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Advice needed regarding MgCl2 analysis and purification

  1. Feb 20, 2013 #1

    I'm a newbie on this forum. My knowledge of chemistry is limited to High School, and what little I've picked up over the years.

    I'm currently buying some minerals from the Dead Sea. There are supposed certain properties of these Dead Sea minerals that have made bathing in them popular for health reasons.

    The main chemical I'm interested in is MgCl2. The assay on what I'm buying says merely, "46.89% MgCl2, 1.83% CaCl2, 0.59% NaCl, 0.31% KCl, with the rest (50.38%) being Water from crystallization".

    This is a combination of salts that is intended for industrial use, but actually seems purer than the "Lab quality" MgCl2 that I bought previously, which was furnished with a more complete analysis from the manufacturer, and contained many impurities that would prohibit its usage for humans.

    As the one from the Dead Sea is intended for industrial use, including feeding to livestock, it is probably not mandated that they provide a complete analysis. However, if I intend to use it personally, or even make a business out of it where I'm retired in Thailand - for conscience sake - I need to have it tested.

    I would be grateful for advice on what kind of test to look for. I already contacted one lab that used some newer technology that, in fact, would not provide a complete chemical analysis. I was wondering if local University Chemistry departments might be a good place to look. There are many chemical testing facilities in Thailand, but the differ in capabilities.

    The next step would be to try to isolate the MgCl2 from the rest of the minerals - making the end product of MgCl2 in crystalline and/or aqueous form. My question is: How difficult or expensive is this to do? How complicated is the process, what kind of equipment is necessary, and, would it be feasible to do starting out on a small scale.

    At present, I'm buying 25 Kg sacks of the Dead Sea minerals for use as bath salts, or mixing it with water for external application. So far I've used it on myself, and find it relieves stress, pain, and improves the skin. Of the few friends I've given it to about 50% report positive results - sometimes in a matter of minutes. I've told them that "I believe" it's OK, but believing isn't good enough. I need assurance of its quality or a way to make it pure.

    Any information you can provide would be of great help.

    Thank you,

  2. jcsd
  3. Mar 12, 2013 #2
    OK, one way to isolate the MgCl2 is to convert it into the insoluble MgCO3 and treat with Cl2 or HCl to regenerate the MgCl2. The precise preparation is as follows:

    1. Add your salts (MgCl2, CaCl2, NaCl, and KCl) to a solution of Selzter water (H2CO3) and ammonia.

    2. Heat to just 50 C to cause the Mg(HCO3)2 to decompose into the insoluble MgCO3. Note, other bicarbonates formed are more stable.

    Chemistry: Basically we are following the Solvay process (see Wikipedia Solvay Process at http://en.wikipedia.org/wiki/Solvay_process ), but using more dilute solutions and the unique low temperature thermal decomposition of aqueous Magnesium bicarbonate (see http://www.newton.dep.anl.gov/askasci/chem99/chem99492.htm ).

    Reaction for NaCl:

    NaCl + CO2 + NH3 + H2O → NaHCO3 + NH4Cl (aq)

    Similarly for MgCl2:

    MgCl2 + 2 CO2 + 2 NH3 + 2 H2O → Mg(HCO3)2 + 2 NH4Cl (aq)

    Then, upon mild heating:

    Mg(HCO3)2 + H2O --Mild Heat--> MgCO3 (s) + CO2 + H2O

    [Edit]: Do not directly treat aqueous MgCO3 with Chlorine as this could form HOCl (along with HCl). The products would then be MgCl2 and also some basic Magnesium hypochlorite. Better to convert the Chlorine water to HCl prior to reacting with MgCO3.

    Alternately, one may be able to recover NH4Cl by concentrating and cooling the solute, precipitating remaining bicarbonates (all after extracting the MgCO3) and thereby forming aqueous NH4Cl. Then, heat the aqueous (or dry) NH4Cl with MgCO3 to form MgCl2:

    2 NH4Cl + MgCO3 --> (NH4)2CO3 + MgCl2

    On heating, the Ammonium carbonate breaks down into NH3 and CO2, thereby driving the reaction to the right.
    Last edited: Mar 12, 2013
  4. Mar 13, 2013 #3
    Thanks AJ for your response. This gives me a solid basis to begin asking questions in Thailand. BTW - for a multitude of reasons, answers do not come easy in this place. I remember talking to many experts in many fields in the US who delighted in sharing their knowledge. Not so here.
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