Potassium trioxalatochromate (III)

Potassium trioxalatochromate(III)
Names:	potassium chromooxalate potassium oxalatochromate(III) potassium trioxalatochromate(III) potassium tris(oxalato)chromate(III))
Formula:	K3[Cr(C2O4)3] (anhydrous) K3[Cr(C2O4)3] · 3H2O (trihydrate)
Molar mass:	433.344 g/mol (anhydrous) 487.389 g/mol (trihydrate)
Crystal system:	monoclinic (trihydrate) α=90°, γ=90°
Shapes:	https://en.crystalls.info/w/uploads/media/4/48/Prolongated_rhombic_prism.json Prolongated rhombic prism https://en.crystalls.info/w/uploads/media/5/52/Needle.json Needle
Color:	dark purple, almost black
Stability:	stable (trihydrate)

Description

Organic coordinate complex, salt of transitional metal chromium, alkaline metal Potassium and organic oxalic acid. From water solutions crystallizes as trihydrate.

Precursors

Reaction between chromium hydroxide, potassium hydroxide or carbonate, and oxalic acid

Chemical equation:

2Cr(OH)₃ + 6KOH + 6H₂C₂O₄ = 2K₃[Cr(C₂O₄)₃] + 6H₂O

2Cr(OH)₃ + 3K₂CO₃ + 3H₂C₂O₄ = 2K₃[Cr(C₂O₄)₃] + 6H₂O + 3CO₂↑

For preparation of 100.00g of potassium trioxalatochromate(III) trihydrate

trihydrate

anhydrous

а 21.14g of chromium hydroxide, 34.53g of potassium hydroxide or 42.53g of potassium carbonate and 77.60g of oxalic acid dihydrate

dihydrate

anhydrous

is required.

Add to the flask with Chromium hydroxide solution a hot potassium oxalate and oxalic acid solution with stirring. After reaction will stop, filter the solution and use it for crystal growing.

Influence of impurities

K3[M(C2O4)3].3H2O (M=Al, V, Cr, Mn, Fe) are all isomorphous, meaning they can be mixed to produce crystals with different colors. Also one can be grown onto a crystal of another instead of dissolving it. Unlike alums, but like Tutton's salts, they can have very different shapes.

Storage conditions

Keep in its original form or under several layers of varnish at average humidity and room temperature. Do not keep crystals near heaters.

Solubility

TableGraph

Temperature	g/100,00 g water
20°C293.15 K <br />68 °F <br />527.67 °R <br />	~20

Gallery

• 

  Potassium trioxalatochromate(III)Andrey Yashin, VKontakteAndrey YashinVKontakte

Sources

• http://www.sciencemadness.org/talk/viewthread.php?tid=150143

Navigation

Oxalates
Salts	Ammonium oxalate ((NH4)2C2O4) • Cobalt(II) oxalate (CoC2O4) • Diglycine oxalate ((NH2CH2COOH)3 · H2C2O4) • Neodymium oxalate (Nd2(C2O4)3) • Oxalic acid (H2C2O4) • Sodium oxalate (Na2C2O4) • Tris(ethylenediamine)nickel oxalate ([Ni(H2NCH2CH2NH2)3]C2O4)
Dioxalatocuprates	Ammonium dioxalatocuprate(II) ((NH4)2[Cu(C2O4)2]) • Potassium dioxalatocuprate(II) (K2[Cu(C2O4)2]) • Sodium dioxalatocuprate(II) (Na2[Cu(C2O4)2])
Trioxalatoaluminates	Potassium trioxalatoaluminate (K3[Al(C2O4)3]) • Sodium trioxalatoaluminate (Na3[Al(C2O4)3])
Trioxalatochromates	Potassium trioxalatochromate(III) (K3[Cr(C2O4)3]) • Sodium trioxalatochromate(III) (Ns3[Cr(C2O4)3])
Trioxalatocobaltates	Potassium trioxalatocobaltate(III) (K3[Co(C2O4)3])
Trioxalatoferrates	Ammonium trioxalatoferrate(III) ((NH4)3[Fe(C2O4)3]) • Lithium trioxalatoferrate(III) (Li3[Fe(C2O4)3]) • Lithium trioxalatoferrate(III)-chloride (Li4[Fe(C2O4)3]Cl) Potassium trioxalatoferrate(III) (K3[Fe(C2O4)3]) • Potassium-sodium trioxalatoferrate(III) (K5Na[Fe(C2O4)3]2) • Sodium trioxalatoferrate(III) (Na3[Fe(C2O4)3])
Ethers	Dimethyl oxalate ((CH3)2C2O4)

Potassium compounds
Salts	Potassium bromate (KBrO3) • Potassium bromide (KBr) • Potassium chlorate (KClO3) • Potassium chloride (KCl) • Potassium chromate (K2CrO4) • Potassium dihydrophosphate (KH2PO4) • Potassium dichromate (K2Cr2O7) • Potassium iodide (KI) • Potassium hydrofluoride (KHF2) • Potassium hydrophosphate (K2HPO4) • Potassium hydrogen phthalate (KC8H6O4) • Potassium metavanadate (KVO3) • Potassium nitrate (KNO3) • Potassium sulfate (K2SO4) • Potassium thiocyanate (KNCS)
Double salts	Aluminum-potassium sulfate (KAl(SO4)2) • Antimony(III)-potassium tartrate (K2Sb2(C4H2O6)2) • Chromium(III)-potassium sulfate (KCr(SO4)2) • Cobalt(II)-potassium sulfate (K2Co(SO4)2) • Copper(II)-potassium sulfate (K2Cu(SO4)2) • Indium(III)-potassium sulfate (KIn(SO4)2) • Iron(II)-potassium sulfate (K2Fe(SO4)2) • Iron(III)-potassium sulfate (KFe(SO4)2) • Lithium-potassium sulfate (KLiSO4) • Magnesium-potassium sulfate (K2Mg(SO4)2) • Magnesium-potassium sulfate-chromate (K2CrO4 · MgSO4) • Manganese(II)-potassium sulfate (K2Mn(SO4)2) • Nickel-potassium sulfate (K2Ni(SO4)2) • Potassium-sodium tartrate (KNaC4H4O6) • Vanadium(III)-ammonium sulfate (NH4V(SO4)2) • Zinc-potassium sulfate (K2Zn(SO4)2)
Complexes	Potassium dioxalatocuprate(II) (K2[Cu(C2O4)2]) • Potassium hexanitrocobaltate(III) (K3[Co(NO2)6]) • Potassium hexachlororhodiate(III) (K3[RhCl6]) • Potassium hexacyanocobaltate(III) (K3[Co(CN)6]) • Potassium hexacyanoferrate(II) (K4[Fe(CN)6]) • Tripotassium-sodium hexacyanoferrate(II) (K3Na[Fe(CN)6]) • Potassium hexacyanoferrate(III) (K3[Fe(CN)6]) • Potassium hexacyanochromate(III) (K3[Co(CN)6]) • Potassium tetraiodobismuthate (К[BiI4]) • Potassium tetraiodomercurate(II) (K2[HgI4]) • Potassium trioxalatoaluminate (K3[Al(C2O4)3]) • Potassium trioxalatocobaltate(III) (K3[Co(C2O4)3]) Potassium trioxalatoferrate(III) (K3[Fe(C2O4)3]) • Potassium-sodium trioxalatoferrate(III) (K5Na[Fe(C2O4)3]2) • Dipotassium-sodium trioxalatoferrate(III) (K2Na[Fe(C2O4)3]) • Potassium trioxalatochromate(III) (K3[Cr(C2O4)3])