In chemistry, the logarithmic pH scale measures whether a solution is acidic, neutral or basic. The standard pH scale runs from 0 to 14. A reading of 7 is neutral, based on the pH of pure water. Acidic solutions have a pH below 7, while basic solutions have a pH above 7. Litmus paper is a chemical indicator that changes its color in response to pH. In acidic solutions, blue litmus paper will instantly turn red.
Put on rubber gloves and goggles.
Cut a one-inch piece of litmus paper.
Dip one end of the litmus paper into the solution, and then take it out immediately.
Observe the color of the portion of blue litmus paper that was in contact with the solution. If it turns red, the solution is acidic. If the litmus paper remains blue, the solution is either basic or neutral.
Blue litmus paper will identify the presence of an acid, but not its pH. To identify the actual pH of a solution, use pH indicator strips, and check the color change against the color-coded pH scale on the box.
Treat unknown liquids as hazardous. Wear gloves and goggles when handling acids and bases, or chemicals suspected of being acidic or basic.