A pH indicator (which can indicate acidic or basic substances) called litmus is a dye extracted from the lichen Roccella tinctoria ("dyer's weed") by boiling. It gives its name to the well-known litmus test.
a ph indicator (which can indicate acidic or basic substances) called litmus is a dye extracted from the lichen roccella tinctoria ("dyer's weed") by boiling it gives its name to the well-known litmus test