pH Indicators - Phenol Red, Bromphenol Blue, Tumeric

[bluenavigator]

I went to various stores, excluding pool supply stores. Seem that bromphenol blue is popular among pet stores. Heard home brewed indicator, using tumeric powder. So far, I know that phenol red is prefered indicator for pH reading. (Pretty much that I am biased already for phenol red.) So I am asking everyone about their experiences/opinions with all or some of these indicators. [img]/ubbthreads/images/graemlins/tongue.gif[/img]

[scbaguy]

Don't know about the blue, but i believe the Phenol red turns colors at just a little below the ph we want. The turmeric turns at the correct ph.
I use the turmeric and love it. It is easy to make, and turns a very very bright red when it changes. I have not used the phenol, but i understnad it turns only pink, maybe hard to tell, maybe not [img]/ubbthreads/images/graemlins/shrug.gif[/img]

Maybe someone who has used both can chime in.

I say get some turmeric. YMMV

[girlmark]

the bromophenol blue (not bromoTHYMOL blue) is for testing for alkaline stuff like soap in your unwashed biodiesel.

the phenol red, phenolpthaleine, and turmeric are for testing for free fatty acids in oil, which is what you want for the titration we do for the oil.

Turmeric and phenolpthaleine give the same reading (just different colors), and phenol red is close enough but just a little bit 'off'. The place where the difference between phenolpthaleine and phenol red matters is when you have REALLY BAD oil and the little difference in readings is suddenly a big one. However most of us don't want to use really bad high-FFA oil (an exeption is when you're doing acid-base processes which are tricky and most people will avoid them), so you should be fine with the pool stuff.

But the turmeric will cost you $2 at the grocery store and you'll have an almost unlimited supply after you've bought your first bottle.

Mark

[babyarm]

How do you mix the turmeric so you can use it. What do you mix it with?

[girlmark]

go to the auto parts store and buy one or two bottles of 'RED' bottle ISo-Heet -that's 99% isopropyl alcohol (the yellow bottle Heet is methanol which you don't want to use for titratoin, but the red bottle is isopropyl).

the exact proportions don't matter at all- it'll just affect the exact depth of color.

Pour 'some' isopropyl into a jar and then add 'some' turmeric (a spoonful to half a cup of isopropyl?)

Do this in the kitchen sink so that if it spills you dont' make a yellow stain on the floor or your furniture or whatever.

I usually let it sit for a few hours till the powdered spice falls to the bottom of the jar, and then pour off just some liquid into another container (again, don't spill it on the furniture, it stains)


Afterwards you can dispense it into your titration jar by using an eyedropper, a syringe, or a small squeeze bottle. You use a few drops or a squirt in the titration.

Mark