A Refinement of the Crystal Structure of Na₂CO₃ · H₂O

The crystal structure of synthetic Na₂CO₃·H₂O has been refined using 1231 unique x-ray diffraction data collected by the peak height method on a diffractometer. R = 0.034. The unit cell is a = 6.474(2), b= 10.724(3) and c = 5.259(2) Å with z = 4 and space group P2₁ab. The calculated density is the same as the observed density, 2.26 g·cm^-3. The structure contains sheets of ${\text{CO}}_3^{2-}$ ions bonded to Na⁺ ions and water molecules roughly halfway between the sheets. Each ${\text{CO}}_3^{2-}$ bonds edgewise to both Na⁺ ions. The Na⁺ ions have irregular but similar coordinations of seven neighbors. Each water molecule is bonded to both Na⁺ ions and forms hydrogen bonds to both neighboring ${\text{CO}}_3^{2-}$ layers.