an overfilled stomach causes heartburn

Boom Advent #9 – Molecular Madness

We said last week in the first Molecule Madness that Christmas is a festival of the senses. Last week we covered the sight of tinsel. This week it’s the wonderful smells and tastes of a fabulous selection of food and drink from mulled wine to turkey and mince pies to chocolate. We can’t resist all of that wonderful Christmas food but that comes with a problem – heartburn – and then it’s time to reach for the aluminium hydroxide.

Too… much… food…

One feeling we don’t like is when we’ve eaten too much food. We’ve all done it, one sprout too many, an extra pig in blanket we thought we could handle and way too much turkey. The problem with eating too much can be indigestion and heart burn.


It’s not a nice feeling. You can’t get comfy, your chest feels on fire, your stomach wants to pop and let’s hope you’re not wearing tight trousers! However, fear not for there is something to help. Antacids, otherwise known as anti-indigestion can help relieve the indigestion and calm our tummies. One popular molecule that is used as an antacid is aluminium hydroxide, Al(OH)3.

Say Hi to Al

In its pure form, aluminium hydroxide is a white powder. A single molecule of aluminium hydroxide contains a single atom of aluminium surrounded by three hydroxide molecules. A hydroxide molecule contains an oxygen and hydrogen atom bonded together. Al(OH)3 has some interesting properties. For one thing, it is amphoteric (am-fo-terric). This means it can behave as both an acid and a base.

Aluminium hydroxide occurs naturally in the mineral gibbsite. However, most aluminium hydroxide is made in factories by the Bayer process. The Bayer process is actually how aluminium oxide is made, but during the process aluminium hydroxide is also made.

Antacid, not Uncle-Acid

So how does aluminium hydroxide work as an antacid?

To start with, what causes indigestion, heartburn or upset stomachs? Our stomach is full of hydrochloric acid. This acid helps in digestion and also can kill many micro-organisms that might harm us. However, sometimes our stomach can produce too much acid, which can lead to indigestion. 

As an amphoteric molecule, aluminium hydroxide can help to reduce the extra acid and calm our stomachs. The reaction between an acid and a base is known as neutralization.

Aluminium hydroxide is preferred to other bases as it does not dissolve in the stomach. This means it can reduce the amount of acid in our stomach, without reducing it so much that our stomach decided it needs to produce more acid again. However, one problem is that it can make you constipated. In short – you find it difficult to poo.

Other uses

Antacids containing aluminium hydroxide are very popular around the world.  In the UK, one popular brand of antacids made over £60 million pounds in 2016. Despite this popularity, aluminium hydroxide has a range of other uses. One other use is as a fire retardant, meaning it is good at slowing down fires. For this reason, it is often mixed with plastics. As well as being an antacid, this molecule is also used to reduce high amounts of phosphates in people suffering with kidney problems.  

After you’ve gobbled all your Christmas dinner, and maybe a second or third helping, you may well be feeling that heartburn and you’ll be reaching for some aluminium hydroxide. In fact, you might end up needing to do the same the day after Christmas, and the day after that! After all, the festive season is as much about the food as it is anything else.


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