AbstractBelieving that the silicon in rice hull must exist as organosilicon compounds, the authors have undertaken a series of researches so as to gain an insight into the problem. In this paper, experiments including treatment with hydrofluoric acid, extraction with various solvents, hydrolysis with acid and boiling with alkali are described. Dialysis of the products resulting from these experiments has shown definitely that silicon passed into aqueous solution even with a pH at which silica might precipitate. Since lignin does not contain ash, it is supposed that the silicon in rice hull may be combined with the polysaccharide part.