EFFECT OF CALCIUM-IONS ON DETERGENCY - PART I - DEVELOPMENT OF A NEW METHOD FOR DETERMINING FREE CALCIUM-IONS IN A WASHING LIQUOR

This paper is concerned with the development of a new method for deter mining free calcium ions in a washing liquor. For the purpose of study ing the influence of calcium ions on detergency, it would be helpful t o determine the behavior of calcium ions in a washing liquor. We have developed a novel colorimetric method for this purpose. Pontachrome Vi olet SW was found to be a suitable dye for indicating the free calcium content. Based on theoretical considerations combining Lambert-Beer's law and the equilibrium between the dye and calcium ions, we introduc ed a new parameter P which is linearly related to the amount of free c alcium ions. A test solution for this method requires an alkaline buff er and can contain a surfactant.