Check the pH of the solution: Take a small piece of test paper on a watch glass or glass piece, use a clean glass rod to draw the test solution to the middle of the test paper, observe the color after the change is stable, and compare it with the standard color chart to judge the solution. Nature 2. Check the pH of the gas: wet the test strip with distilled water first, stick it to one end of the glass rod, and then send it near the mouth of the container containing the gas to be measured. Observe the color change and judge the nature of the gas. (The test strip cannot be touched. Wall

note:

1. The test strip cannot be directly extended into the solution.

2. The test strip must not touch the test tube mouth, bottle mouth, duct mouth, etc.

3. When measuring the pH of the solution, the test strip must not be wetted with distilled water in advance because the wetted strip corresponds to dilute the solution being tested. This can lead to inaccurate measurements. The correct method is to use a glass rod that contains the solution to be tested. The middle of the test strip, after the test strip is discolored, is compared with a standard color chart to determine the pH of the solution.

4. After the test paper is removed, the test paper container should be tightly closed to prevent contamination by some of the laboratory's gases.