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Comment by rubicks | Hacker News Reader

Ex-undergrad-assistant in a organic synthesis lab, here. I am extremely familiar with glass cleaning procedures, having done it nearly daily for one long semester.

Base bath is how you clean glassware.

The base bath was a _saturated_ solution of KOH (potassium hydroxide) in a 10-gallon PTFE (molded "teflon"). You knew it was saturated by the KOH precipitate at the bottom.

You take your "dirties", making absolutely sure they had no residual acid on them, and ever so slowly, ease them into the bath. 24 or 36 hours later, remove them and repeat with the next batch.

After a few dozen cycles, you have to change out the base for fresh stuff. For that, you needed a face shield, shoulder gloves, and extremely steady hands.

Tedious, dangerous work.

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Yup, had this job as an undergrad, too, in a national lab on campus. Standard process was something like rinse in regular water, scrub with detergent, spray off with de-ionized water, 5-minute dunk in aqua regia, dunk in more de-ionized water, then alcohol rinse and set aside to dry.

Wore butyl gloves and apron and a face shield. Accidentally raised my hands above horizontal once and didn't notice a trickle of acid over the edge of the gloves. Next time that shirt came out of the wash the sleeves were shredded.

Our aqua regia bath was also about 10 gallons, but it was in a WW2-era fume hood and it looked like it was made of some kind of metal in a concrete shield, that had been partially eaten away. One time a cockroach the length of my thumb fell into the bath while I was working - I heard the splash, and by the time I turned my head to see what happened, it was mostly just exoskeleton. I quit that job pretty soon after that.

Heh. I never had the pleasure of working with aqua regia. I watched a grad student burn himself with it once. We were filling out incident forms for a week.

for anyone curious, this guy uses it all the time to refine gold, it's very interesting work: https://www.youtube.com/@sreetips

Nasty liquids that clean the glassware is one thing... nasty liquids that would dissolve the glassware (and you) takes it up another level. I was happy when I got past that part of my experimental career.

To save people looking it up, _aqua regia_ (wikipedia- 'literally "regal water" or "royal water"') is a mixture of nitric acid (HNO3) and hydrochloric acid (HCl) in a 1:3 ratio.

It was used by alchemists, as it can dissolve gold.

niels bohr dissolved the nobel prize medals of colleagues in it and left it on his office shelf during wwII - the committee recast them after the war https://www.aip.org/history-programs/news/invisible-prize

Yeah, we did this. Two big plastic - just polypropylene, I think - boxes under the main sink. One acid and one base.

After daily use for 4 years it felt very routine. Glad I don’t do it anymore though.

I used to love how shiny the glassware was after coming out of the base bath. Lovely!

I know nothing of chemistry in a professional setting. What happens to all the byproducts and stuff you use to clean? I assume you can't just dump everything into one big barrel and send it off to the landfill.

My lab actually did have 88-gallon barrels for waste; one each for aqueous waste, organic waste, and ether waste. Ether waste was kept separate because we produced a lot of it and because it had to be treated with preservatives to prevent the formation of explosive peroxides.

Anywho, the old base had to be (gently) neutralized with acid before being dumped into the aqueous waste barrel. This had to be done slowly because exothermicity and dissolution heat.

Iirc, the waste barrels were taken back by Sigma Aldrich, to be batched, filtered, and re-distilled into reagent-grade solvents. Circle of life.

The waste is sorted by type e.g. if it contains heavy metal salts versus nasty organics. Quite a lot of this is recycled. Heavy metal concentrates are cheaper to refine than fresh ore; quite a few labs sell their waste to companies that extract the underlying metals. Nasty organics are often incinerated, which renders them harmless.

There is an entire industry around optimally managing chem lab waste. It doesn’t go to the landfill unless it has been thoroughly processed for both value and toxicity. Industrial chemistry is a low-margin business, companies extract every bit of value from their waste stream that they can.

You need to wash the glass in a weak acid (1N HCL) after rinsing. Otherwise, the surface of the glass remains strongly basic and if you work with any base sensitive molecules, it can break them up pretty quickly.

why can't you siphon the base bath instead of having extremely steady hands

i'm also sort of surprised this treatment doesn't corrode the glass. i guess borosilicate holds up to things that would ruin soda-lime glass

You probably could, assuming you had ptfe tubing (we didn't) but then controlling the flow velocity is harder. Heat of dissolution is real.

ptfe tubing is cheap but i was thinking a borosilicate siphon

i don't think you'd have any heat of dissolution involved with a siphon

never done this tho, sounds scary

hate to be the one to prime the siphon

maybe prime it with water?

I've not run the numbers...but mixing saturated KOH solution with plain water could still be dangerously exothermic.

sure, but you can fill the drain bucket with enough water to keep it from boiling over

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