Expert: Dr. Henry Boyter, Jr. - 7/3/2005

Question
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Followup To
Question -
Dear Dr.Henry Boyter,
In a peer-reviewed paper one can read :" In the process of converting flax to linen, the material was 'retted', i.e fermented, a practice which required submerging the material in natural bodies of water for extended periods of time.(...)During this process the natural ion exchange properties of cellulose operate and two ions found commonly in natural waters that most strongly bind in this way are Ca and Fe(...)"
My question is : if 2 old linen fabrics are found to contain roughly the same amount of Ca and Fe, must we absolutely conclude that the flax fibers were retted in the same locality where the same trace elements are present? In other words, does the equilibrium state strongly depend on the concentration of Ca and Fe in the water ?
Thank you very much for your answer.

Answer -
Several problems:

1. Iron and calcium concentrations are not constant in natural waters.  They can vary by season and rainfall.

2. Iron and calcium will bind at different rates, so you have to take that into account.

3. Iron and calcium concentrations can be the same at different locations.

I think if you had samples with very high iron and calcium levels, you could suggest they came from a site where there was high iron and calcium or maybe rule out sites that don't.  You might also look for more trace metals to see if you can see patterns (like the rare earths).  But again, climate is going to make a difference.  I know with pottery, rare earths have been used to examine relationships to Nile flooding.

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Thank you very much for your answer.
In order to complete my understanding, is there a general formula providing the level of a cation bounded on cellulose at equilibrium as a function of the initial concentration of the cation in the water and other parameters ?
Best Regards  

Answer
Not really.  You could study the chemical equilibriums, but they are so dependent on ALL the metals, salts, and other stuff present, not to mention pH, no general equation could be written.  You would need to work that out from source water and actual experimentation.