Section 180.1237 - Sodium metasilicate; exemption from the requirement of a tolerance(a) An exemption from the requirement of a tolerance is established for residues of sodium metasilicate in or on all food commodities when used in accordance with approved label rates and good agricultural practices as a plant desiccant, so long as the sodium metasilicate does not exceed 4% by weight in aqueous solution.(b) An exemption from the requirement of a tolerance is established for residues of sodium metasilicate in or on all food commodities when used in accordance with approved label rates and good agricultural practices as an insecticide and fungicide, so long as the sodium metasilicate does not exceed 2.41% by weight in aqueous solution. 71 FR 19441 , Apr. 14, 2006