LITMUS BLUE INDICATOR PAPERS
litmus paper turns red under acidic conditions, and red litmus paper turns blue under basic or alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at 25 °C (77 °F). Neutral litmus paper is purple.
Application
APPLICATION: Litmus paper is a filter paper that has been treated with a lichen-provided natural-soluble dye.