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Discussions on this list, like the one below, frequently trigger my 
thinking
with regard to my work on prehistoric salt sites.  There is a well known 
ash process widely used in the salt industry in many countries.  That is 
halophylic plants, coconut husks, peat and wood are burned and seawater 
poured through this ash to increase the salt concentration of seawater in 
order to make it economic to boil.  I recently discovered there is a 
reaction taking place in the ash which preciptates much of the magnesium 
in seawater to make the salt more fit for use, and I am wondering if some 
on the list might have some thoughts on this.  

with thanks and best wishes,

Bea


>Dear colleagues,
>
>Jay's reacton triggered a latent part of my memory! Freek Braadbaart has 
>investigated the chemical and physical aspects of carbonisation in cereals 
>and pulses. He charred material arteficially in a muffle furnace at 
>different temperatures and at different heating rates. One of his main 
>conclusions was that already at low temperatures, all proteins are 
>converted into aromatics (benzene; cyclo-hexane). The material is even 
>still brownish at these temperatures. There are much higher temperatures 
>needed to arrive at the black material we usually find as charred plant 
>remains. A recent publication of Freek can be found in VHA 17.1, including 
>graphs with temperatures.
>
>If we take these observations into account, it should be impossible to 
>retreive ancient DNA in charred archaeological material, as this is a 
>chain of essentially four different proteins. I wonder whether researchers 
>of DNA from charred remains have ever considered the implications of 
>Freek's observations, or whether there are good arguments in pro of 
>preservation of charred archaeological DNA.
>
>I would very much like to provide desiccated material as Jay requests, but 
>unfortunately we don't have the appropriate preservation conditions for 
>that in the Netherlands. But, Jay,  if waterlogged material, e.g. from 
>medieval cesspits, would also be a possible source of DNA, please mail me, 
>I can supply material of many globular Brassicaceae (Brassica, Raphanus, 
>Sinapis) in that case (although Sinapis alba will be impossible in larger 
>numbers, these are found only very occasionally). The morphologically 
>based identification of Raphanus sativus for the Roman Period by Janneke 
>Buurman would be one of the ideal (but waterlogged...) targets!
>
>With kind regards,
>
>oTTo
>
>
>
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Hon. Secretary Los Angeles Branch, Oxford University Society
AIA Board member, Los Angeles,
UCLA Institute of Archaeology Associate