Birch, Stewart, Kolasch & Birch
Process for cleaning silicon mass and the recovery of nitric acid
 In a process for cleaning a silicon mass with a acid washing solution, a waste solution containing a mixed acid composed of nitric acid and hydrofluoric acid is introduced to a distillation step, and hydrofluoric acid is introduced to a distillation cooling portion to prevent precipitation of silicon dioxide. The waste cleaning liquor is distilled to recover nitric acid. 
Hi-Silicon, Co., Ltd.
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H01L H01L
inventional inventional
Hideo Mitsutoshi Kazuhiro
Ito Narukawa Sakai