Sciencemadness Discussion Board

glassware etching and vaccum distillation

dactyl - 21-1-2017 at 07:42

Is this 1000 ml 24/29 round bottom flask safe for vaccum distillation? This flask was kept in a concentrated ethanol/water mixture which resulted in some of the NaOH settling out. Two days later the contents were disposed and the bottom of the glassware seems to have changed.

IMG_6781.jpg - 557kB

unionised - 21-1-2017 at 08:10

I'd not risk it.

Maroboduus - 21-1-2017 at 10:00

If a mixture of water and ethanol did THAT to your flask it must be made of cobwebs and unicorn farts.

Perhaps you mean a concentrated solution of NaOH in water/ethanol. Either your post is somewhat equivocal, or my reading skills are not up to par today.

I actually have a 250 ml Erlenmeyer almost that bad which I have used to vacuum distill diethyl sulfate. (if you listen closely you can probably hear the members of this board collectively cringing as they read that). That was a major mistake.

Get a new flask. Vacuum implosion is NOT something you want to be around, and the implosion risks get worse with larger flasks.

Of course keep the old one as a sacrificial flask for glass-corroding reactions. Boiling down phosphoric acid, re-fluxing stuff in strong alkalai, etc

If that flask is 'crusty' when it's dry you might be able to remove some of the crust with OTC lime and scale removers. (In the US there's 'LIME AWAY")

[Edited on 21-1-2017 by Maroboduus]

phlogiston - 21-1-2017 at 12:14

Doubly cringeworthy if you used an erlenmeyer indeed, not a round bottom flask.

dactyl - 21-1-2017 at 13:12

@Maroboduus

You are correct it was a concentrated solution of NaOH in ethanol and water; I was somewhat imprecise.
The solution was likely saturated as some of the NaOH separated out; the NaOH was not reagent grade but it was from Rooto crystal drain opener which claims to have a 99% purity.

gdflp - 21-1-2017 at 13:42

Quote: Originally posted by dactyl  
@Maroboduus

You are correct it was a concentrated solution of NaOH in ethanol and water; I was somewhat imprecise.
The solution was likely saturated as some of the NaOH separated out; the NaOH was not reagent grade but it was from Rooto crystal drain opener which claims to have a 99% purity.

Rooto NaOH is fairly pure, I haven't had an issue with it for rudimentary uses. I fully agree with the others though, I wouldn't trust that flask for much now, certainly not under vacuum.

Maroboduus - 21-1-2017 at 15:07

Quote: Originally posted by phlogiston  
Doubly cringeworthy if you used an erlenmeyer indeed, not a round bottom flask.


That was back when I had a grand total of 3 tapered joint flasks(250, 100, and 10), so my options were extremely limited.
I was also working from an ancient text which described diethyl sulfate as non-toxic. And an ancient lab-manual which was very cavalier about the dangers of vacuum on flat-bottom glassware.

In retrospect I'm not sure what would have been worse: the flying glass or the shower of diethyl sulfate that would have gone along with it.

They sure lived dangerously back then. That old manual had a reaction where they told you to wrap the glassware in a blanket to protect yourself from explosions. (the Marsh test for arsenic?)



dactyl - 21-1-2017 at 19:08

Is diethyl sulfate's acute toxicity exaggerated?
P.S What source was it which described diethyl sulfate as non-toxic?

Maroboduus - 22-1-2017 at 20:08

Introduction To Organic Chemistry
Lowry and Harrow (1928)
Is the first that comes to mind. They also say benzene is intoxicating if you drink it!

I'm pretty sure my mid 1940s version of the Encyclopedia Americana says diethyl sulfate is non-toxic, and I think I've also seen this in a few older books.

I don't think the acute toxicity is really high at all. My 1989 Merck says the LD50 in rats is 880 mg/kg.
They also say, "reasonably expected to be a carcinogen", but they do say that about a lot of things in the lab.

However it seems the general opinion on the threads around here, like the sodium ethyl sulfate thread, is that it's pretty bad.

I'm not sure just how accurate that is, but the concern seems to be centered around the fact that it's an alkylating agent, and that it would cause cancers and genetic mutations.

However I've seen some old (1920s) follow-up research on people exposed to mustard gas in WWI that seemed to indicate that THAT particular alkylating agent wasn't all that bad in terms of cancers. This may very easily just be a bad study, or a dishonest one(seems to have been done by the military, and they might've wanted to downplay the long term damage done to all those veterans). And it is a different compound, although a similar type.

Either way, I will make this stuff in future if I need it. It's such a damn easy way to get a fairly potent alkylating agent from incredibly common materials.

I will, however, treat it like liquid death just to be on the safe side. (and use a somewhat better flask).

[Edited on 23-1-2017 by Maroboduus]

EDIT: I must admit that when writing this post I had a burning desire make some sort of joke about it's effects on chromosomes, and how exposure to it might make it necessary to change your screen name from dactyl to Polydactyl.

However I am trying to be more serious in my posts, and to remember that my 'sense of humor' isn't one of my strengths.

[Edited on 23-1-2017 by Maroboduus]

[Edited on 23-1-2017 by Maroboduus]

[Edited on 23-1-2017 by Maroboduus]

harderm - 23-1-2017 at 23:41

Quote: Originally posted by Maroboduus  
Quote: Originally posted by phlogiston  
Doubly cringeworthy if you used an erlenmeyer indeed, not a round bottom flask.

They sure lived dangerously back then. That old manual had a reaction where they told you to wrap the glassware in a blanket to protect yourself from explosions. (the Marsh test for arsenic?)


Way, way back I had a mineralogy set (I still have the manual.) which listed as a standard charcoal block identification roasting the mineral and sniffing any fumes produced. If it smelled like garlic, why it must be an arsenide/arsenate! Fortunately, I never got my little hands on any arsenide ores. To think that today you can buy chemistry sets so safe they contain NO CHEMICALS!

Maroboduus - 24-1-2017 at 09:18

Quote: Originally posted by harderm  
Quote: Originally posted by Maroboduus  
Quote: Originally posted by phlogiston  
Doubly cringeworthy if you used an erlenmeyer indeed, not a round bottom flask.

They sure lived dangerously back then. That old manual had a reaction where they told you to wrap the glassware in a blanket to protect yourself from explosions. (the Marsh test for arsenic?)


Way, way back I had a mineralogy set (I still have the manual.) which listed as a standard charcoal block identification roasting the mineral and sniffing any fumes produced. If it smelled like garlic, why it must be an arsenide/arsenate! Fortunately, I never got my little hands on any arsenide ores. To think that today you can buy chemistry sets so safe they contain NO CHEMICALS!


Yes, it has been quite a change over the years. Mercury was a fun thing for children to play with when I was a kid. They'd roll it around in their hands.

But please try to be more careful with the quote function here. You've got Phlosgiston saying both his and my words, and you've got me saying your words.
This doesn't really matter much in this case except making things a little confusing, but an error like this could in some circumstances make it seem that people are saying things they violently disagree with. Or even make it look like they're giving dangerous, or dumb advice.

This is a mistake I have made too. It's easy to accidentally erase a bit too much when you edit a quote and mess up the quotation parameters.