Date: Tue, 2 Nov 2010 15:04:56 -0700
Reply-To: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: Mike Hurwitz <tesla**At_Symbol_Here**LMI.NET>
Subject: Re: Acid Digestions
In-Reply-To: <4CD044BD020000BA00021F23**At_Symbol_Here**gwsmtp1>


That recipe looks close to "Aqua Regia" depending on the concentrations of the starting materials. My lab has done a lot of these types of reactions. It's actually fairly critical not to lose any liquid volume. For your case I would use a 100mL test tube. A hot water bath, heating block, or sand trap to heat only the bottom 30% of the tube, and then put a fan blowing accross the top. Then top it with a single holed neoprene stopper. The top of the test tube will act like a condenser and you will lose very little liquid. Of the three I recommend a sand trap (which is just a metal tray with sand in it). If a water bath is used it's harder to cool the top due to water vapor constantly leaving. Also, the reaction of Aqua Regia does generate gas, so you have to make sure the system is never fulled sealed. The single holed stopper is optional, and if you don't have one with large enough hole just skip it. If you're still interested in abatement material: Severn Trent will provide a dry media scrubbing material that looks like little balls. It can easily be put into an extra column and used to scrub just about anything. Once again though, it's very important not to let pressure build up. If you're a school, severn trent should give you a pretty good deal on a small amount of media. In cases where we've had to run large amounts of samples that needed to be scrubbed, we've used vials with silicon septa on top. then we've made manifolds with barned T-fittings and tubing, and put needles on the end. You push the needles through the top of silicon septa and everything runs through to the media. Cheers, Mike > > Good afternoon, > > > I have a researcher who wants to perform acid digestions involving about > 20 mLs of concentrated hydrochloric acid and 5 mLs of concentrated nitric > acid which are mixed with her soil, then slowly heated to 95C until most > of the acid has evaporated. The methodology, developed by outside > researchers, is outlined in a journal article which makes no mention of > the use of scrubbers, special fume hood lining, etc. > > > The researcher will be wearing a face shield, rubber apron, goggles, lab > coat and thick nitrile gloves, with tape around the glove/labcoat > interface. I think we have the PPE down pat. > > > The process is planned to be carried out in a fume hood, using an open > vessel on a hot plate. My concerns is whether we should be using some > sort of capture system or scrubber for the acid that is evaporated. I am > trying to find out what the ductwork for the fumehood is made of, but it > is not a stainless steel hood and I am betting the ductwork is not, > either. The researcher is planning on doing somewhere between 20-100 > samples, depending on how things go, so roughly 400 mLs to 2000 mLs of > concentrated acid may be sent through the ductwork... > > > I found one review article on acid digestions that stated "...acid > digestion must be conducted in a fume cupboard with efficient scrubbers > installed..' [Matusiewicz] but no reference to actually how this is done. > > > Any suggestions, citations, etc. would be most helpful.. > thanks to all, > Margaret > >

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