Australia's Science Forum

Hi Everyone
I am having trouble making Litmus Solution. I have tried 2 recipes. One says to add 10g of Litmus, boil then filter. The filtering takes a long time.
The other says to add 5g and stand for 24hrs then add 2 drops of Sodium Hydroxide. After I make the solution it is a nice purple colour but after it sits for a couple of days it turns a reddish brown colour. Can anyone help?

Litmus Boil 5g in a litre of water. Stand, Filter
Aways worked will for us

I'd try posting this question on Science Assist for Teresa Gigengack.

If it's turning red over time, possibly the solution is absorbing CO2 increasing the overall acidity. Make sure it's stored in a sealed bottle.
If this is what is happening, then a bit more NaOH to elevate the pH will return it to blue.