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The Dos and Don’ts of Weighing Dangerous Chemicals

Posted in: Basic Lab Skills and Know-how
The Dos and Don'ts of Weighing Dangerous Chemicals

A lot of chemical reagents are relatively nonhazardous.
But there are just as many that are extremely hazardous, which means you’ll want to take precautions to reduce any risk of exposure, repeated exposure and of course, accidental contamination of anything – or anyone – that walks out of the lab at the end of the day.

None of this will be a worry when you handle hazardous lab chemicals like a pro! Here are a few practical suggestions on what you should (and shouldn’t) do when weighing hazardous chemicals.

Please do:

Read the MSDS first.That way you can save yourself a lot of headache down the road when you know what your item can do, and know how to protect yourself and not let it do bad things to you. Most importantly, the MSDS is the deciding guide for whether you will weigh on the bench, in the hood, or in an isolated box.

? Wear your PPE. Remember your three Gs, gloves, goggles and garment (which could include a gown, apron or coat). Double check the MSDS to see if that covers everything!

? Give your colleagues a heads-up so they’re aware that you’re working with dangerous materials. That lets them know you want undivided attention to your task until it’s completed.

? Use the fume hood when measuring volatile liquids. In case of accidental spills, you can pull the sash closed to contain the fumes and then call for help, without having to evacuate the lab for the rest of the day.

? Cap your containers. With DI water in one lab, chemicals in another and stir bar and hot plate in a third, you risk spilling your chemical out in the public hallways when scurrying between them. Take care to keep your chemical in a closed container (no open weigh boats, including that of a second weigh boat held as a cover on top of the first!) as much as possible when walking about – even in one lab.

? Use rigid weigh boats. Cut pieces of wax paper just won’t cut it. Grab the edges to move it an inch…poof! Powder explodes all over the scale, the bench, sometimes even you. You’re less likely to spill with a rigid plastic container, though be aware that for small granules like paraformaldehyde, static electricity can wreak havoc on your technique, sending the chemical flying onto the bench.

? Clean the scale when you’re finished. This is a courtesy to the next user: If you stumble upon a stray powder, dust or dried out stain, how do you know for certain that it is non-hazardous? Your colleagues will thank you for taking a few seconds to help keep the chemicals area hazard-free.

Please do not:

? Use just any plastic bottle when measuring liquids. They’re not created equal. Some chemicals, like chloroform, will eat straight through the bottom, giving you a crash-course in spill control. Use a robust container instead, like a chemically compatible plastic bottle or glassware.

? Weigh near your office, computer, break room or your backpack.The goal is to add the chemical to a science experiment, not bring it home with you!

? Use a single weigh boat for a recipe that calls for 100s of grams. Ever seen anyone try to add 500g of powder into a narrow mouth bottle? It’s a spectacular accident. If you’re limited by the size of your weigh boats – or measurement of your scale – divvy it up amongst a few boats, adding the weights up as you go.

? Double dip. Select a clean scoopula, tongue depressor or other tool before diving in to the next container on your list. Discard or thoroughly wash all the tools that you use.

? Weigh out extremely hazardous chemicals if you absolutely don’t have to. Here’s where it pays to shop around: see if your favorite chemical is available in pre-measured aliquots the next time your lab manager is placing orders. When it’s not, take turns measuring out a set of single-use tubes from a primary bottle so your colleagues ultimately handle a very small amount of a hazardous chemical at a time, right when they need it.

? Become distracted by a phone call, email, coworkers, etc. Not everyone is comfortable with all the chemicals in the lab. That goes double for the variety of hazards associated with them. Focused work allows you to weigh out any chemical to a bottle, put it into solution and then use it in an experiment without the chance of it ending up forgotten in a dark corner of the lab.

It’s as easy as that!

What other tips would you give our readers about weighing hazardous chemicals?

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