Thanks Keith. Pieter Koole
----- Original Message ----- From: "Keith Addison" <[EMAIL PROTECTED]> To: <Biofuel@sustainablelists.org> Sent: Sunday, June 19, 2005 2:05 PM Subject: [Biofuel] Fw: Electronic PH meter > 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/ > _______________________________________________ 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/
