A strip of paper that is chemically treated with a dye named litmus. This strip is placed in the liquid whose pH is being determined. The use of litmus paper, which is red at any pH less than 5 and blue at any pH greater than 8, allows an inspector to determine only whether a solution is acidic or basic. More precise pH determinations can be found by using pH TEST PAPER, which compares subtle color differences to a color chart to indicate pH level.
