Chemical element of metals. Cu comes from Cuprum, Fe comes from Ferrum, Ag from Argentum. The symbols were not followed by a period (full stop) as with abbreviations. Later chemical elements were also assigned unique chemical symbols, based on the name of the element, but not necessarily in English. For example, sodium has the chemical symbol 'Na' after the Latin "natrium". The same applies to "W" (wolfram) for tungsten, "Fe" (ferrum) for iron, "Hg" (hydrargyrum) for mercury, "Sn" (stannum) for tin, "K" (kalium) for potassium, "Au" (aurum) for gold, "Ag" (argentum) for silver, "Pb" (plumbum) for lead, "Cu" (cuprum) for copper, and
Potassium alum a liquid known as "dousa" (), and used as an undercoat for paper sizing. Alum is an ingredient in some recipes for homemade modeling compounds intended for use by children. These are often called "play clay" or "play dough" for their similarity to "Play-Doh". Potassium alum was formerly used as a hardener for photographic emulsions (films and papers), usually as part of the fixer. It has now been replaced in that use by other chemicals. Potassium alum may be a weak irritant to the skin. Potassium alum Potassium alum, potash alum, or potassium aluminium sulfate is a chemical compound: the