What Is Potassium Tetraoxalate Dihydrate?

Potassium tetraoxalate dihydrate (KH3(C2O4)2·2H2O) is an acidic potassium oxalate salt composed of one potassium ion, three replaceable acidic protons from two oxalate units, and two water molecules of crystallization. It is classified as a primary standard reference material in analytical chemistry, most notably used for the preparation and verification of low-pH buffer solutions. The compound is stable in air, making it convenient for long-term bench storage and routine laboratory use without special precautions against atmospheric degradation.

Solubility and Physical Properties

Potassium tetraoxalate dihydrate dissolves readily in hot water, with a solubility of approximately 1 part in 12 parts boiling water, and more slowly in cold water at approximately 1 part in 60 parts. It is only slightly soluble in ethanol, which limits its use in non-aqueous systems. These solubility characteristics are important when preparing standard buffer solutions: dissolution at elevated temperature followed by cooling to the working temperature is recommended to ensure complete dissolution and accurate concentration. The crystalline solid appears as colorless to white crystals or powder.

Note: Exact melting point, density, and molecular weight values are not provided in the current source material and should be verified against the product certificate of analysis or a validated reference before use in regulated applications.

Laboratory Applications and Usage Protocol

The primary application of potassium tetraoxalate dihydrate is as a pH buffer reference standard, particularly for calibrating pH meters and electrodes in the acidic range. A standard solution prepared from this compound at a defined concentration and temperature provides a well-defined, reproducible pH value that traceable calibration relies upon. When preparing buffer solutions, researchers should use freshly boiled and cooled purified water to minimize dissolved CO2 interference. All glassware should be thoroughly rinsed with the buffer solution before use. Store prepared solutions in tightly sealed containers and replace them regularly to avoid concentration changes from evaporation or microbial growth.

Note: The specific certified pH value of a potassium tetraoxalate dihydrate buffer at standard concentration and temperature (e.g., 25 °C) should be confirmed against current NIST or equivalent national standards documentation, as this value is not explicitly stated in the supplied source material.

Storage, Handling, and Safety Considerations

Potassium tetraoxalate dihydrate is stable in air, which simplifies storage requirements. It should be kept in a tightly closed container in a cool, dry, well-ventilated area away from incompatible materials. As an oxalate compound, it is mildly toxic if ingested and may cause irritation to skin, eyes, and respiratory tract on prolonged or repeated exposure. Standard laboratory personal protective equipment — including gloves, safety glasses, and a lab coat — should be worn during handling. Consult the Safety Data Sheet (SDS) for P100094 for complete hazard information before use, as detailed toxicological and regulatory data are not fully enumerated in the current source material.

Ordering Information and Availability

Potassium tetraoxalate dihydrate is available from Aladdin Scientific under SKU P100094. Researchers and procurement teams can contact Aladdin Scientific for current pricing, pack sizes, purity specifications, and certificate of analysis documentation. For questions about regulatory compliance, bulk orders, or custom specifications, please reach out to the Aladdin Scientific customer service team.