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<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>Richard A. Robie</dc:contributor>
  <dc:creator>Bruce S. Hemingway</dc:creator>
  <dc:date>1973</dc:date>
  <dc:description>&lt;p&gt;The enthalpies of formation, &lt;i&gt;&amp;Delta;H&amp;deg;&lt;sub&gt;f,&lt;/sub&gt;&lt;/i&gt; of huntite,&amp;nbsp;CaMg&lt;sub&gt;3&lt;/sub&gt;(CO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;4&lt;/sub&gt; , and artinite, Mg&lt;sub&gt;2&lt;/sub&gt;(OH)&lt;sub&gt;2&lt;/sub&gt;CO&lt;sub&gt;3 *&amp;nbsp;&lt;/sub&gt;3H&lt;sub&gt;2&lt;/sub&gt;O, have been determined&amp;nbsp;by HCl solution calorimetry using a constant-volume isoperibol&amp;nbsp;reaction calorimeter. For the reaction CaO(c) + 3MgO(c) + 4CO&lt;sub&gt;2&lt;/sub&gt; (g)&amp;nbsp;= CaMg&lt;sub&gt;3&lt;/sub&gt;(CO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;4&lt;/sub&gt; (c), the enthalpy change at 298.15 K, &lt;i&gt;&amp;Delta;H&amp;deg;&lt;sub&gt;298&lt;/sub&gt;&lt;/i&gt; , is&amp;nbsp;-123,203&amp;plusmn;145 cal mol&lt;sup&gt;-1&lt;/sup&gt;. For the reaction 2MgO(c) + 4H&lt;sub&gt;2&lt;/sub&gt;O(l)&amp;nbsp;+ CO&lt;sub&gt;2&lt;/sub&gt;(g)=Mg&lt;sub&gt;2&lt;/sub&gt;(OH)&lt;sub&gt;2&lt;/sub&gt;CO&lt;sub&gt;3 *&amp;nbsp;&lt;/sub&gt;3H&lt;sub&gt;2&lt;/sub&gt;O(c), we obtained -45,132&amp;plusmn;100 cal&amp;nbsp;mol&lt;sup&gt;-1&lt;/sup&gt;. These results combined with the standard enthalpies of&amp;nbsp;formation of CaO, MgO, H&lt;sub&gt;2&lt;/sub&gt;O, and CO&lt;sub&gt;2&lt;/sub&gt; lead to&amp;nbsp;&lt;i&gt;&amp;Delta;H&amp;deg;&lt;sub&gt;298&lt;/sub&gt;&lt;/i&gt; (huntite) =&amp;nbsp;-1,082,600&amp;plusmn;375 cal mol&lt;sup&gt;-1&lt;/sup&gt; and&amp;nbsp;&lt;i&gt;&amp;Delta;H&amp;deg;&lt;sub&gt;298&lt;/sub&gt;&lt;/i&gt; &amp;nbsp;(artinite) = -698,043&amp;plusmn;170 cal&amp;nbsp;mol&lt;sup&gt;-1&lt;/sup&gt;. Using recently determined values for the standard entropies of&amp;nbsp;huntite, CaMg&lt;sub&gt;3&lt;/sub&gt;(CO&lt;sub&gt;3&lt;/sub&gt;)&lt;sub&gt;4&lt;/sub&gt;, and artinite, Mg&lt;sub&gt;2&lt;/sub&gt;(OH)&lt;sub&gt;2&lt;/sub&gt;CO&lt;sub&gt;3&lt;/sub&gt;&amp;nbsp;* 3H&lt;sub&gt;2&lt;/sub&gt;O, and of Mg,&amp;nbsp;Ca, C, O&lt;sub&gt;2&lt;/sub&gt;&amp;nbsp;, and H&lt;sub&gt;2&lt;/sub&gt; , we calculate &lt;i&gt;&amp;Delta;G&amp;deg;&lt;sub&gt;f,298&lt;/sub&gt;&lt;/i&gt;&lt;sub&gt;&amp;nbsp;&lt;/sub&gt;(huntite) = -1,004,707&amp;plusmn;390&amp;nbsp;cal mol&lt;sup&gt;-1&lt;/sup&gt; and&lt;i&gt; &amp;Delta;G&amp;deg;&lt;sub&gt;f,298&lt;/sub&gt;&lt;/i&gt;&lt;sub&gt;&amp;nbsp;&lt;/sub&gt;(artinite) = -613,924&amp;plusmn;180 cal mol&lt;sup&gt;-1&lt;/sup&gt;.&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:language>en</dc:language>
  <dc:publisher>U.S. Geological Survey</dc:publisher>
  <dc:title>A calorimetric determination of the standard enthalpies of formation of huntite, CaMg3 (CO3)4 , and artinite, Mg2(OH)2 CO3 * 3H2O, and their standard Gibbs free energies of formation</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>