I’ve mentioned in a few shows that different salts burn different colours and I always joke about how rubbish it is that the salt we put on our food (sodium chloride) burns orange. Fire is orange anyway! 

Potassium chloride is a salt which burns purple - I ordered some online in bulk; and you’ve got 2 grams in your bag. It’s safe to touch - it gets added to foods as a salt alternative to make them ‘low sodium’. But DON’T EAT IT - you have to check with a doctor before taking it as a food supplement. If potassium chloride is mixed with hand sanitizer (which is mainly ethanol, a fuel) and burned in a certain way, a purple flame can be seen.

IT'S THE HAND SANITIZER THAT MAKES THIS SOMETHING ONLY ADULTS SHOULD BE READING! I only use a tiny amount but if something goes wrong the flame can only be put out by smothering - with soil or sand - or it can be left to burn out on a baking tray.  WATER DOESN'T PUT OUT THE FIRE. It's very dangerous to put water on burning hand sanitizer - it just spreads it further. AND ethanol burns with an invisible flame so I had to be aware of this and leave all the items on the baking tray for some time after the activity.  

Just sticking the potassium chloride on a teaspoon and holding it over a candle won't work - you know I tried! Chemistry teachers do something called a flame test - after a lot of experimenting I worked out a method that let me see a purple flame. I used:

• 2g of potassium chloride

• 2g of household salt

• A plate

• Hand sanitizer (which mainly ethanol, a fuel)

• A baking tray

• Two forks

• Two teaspoons

• Candle

• Matches

Safety precautions: I did this standing up (so I could jump backwards if something went wrong), with hair tied back, and some swimming goggles on in case it spat, in a well-ventilated area.

I squeezed the hand sanitizer out into two more-or-less equally sized blobs on the plate, far apart from each other. They looked like two clear pennies on either side of the plate. I put the sachet in the bin straight away.

I mixed 2g of potassium chloride into one of the blobs, and about the same amount of household salt into the other blob, and mixed them with teaspoons. They had the consistency of melting hailstones.

I washed my hands to be sure I didn't have any hand sanitizer on them, then I put a candle in the middle of a baking tray and lit it.

I scooped up a small amount of the potassium chloride mixture with the fork and held it over the very top part of the flame. It burned purple. I repeated this until the mixture was used up and then washed the fork, and washed my hands again.

Then I repeated the steps with the household salt mixture and discovered that I've been doing 'normal salt' a real disservice - it very clearly burns bright orange, not the same colour as the candle flame at all.

If you're unsure about this activity, don't do it! Put the bag in a safe place and wait until you have access to a trained chemistry teacher, or me!