Hacker News Reader

Comment by gavinward | Hacker News Reader

I think Hydrofluoric acid is probably the substance you're describing which leaches the calcium out of your bones. It will certainly burn you too though. It's a common byproduct from heating fluorinated gases and is sometimes used in its own right for wet etching.

As an aside, I love it when they tell you in the safety WBT what the highly toxic gas smells like.

View on HN

For lower concentrations (< 50%) HF burns aren't always immediately visible (and often not immediately painful), which can delay treatment as people may assume it's not serious.

Yes it can destroy your nerves faster than you register pain, so you might not even feel the damage HF caused

Reminds me of something from chemistry class but I can"t remember exactly what it was (this was several decades ago now), I think it was sometimes used for etching glass, but if it got into your body -- I'm not sure if getting it just on your skin was necessarily a lethal hazard -- it would leech the calcium from your bones and was considered an especially nasty way to go. Our prof was helping her father in law clean out his garage and he had a bunch of it in a container, bought in the 60's or 70's for a glass etching kit, and was like "Okay I'm getting rid of this, but have you got any other hobbies you've been meaning to get around to that I should know about?".

Sorry I believe it was copper etching maybe, probably not glass. Been a while...

I'd think copper would mean ferric chloride, which isn't that bad.

Oh fun, we have used it in school to etch PCBs. Right outside of the class room with no protective equipment of course. It was in a bucket.

HF is released in lithium ion battery fires. Just one reason why the correct response to such a fire is GTFO as fast as you can.

Rechargeable lithium batteries pose a higher risk than single-use lithium batteries. Only the rechargeable ones have a thermal runaway hazard. I figured it was wise to get rid of old rechargeable lithium batteries that I no longer need or use.

Fwiw, there is a BurnBuster brand of fire extinguisher for stopping lithium runaway. See ASIN B0DZ9R7Q51. It is a ripoff but probably good to have.

Single use ones too can contain fluorine, but not the runaway risk. Nevertheless, they require significant care to avoid shorting during storage. Never store them loose or where they can contact each other. Tape them well from all sides, and put them in a sealed ziploc bag before disposing.

Reading through https://www.mass.gov/doc/toxicology-of-the-lithium-ion-batte..., especially seeing the skin impact of a battery combustion in someone's pocket, is enough to make me think I should keep an inventory of every Li-ion battery in the house.

Some places would mix it with nitric acid so the yellow stain would tell you that you had been exposed.

Other fun chemicals used in fabs were Silane (CSi4), methane w/ silicon instead of hydrogen, used to form a silicon dioxide layer for etching* w/ HF and final step of protection. It would spontaneously combust on contact with air, so when you popped a tank fitting it would leave a white powder residue. Silicon dioxide is used as a food additive so AFAIK that wasn't dangerous.

Phosgene was also used as a dopant. If the alarm for that went off you really got out ASAP.

Arsine was a dopant also.

This is what I sort of remember from working on slacker job in silicon fab a long time ago when the number of transistors per chip was 1. I did say a long time ago.

* You could also just oxidize the outer layer of the silicon wafer itself w/ water vaper at high temps.

Silane is like Methane, but with Silicon instead of Carbon (SiH4). Thanks god for doping was used Phosphine (PH3) and not Phosgene (COCl2), both are nasty, but the second is more. Plus I don't know how much is used, since nowadays doping is typically done by ion implantation rather than gas diffusion

Not enough caffeine. And yeah, it would have been phosphine since it was phosphorous that was the dopant.

Reply on news.ycombinator.com