Expert: Dr. Henry Boyter, Jr. - 6/25/2006

Question
My goal is to separate the trace minerals from the salt to study and analyze them. The sea salt I am  working with now is 98.32% sodium choloride but the other 1.68% is made of fify or so trace minerals that I can study like clacium, potassium, sulphur, magnesium, iron, phosophorus, iodine, manganese, copper, zinc, etc. So what I need is unrefined salt that has not been kiln dried, bleached, treated with anticaking agents, or otherwise altered with chemicals. Would either rock salt for ice melting or salt use for water softening meet those criteria?
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Followup To

Question -
Electrolysis would seem to be preferred method given my limited resources. Can you offer any advice on how to setup the process under the right conditions?

Do you happen to know an inexpensive source of unaltered salt? Right now I am paying $5 a pound for sea salt and with the experiments I have planned I estimate I will need upwards of 100 lbs of salt.  
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Followup To

Question -
how do you separate trace elements from salt with the goal of preserving the trace elements?

Answer -
You could do it with ion exchange or selective electrolysis.  In ion exchange, the trace elements would stick to the resin and the salt would pass through.  Then you wash the rsin with acid to get the trace elements back off.  You would use the resin until it only had trace elements and would not retain sodium.  Electrolysis would just plate out the trace elements will the sodium would not plate out if the correct conditions were used.  There are chemical ways to do this, but those are not very efficient, but for most of time those were the only ways (web search for qualitative analysis).  You could also use ultrafiltration/nanofiltration where the majority of the trace elements would filter out, but the majority of salt and some trace elements would filter through.  This can be improved by using sequestering reagents to complex the trace elements.

Note, all these work with trace elements.  If you go to ultratrace like gold or silver in seawater, it is a totally different game.

Answer -
By my quick calculation, 100 lbs will produce at 100% efficiency maybe 10-75 micrograms of trace metals.  You will not even be able to see it most likely.  Electrolysis setups can be found by a google search.  You will find thousands of pages.  The cheapest salt will be that used for ice melting and that used for water softners.  You can get them at Lowes, etc and water treatment companies.  Not sure what you are trying to do, but think it through completely.

Answer
You will just have to check the ingredients.  Looking at your list

calcium, potassium, sulphur, magnesium, iron, phosophorus, iodine, manganese, copper, zinc

I would only consider the manganese, copper, and zinc as trace elements, so you need to define the term in your case.  The others I would call macro nutrients.  i should have asked that to begin with.  Sorry.

Note that the techniques I gave you will not work for S,I,P since they will be in a negatively charged state.  Potassium and magnesium can not be done by hydrolysis, but can be done by ion exchange.  If you just want to know how much is there, AA or ICP spectroscopy will give you the answers for the metals.