Fill your burette with a ’rainbow’ by using this practical that shows students the effervescent reaction between acid, sodium carbonate, and universal indicator
With a little universal indicator, acid, and sodium carbonate, students will be amazed by the effervescent reaction that causes a ’rainbow’ to appear.
This experiment should take five minutes.
- Eye protection
- Burette, 50 cm–3
- Retort stand with boss and clamp
- Cotton wool plug
- Universal Indicator solution
- Hydrochloric acid solution, 10 cm3, 2 mol dm–3
- Sodium carbonate solution, 20 cm3, 1 mol dm–3
Health, safety and technical notes
- Read our standard health and safety guidance
- Always wear eye protection
- Hydrochloric acid is low hazard (see CLEAPSS Hazcard HC047a).
- Sodium carbonate is low hazard (see CLEAPSS Hazcard HC095a).
- Clamp the burette vertically.
- Add 0.5 cm3 of the Universal indicator solution followed by 10 cm3 of the hydrochloric acid to give a clearly visible red colour.
- Add 20 cm3 of the sodium carbonate solution.
- Insert a loose plug of cotton wool in the top of the burette.
- The sodium carbonate and hydrochloric acid react, with effervescence, and the burette will be filled with liquid showing a ‘rainbow’ of all the colours of Universal indicator from red through orange, yellow, green and blue to purple.
Place the burette against a white background to show the colours to best advantage.
- PDF, Size 0.12 mb
This practical is part of our Chemistry for non-specialists collection. This demonstration was developed in this form by Grant Birchby and Alan Matear of Blackburn College for the RSC.