Explanatory notes
… (Na 2 SO 4 .10H 2 O) is known as Glauber’s salt. Impure forms of disodium sulphate (90 ‑ 99 % purity), … or natural aluminium silicates, with sulphuric acid; the impurities are mainly iron compounds. In the hydrated state … paper, paperboard, lutings, lakes, colours, etc. It is impervious to X‑rays and is therefore used (pure) in …