Phenol Red is used for pH measurement. The tablet produces characteristic colour changes when dissolved in the water sample. The pH value is important for the disinfection effect of water care products. It can also cause corrosion or precipitation and thus damage materials. The Lovibond® tablets contain thiosulphate to compensate for the disturbing influence of chlorine on the measurement in pool water analyses. In addition, the carbonate levels, temperature and buffer capacity of the water sample can influence the measurement and should therefore also be kept in mind. This tablet has been developed for use in photometers.