PH describes the degree of acid-base of water solution, and is expressed by pH value. In the thermodynamic standard condition, the aqueous solution of pH=7 is neutral, pH<7 is acidic, and pH>7 is alkaline.

The range of pH is between 0~14, which is only suitable for dilute solution. The pH value of hydrogen ion concentration or hydroxyl ion concentration greater than 1mol/L is directly expressed by concentration.

In Silica Industry, how to test PH Value?

○ Equipment : PH meter, industrial scale, bottle with stopper

○ Method(double samples)

○ Method

① Weigh 3g sample (precise to 0.1g) with an industrial balance and put it into a conical flask with a stopper(50ml). Add 30ml of distilled water to make a 10% aqueous suspension. If the sample is not wet, add 3 – 5ml (95% ethanol), then covered with a stopper.

② Shake vigorously for 1min and leave it for 5min.

③ At the test temperature, calibrate the instrument with a standard buffer solution similar to the sample according to the instrument operating procedure.

④ Remove the plug and measure the pH of the suspension.

Note: The difference between the two determination results does not exceed 0.3PH