- Take 100 cm. A long glass tube opened at both ends.
- Plug a cotton piece, soaked in NH, solution at one end and a cotton place, soaked in HCl solution at other ends.
- The vapors of both these gases escape into the glass tube simultaneously.
- The vapors of both NH3, & HCl are invisible. But when they meet with each other. They produce white fumes of NH4Cl.
- The NH3, gas diffuses from cotton plug (Higher concentration) into the tube (lower concentration). Similarly. HCl gas also diffuses from cotton plug (Higher concentration) into the tube (lower concentration).