Red and Blue Litmus

• Litmus was first used in 1300AD by Spanish alchemist Arnaldus de Villa Nova. From the 16th century on, the blue dye was extracted from some lichens.
• In an acid, both red and blue litmus paper will turn red
• In an alkaline solution, both red and blue litmus paper will turn blue
• In a neutral solution both litmuses will stay their original colour