| 摘要 |
<p>Impure CaSO4 2H2O (I) from phosphoric acid process is treated to remove organic and aq. insol. mineral matter, dried or hydro-thermally dehydrated above 100 degrees C to give the hemihydrate (II) or anhydrous salt or a mixt., rehydrated at below 100 degrees C pref. 80-95 degrees C to give (I) which is sepd. and then subjected again to drying and hydrothermal dehydration to give pure (II).</p> |
