>I just had this conversation with Girl Mark yesterday at her excellent >class. > >She had some 90% (not 100%) KOH and gave a very general guideline that >if it were 100%, we'd start with something like 4.9 to 6 g for our >calculations, and then add whatever we'd calculated from our Titration >process that we would need. In our case, we had some good stuff, with >a Titration of 2. So, we might use 4.9+2=6.9, or maybe more if we >took 4.9 as the 'low' figure and wanted a 'middle' figure we could use >5.5+2=7.5 > >But, since we had 90% and not 100% KOH, we weren't done calculating. >After the class, I had to correct my calculation. I make it to be >that at 90% KOH, our base-range should be: 5.44 to 6.67 (where 90% of >5.44 is 4.9 and 90% of 6.67 is 6). So, if we used 5.44+2=7.44 for >that 1 liter batch, that might be correct, or maybe a little more if >we wanted to not use the 'low' figure. Is this about right? Hope so. > >MM
Hi MM KOH is never 100%, highest seems to be 92%. Your calculation is about right. As for "low" and "high" figures for the base amount, stick to the low figure (3.5 g NaOH = 4.9 g KOH) for low-titration oil like that. Low titration would be anything less than about 3 ml. See: The basic lye quantity -- 3.5 grams? http://journeytoforever.org/biodiesel_make2.html#lye3.5 Re KOH: KOH is not as strong as NaOH -- use 1.4 times as much KOH (actually 1.4025 times). Titration is the same, just use a 0.1% KOH solution instead of NaOH solution, and use 1 gm of KOH for every milliliter of 0.1% solution used in the titration. But instead of the basic 3.5 grams of NaOH lye per liter of oil, use 3.5 x 1.4 = 4.9 grams of KOH. So, if your titration was 5 ml, use 5 + 4.9 = 9.9 gm KOH per liter of oil. One more complication -- check the purity of your KOH, it's generally not as pure as NaOH. Anhydrous grade KOH flake is usually about 92%, sometimes less -- check the label. We use half-pearls assayed at 85%. Adjust the basic quantity accordingly: the basic 4.9 grams would be 5.8 (5.775) grams for 85% KOH, or 5.3 (5.33) grams for 92% KOH. -- From "More about lye" http://journeytoforever.org/biodiesel_make2.html#lye Best Keith > >On Fri, 21 May 2004 20:31:33 +0900, you wrote: > > >Hi Luc > > > >What is the concentration of your potassium hydroxide? I think from > >your figures below that you're presuming 100% concentration, same as > >NaOH (or nearly), but KOH is less concentrated and you have to allow > >for that. I don't have much faith in your figure of "basic 4.9 > >potasium", it should be more, according to the concentration. > > > >Are you titrating with a KOH solution or a NaOH solution and then > >converting the results to KOH? > > > >>More about lye > >>http://journeytoforever.org/biodiesel_make2.html#lye > >> > >>KOH is not as strong as NaOH -- use 1.4 times as much KOH (actually > >>1.4025 times). Titration is the same, just use a 0.1% KOH solution > >>instead of NaOH solution, and use 1 gm of KOH for every milliliter of > >>0.1% solution used in the titration. But instead of the basic 3.5 > >>grams of NaOH lye per liter of oil, use 3.5 x 1.4 = 4.9 grams of KOH. > >>So, if your titration was 5 ml, use 5 + 4.9 = 9.9 gm KOH per liter of > >>oil. > >> > >>One more complication -- check the purity of your KOH, it's generally > >>not as pure as NaOH. Anhydrous grade KOH flake is usually about 92%, > >>sometimes less -- check the label. We use half-pearls assayed at 85%. > >>Adjust the basic quantity accordingly: the basic 4.9 grams would be > >>5.8 (5.775) grams for 85% KOH, or 5.3 (5.33) grams for 92% KOH. > >> > >>KOH dissolves in methanol much more easily than NaOH does, and > >>doesn't "clump" together as NaOH can do. > > > >Do a comparison with sodium, and I'd also suggest the "poor man's > >titration" that Todd outlined for Pierre a few weeks ago. > >http://infoarchive.net/sgroup/BIOFUEL/33676/ > > > >Instead of using jars, do a blender batch for each sample, same as > >you're doing now. That will mean agitation, temperature etc are just > >the same, with the KOH amount the only variable. You're more > >interested in tests using more KOH than less. > > > >Best > > > >Keith > > > > > >>I successfully made one batch using WVO but that required a double > >>processing and came away matching all the numbers I have read about, > >>BUT twice now I have doen the folowing and with nearly the same > >>results. Could someone please point out the flaw ? > >>WVO = 500ml heated to 130F. > >>Using the "Better Titration method I titrate it using a PH meter to > >>be 1gr extra (4ml%4=1). then I add that to the basic 4.9 potasium > >>Hydroxide for 5.9gr and then divide by two (for the 500ml batch) > >>The methoxide is very well mixed and I add it to the blender oil > >>(still at 130F) slowly and let it blend for 15-18 minutes. > >>After settling I get a distinct seperation of very dark, almost > >>black on the bottom and a redish dark top layer (the BD) but as soon > >>as I put it to the shake test (150ml unwashed BD to 150ml water at > >>room temp) I get mayonaise that won't completely break even after > >>two days. > >>I got to be doing something wrong here. I am going to try one more > >>time using sodiuk instead of potassium and see if I get the same > >>results and then I will have to start questioning the PH meter and > >>the source of WVO, not to mention my ability to understand a laid > >>out process. > >>Should I dump the PH meter and go with strips ? Maybe use the other > >>liquid penolphalene (or something like that) that makes it go > >>magenta for 10 seconds when it reaches 8.5 PH? > >>My scale is top shelf electronic. The chems are fresh from the chem > >>supply house, the oil was still warm when I sampled it :) I am using > >>100% isopropyl (I now have LOTS of it,4.5lt)I mix in the oil while > >>the jar is sitting in warm water and it never really does get 100% > >>clear but I keep on stirring it throughout the titration process aas > >>I add the .01% lye solution (made according to the Better Titration > >>specs) > >>I am now thoughroughly stumped as to what I did wrong. > >> > >>Luc ------------------------ Yahoo! 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