Cobolt Chloride is it ok in the safe?

Calcium sulfate is very safe. Chances are you're surrounded by it because it's the main ingredient in drywall. The calcium sulfate in drywall is already hydrated (it's gypsum). I don't recommend heating drywall to use as a desiccant. It has binders and organic materials that may decompose, and once heated, will be partially in the form of a fine, white powder that will drift through the air and settle on coins, people, etc. If you've ever cut drywall, you know what I mean.

Drierite (calcium sulfate) is still available with or without an indicator. It's in nodule form, but can also be a little dusty. If you use it, pour it into an open container or porous sack away from coins. Then, after the dust has settled, place the container or sack in proximity to the coins.

Cal

 

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I am a retired Research Chemist and we used silica gel with cobalt chloride for many years to dehydrate samples. Around the mid-1990's we found out that cobalt chloride was a cancer-causing agent and decided to exchange it. (Google it as something like silica gel cobalt chloride cancer banned Europe)

Unlike in the USA, in Europe, silica gel with cobalt chloride has been banned since July 2000 and replace it with the "safer" orange" silica gel, called Sorbead Orange® Indicating Silica Gel. The main ingredient is methyl violet, formulated to change from orange to green, or orange to colorless. Methyl violet is the lesser evil of the two, it is also toxic and potentially carcinogenic, but is "safe enough to have medicinal uses".

That gave us two options, continue using regular silica gel (without the cobalt chloride or methyl violet) or calcium chloride, which is safe and a very strong dehydrator. In either case, use them with a small digital relative humidity meter. We decided to go with the old proven, stronger dehydrator, calcium chloride.

In my case, I keep my valuable copper coins, zinc coins, toned coins and my valuable silver coins in a sealed drying chamber (got it at an auction many years ago) with calcium chloride, away from my coin, as mentioned, you do not want chlorides (including sulfates or nitrates) or water in contact with your coins.

However, I do have to monitor now and then because calcium chloride will continue to absorb humidity even when it becomes liquid and can become messy, but it never near and possibly come in contact with any of my coins. To avoid this, I dehydrate the calcium chloride using my oven about every six months. Not a big deal since silica gel has to go through a similar process, but I would never put silica gel with cobalt in my oven to dehydrate it.

For my safe, I keep four large sacks of clear silica gel (approx. 2"x6"x2") at the bottom and an old analog humidity meter. I dehydrate them in my oven more often because I leave the door open while I "playing" with my coins.

The bottom line, I also would recommend silica gel without any indicator to prevent your copper-based coins from being exposed to humidity (I can go into the details of why, but I already made this reply too long) and get a simple digital or analog meter to monitor the humidity.

Hope this helps... and sorry for the long explanation...

 

Good point @calcol, I forgot about Drierite, it is also cheaper than calcium chloride. It also available with or without cobalt chloride as an indicator but it also has to be oven-dehydrated like silica gel or calcium chloride.

I do not use it because it is not as strong dehydrator as the other two, but does get the job done... eventually

 

OK, it is a good idea to protect coins from moisture (and from oxygen...but that's a different story) and desiccants seem to be a good way to do it. Calcium sulfate is a good desiccant, with or without cobalt chloride indicator. In graduate school we often used magnesium sulfate, which I think is a faster agent. Both of these desiccants suffer from then problem of dusting. Agents which have much less chance of being problematic include silica gel and one people haven't mentioned, molecular sieves. Either of these should present less dusting problems. The inclusion of cobalt chloride in some form should not be a problem, as long as you don't eat it. I know cobalt chloride test strips have been common in many labs I have worked in, and AFAIK, cheap. Buy a tube and you have perhaps a hundred reusable test strips. They are activated by "roasting" over a flame till they turn blue and indicate moisture by turning pink. @BadThad might have something to add too.

 

It strikes me that the "carcinogenic" concerns about cobalt chloride are probably more large-scale -- do we get in trouble with water quality if we use this, and dispose of it, on an industrial scale? -- than small-scale ("will I get cancer if I put this in my safe?").

I'm not surprised, and not necessarily displeased, if large organizations have decided to stop using dessicants with cobalt chloride as an indicator. But if there's still old stock around, I can't see any harm in using it; indeed, using it is probably better than putting it in the trash.

 

Anyone can buy indicating Drierite from Amazon, Staples, etc.. There are no skulls on the bottle or large print warnings. The SDS has the expected CYA warnings about the possibility of poisoning, cancer, blindness, impotence, the sun going out, etc. Some of the warnings apply to the calcium sulfate (aka gypsum, aka drywall) rather than cobalt.

Cal

 

I don't know why anyone would use cobalt chloride as a desiccant when there are ample, cheap, commercial desiccants in the marketplace. Even something as simple as rice works.

The absolute best thing to use is a dehumidifier. Put it right next to your safe! Then you won't have to replace desiccants ever again. They are less than $200, I'd say that's money well spent. The packs should only be used inside ziplocks anyway, they just don't last long when exposed to air constantly.

 

The carcino concern is due to cobalt radioactive isotopes which may be present. There are MANY isotopes:

https://en.wikipedia.org/wiki/Isotopes_of_cobalt

 

The cobalt in humidity indicators is the natural isotope, which is stable.
Cal

 

Cobalt chloride is NOT a desiccant. It is a humidity indicator that allows visual inspection of the state of a true desiccant. Dehumidifiers can be used. There is more initial outlay for them, they use electricity, and either have to have a sewer drain or a collection container that has to be emptied periodically.

Cal

 

It makes no sense to me to put the desiccant should be used inside a zip lock bag, it defeats the purpose of why you want to use them, that is, to remove the humidity around your coins.

 

Found this reference, it should clear up a lot of the health questions regarding the use of cobalt chloride or methyl violet as an indicator

https://www.nps.gov/museum/publications/conserveogram/02-15.pdf

Be safe!