Sciencemadness Discussion Board

Stability of Bromocresol Green in very dilute HCl?

DistractionGrating - 18-5-2016 at 10:41

I want to make a mixed reagent consisting of appx. 0.002M HCl and 0.005% BCG in aqueous solution. I also want to be able to store this reagent for months. Can I expect BCG to remain stable for long periods in this solution? I did UTFSE and also asked Google, but no luck.

unionised - 18-5-2016 at 12:04

0.002M HCl probably won't be stable for months.
It depends what you keep it in, but if you use a glass bottle the HCl will attack the silicates and form (mainly) NaCl.

The dye is probably fairly stable if you keep it in the dark.

What do you want it for?

DistractionGrating - 18-5-2016 at 14:18

I have found 0.002M HCl to be stable enough for my purposes (acid-base titrations) when stored in HDPE bottles.

I want to use the combined reagent for an autotitration device. I'm getting excellent repeatibility with the current prototype. Someone raised the question of BCG stability in HCl, though, hence my question.

So far, I can say that the combined reagent is good for at least a week or so, but I've been going through it so quickly during testing that I've not yet kept it for any longer than that. Of course, I'm setting some aside now to test later, but thought it wouldn't hurt to ask here.