Lateral variation in the concentration of Ni2+ in a nickel-containing,
flat silica gel plate, caused by migration of the dopant during dryin
g (60 degrees C), was measured spectrophotometrically as a function of
absorption of Ni2+ at 393 nm. Compositional variations along individu
al lines of measurement could be expressed as second order polynomials
, and the overall distribution took the form of a shallow basin with a
minimum at the central region of the gel plate.