The pH value is a value to measure the acidity and alkalinity of an aqueous solution, also known as the hydrogen ion concentration index and the pH value. Its range is 0~14, which is the negative number of Lg of the hydrogen ion concentration in the water body. The pH<7 is acidic, the smaller the acidity, the stronger the acidity, the pH=7 is neutral, the pH>7 is alkaline, and the larger the alkaline is, the stronger it is.
Generally, a pH meter or pH test paper is used to measure the acidity and alkalinity. Acidity meter, referred to as pH meter for short, consists of three parts: reference electrode, glass electrode and ammeter. A glass electrode was used as the indicating electrode, and a saturated calomel electrode was used as the reference electrode. The acidity meter has high measurement accuracy and can be accurate to 0.01pH.
pH test papers include wide-ranging test papers and precision test papers. Use a glass rod to dip a little of the solution to be tested onto the test paper, and then the pH value of the solution can also be obtained according to the color change of the test paper and compared with the color comparison card. Broad pH test paper has a measuring range of 0-14 and a color interval of 1, which is a rough test method. The color interval of the precision pH test paper can be 0.5, which is more accurate than the broad pH test paper.
