It was found that potassium forms on rhenium electrodes during plasma electrolysis in K2CO3/H2O and K2CO3/D2O solutions, and the new potassium has unnatural isotopic ratios. The isotope K-41 increases from the natural abundance, 6.7%, to as much as 32-37%. The percentage of K-41 in the potassium contamination in a rhenium electrode before electrolysis was close to the natural isotopic abundance (6.7%). This result suggests that the K-41 was enriched by some unknown process connected with a vigorous discharge of plasma electrolysis.