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What it is. This sodium hydroxide solution is a 0.5 N (0.5 M) base, about 2% sodium hydroxide, supplied in a 1-gallon size. It is a clear, colorless alkaline solution used for titrations, saponification, pH adjustment, and cleaning tasks requiring moderate strength.
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Molar equals normal. Sodium hydroxide releases one hydroxide ion per formula unit, so 0.5 N equals 0.5 M. Each liter contains about 20.00 g of NaOH, which corresponds to the 2% figure on the label, and each milliliter neutralizes 0.5 millimole of acid, equal to 18.23 mg of HCl (calculated).
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A middle strength. At 0.5 N, the solution sits between routine 0.1 N titrant and 1.0 N stock. It keeps titration volumes practical for samples with moderate acid content and serves as a stock for 0.1 N base by accurate fivefold dilution with carbon dioxide-free water.
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Titrations and acidity. Labs use 0.5 N sodium hydroxide to titrate acids in foods, process streams, and chemical products, using phenolphthalein or a pH meter for the endpoint. Pair it with Lab Pro's Phenolphthalein Indicator 1% in IPA (1 Pint, 20 L).
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Standardization. Sodium hydroxide is not a primary standard because it absorbs moisture and carbon dioxide. Standardize it against dried potassium hydrogen phthalate (KHP), and restandardize periodically because dissolved carbon dioxide forms carbonate and reduces effective strength.
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pH adjustment and cleaning. The moderate strength allows controlled pH adjustment of buffers, media, and waste without large volume changes, and dilute caustic is effective for removing fats and organic residues from glassware and equipment.
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Handling at a glance. At 0.5 N, sodium hydroxide can cause serious eye damage and skin irritation. Wear chemical splash goggles and gloves, rinse splashes immediately with water, and keep it away from aluminum, zinc, and acids.
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Calculating results. Acid content equals the titrant volume multiplied by the standardized normality and by the acid's milliequivalent weight. For hydrochloric acid, each milliliter of 0.5 N sodium hydroxide corresponds to 18.23 mg.
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Related products. For other strengths, see Lab Pro's Sodium Hydroxide 0.1N/M, 1 Gallon and Sodium Hydroxide 1.0N/M, 1 Quart / 1 Gallon.
Technical Specifications
| Chemical Name |
Sodium hydroxide, aqueous solution |
| CAS Numbers |
1310-73-2 (sodium hydroxide); 7732-18-5 (water) |
| EC Number (NaOH) |
215-185-5 |
| Synonyms |
Caustic soda solution, NaOH solution |
| Formula (active) |
NaOH |
| Molecular Weight (active) |
40.00 g/mol |
| Concentration |
0.5 N (0.5 M), about 2% NaOH |
| NaOH Content |
About 20.00 g/L (calculated) |
| Neutralizing Capacity |
1.00 mL = 0.5 mmol acid; 18.23 mg HCl (calculated) |
| Typical Indicator |
Phenolphthalein |
| Primary Standard |
Potassium hydrogen phthalate (KHP) |
| Appearance |
Clear, colorless liquid |
| Storage Note |
Absorbs CO2; keep tightly closed |
| Exposure Limit (NaOH) |
NIOSH REL 2 mg/m³ ceiling |
| Package Size |
1 gallon |
Applications / Common Uses
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Acid titrations: Titrates acids at moderate concentrations.
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Saponification: Hydrolyzes fats and esters.
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Standard dilutions: Prepares 0.1 N NaOH by fivefold dilution.
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pH adjustment: Raises pH of buffers, media, and waste.
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Equipment cleaning: Removes fats and organic residues.
Storage, Handling & Shipping
Store tightly closed at room temperature, away from acids and reactive metals. Sodium hydroxide solutions absorb carbon dioxide from the air, so keep the container sealed and restandardize when results depend on exact normality.
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Incompatible materials: Acids, aluminum, zinc, tin, and other reactive metals.
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Exposure limit (NaOH): NIOSH REL 2 mg/m³ ceiling.
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Spill response: Contain, neutralize cautiously with a weak acid, and rinse with water.
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First aid: Eyes: flush with water for at least 15 minutes and seek medical attention. Skin: rinse thoroughly.
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