Analytical Sciences

Abstract − Analytical Sciences, 22(12), 1559 (2006).

Application of Liesegang Ring Formation on a Gelatin Film to the Determination of Sulfate Concentration in Individual Rain Droplets
Ken'ichi NARITA, Kiyoshi MATSUMOTO, and Manabu IGAWA
Department of Applied Chemistry, Faculty of Engineering, Kanagawa University, 3-27-1, Rokkakubashi, Kanagawa, Yokohama 221-8686, Japan
The determination of SO42- concentration in individual rain droplets can be achieved using a gelatin film containing 5 mM barium chloride and 5 mM barium nitrate. SO42- in droplets reacts with barium chloride in the film to form the characteristic Liesegang rings. The areal ratio of the ring to the droplet print (ARRD) on the film is a good indicator for determining the SO42- concentrations in an individual droplet. Interference by NO3- in determining SO42- concentration can be avoided by adding barium nitrate to the gelatin. Measurements of SO42- in rainwater samples by this method agreed well with those from ion chromatography. The individual analysis of rain droplets by this method indicated that the concentrations of SO42- were largely different with a 5-order magnitude, even among individual rain droplets collected simultaneously, and were higher in smaller rain droplets.