Chemical Identity and Physical Properties

Barium dihydrogen phosphate, with the molecular formula Ba(H₂PO₄)₂ and CAS number 13517-08-3, is an inorganic salt formed from barium and dihydrogen phosphate anions. It presents as a white crystalline powder with a molecular weight of approximately 331.31 g/mol.

The compound is notably more water-soluble than many other barium phosphate salts, such as barium phosphate (Ba₃(PO₄)₂), making it particularly useful in applications requiring dissolved barium or phosphate species in aqueous media. Its aqueous solutions are mildly acidic due to the dihydrogen phosphate anion. The compound is insoluble in common organic solvents such as ethanol.

Upon heating, barium dihydrogen phosphate undergoes dehydration and can convert to barium metaphosphate or other condensed phosphate phases depending on temperature and atmosphere, a property relevant to its use in high-temperature ceramic and glass processing.

Synthesis and Preparation

Barium dihydrogen phosphate is typically prepared by reacting barium carbonate or barium hydroxide with an excess of phosphoric acid under controlled conditions. The general reaction using barium carbonate is as follows:

BaCO₃ + 2 H₃PO₄ → Ba(H₂PO₄)₂ + H₂O + CO₂

The use of excess phosphoric acid ensures that the dihydrogen phosphate form is obtained rather than barium hydrogen phosphate (BaHPO₄) or barium phosphate (Ba₃(PO₄)₂). The product is isolated by evaporation and crystallization from the aqueous solution. Purity can be confirmed by gravimetric analysis, ICP-OES for trace metal impurities, and phosphorus titration.

For research-grade applications, commercially sourced reagent-grade barium dihydrogen phosphate, such as Aladdin SKU B302451, is preferred to avoid the need for in-house synthesis and to ensure consistent lot-to-lot quality.

Laboratory Applications

Barium dihydrogen phosphate finds application across several research domains:

• Ceramics and Materials Science: It is used as a precursor or flux in the synthesis of barium phosphate-based ceramics, bioceramics, and phosphate glasses. Its controlled thermal decomposition allows researchers to tailor phosphate stoichiometry in sintered materials.
• Analytical Chemistry: The compound serves as a source of precisely metered barium and phosphate ions in gravimetric and titrimetric methods, as well as in the preparation of calibration standards for ICP and ion chromatography.
• Crystal Growth Research: Barium dihydrogen phosphate is investigated in nonlinear optical (NLO) crystal research, as various barium phosphate systems exhibit interesting optical properties.
• Biological and Environmental Research: As a soluble phosphate salt, it can be used to prepare defined phosphate media or to study phosphate interactions with barium in environmental matrix studies.

Researchers should note that because barium salts are toxic, all applications must be conducted with appropriate containment and disposal protocols.

Safety, Handling, and Storage

Barium dihydrogen phosphate should be treated as a harmful substance. All barium salts are associated with barium toxicity, which primarily affects the cardiovascular and neuromuscular systems upon significant exposure. Key safety practices include:

• Personal Protective Equipment (PPE): Wear nitrile gloves, safety goggles, and a laboratory coat. For operations generating dust, use a NIOSH-approved particulate respirator.
• Ventilation: Handle in a well-ventilated fume hood, especially when weighing powders.
• Storage: Store in a tightly sealed container in a cool, dry, well-ventilated location away from incompatible materials such as strong oxidizers and strong acids.
• Waste Disposal: Dispose of barium-containing waste in accordance with local, regional, and national regulations. Do not pour barium salt solutions down the drain without appropriate treatment.
• First Aid: In case of skin or eye contact, flush with copious water for at least 15 minutes. Seek medical attention if ingested or inhaled in significant quantities.

Consult the Safety Data Sheet (SDS) for Aladdin SKU B302451 for full regulatory classification, transport information, and emergency response guidance.