Keith, Saponification of oils essentially cracks the tri-glycerides in the base oil and converts them into FFAs, which are then converted to soap.
When using the FFAs from the glycerine recovery process of biodiesel making there is no glycerin to cleave (as there are no glycerides in the feedstock), thereby saponification happens at a considerably faster rate. Whether the FFAs are being used by soapmakers accustomed to cooking the oils for lengthy periods before trace, or those who prefer cold processing (no exterior heat inputs) this will completely wig them out. If using nothing but recovered FFAs the mix will need to be spooned into moulds, as it goes beyond trace almost immediately and does not pour in the traditional sense. Whether or not the qualities of the finished soap are desireable will depend largely on the original base oil. If traditional soap from that oil never made a hard bar or lathered well, don't expect the soap from FFAs of the same oil to behave any differently. Also, the soap will have no glycerin in it, so it will posess considerably less emolient character than what a person is accustomed to with homemade soaps. The bit in brackets in the paragraph immediately below simply accounts for raised volumes of fluids due to the addition of gram weights of solids, such as catalyst. No different than taking a liter of water and adding a 2 cm in diameter steel ball bearing. There is no more water in the flask, even though it appears so. > >You can roughly calculate the glycerin fraction to be ~79 > >milliliters for every liter of oil processed.procedure. The > >balance of the crude glycerin layer will be FFAs, which can be > >roughly considered the same as a base oil. (If you want to get > >"critical," subtract 0.40 ml from the initial volume for every > >gram of catalyst deemed to be present in the crude glycerin when > >calculating what fractions of the crude glycerin are FFAs and > >glycerin.) As for whether or not 23% FFA feedstock can be converted to biodiesel, or at least the remaining 77%, using a straight base method, I can't see any reason why not. A person could test the theory by procuring lab grade stearic acid and combining it proportionally with a virgin oil of known FFA proportion. Most of what we've been doing here has been geared towards acid/base with a shift towards elevated temperature and pressure. If a person was curious to see what difference elevated pressure can make on an acid/base reaction, some testing could be conducted using a small pressure cooker of the type found in commercial restaurants. They're not rated for very much pressure, but that can be partially compensated for by increasing reaction time. I certainly wouldn't suggest that anyone unfamiliar with HTP reactions approach such experimentation casually (also to be read "carelessly"). I would also suggest that such testing be done exterior to one's home. Would be very interesting to see what kind of temperature and pressure could be achieved using strictly solar and a blackened pressure cooker. This could reduce some of the energy inputs needed in backyard or back country environments, for both an acid/ base or a straight base reaction. Sad, but true... http://www.biodiesel.org/resources/reportsdatabase/reports/gen/ge n014.pdf A little bench top testing makes it pretty obvious to anyone that an enormous range of biodiesel will dissolve in methanol. Which makes evaporative recovery from the biodiesel extremely important in all production, whether commercial or backyard, whether home biodieselers want to believe so or not. Todd Swearingen ----- Original Message ----- From: Keith Addison <[EMAIL PROTECTED]> To: <biofuel@yahoogroups.com> Sent: Tuesday, August 27, 2002 4:04 AM Subject: Re: [biofuel] boiling glycerine/soap > Hi Todd > > Very interesting post. > > <snip> > > >of variables. (If you are using crude glycerin from WVO, it is > >doubtful that you will be terribly pleased with the resulting > >fragrance of your finished soap product.) > > Um, no, indeed, it's fairly disgusting. Filtering the stuff first > through clumping cat litter might help (fuller's earth), or maybe > charcoal. > > This FFA soap in the crude glycerine layer is pretty much the same as > soapstock (FFAs removed from commercial cooking oil by caustic > refinement). Despite the name, is it possible to make good soap out > of soapstock, do you know? > > >You can roughly calculate the glycerin fraction to be ~79 > >milliliters for every liter of oil processed.procedure. The > >balance of the crude glycerin layer will be FFAs, which can be > >roughly considered the same as a base oil. (If you want to get > >"critical," subtract 0.40 ml from the initial volume for every > >gram of catalyst deemed to be present in the crude glycerin when > >calculating what fractions of the crude glycerin are FFAs and > >glycerin.) > > Sorry, Todd, the bit in brackets has me gazing blankly into the > middle distance. Can you explain? The initial volume of what? - the > glycerine layer or the oil processed? Is the 0.40 ml per gram an > indication that you can calculate volume of FFAs in the oil from the > amount of catalyst used? I tried to figure that before and was told > it's difficult because there are different FFAs present with > different molecular weights and in varying proportions. I can > understand that, but a rough guide would be useful just the same. > > I tried to work back the other day after processing some high-FFA > oil, calculating the volume of oil and methanol against the > production of biodiesel (washed) and the volumes of separated > glycerine and FFA, but wasn't too confident in the results. I ended > up with 26% FFAs and 11% glycerine, which together would have > contained about 6% of excess methanol (all percentages of original > volume oil). Make it 50-50 (?) for the methanol and that leaves 23% > FFAs and 8% glycerine, which goes nicely with your figure of 79 > millilitres glycerine. The 23% FFAs represented 13.65 gm lye/litre of > oil, which makes 1.7% FFAs per gram. Does that make sense? Can you > really do 23% FFA oil with a single-stage process? The oil titrated > at 9.15 ml, not very nice oil. (I thought they were very kind to give > it to me for nothing, I didn't even have to make a contribution > towards the funeral costs of the clientele.) Go acid-base, for sure, > but I'm trying to figure stuff, so this was single-stage. > > It's said most of the excess methanol ends up in the glycerine layer, > but I've been reading some studies saying it's about half-half in the > glyc and in the biodiesel. "... about half of the excess methanol is > in solution with the ester phase and half is with the glycerin > phase." From: "Determining the Influence of Contaminants on > Biodiesel Properties", Jon H. Van Gerpen et al, Iowa State University > July 31, 1996: > http://www.biodiesel.org/resources/reportsdatabase/reports/gen/ge n014.pdf > > Interesting study, by the way. > > Keith > > >You will need to balance how much of the crude glycerin layer you > >add to any soap recipe. The volume will be limited by how much > >catalyst, base oil and/or glycerin is called for. > > > >If you choose to incorporate the use of biodiesel co-products > >into your soap making, it will be helpful to log the inputs and > >co-products for each batch and keep the co-products from > >different batches labeled and separate from each other. This will > >make these crude forms of back measuring considerably more > >accurate than just "guesswork," yielding more consistent results > >in your soap manufacturing. > > > >Todd Swearingen ------------------------ Yahoo! Groups Sponsor ---------------------~--> 4 DVDs Free +s&p Join Now http://us.click.yahoo.com/pt6YBB/NXiEAA/MVfIAA/FGYolB/TM ---------------------------------------------------------------------~-> Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://archive.nnytech.net/ Please do NOT send Unsubscribe messages to the list address. 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