Estimation method for carbonate in natural alkaline soda lake-waters

Abstract

Natural, inland alkaline soda waters form a particular type of saline waters, characterized by a permanent alkaline chemical property. In many cases only the total alkalinity by methyl-orange titration is reported, without phenolphthalein titration. Therefore, a reliable estimation of carbonates from total alkalinity is essential for a precise scientific chemical classification. The concentration of bicarbonate [HCO3‒] can be reliably estimated in waters using the Advanced Speciation Method (ASM) if methyl-orange total alkalinity titration and pH data are available, while the concentration of carbonate [CO32‒] is not reliably estimated by the ASM when interfering factors with acid/base properties (e.g., phosphate, silicate, ammonia, etc.) are present in significant concentrations in natural waters. Therefore, here I present and prove an experimental polynomial function for carbonate estimation with the following equation based on the concentration of bicarbonate:[CO32‒] = -2.878E-7 ± 5.438E-8 × [HCO3‒]2 + 0.069±0.003 × [HCO3‒]This Boros's carbonate estimation method can contribute to a more efficient evaluation of field water samples with several analytical difficulties.•Bicarbonate can be reliably estimated using the Advanced Speciation Method (ASM).•Estimation of the carbonate concentration using ASM in the presence of interfering acid/base factors in alkaline waters.•Experimental polynomial function for reliable carbonate estimation in alkaline soda waters.