[en] A new color reaction of ( Ru(Hedta)(H2O)] with some compounds that contain groups C-SH or C=S has been found. Alkanethiols, cysteine, thiourea and thiosulfate assume pink to reddish brown color, while benzenethiols show blue color. It was suggested that the coloration is due to the anation of ( Ru(Hedta)(H2O)] with sulfur-containing compounds. (auth.)