Calcium hypochlorite

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Calcium hypochlorite
Chemical formula Ca(OCl)2
OTP appearance white/grey powder 
Molar Mass(g/mol) 142.98 
Melting Point(°C) 100 
Density(g/cc) 2.35 
Solubility in water(g/L) 210
NFPA 704
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Calcium hypochlorite is the simplest hypochlorite to produce and isolate.

Uses

Justification Questioned

Other

Natural occurrence

Calcium hypochlorite does not appear naturally

Hazards

Toxic and irritating

Production

Synthesis

Combined hydroxides

  1. Gather 37ubm calcium hydroxide
  2. Gather 40ubm sodium hydroxide
  3. Gather 80ubm chlorine gas
  4. Prepare a saturated solution of the hydroxides
  5. Bubble (and recirculate) the chlorine through the hydroxides
    Ca(OH)2(aq) + 2 NaOH(aq) + Cl2(g) Ca(OCl)2(s) + 2 NaCl(aq) + 2 H2O

In the absence of sodium hydroxide, a mixture of calcium hypochlorite and calcium chloride is produced. This mixture is difficult to separate, and the -chloride attracts water from the air which decomposes the -hypochlorite. Removal of the calcium chloride is required to stabilize the bleach.

Separating the sodium chloride from the calcium hypochlorite can be accomplished by gravity separation of a dense slurry of well-over-saturated solution rich with with crystals of both products. Agitating the slurry in a tall cylindrical container will gravitically sort the salt crystals (which are larger and denser) from the hypochlorite crystals (which are smaller and lighter).

  1. Evaporate the mother liquor until it forms a cloudy crystal-rich supersaturated slurry
  2. Fill a tall cylindrical container with the slurry
  3. Agitate the solution steadily, allowing gravity to separate the crystals
  4. Decant the slurry into three parts: the top 30%-40%, the bottom 30-40%, and the remainder (the mother liquor and "middle" slurry)
  5. Filter the top 30-40%
  6. Return the filtrate to the mother liquor
  7. Dry the residue completely. This is the hypochlorite cake
  8. Wash the hypochlorite cake with a small amount of distilled water
  9. Filter
  10. Return the filtrate to the mother liquor
  11. Dry the residue completely. This is the refined hypochlorite
  12. Filter the bottom 30-40%
  13. Return the filtrate to the mother liquor
  14. Dry the residue completely. This is the salt cake
  15. Wash the salt cake with a small amount of distilled water
  16. Filter
  17. Return the filtrate to the mother liquor
  18. The residue is primarily salt with some toxic impurities. It is not safe for consumption. Discard or retain for other purposes.

This process can be repeated until there is no more mother liquor to evaporate. The salt cake will contain primarily sodium chloride. The hypochlorite cake will contain primarily calcium hypochlorite.

References

See Also