The pH test paper is also known as pH test paper, which displays orange-red color when the pH of the solution to be tested is <7 indicating acidity, yellow-green color when the pH of the solution to be tested is =7 indicating neutrality, and purple-red color when the pH of the solution to be tested is >7 indicating alkalinity. pH test paper is clinically used to detect the acidity and alkalinity of urine, vaginal secretion, obstetrics to identify whether there is premature rupture of membranes, etc. When testing with a dry glass rod dipped in the solution to be tested or with a rubber-tipped pipette to suck the solution drops in the middle of the test paper, according to the color change of the test paper and the standard colorimetric comparison card, to be able to determine the acidity and alkalinity of the solution. The solution to be tested pH <7 indicates that the acidity shows an orange-red color, the stronger the acidity, the redder the color. When the solution to be tested is neutral, pH=7, it shows a yellowish-green color. When the pH of the solution to be tested is more than 7, which means alkaline, it shows a purple-red color, and the more alkaline it is, the deeper its purple color is. In addition, the results of the test may be affected if the pH test paper is contaminated or has exceeded its expiration date.