Chris,
Good to hear from you.
I asked why the treated WVO didn't titrate lower.
Chris:
> There just might not be enough NaOH in the glycerine cocktail to
> neutralize all ffa's. Longer treatment will make no difference if this is
> the >case.
I was curious because the WVO still has FFAs (titrated 1.8) and the
glycerine mix still is caustic (pH ~ 8).
(I'm going to switch the order of my ques/your answers, in order to ask
a question)
Tom:
>> - I didn't notice tallow in the WVO I loaded into the processor, but
>> it was clearly evident in the settled mix after treatment; same temp as
>> the original WVO was. Any explanation? (Could be I just didn't see it)
Chris:
> We've also observed this. I believe that it is not tallow but soap formed
> during treatment. The soap is translucent gelly. The glycerine settles out
> at the bottom from the soap.
Wouldn't this glycerine-insoluble soap also be a water-insoluble soap?
Tom: re: adding acid to increase solubity of soap.
>> Does decreasing pH increase the solubility of otherwise water insoluble
>> soaps?
Chris:
> If a substance is insoluble in polar water it will be more insoluble in
> more
> polar acid solution unless solubility constants (Ksp) are involved but I
> think this is not the case here.
Is it possible that a substance (soap) is soluble in glycerine when the pH
is 9, but less soluble when the pH is 7 or 8? i.e. "it will be more
insoluble in more polar acid solution"
Such a substance would separate (----> gel layer?) from the "treated"
glycerine, but not be observed in the raw glyc cocktail.
My thinking: Maybe the water-insoluble soap is not made more soluble by the
change in pH, but less soluble. It is then separated out during settling
-----> "treated" glycerine mix that will not clog my sprayer and, fingers
crossed, compost as well as the glycerine that I acid-split from the mix
once upon a time.
This might explain the increased foaming of the "treated" glycerine vs
untreated when shaken in water. It doesn't explain why untreated glycerine
foams better when a small amount of acid is added to it. (???)
Let me ask one more thing:
When you say:
> If a substance is insoluble in polar water it will be more insoluble in
> more
> polar acid solution ......
What if it is not a more polar acid solution that is produced. What if
the solution is alkaline to start (first wash or the raw glyc mix), and the
acid simply decreases alkalinity.
Would a decrease in alkalinity, towards neutral make the solution less
polar and thereby effect solubility?
I should have paid more attention in chemistry class,
Tom
----- Original Message -----
From: "chris" <[EMAIL PROTECTED]>
To: <sustainablelorgbiofuel@sustainablelists.org>
Sent: Friday, March 21, 2008 3:30 PM
Subject: Re: [Biofuel] Treating WVO w. Glycerine Cocktail
>
>
>> -----Original Message-----
>> From: [EMAIL PROTECTED]
>> [mailto:[EMAIL PROTECTED] On Behalf
>> Of Thomas Kelly
>> Sent: Wednesday, March 19, 2008 3:56 PM
>> To: biofuel
>> Subject: [Biofuel] Treating WVO w. Glycerine Cocktail
>>
>> Questions: (Take your pick)
>> - FFAs are very weak acids. Is this why the WVO titration did not
>> drop to zero?
>> Would longer treatment or more glyc. cocktail be needed to further
>> lower FFAs?
>
> There just might not be enough NaOH in the glycerine cocktail to
> neutralize
> all ffa's. Longer treatment will make no difference if this is the case.
>
>> - A while back it was suggested that I add a small amount of
>> phosphoric acid to my first wash to help remove water insoluble soaps.
>> Does decreasing pH increase the solubility of otherwise water insoluble
>> soaps?
>
> If a substance is insoluble in polar water it will be more insoluble in
> more
> polar acid solution unless solubility constants (Ksp) are involved but I
> think this is not the case here.
>
>> - I didn't notice tallow in the WVO I loaded into the processor, but
>> it was clearly evident in the settled mix after treatment; same temp as
>> the original WVO was. Any explanation? (Could be I just didn't see it)
>
> We've also observed this. I believe that it is not tallow but soap formed
> during treatment. The soap is translucent gelly. The glycerine settles out
> at the bottom from the soap.
>
>> - The odor of the glycerine was distinctly less offensive after
>> treatment. I suspect there was less methanol present. The temp of the
>> mix never even reached 80F (27C). I can't imagine that it was used to
>> form methyl esters. Is the presumed "missing" methanol now dissolved in
>> the WVO (90 L WVO vs 9 L of glycerine).
>> Any other reason for the change in odor?
>
> I suspect the same.
>
>>
>> My this has become quite wordy. Sorry 'bout that
>> Tom
>
> Best regards,
> Chris Tan
>
>
>
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