Chemical waves of the Belousov-Zhabotinsky reaction are frozen in by precipitation of intermediates in a layer of silica gel using silver nitrate for the precipitation reaction. The distribution of the precipitate corresponds to the global topology of propagating chemical waves. Inside the wave front (width 180-200 mu m) an additional thin precipitation band (width 10-40 mu m) of dense precipitate is formed. This sharp band vanishes first in annihilating waves. It surrounds the tip of spiral waves and disappears at the back side of the tip nearly half a front width away at a point, which can be localized in the range of 30 mu m. Comparison with spectrophotometric images of rotating spirals indicates that this point is located close to the rotation center of the spiral and may be associated with a chemical singularity in the core region of the spiral wave.