Periodic precipitation of calcium carbonate in agar gel: estimation of flocculation value and factors influencing it

Abstract

The experimental condition for obtaining periodic precipitation of calcium carbonate in agar-agar gel is investigated. The nature of periodic precipitation depends on the concentration on the inner and outer electrolytes, gel medium, and its pH. The presence of certain impurities strongly influences the periodic precipitation. The "spacing law" of Jablczynski and the time law are verified in this system. The dependences of velocity constant (K = x_n/(t_n)½) and spacing coefficient (ρ = (x_n+1)/x_n) on the above factors have been studied in detail. K is found to vary nonlinearly with the concentration of inner and outer electrolytes but to vary linearly with pH value of the medium and the reciprocal value of the concentration of the gel medium. The spacing coefficient is inversely proportional to the concentration of the outer electrolyte, pH value, and density of the gel medium. But it is directly proportional to the concentration of the inner electrolyte. The spacing coefficient and the position of the first ring are affected by the presence of impurities such as copper, cadmium, and magnesium acetates. Exposure to light and γ-radiation of 5 mCi strength cobalt-60 produces no change in the ring formation and spacing coefficient. Using Shouji Shinohara's revised coagulation theory the flocculation value F = Γ + C₃₀, where G is the characteristic constant concentration of the outer electrolyte where flocculation starts and C₃₀ is the reduced concentration of the reaction product, is calculated. The dependence of the concentration of gel medium and pH value of the gel medium on flocculation value is discussed.