carbon dioxide from the air to form potassium carbonate, which lowers the effective hydroxide content over time. Keep containers sealed and avoid leaving the solution open to air.
- Related products. For titration work, Lab Pro supplies Potassium Hydroxide 0.1 N Solution, 1 Gallon and alcoholic Potassium Hydroxide 0.5 N in Methanol, 1 L.
Technical Specifications
| Chemical Name | Potassium hydroxide, aqueous solution |
| CAS Numbers | 1310-58-3 (potassium hydroxide); 7732-18-5 (water) |
| EC Number | 215-181-3 |
| Synonyms | Caustic potash solution, potash lye, KOH solution |
| Formula (active) | KOH |
| Molecular Weight (active) | 56.11 g/mol |
| Concentration | 45% (w/w) |
| Specific Gravity | About 1.45 to 1.456 |
| Approximate Molarity | About 11.7 M (calculated) |
| KOH per Liter | About 650 g (calculated) |
| Boiling Point | About 132 °C |
| Freezing Point | About -29 °C |
| Appearance | Clear, colorless liquid, odorless |
| Water Solubility | Miscible |
| Hazard Statements | H290 (corrosive to metals), H302 (harmful if swallowed), H314 (severe burns) |
| DOT | UN1814, Potassium hydroxide solution, Class 8, PG II |
| Exposure Limit | NIOSH REL 2 mg/m³ ceiling |
| Package Size | 1 pint |
Applications / Common Uses
- Silicon etching: Anisotropically etches silicon in MEMS processing.
- Soap making: Saponifies oils into soft and liquid soaps.
- Alkaline electrolytes: Prepares battery and fuel cell electrolytes.
- Heavy-duty cleaning: Degreases and strips organic residues.
- pH control: Raises pH in water treatment and processing.
Storage, Handling & Shipping
Caution: 45% potassium hydroxide causes severe skin burns and eye damage, is harmful if swallowed, and is corrosive to metals. Wear chemical splash goggles, a face shield, and alkali-resistant gloves, and always add base slowly to water when diluting.
Store tightly closed in a cool, dry corrosives area for bases, separated from acids, reactive metals such as aluminum and zinc, and organic halogen compounds. Keep containers sealed to prevent carbon dioxide absorption and use secondary containment.
- Incompatible materials: Acids, aluminum, zinc, tin, and other reactive metals, and organic halogen compounds.
- Exposure limit (potassium hydroxide): NIOSH REL 2 mg/m³ ceiling.
- Spill response: Contain with inert absorbent, neutralize cautiously with a weak acid, and rinse with water.
- First aid: Skin or eyes: flush with water for at least 15 minutes and seek immediate medical attention.
- GHS signal word: Danger.
- DOT / shipping: UN1814, Potassium hydroxide solution, Class 8, PG II.
Related Categories & Services
- Shop Bases for related products in this category.
- Explore Inorganic Chemicals and ACS Grade Laboratory Chemicals.
- Vendor Managed Inventory (VMI) Program: Lab Pro can stock, track, and replenish this item on site so it never runs out. Contact info@labproinc.com or 888-452-2776 to set up a VMI assessment.
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FAQs
What is 45% potassium hydroxide used for?
It is used for anisotropic silicon etching in MEMS fabrication, making soft and liquid soaps, preparing alkaline battery and fuel cell electrolytes, heavy-duty cleaning and degreasing, biodiesel catalyst preparation, and pH adjustment in water treatment and chemical processing. It is also used to prepare dilute KOH solutions for laboratory titration and cleaning.
What is the molarity of 45% KOH?
With 45 g of KOH per 100 g of solution and a specific gravity near 1.45, the solution contains about 650 g of KOH per liter, roughly 11.7 M. Check the lot certificate for exact assay and density when your calculations require precision. Use the certificate values when exact.
How do I dilute 45% potassium hydroxide safely?
Work with goggles, a face shield, and alkali-resistant gloves, and add the KOH solution slowly to cold water while stirring. Never add water to concentrated base. Dilution releases heat, so allow the solution to cool before adjusting the final volume. Label the diluted solution clearly.
Why does KOH etch silicon unevenly?
Hot KOH attacks the silicon crystal faces at sharply different rates, etching the (100) planes much faster than the (111) planes. That anisotropy produces sharp, predictable shapes such as V-grooves and pyramid-shaped pits, which are useful in MEMS device fabrication. Temperature and concentration control the etch rate.
What metals should KOH not contact?
Concentrated potassium hydroxide attacks aluminum, zinc, tin, and their alloys, releasing flammable hydrogen gas. Store and handle it with compatible materials such as polyethylene, polypropylene, or certain stainless steels, and keep it away from galvanized and aluminum equipment. Glass is also slowly attacked by hot concentrated base, so avoid long-term storage in glassware.
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