Explanatory notes
… in the form of powder or small scales, micaceous flakes or vitrified lumps, with transparent edges, ash‑grey or bluish … water); for the manufacture of borosilicate glass (low coefficient of expansion), vitrifiable compounds, Guignet’s … when the H 3 BO 3 content exceeds 85 %, the acid is classified in this heading. Metaboric acid (HBO 2 ) n is …