When it comes to laboratory safety, you should never cut corners to save money.
A few months ago, I had a teflon beaker melt on a yellow hotplate which we had purchased for the lab to replace a hotplate that died. Unfortunately, when inexpensive hotplates “die” they tend to heat up very hot, which can be very dangerous. I’m not sure exactly what happens, but I think that over time acid corrosion affects the thermocouple so that the hotplate can no longer regulate temperature properly.
I use some very strong acids in my chemistry– concentrated nitric acid, hydrofluoric acid, and perchloric acid. I need to use strong acids because I am dissolving rocks. As you can imagine, dissolving rocks is no easy task– those silicate bonds are difficult to break. Because I use such strong, corrosive acids, I think the electronics of an inexpensive hotplate are easily corroded. I wish the hotplate would just switch off or cool down when it becomes corroded. Unfortunately, when this model of hotplate dies because of acid corrosion, it dangerously ramps up in temperature, melting teflon beakers filled with acid and rock powder.
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| Good hotplate. Note the lack of melted beakers. |
Most of the hotplates in lab are home-made with heating tape and will not fail in such a catastrophic way. However, these hotplates do not reach high enough temperatures to dry down perchloric acid, which I must use in my dissolutions. I’m not the only one who uses perchloric acid– there are others in the lab who have used this dangerous acid. To dry down perchloric, we use a special venting system (so we don’t inhale the vapors) and use a store-bought hotplate. We’ve been using the Cimarec hotplate made by ThermoScientific. This is a BAD HOTPLATE. I bought a brand-new Cimarec back in October or so, and it has already failed by overheating. The Cimarec we had before that lasted less than a year before it melted a single teflon beaker.
When the beaker melted on the previous Cimarec hotplate, I was very concerned. I was very sad to lose a sample, of course, as my chemistry takes MONTHS so the loss of even a single sample is very unfortunate. The bigger problem, however, is the possible risk of fire by melting a plastic beaker containing very strong acids and rock powder. I looked into what types of hotplates we could purchase that would not fail in such a catastrophic manner. The problem? The “safe” hotplates cost about $3,000 whereas the “unsafe” Cimarec hotplates cost only about $300. My primary advisor had just left for another institution, so there was no way that he was going to buy a $3,000 hotplate to leave behind. The lab technician advised that I buy another Cimarec since “it was unlikely” that it would fail again before the labwork for my thesis was completed. I listened to the lab technician and my one advisor (I’ve got two actually), which was a mistake. I should have insisted that we purchase the expensive hotplate. Or I should have insisted that I be allowed to dry down my perchloric samples in another lab with safe hotplates.
But I bought the new Cimarec hotplate and the technician helped me install it. I did change my behavior– I didn’t leave the hotplate alone during the day, and I switched it off overnight. However, I didn’t watch it every minute– it’s just not practical to do so.
Today the inevitable happened. I put two 120 mL teflon beakers and their lids on the yellow hotplate to dry down. I went to work on something else in the lab, but after about 30 minutes I smelled some smoke. This is what I found:
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| Bad hotplate. |
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| Note the lowness of the temperature dial. I had it set to 125 deg C, well below the melting point of teflon plastic. |
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| Only a beaker lid rim remains. |
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| Bad teflon goo. |
I immediately unplugged the hotplate and called security. No one was hurt, and there was no fire. But someone could have been hurt, and there could have been a fire. I have already filed an extensive safety report and plan to meet with the safety officers in the near future. Although a new, fancy hotplate may not be installed in time for my thesis work, I plan to do everything possible to make sure that an expensive but safe hotplate is installed. There is a new scientist about to take over the lab (a replacement for my advisor), and he agrees with me. He made a fuss about the hotplate as well, and he’s trying to insist that his start-up allow for the purchase of several of the expensive but safe models of hotplate. I hope that the accident today gives him leverage to insist on the money he needs for the safe hotplates.
This time, I think my advisor and the lab technician will take my request for an expensive hotplate seriously. If not, an accident like this may happen again. After all, those who do not learn from history are doomed to repeat it. If any of you use the Cimarec hotplates to dry down acids, please seriously consider abandoning use of this type of hotplate.
As for my chemistry? I’ve already asked the scientist across the hall if he would dry down my samples for me in his expensive dry-down system. He has generously agreed and also offered to help me insist that the lab (which is going to be rebuilt for the new scientist) contain the safe hotplates.
A final note is that I am mourning the loss of the two peridotite samples that melted earlier today. I had been dissolving these samples for several months, so I’ve now lost months of chemistry. Fortunately, I only lost two samples.
Georneys 
For a runaway heating event like THAT, either the electronics shorted, leaving the unit full on OR the coils began shorting a few windings at a time.For this to be apparently habitual decries of a horrible design that should NEVER have gained either the Canadian and US certification OR European safety certifications! Something is seriously awry!Have you contacted the vendor over their hazardous product?I'm shocked that they don't have an overheating sensor on the unit! I'm betting that the electronics is not in a sealed unit, such as epoxy potted, but instead open to the air, where the acid fumes etch away at the solid state components. Something incredibly stupid to have in a chemical lab hot plate!
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Stephen: I agree. Yet this is a very popular hotplate model bought by chemistry labs. Please, feel free to send ThermoScientific an email about their Cimarec hotplates.
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Wow. I had no idea that the chemical analysis of rocks could take so long. Months, you say? Wow. That would really piss me off – to lose my work (MONTHS of work) because a manufacturer's product was not up to snuff.
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Evelyn, as I am not their customer, they'd disregard my comment or complaint.Whereas if I registered a complaint along with YOUR customer complaint, it WOULD register.MY complaint would only be regulatory, without a complainant. With yours would be regulatory AND one of statue, due to warranty.Together, we can accomplish what cannot be done separately.
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Ben, beautiful work! The shots of the alnmuuim legs are very nice they remind me of modern architecture when I was a kid in Iowa. I love the Glastherm, too. Now I understand why Scott cut me a piece of that before turning my new idler wheel, too. Is the Glastherm brittle? I’m wondering about using it for legs cut two 1 -wide strips of it, stand them on edge, and attach them to the heating block using L brackets (or channel). I may have to beg Scott to throw a couple of strips into my package for upgrading my hotplate!
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Keep us updated on how the investigation by the company goes! I'm betting on exposed components, mostly due to not considering acid fume environments.Let's face it, YOUR environment is FAR, FAR different than MOST OTHER chemistry lab environments. Protracted heat AND high molar solution acids…
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Stephen: Yes, it's true that we use somewhat harsh acids. But the manual implies that it's fine to use these dangerous acids, even in strong molarities. If the hotplate had just stopped working (turned off), we would not have been upset. We know our acids are very corrosive, and we wouldn't mind having to buy new hotplates often. However, when this hotplate failed it failed dangerously. My worry is that in other labs using less strong acids, this failure will just take longer– maybe years instead of months– but wouldn't it be just as catastrophic in the end? Seems like a poor design to me. Also, you'd be surprised at how many scientists– and not just geochemists– use these strong acids in their research. Or other ones that are nasty in different ways :-).
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evelyn, I sent you an email. I am local but might have a substitute I can loan you. I would not use a hot plate for this, I would use a sand bath or a dedicated heating apparatus. I am very curious, what is it that you are trying to do that takes months of high molar HClO4?
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In the US, yam and sweet potato can be cosnfuing. The sweet potato is not a yam, but for some reason the red or orange sweet potatoes are called yams, especially in the South Maybe they taste something like real yams (which I’ve never had). So sometimes they are called yam sweet potatoes . And sometimes yams are called yams (not sweet potatoes) . But real yams are uncommon, except in groceries with lots of customers from the Caribbean.And the pale, whitish variety of sweet potatoes are always called sweet potatoes, but who eats them? Sweet potato pie, mashed sweet potatoes, sweet potato french fries, and are made with the orange sweet potatoes. Candied yams are made with the orange sweet potatoes, too.
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Evelyn, true. I know of a few labs, even very, very small labs that use some rather strong chemicals in general. One of my old clients has a hole in his ceiling from a cleaner he was making. He let it sit to be certain it was stable.It wasn't.I can think of a few other chemicals that would become extremely hazardous if the beaker melted, as they'd not evaporate, but would become volatile. There SHOULD be an overheating sensor in the unit, even if it's only a metallic strip that opens when it melts at that beyond normal operation temperature.
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Hi guys,Thank you all for commenting!Lauren I hope you enjoy!Tanya Your site looks great, I’ll check out your recpies too.Family Nutritionist I’ve actually never tried meatloaf, can you recommend a recipe? Yes, the kumara is sweet potato, or is it also called yam in the USA?Ruth you can let me know if you do try any of them out!
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