Permutit

PERMUTIT, artificial sodium and aluminum silicates, NaOAlH₆Si₂O₈ (zeolites), obtained by fusing aluminum silicate, soda, and sand. Natural minerals very similar in composition to P. are called zeolites and consist of aluminum bisilicate and sodium aluminate silicate. P. is used mainly for removing water hardness, as well as for removing iron and manganese from it, since sodium in P. is easily replaced by calcium, magnesium, iron, manganese, etc. The retention of Ca (and Mg) by P. occurs according to the formula: n.Na₂ + Ca(HCO₃)₂ = 2NaHCO₃ + P.Ca; n.Na₂ + CaSO₄ = Na₂SO₄ + P.Ca. A filter loaded with permutit sand gradually loses its effectiveness; for regeneration it is treated with a 10% solution of NaCl; regeneration is quick and is usually done directly in the filter. For removing iron and manganese from water in the paper industry, dyeing, and laundry, oxidative permutit filters are used, obtained by treating permutit with Mn salts followed by oxidation with KMnO₄. Iron and manganese salts present in water are oxidized by such a filter into sparingly soluble Fe(OH)₃ and Mn(OH)₃. Such a permutit filter is regenerated by treating it with a 1% solution of KMnO₄. There are permutit filters for special purposes that retain K, O, NH₃. Permutit is also used in determining ammonia and urea in blood and urine.