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Cobalt chloride first made an impact on my life when I was a small child - I was given a cheap little ornament that was supposed to be able to predict the weather. It was made of a chalky-white material and seemed to be brushed with magic! My beautiful ornament could change colour from pink, through various shades of lavender, to blue. Blue was supposed to indicate good weather, pink was for rain.

The magic, I found out some years later, was cobalt chloride, (or to be more specific, cobalt II chloride or cobalt dichloride). Anhydrous cobalt chloride, CoCl2 is a blue salt, but the the hydrated form, CoCl2.6H2O is red and a thin film of chemical on an ornament readily changes state depending on the humidity of the atmosphere. Unfortunately humidity is not a very good predictor of the weather and I was soon disappointed with my new 'toy', although I still loved to see the colours change.

Hmm, I haven't seen one of those for years - I wonder why...?


Properties of CoCl2.6H2O

Molecular weight: 237.93
Health Rating: 3 - Severe (Poison)
Flammability Rating: 0 - None
Reactivity Rating: 0 - None
Contact Rating: 1 - Slight. May cause dermatitis
Lab Protective Equip: GOGGLES; LAB COAT; VENT HOOD; PROPER GLOVES
Storage Color Code: Blue (Health)

Uses

  • Food additive - a source of vitamin B12 *
  • In the tire industry - it improves the bond between the steel and the rubber in steel radial tires
  • It is used in the textile industry where it acts as a mordant binding the colorant to the fiber
  • Cobalt chloride can also be used in the magnetic tape industry where it can be used as a dopant
  • It has uses in the printing industry
  • It is a humidity indicator

*Vitamin B12 is synthesized in the guts of animals by bacteria, it is not absorbed from food. The molecule has a Cobalt atom at its centre - Cobalt is a trace element so giving dietry supplements may be important.

WARNING! HARMFUL IF SWALLOWED OR INHALED. CAUSES IRRITATION TO SKIN, EYES AND RESPIRATORY TRACT. MAY CAUSE ALLERGIC SKIN OR RESPIRATORY REACTION. CHRONIC EXPOSURE MAY AFFECT THYROID, LUNGS, HEART, AND KIDNEYS


I think I know now!


http://freeweb.pdq.net/headstrong/humid.htm
http://www.jtbaker.com/msds/c4928.htm
http://www.hallchem.com/HProd.html#CChloride

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