Yoshida et al. (1976) determined Si gravimetrically in rice straw in conjunction with the analysis of other elements. After chemical oxidation of the organic matter and acid dissolution of all remaining components of the straw except for Si, the remaining residue was assumed to be SiO 2 (termed "crude silica"), which was removed by filtration. The dried precipitate was transferred to a weighing vessel, and the increase in weight was assumed to be SiO 2.Although requiring only relatively common and simple laboratory equipment, the gravimetric methods for determining Si in plant tissue, nevertheless, are time consuming and laborious, especially if only an analysis for Si is required. Elliott et al. (1988) described a "rapid" gravimetric procedure for the determination of Si in plant tissue that reduced analysis time and handling of individual samples through the use of fritted glass Gooche crucibles. The plant material is destroyed by heat and chemical additions, and the SiO2 residue is weighed
directly in the crucible as tile increase in weight over the crucible alone.