100 Strips/Box PH Test Strips Red Litmus Blue Litmus Paper Quick Test PH Paper

When encountering alkaline solution (pH>8), the red litmus paper turns blue, and when encountering acid solution (PH<4.5), the blue litmus paper turns red. When the pH value of the solution is between 4.5-8.0, the red litmus and blue litmus papers will not change color.

eBay