Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: Marisa Oosthuizen on 19/08/2009 14:30:02

Title: Why didn't our silica gel change colour?
Post by: Marisa Oosthuizen on 19/08/2009 14:30:02

Marisa Oosthuizen  asked the Naked Scientists:
   
Hi Chris
 
We doing a science project about silica gel. I've used the silica gel that we find with cartridges to dry some flowers for this project. In the previous articles of silica gel they say the colour changes; ours didn't.  

After we dried it in the Microwave it turned orange to very light brown and after we put the flower in there it didn't change back to white.
 
Another thing is that after we dried the flowers and put it in a sealed container, it was damp again.   Can you explain this to me?
 
Regards
 
Marisa Oosthuizen

What do you think?

Title: Why didn't our silica gel change colour?
Post by: Bored chemist on 19/08/2009 19:15:26

I think you may be using cheap silica gel. The expensive stuff has something added - often a cobalt salt- to indicate whether it is wet or dry.
Since cobalt is rather toxic some manufacturers have replaced it but, in my opinion, nobody was eating the cobalt laced stuff and the new ones just are not so good at indicating humidity.