Note 27 — Chapter XVIII · SILICON AND THE OTHER ELEMENTS OF THE FOURTH GROUP
George Kamensky translation
It must be recollected that although acids seem to act only feebly on the majority of silicates, nevertheless a finely-levigated powder of siliceous compounds is acted on by strong acids, especially with the aid of heat, the basic oxides being taken up and gelatinous silica left behind. In this respect sulphuric acid heated to 200° with finely-divided siliceous compounds in a closed tube acts very energetically.