Hi all,
cheers Darrel
I should also have said that you don't want to add the sodium hydroxide (NaOH) if you make your own up for the drop checker, as the solution will be much too alkaline, and no amount of CO2 will make it change colour.4% solution of sodium hydroxide. Add 20 mL of alcohol and dilute to 1 L with distilled water.
The solution should be deep blue. If it is green, add sodium hydroxide solution drop by drop until the solution turns blue.
cheers Darrel