A SAP value could be run in about an hour but most pc labs don't have the condenser / heater set up.
-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Wednesday, September 24, 2003 12:01 AM
To: [log in to unmask]
Subject: Re: [TN] Saponifier Concentration
Sorry, Rudy, I VERY strongly disagree that pH can be used to determine
saponifier solution. If we take the data sheet of one well known saponifier:
pH of concentrate: 11.9 ± 0.5
pH of 10% solution: 11.5 ± 0.5 (my comment: recommended concentration)
pH of 5% solution: 11.4 ± 0.5
Why is this? Because the MEA is strongly buffered. If the pH falls below
11.0 (ie 10% solution at bottom of tolerance range), then it is already
far beyond useless. Also, the answer would be influenced by the
alkalinity of the resultant soaps. This would not be the case with
titration, provided the end point was higher than the pH of the soap
solutions (typically 8 to 8.5).
Saponifier solutions also contain solvents, such as diglycol ethers,
because not all the flux residues are saponifiable. These can also be
exhausted (by saturation), and usually at a different rate to the
amines. It is very probable that these will have a somewhat greater
effect than the MEA on the refractive index, but a saturated solvent and
a fresh one will have little difference in the RI. Similarly, the effect
of the saponified carboxylic acids (soaps) on the RI will be unpredictable.
I stand by my earlier post that titration with a carboxylic acid to a
given pH would be the most reliable method of determining the
effectiveness of the amine, although I agree that it would not help to
determine the unsaturated solvent content, but neither would pH nor RI.
A refractometer could be used successfully for measuring the
concentration of a fresh (ie unused) bath only. I believe that only a
careful, but complex, combined wet analysis and spectography would give
you the full answer.
Brian
PS Just before pressing the Send button, I had the brainwave of looking
at Cala & Winston's book. Frank Cala is the saponifier guru at Church &
Dwight. I was relieved to find he agreed with me along the broad lines
(p. 76), but he also suggests that titration kits are available from
saponifier suppliers, precalibrated for their products.
Roger Cook wrote:
> Can anyone recommend a method/equipment for testing the concentration of
> saponifier ? We currently use a Brixstix refractometer.
> Thanks
>
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