DIFFUSION OF HNO3 IN ICE

We designed a series of experiments to verify the value of the diffusi on coefficient of HNO3 in ice at -15 degrees C using a serial sectioni ng technique. Our first series of experiments with diffusion times of 70 to 100 h gave an average value of about 1.7 x 10(-11) cm(2) s(-1) ( StD 0.8 x 10(-11)) and a second set of experiments at 1000 h resulted in an apparent diffusion coefficient of 10(-12) cm(2) s(-1). Our concl usion is that the observed gradients of HNO3 in ice were spurious and the result of serial contamination of the surfaces during sectioning o f the ice. We call the diffusion coefficients ''apparent'' because in the present experiment we could not distinguish between an undetectabl e diffusion coefficient and undetectable solubility. In either case, t he validity of the previously published results is questionable.