1. Put baking soda in the baking tray first, and then smooth it.

2. Put the baking tray in the oven and bake at 200 degrees for 20 minutes.

After 3.20 minutes, prepare a small bowl of pure water, and then put the baked baking soda into the small bowl.

4. Stir well until there are no particles in the water.

At first, the water was turbid. After five minutes of silence, the water will become clear. After the water becomes clear, it can be used at room temperature the next day.