Preparation of Chromium (III) Salts

  1. OK, so i have Cr(III) Oxide, Cr2O3, and i wish to dissolve this in conc. HCl to form Cr(III) Chloride - however, at room temperature, this reaction just doesn't seem to work readily - i would have thought it would. Would heating facilitate the desired reaction? Would the use of another acid, such as conc. Sulphuric acid, react more readily with the oxide without the need for heat?
     
  2. jcsd
  3. mrjeffy321

    mrjeffy321 882
    Science Advisor

    Look here,
    http://www.roguesci.org/theforum/chemistry-related/4725-review-chromium-compound-synthesis.html

    A few quotes from the site,
    You might try making some Chromium Oxide thermite to produce Chromium metal, then use this to prepare CrCl3.
     
  4. I don't have Al to do a thermite reaction - i wonder if heating with charcoal will do it?

    I'll try milling the powder very fine, and try conc. H2SO4 and see if it is any different.

    I'm actually trying to synthesize Na2Cr2O7.
     
  5. mrjeffy321

    mrjeffy321 882
    Science Advisor

    Here are instructions for the preparation of K2Cr2O7,
    http://www.frogfot.com/synthesis/kdichromate.html
    You easily substitute Sodium Salts into the reaction (as opposed to Potassium) to make it Na2Cr2O7.
    Using this method, you could use your Cr2O3 as it is, without reacting it with acid first.
     
    Last edited: Jul 2, 2006
  6. GCT

    GCT 1,769
    Science Advisor
    Homework Helper

    What reagent grade of the chromium III oxide are you employing? You may need to recrystallize the oxide. Or at times, the sample may have aged to much and undergone chemical changes (redox reactions with oxygen for example). It may be the case that something is redoxing the Cr III in the sample.

    Are you having trouble with the reaction overall or just the dissolution of the sample oxide?
     
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