We designed a series of experiments to verify the value of the diffusion coefficient of HNO3 in ice at -15 ¿C using a serial sectioning technique. Our first series of experiments with diffusion times of 70 to 100 h gave an average value of about 1.7¿10-11 cm2 s-1 (StD 0.8¿10-11) and a second set of experiments at 1000 h resulted in an apparent diffusion coefficient of 10-12 cm2 s-1. Our conclusion is that the observed gradients of HNO3 in ice were spurious and the result of serial contamination of the surfaces during sectioning of the ice. We call the diffusion coefficients apparent because in the present experiment we could not distinguish between an undetectable diffusion coefficient and undetectable solubility. In either case, the validity of the previously published results is questionable. ¿ 1998 American Geophysical Union