Skip main navigation

New offer! Get 30% off your first 2 months of Unlimited Monthly. Start your subscription for just £35.99 £24.99. New subscribers only T&Cs apply

Find out more

How to make a medicinal lava lamp

Andy Parsons walks us through the making of a medicinal lava lamp, and how to dispose of the completed lamp safely.
Penicillins are sometimes used in combination with other medicines. For example, for people who have peptic ulcer disease and are known to be infected with a bacteria called Helicobacter pylori, at least two antibiotics are used. This is in addition to medicines, which are used to reduce the acid secretion in the stomach and a bismuth-containing compound used to protect the stomach lining from acid. This so-called triple therapy is complicated because it involves taking as many as 20 pills a day. To reduce the number of tablets a patient has to take, sometimes a pill can contain more than one active substance, such as antacid tablets.
Alka-Seltzer is a medicine that works as both a pain reliever and an antacid - it relieves minor aches and pains, an upset stomach, headaches, and indigestion. The pain-relieving agent is aspirin while the antacid that helps neutralise stomach acidity, which can cause heartburn, is formed from sodium bicarbonate. Sodium bicarbonate is commonly called baking soda. The tablets also contain citric acid, a weak acid that adds flavour - interestingly, as we will see it also provides an important source of hydrogen ions. To take the Alka-Seltzer tablets, they first need to be dissolved in water.
In the solid tablet the sodium bicarbonate and citric acid do not react, but when placed in water they react in an acid-base neutralisation reaction, producing sodium citrate, water and lots of bubbles of carbon dioxide - hence the fizzing. It is the sodium citrate, which acts as the antacid, when the mixture of Alka-Seltzer and water is ingested. In this activity we will make use of this reaction and the release of carbon dioxide to form a colourful lava lamp. Adding a tablet of Alka-Seltzer to a mixture of vegetable or olive oil with a smaller amount of water, in a bottle, produces the desired effect.
The bubbles of carbon dioxide in the water make buoyant blobs that float in the vegetable oil - when they reach the surface, the bubbles pop so the blobs of water become less buoyant and sink again. To stamp your personality on this experiment, try adding a food colouring to the mixture, and see what happens. Try adding small pieces of more than one tablet. What about repeating with warm water, or with cold water? Were there a lot more bubbles produced, initially, in the hot compared to the cold water? For an authentic lava lamp, place the bottle in a darkened room and backlight the ‘lamp’ with a torch. Don’t forget to take photos and to post your spectacular results.

What ingredients do you need?

As well as the active ingredients contained within a single pill or capsule, there are inactive substances called fillers and flavourings, and also buffers to maintain the optimal pH at which the active ingredients will be effective.

The following ingredients will be required:

  • Alka-Seltzer tablets
  • A selection of food colourings
  • Cooking, olive or vegetable oil

The following items will be required:

  • A tall, clear glass

Ensure that you read through all of the instructions before beginning the experiment to ensure that you understand exactly what will happen at each step.

Step 1: Measuring

Fill approximately one-fifth of the glass with tap water.

Fill the remainder of the glass with cooking or vegetable oil. Ensure to leave a small gap between the oil level and rim of the glass as some “foam” may be produced.

If you wish to add any food colouring for an enhanced effect, then do so now. Different quantities of food colouring will produce different shades of the relevant colour.

Step 2: Adding the active tablet

Take your Alka-Seltzer tablet and drop it centrally into the glass. It should sink to the bottom of the glass and after a few moments bubbles should begin to form.

Repeat the experiment with different shades of food colouring, or alternatively different liquids in place of water. Do different temperatures of water produce different results? Will crushing the tablet into smaller pieces produce more bubbles? If cabbage juice is used in place of the food colouring, why is there a change of colour?

Be creative, add a backlight to create a true “lava lamp” effect or try dropping in small pieces of glitter to see what happens.

How to dispose of a lava lamp safely

Dispose of the completed lava lamp safely. We strongly advise to not consume the “lava lamp” at any stage of the experiment.

Dispose of the lava lamp down the sink, washing equipment thoroughly with cold water, once complete. It may be necessary to use warm water to wash away the oil (even though we normally use cold water to wash up after an experiment).

This article is from the free online

Exploring Everyday Chemistry

Created by
FutureLearn - Learning For Life

Reach your personal and professional goals

Unlock access to hundreds of expert online courses and degrees from top universities and educators to gain accredited qualifications and professional CV-building certificates.

Join over 18 million learners to launch, switch or build upon your career, all at your own pace, across a wide range of topic areas.

Start Learning now