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I was looking up silica gel beads on wiki and noticed that some (and from experience most) are doped with a colouring agent to indicate that they have absorbed all that they can.

The wiki page says that usually Cobalt (II) chloride or Methyl violet is used, both of which are toxic. But it mentions nothing about what quantity these become toxic? I assumed the quantity in a normal silica gel bag (that come in shoes for example) isn't enough to be harmful, otherwise why would they be using it?

Also, it mentions that

"Crystalline silica dust can cause silicosis but synthetic amorphous silica gel is indurated, and so does not cause silicosis."

Are the silica gel beads synthetic amorphous, i.e. do not cause silicosis?

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Same wiki page contains link to CoCl2 wiki page, that contains ld-50. It is more or less what should answer your first question. As for second question: no, silicosis is caused by silica DUST, and silica gel is amorphous, but compact. –  permeakra Nov 25 '12 at 10:42
    
@permeakra I'm answering as have not got the rep to comment yet. What if you crushed silica gel to dust, would this cause silicosis? –  Regie Nov 25 '12 at 11:38
    
@Regie If you will breath in said dust on regular basis in significant amounts, then it possibly can. One-time exposure should not be a problem. –  permeakra Nov 25 '12 at 18:13
    
@permeakra Again, answering as I cannot comment :(. If Silica gel is amorphous, doesn't this mean it is not crystalline, and according to the wiki page only crystalline silica dust can cause sillicosis. Or am I mistaken? –  Regie Nov 25 '12 at 23:21
    
@permeakra Since Regie can't comment here (and we have to convert to comment every time), could you please continue this discussion on this relevant post of his? –  ManishEarth Nov 26 '12 at 7:00
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1 Answer 1

Cobalt poisoning is apparently very rare. The only situation in which cobalt poisoning is a serious problem is when it is exposed directly to your bloodstream (Recently it has been an issue with people who have undergone certain hip implants -- see this page).

The amount of Cobalt chloride in silica gel balls would be absolutely harmless. According to most sources, you have to be exposed to significant amounts of cobalt (at least more than 20g for an average adult) for a long period of time for symptoms to appear.

Note: Cobalt is actually necessary for our body (in small amounts) in the form of Vitamin B12.

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