Crystal structure of decacalcium tetrapotassium hexakis (pyrophosphate) nonahydrate

The crystal structure of Ca₁₀K₄(P₂O₇)₆·9H₂O has been determined by single crystal X-ray diffraction. Crystals are hexagonal, space group P6₃cm witha=11.761(1),c=9.770(1) Å, andZ=1. The structure was refined toR=0.028 andR_w=0.037 for 468 reflections withI3(I). The structure consists of a compact assembly of Ca and P₂O₇ ions arranged in layers perpendicular to thec-axis in a hexagonal array with relatively large open channels along thec-axis. The K ions and the water molecules are located in these open channels and are disordered.Certain commercial materials and equipments are identified in this paper to specify the experimental procedure. In no instance does such identification imply recommendation or endorsement by the National Institute of Standards and Technology or the ADA Health Foundation or that the material or equipment identified is necessarily the best available for the purpose.