Hello Pieter
Hi,
Is phenolphtalein the same as phenol red ?
No.
You've already got the link, below:
> > Basic titration
> > Better titration
> > pH meters
> > Phenolphthalein
> > http://journeytoforever.org/biodiesel_make2.html#titrate
It says:
"Phenolphthalein is often confused with "phenol red", obtained at
pool supply stores and used for checking water. It's not the same
thing, and phenol red won't really do for titrating WVO, its pH range
isn't broad enough. It ranges from pH 6.8, at which point it's
yellow, through orange, to a maximum of pH 8.2, red. For accurate
titration you need to be able to measure pH 8.5.
"Phenolphthalein is colorless up to pH 8.3, then it turns pink
(magenta), and red at its maximum of pH 10.4. When it stays pink for
more than 10 seconds, it's measuring pH 8.5.
"With good-quality oil with low FFA levels you might just get away
with using phenol red for titration, but for higher FFA levels it
isn't accurate enough. Use 1% phenolphthalein solution (1.0w/v%)."
Why don't you read the whole page, Pieter? Both pages:
http://journeytoforever.org/biodiesel_make.html
Make your own biodiesel
http://journeytoforever.org/biodiesel_make2.html
Make your own biodiesel - page 2
Keith
Met dank en vriendelijke groet,
Pieter Koole
----- Original Message -----
From: "bob allen" <bob at ozarker.org>
To: <Biofuel at sustainablelists.org>
Sent: Saturday, June 18, 2005 3:52 PM
Subject: Re: [Biofuel] Fw: Electronic PH meter
> Howdy Kieth and Willem, the issue of the use of a pH meter as opposed to
other methods for
> determination of the end point of a titration comes up from time to time.
It seems that many
> believe one really needs a pH meter. I think not and here is why.
Although a pH meter may be more
> accurate if all the variables were tightly controlled, they're not. How
accurately can one measure
> the 1 ml of oil? One maybe two significant digits? If different oils have
different densities,
> (they do but small) then one should really adjust the volume of oil used
in the titration
> accordingly. Because density is a function of temperature, how accurately
does one know the
> temperature? How accurately can one prepare the titrant solution? How
accurately can one measure the
> titrant? Finally the titration is done in a nonaqueous heterogeneous
solution, hence pH isn't even
> strictly defined; pH being defined as minus the log of the hydrogen ion
concentration in water. If
> you heat the oil/isopropyl alcohol mix to get homogeneity, the hydrogen
ion concentration changes.
> (It is actually worse, it is the hydrogen ion activity, but that is
another matter.)
>
>
> Hence use of a pH meter to me is overkill. What you get is a very precise
endpoint for a titration
> which is really fairly inaccurate, due to the aforementioned difficulties
in the volumetric
> measurements, temperature, etc.
>
> I use phenolphthalein to determine the endpoint. It is quick, requires no
calibration, costs a heck
> of a lot less than a pH meter, and provides sufficient precision for the
measurement at hand.
>
>
> > Hi Willem
> >
> >> Hi all,
> >>
> >> I am slowly getting the parts together to construct a small biodiesel
> >> set-up
> >> (approx. 30 litres).
> >> When I told a friend recently avout my plans he gave me an electronic
PH
> >> meter, pen type. Accuracy is 1 decimal. He said this would replace the
> >> titration, but could give me no more info.
> >
> >
> > It won't replace titration, you use it for titration. You can use
> > phenolphthalein, or pH test strips, or a pH meter - whichever you use,
> > titration involves measuring the pH. See:
> >
> > Basic titration
> > Better titration
> > pH meters
> > Phenolphthalein
> > http://journeytoforever.org/biodiesel_make2.html#titrate
> >
> > pH meters are best, IMO. You need to calibrate them often (get
> > calibration fluid from a lab supply) and you have to look after them
> > properly. There's a "Technical tips" link at the url above.
> >
> > Best wishes
> >
> > Keith
> >
> >
> >> Can anyone tell me if this is so and how I convert the reading to the
> >> amount
> >> of lye to be used?
> >>
> >> Best regards,
> >> Willem
> >
_______________________________________________
Biofuel mailing list
Biofuel@sustainablelists.org
http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org
Biofuel at Journey to Forever:
http://journeytoforever.org/biofuel.html
Search the combined Biofuel and Biofuels-biz list archives (50,000 messages):
http://www.mail-archive.com/biofuel@sustainablelists.org/
