pH-Fix indicator sticks are for the rapid measurement of the pH of a water sample. Additionally they can be used for monitoring the pH of a sample during analysis to avoid errors due to weakly buffered solutions. For this purpose pH-Fix indicator sticks are clearly superior to other pH papers.In contrast to conventional indicator papers, the indicator dyes of pH-Fix sticks are chemically bonded to the cellulose fibres (DE-PS 24 36 257).