Chemical　separation　of　MgO　from　dolomite　ore，CaMg（CO3）2，has　been　studied　for　the　purpose　of utilization　of　mineral　resources　in　a　favored　technique．The　separation　technique　is　based　on　the following　characteristics， 1）　Remarkable　difference　in　hydration　tendency　between　CaO　and　MgO，calcined　dolomite，results　the 　ready　converstion　to　Ca（OH）2　when　calcined　dolomite　is　slaked　in　water．Assuming　that　MgO　is hydrated，the　solubility　in　100ml　H2O　is　extremely　low（9×10-4g）in　comparison　with　Ca（OH）2（0.15g）． 2）　Addition　of　a　strongly　acidic　cation　exchange　resin，H-form（H－R） to　an　aqueous　suspension containing　calcined　dolomite　results　in　a　selective　ion　exchange　reaction　with　the　dissolved　 Ca（OH）2，which　follows　to　consecutive　dissolution　of　Ca（OH）2　powder　to　remain　MgO　powder． 3）　MgO　powder　is　separated　effectively　by　sieving　or　by　floatation　method　from　the　precipitated 　mixture　with　Ca－R2． 4）　Ca－R2，Ca－resin　formed　by　the　exchange　reaction，is　regenarated　for　reuse　as　H－R． 　The　study　was　done　to　confirm　the　foregoing　facts　using　CaO　and　MgO　chemicals　with　high　purity　（4N），followed　by　a　laboratory　demonstration　to　obtain　MgO　powder　from　dolomite．

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　Recently，special　steel　making　is　a　newly　developed　blowing　technique　of　BOF　metaliurgy，utilizing　low　cost　several　ore．ln　this　case，it　has　caused　with　high　temperature　and　strong　agitation． 　When　evaluation　of　refractories　was　investigated　by　conventional　corrosion　test（rotary　slag　test　and　so　on），it　was　difficult　to　select　suitable　refractories，particularly　bath　and　bottom　zone．ln　this　study，we　made　an　attempt　to　test　dynamic　corrosion　on　the　subject　of　MgO－C　and　MgO－CaO－C　system　refractories，using　a　high　capacity　indiuction　furnace． 　A　simulation　study　has　been　performed　to　establish　countermeasure　against　suitable　corrosion　to MgO－C　and　MgO－CaO－C　system　refractories　lining　in　BOF，and　obtained　satisfactory　results　both　in laboratory　and　actual　mills．

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