[Robertsays]

hi, im going to be doing an experiment with perchloric acid and silicate materials. Just adding nitric acid, then perchloric acid to some ground ore, and letting it digest on a hot plate. I've read lots of information on how to prevent any accidents, but I can't find any information on what to do if the digestion of the sample gets out of control.

Should I just remove the beaker from the hot plate as quickly as possible? Im worried that it might start to spit while i remove it. I cant just turn off the hot plate because they take a long time to cool down.

Someone told me that adding warm water might help, but ive read that you should never add water to perchloric acid, only add perchloric acid to water etc.

[Arkcon]

First and foremost, perchloric acid digestions are performed in a perchloric acid hood, that is in good working condition.  Such a hood has an abundance of plastic parts, and a constant water spray, to take excess perchloric acid vapors away, so that explosive heavy metal perchlorates don't form on metal surfaces. 

If you neglect this, someday, someone will be tasked with taking apart the hood for maintenance, and the second to last thing to go through their head will be "what were they doing here".  The last thing to go though their head, of course, will be a piece of the hood.

If you have tongs to move the beaker off the hotplate, and the sash is as far down as it can be during the digestion, you should be ok for normal digestions, or mild spitting.  Working with the smallest sample possible, is of course, a good idea.  Some long armed neoprene gloves, aren't a bad idea either.

[Robertsays]

thanks for the response