Fig. 3. Powder X-ray diffraction patterns of synthetic potassium zinc hexacyanoferrate(II) nonahydrate, K₂Zn₃[Fe(CN)₆]₂ x 9H₂O (the intensity scaling factor is 0.1 and CN is cyanide), and five blast furnace sludge samples before and after a treatment with a NaOH solution. Some peaks are marked with corresponding d spacings in nm.