0 . 4 % ▁U 3 O 8 . ▁ ▁Dig estion : ▁Cr ushed ▁mon az ite ▁is ▁mixed ▁with ▁highly ▁concentr ated ▁sul fur ic ▁acid ▁( 9 3 % ▁acid ) ▁at ▁feed ▁temper atures ▁of ▁ 1 5 0 ▁to ▁ 1 8 0   ° C . ▁ ▁The ▁ratio ▁of ▁acid ▁to ▁ore ▁var ies ▁depending ▁on ▁the ▁concentration ▁of ▁the ▁ore ▁( un able ▁to ▁find ▁ratio ▁range ). ▁ ▁The ▁dig ester ▁is ▁stir red ▁vig or ously ▁with ▁a ▁robust ▁ag it ator ▁and ▁oper ates ▁at ▁temper atures ▁between ▁ 2 0 0 ▁and ▁ 3 0 0   ° C . ▁ ▁Ac id ▁is ▁charged ▁into ▁the ▁re actor ▁and ▁he ated ▁before ▁the ▁ore . ▁ ▁The ▁ins ol ub le ▁product ▁co ats ▁the ▁gra ins ▁of ▁cr ushed ▁ore . ▁ ▁The ▁temperature ▁in ▁the ▁re actor ▁r ises ▁due ▁to ▁heat ▁released ▁from ▁the ▁ex oth erm ic ▁re actions . ▁ ▁After ▁~ 1 5 ▁minutes , ▁the ▁vis cos ity ▁of ▁the ▁solution ▁has ▁increased ▁and ▁the ▁solution ▁is ▁similar ▁to ▁a ▁d ough . ▁ ▁The ▁product ▁react s ▁for ▁ 3 ▁to ▁ 4 ▁hours . ▁ ▁It ▁is ▁then ▁removed ▁from ▁the ▁dig ester ▁before ▁the ▁solution ▁hard ens . ▁The ▁ratio ▁of ▁sul fur ic ▁acid ▁to ▁sand ▁removed ▁is ▁ 1 . 6 ▁to ▁ 2 . 5 . ▁ ▁D iss ol ution : ▁The ▁contents ▁of ▁the ▁re