Laser power supply fun

[tocket]

What's this? You're discussing nasty chemicals in the absence of the resident chemist? How could I have missed it? I deal with these things on a daily basis. Well, not really... but I have dealt with chemical warfare agents like mustard gas. Now that stuff was made for the single purpose of being nasty!

Hydrofluoric acid is actually not a particularly strong acid; its corrosiveness is instead in large part due to the fluorine ion which likes to bond very strongly with pretty much everything. This is very noticeable when it comes in contact with glass for example. However, most plastics are completely resistant to it. Especially teflon (PTFE), which is already a fully fluorinated polymer.

Today I had to throw away a bottle of hydrazine, that was a sad moment. I put it right next to an old 500g bottle of picric acid (toxic, highly explosive, extremely sensitive salts with heavy metals).

But seriously, all this talk about everything being so dangerous... it's mostly exaggerated. People are afraid of everything these days. Yet, chemists live longer than ever before despite being exposed to all sorts of supposedly nasty stuff now.

[Jem]

Hi Tocket

Nice to see you on this thread. We missed you but I guessed you'd stumble across it eventually

Jem

[tocket]

Hehe, thanks Jem.

I forgot to say, heating any fluorine containing polymer to decomposition will generate lots of unpleasant products like hydrofluoric acid. That is probably what Rob was talking about. However, in this context HF is one of the least harmful decomposition products. Others are toxic enough to be classed (banned) as chemical warfare agents. In other words, take it easy with your teflon coated frying pan or your gore-tex jacket!

[heroic]

I forgot to say, heating any fluorine containing polymer to decomposition will generate lots of unpleasant products like hydrofluoric acid. That is probably what Rob was talking about. However, in this context HF is one of the least harmful decomposition products. Others are toxic enough to be classed (banned) as chemical warfare agents. In other words, take it easy with your teflon coated frying pan or your gore-tex jacket!

I remember when I accidentally melted down a sonar transducer array which had PTFE wiring (it was designed to go into a high temperature, high pressure water bath at about 400 degrees C, for scanning welds- best not to ask). The story of how I melted it down isn't very interesting (software bug caused it to catch fire- silly me). What is interesting is that the resultant cloud of HF-containing smoke caused the lab to be closed for three days while they had specialists in to scrub all the surfaces.

Fortunately, I'd written literally all the DSP code for that system, so they couldn't fire me. But they did think hard about it.

HF isn't a strong acid, but it is extremely toxic, and those fluorine ions just keep going and going. Even ceramic oxides don't stop 'em, 'cause fluorine just pulls the oxygen off and eats them up yum yum. Nasty.

I always wanted to get hold of some liquid fluorine, though. Just to see what it would do. Probably "kill you and eat your bones".

[FrankenPC]

I've got a half gallon left of dichloromethane sitting in my garage. You can take the nastiest, clogged carb on the planet, heat up the DCM a tad and dip the carb parts in. ALL GONE! Clean as a whistle. But, so is the DCM. When it gets warm it evaporates like crazy. I don't think you can buy DCM anymore. So I'm holding onto it like it's gold.

And yes...I know it's toxic and a carcinogen. I have a heavy duty chemical respirator I wear when I'm cleaning my car parts I must look like something out of The Hills Have Eyes.

[heroic]

It's toxic, a carcinogen, an unbelievably potent greenhouse gas, plus it eats the ozone layer- you're a class act and no mistake

Not that I'm one to talk. I used to use freon to chill bearings to get them out of motorcycle engines.

[tocket]

Oh yes, DCM is really good stuff. It has excellent solvent power, doesn't smell much and is easy to evaporate. It is easily my favorite solvent (and I've used quite a few).

There are unfortunately some concerns regarding its toxicity. Because of this it is getting harder and harder to come by. In Sweden it's banned for all commercial use and only a few industrial processes (mainly pharmaceutical) are allowed to use it. It's allowed for research purposes though. I use liters of DCM every week.

It isn't classed as toxic (only harmful) and it's only a suspected carcinogen (but what isn't?). It's my opinion that you'd practically have to bathe in the stuff on a daily basis to be in any serious risk. If you look at the animal studies that's basically what they do.

Wearing a respirator is probably a good idea though, because it is so volatile and does exhibit a certain degree of acute toxicity. I work with it in a fume hood, so I'm only exposed to it when I spill it on my hands (which is pretty much all the time).

[FrankenPC]

Oh yes, DCM is really good stuff. It has excellent solvent power, doesn't smell much and is easy to evaporate. It is easily my favorite solvent (and I've used quite a few).

There are unfortunately some concerns regarding its toxicity. Because of this it is getting harder and harder to come by. In Sweden it's banned for all commercial use and only a few industrial processes (mainly pharmaceutical) are allowed to use it. It's allowed for research purposes though. I use liters of DCM every week.

It isn't classed as toxic (only harmful) and it's only a suspected carcinogen (but what isn't?). It's my opinion that you'd practically have to bathe in the stuff on a daily basis to be in any serious risk. If you look at the animal studies that's basically what they do.

Wearing a respirator is probably a good idea though, because it is so volatile and does exhibit a certain degree of acute toxicity. I work with it in a fume hood, so I'm only exposed to it when I spill it on my hands (which is pretty much all the time).

You bring up a good point. Nitril gloves disintegrate upon repeated contact with the stuff. Also, if you get enough on your skin it can leave behind a really itchy red rash. At least it did on my skin. But, this was warmed DCM. Which is far more volitile than chilled DCM.

Anyway, I was told by the chemist shop I purchased it at that the US government has banned personal sale due to it's use in illicit drug manufacturing. Great...yet one more thing banned here in the US.

[tocket]

Nitrile gloves are what we use in the lab, but they are indeed useless against DCM. Wearing gloves may even increase exposure, as the solvent penetrates the gloves very quickly and then stays trapped inside the glove.

I've only recently started using gloves regularly in the lab. Earlier it was just for dealing with especially nasty chemicals like bromine or phenol. I don't really use them to protect myself though, but rather to minimize contamination. The stuff I synthesize is often highly fluorescent and if I'm not working cleanly it quickly becomes obvious.