Bromothymol Blue Indicator

[Vick]

I have just made some Bromothymol Blue indicator. Method used is: 2g bromothymol blue powder, 100ml ethanol and 500ml distilled water.

My solution is an orange/red colour. Do I add a couple of drops of NaOH to make it go blue? If so, will this effect the titration that year 12 will be doing (HCl, NaOH and vinegar).

Thanks

[Robb]

Hi Vick,

What you need to do is to add NaOH (0.5M) until the Bromothymol blue solution changes to green. Only then is it ready for use.

I suggest using 0.5 Molar because the change fron Red/Orange to Green won't be so sudden.

Using Sodium Hydroxide to change the Orange/red colour you currently have to green will not affect the colour change during the Acid/Base pH titrations that your seniors will do.

The colours that the Bromothymol blue will change to are:

Acidic Environment:- Red/Orange
Alkaline Environment:- Blue

Hope this has been helpful.

Cheers,

Robb.....

[Vick]

Robb

Thanks for your help.

Vicki