Re: [Biofuel] pH question

[Jan Warnqvist]

I have already been critizised for leaving out the sub-understood meaning that the determinations should be carried out in a water phase, since the H30 and OH ions are not detectable any where else. Jan ----- Original Message ----- From: A. Secco To: Biofuel@sustainablelists.org Sent: Monday, January 30, 2006 4:15 PM Subject: Re: [Biofuel] pH question Dear Jan, If I understand correctly something can be wrong with the pH measurements which Andrew made and reported. The pH can only be measured in an aqueous system and not in an oil/fatty phase. It has no sense to put the probe in the oil phase to measure pH. Remember that pH only applies were the water equilibrium constant works. Instead of measuring through an pH electrode it is more convenient and accurate to measure the total acidity of the oil phase which is made throug a titration with NaOH and reported as "acid value"   Andres Secco ----- Original Message ----- From: Jan Warnqvist To: Biofuel@sustainablelists.org Sent: Monday, January 30, 2006 3:30 AM Subject: Re: [Biofuel] pH question Hello Andrew, not to worry, that pH value is quite in order. When you judge the result of a correctly performed pH determination, you should be aware of that the pH scale is logaritmic. Example: pH 7 means that the amounts of H3O( acidic) and OH (hydroxide)ions are the same amounts, that is 10 powered by - 7 moles per dm3 = 0,0000001 moles/dm3. If you have pH 6, this means that the H3O ions are ten times more than the OH ions, H3O= 10 powered by -6 moles/dm3 = 0,000001, and the OH ions are 10 powered by -8 moles/dm3 = 0,00000001 moles/dm3.For pH 2 you have a concentration for the H3O ions of 10 powered by -2 = 0.01 moles/dm3 and the corresponding value for OH is 10 powered by -12 = 0,000000000001 moles/dm3. This means that if a pH determination drops from pH 1 to pH 2, much more has actually happend than a drop from pH 6 to pH 7. The reason for pH 6 on biodiesel could be that there is a content of free fatty acids or other acidic remains in the biodiesel. Is this right, Bob ?   Jan Warnqvist ----- Original Message ----- From: Andrew Leven To: Biofuel@sustainablelists.org Sent: Monday, January 30, 2006 2:09 AM Subject: [Biofuel] pH question Hello, I've made and washed 4 test batches  from different wvo oil sources and have come up with some quite clear, light amber colored BD but it all seems to test out at pH 6 + or -. This seems a bit low. Any ideas about what would cause a consistent low reading like this? Andrew Leven _______________________________________________ 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/ Visita www.tutopia.com y comienza a navegar más rápido en Internet. Tutopia es Internet para todos. _______________________________________________ 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/

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