MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Acid and alkali. Bottles of sulphuric acid and sodium hydroxide or caustic soda (an alkali or base) solutions. Acids are substances which produce an excess of hydrogen ions when they are dissolved in water. Alkalise are substances which produce an excess of hydroxide ions when they dissolve. The 1M and 2M on these bottles' labels referred to the concentration of the solutions in them, the sodium hydroxide being twice as concentrated as the sulphuric acid. Acids and bases react to neutralise each other to produce a salt and water.
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