Explanatory notes
… or magnesia) and sometimes with other substances (e.g., asbestos, hair, sawdust, coal dust). These articles are … usually agglomerated with clay; refractories based upon beryllium oxide, thorium oxide, cerium oxide, etc. (7) … straw, sawdust, peat fibre, etc., the organic matter having been burnt away during the firing process to leave a porous …