Wolframates
The salts of tungstic acid are called tungstates . They are chemically related to chromates and molybdates .
Tungstates are known in the various ratios between acids and bases , the simplest form being the orthotungstate WO 4 2− . In the past, the salts were classified according to the ratio, so the salts of paratungstic acid were also called paratungstates and those of pacific acid were called pertungstates, although other forms such as isotungstic acid, metatungstic acid or polyungstic acid also existed by name.
In addition to sodium paratungstate Na 10 W 12 O 41 + 28 H 2 O and potassium tungstate K 2 WO 4 , which serve as a fire retardant for wood and highly flammable substances, also as a pickling agent in dyeing, many salts are used as paints, such as nickel tungstate NiWO 4 (green), chromium tungstate (green), cobalt tungstate (violet), tin tungstate (indigo blue), barium tungstate BaWO 4 (tungsten white ) and iron tungstate FeWO 4 (chamois). Furthermore, ammonium tungstate (NH 4 ) 10 W 12 O 41 , lithium tungstate Li 2 WO 4 and sodium tungstate Na 2 WO 4 serve as catalysts in organic syntheses. Magnesium tungstate MgWO 4 and above all lead tungstate PbWO 4 are used as modern scintillators in particle physics . Concentrated solutions of sodium poly tungstate (3 Na 2 WO 4 · 9 WO 3 · H 2 O) are used as heavy liquids because of their high density .
Of course, tungstates come in the form of the mineral scheelite ( calcium tungstate CaWO 4 ), wolframite (mixed crystal), ferberite (iron tungstate), hubnerite ( manganese tungstate ), sanmartinite (iron-zinc-tungstate mixed crystal), stolzite (lead tungstate), krasnosels Cuproscheelite ( copper tungstate ) and some others.
Web links
Individual evidence
- ↑ Entry on sodium tungstate. In: Römpp Online . Georg Thieme Verlag, accessed on June 13, 2014.