Underwater Sodium - Periodic Table of Videos

Aqueous solutions[edit]

Sodium tends to form water-soluble compounds, such as halides, sulfates, nitrates, carboxylates and carbonates. The main aqueous species are the aquo complexes [Na(H₂O)_n]⁺, where n = 4–6.^[24] The high affinity of sodium for oxygen-based ligands is the basis of crown ethers; macrolide antibiotics, which interfere with Na⁺ transport in the infecting organism, are functionally related and more complex.^{[citation needed]}

Direct precipitation of sodium salts from aqueous solutions is rare because sodium salts typically have a high affinity for water; an exception is sodium bismuthate (NaBiO₃).^[25] Because of this, sodium salts are usually isolated as solids by evaporation or by precipitation with an organic solvent, such as ethanol; for example, only 0.35 g/L of sodium chloride will dissolve in ethanol.^[26] Crown ethers, like 15-crown-5, may be used as a phase-transfer catalyst.^[27]

Sodium content in bulk may be determined by treating with a large excess of uranyl zinc acetate; the hexahydrate (UO₂)₂ZnNa(CH₃CO₂)·6H₂O precipitates and can be weighed. Caesium and rubidium do not interfere with this reaction, but potassium and lithium do.^[28] Lower concentrations of sodium may be determined by atomic absorption spectrophotometry^[29] or by potentiometry using ion-selective electrodes.^[30]