All impurities do not act in a similar way.
This result he considered to be due, not to any removal of impurities, but to an actual splitting-up of the yttrium molecule into its constituents, and he ventured to draw the provisional conclusion that the so-called simple bodies are in reality compound molecules, at the same time suggesting that all the elements have been produced by a process of evolution from one primordial stuff or "protyle."
Ferric hydrate, iron soaps and all insoluble impurities are precipitated.
Taylor bag filters are generally used for clearing the melted liquor of its mechanical impurities.
The slight variations in specific gravity are due to the presence of small amounts of arsenic, sulphur or tellurium, or to enclosed impurities.