My favourite toxic chemicals #toxiccarnival

Sciencegeist has set the challenge for a bloggy carnival for us chemists, aimed in part to combat ‘chemophobia’. You know, the ‘oh noes teh chemicalz iz teh badz’ attitude that’s pretty pervasive. I personally would just give up on the anti-chemical thing and move on, but that’s another blog post. The brief seems largely to be to pick a chemical that might be notable for its toxicity and point out all the really great stuff it does, chemistry that we couldn’t really live without.

What to pick? Seriously you could pick almost any chemical and call it toxic (remember the dose makes the poison), and then point out it’s usefulness. You could pick one of the components of petrol (gasoline), aspirin or any other drug, you could pick carbon dioxide or oxygen, and there are a whole host of ‘nasty but useful things’ that may not quite fall into the ‘stuff I’d never work with’ list but are certainly on the ‘stuff I wont let the students play with’ list.

One such chemical would be hydrogen fluoride, or hydrofluoric acid in aqueous solution. HF is deceptively simple in it’s structure – no complex organic frameworks here. It’s power is evident when you consider it’s used for etching glass. But surprisingly, it’s also used in a number of household products, particularly those for cleaning and removing grease and tough stains.

If you’re anything like me, you probably read the label on household cleaning products and view the ‘wear gloves’ indications with a degree of scepticism. Possibly even thinking that if supermarket X or home renovation store Y will sell it, it can’t be that bad.  Well it can.  And it is. If you google ‘HF in household products’ or similar there are a lot of reports of people being harmed by such products. Yes they are anecdotes and not necessarily the basis of good safety information (don’t get me started on mobile phones igniting solvent vapours in laboratories again), but this chemical is dangerous.

So why is it in household products? Are glass etchers more foolhardy than other craftspeople? Should we all be cleaning out our under-sink cupboards, rooting out anything with a glimmer of HF?  It’s there because it is good at what it does, and there’s something to be said for something that does its job efficiently in low concentration as opposed to something that requires a greater concentration to do less.  But what we must be doing is using it appropriately and in accordance with the guidelines on the label. When they say don’t mix it with other products, they generally mean it. When they say wear gloves, they mean it. The concentration in household products varies, and I suspect may not always be disclosed (depending on country and legislation). So caution seems warranted.

I’ve worked in labs where HF has been in use for a number of reactions. We’ve always had a tube of antedote cream on standby.  If I may quote wikipedia:

Hydrogen fluoride gas is a severe poison that may immediately and permanently damage lungs and the corneas of the eyes. Aqueous hydrofluoric acid is a contact-poison with the potential for deep, initially painless burns and ensuing tissue death.

The scary bit is the ‘initially painless burns’. People don’t immediately realise something has gone wrong. Those who use HF in the lab are pretty meticulous workers and for good reason. I’ve been the recipient of a phone call that started ‘I’ve spilled HF down me, we have to go to hospital’.

At the end of the day, chemicals are to be used and respected for appropriate tasks. If you can’t respect the power of some chemicals, you have no business setting foot in a chemistry laboratory. But it’s a very different matter when you’re taking things into your home. Then you need to read the labels, and cut through manufacturer hyperbole to workout what products you really want lurking in the kitchen cupboard. But do not assume for one minute that just because it comes from the same place you buy your strawberries and milk, that it is somehow harmless.




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