Potassium ferrocyanide

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Potassium ferrocyanide
Chemical formula K4(Fe(CN)6)
OTP appearance yellow crystals 
Molar Mass(g/mol) 368 
Melting Point(°C) decomp 
Density(g/cc) 1.85 
Solubility in water(g/L) 289 
Solubility in ethanol(g/L) insoluble
NFPA 704
NFPA704.png
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Uses

Other

  • Precursor to Prussian blue on WHO LEM
  • Production is a relatively safe sink for cyanides

Natural occurrence

  • does not occur in nature

Hazards

  • "nontoxic"
  • Do not heat or acidify, these actions may produce free cyanides.

Production

Synthesis

via nitrogenous biomass

This general process is repeated in many texts including Industrial Chemistry[1] and Manual of Chemical Technology[2]

  1. Melt 100ubm potassium carbonate in a container devoid of oxygen
  2. Add 75-400ubm of nitrogenous biomass (feathers, horn, skins, leather, dry blood) directly to the melt
    N.B.: Production of solvated potassium cyanide and potassium sulfate KCN,K2SO4
  3. Allow to cool
  4. Mix with water
  5. Filter
  6. Recycle residue (or dispose of carefully, it may be toxic)
  7. Retain filtrate (it contains potassium cyanide, which is very poisonous/toxic)
  8. Add 10 ubm iron filings to a basic solution
    6 KCN + Fe + 2 H2O
    {OH-
    }
    K4(Fe(CN)6) + 2 KOH + H2

via hydrogen cyanide

  1. Combine iron (II) chloride and calcium hydroxide in water
  2. Bubble hydrogen cyanide through the mixture
    2 FeCl2(OH)2(H2O)2 + 4 Ca(OH)2 + 12 HCN 2 Ca2[Fe(CN)6] + 14 H2O + 4 HCl + O2
  3. Combine with 2 molar equivalents of potassium chloride, precipitating the calcium/sodium salt
    Ca2[Fe(CN)6] + 2 KCl CaK2[Fe(CN)6(s)] + CaCl2
  4. Combine with potassium carbonate
    CaK2[Fe(CN)6](aq) + K2CO3(aq) K4[Fe(CN)6](aq) + CaCO3(s)
  5. Filter
  6. Discard residue (calcium carbonate)
  7. Evaporate filtrate leaving potassium ferrocyanide

Testing

Storage

Disposal

See Also

References

  1. Paul, B. H., PhD (1878) "Industrial Chemistry"; pp80.
    Longmans, Green & Co
    link courtesy Google.
  2. Von Wagner, Rudolf (1897) "Manual of chemical technology"; pp474-477.
    D. Appleton & Co.
    link courtesy Hathi Trust.