Just wondering about a test I need to do at work next week...

The test establishes the break-through time of protective gloves to various acids/bases/solvents. The sample is held in a PTFE cell, forming a seal between the two halves of the cell. One half of the cell is filled with the challenge chemical and the other side with distilled water. The conductivity of the distilled water is measured over time to determine the rate at which the challenge chem permeates the sample.

The halves of the cell are unsealed to the atmosphere and the test must run for up to 8hrs. The lab is maintained at a constant 22*C and 50% RH.

A glove manufacturer has requested testing with some challenge chems that haven't been used before by anyone working in the department. One of these is Ethylamine, which has a boiling point of only 16.6*C.

I presume that the level of challenge chemical in the cell shouldn't fluctuate, as it could skew the results.

I'm wondering if the low BP of this chem is going to present a problem. Each cell contains ~50ml of chem and exposure to the atmosphere is a ~3/4" dia hole.

Would a simple piece of tape over, or a bung in this hole eliminate the problem? Or would this pressurise the cell, thus skewing the results by forcing the chem through the test sample?

Storing the ethylamine shouldn't be a problem as it can go in the Foul Smelling Fridge of Doom. It's opened very rarely and anyone doing so becomes very unpopular. Having to hunt around in there for a chem is an eye-watering and rather unpleasant experience.

Not sure what actually is responsible for the awful smell, since I don't care to take the time ot examine its contents. There's definitely some 100% NaOCl in there, which I think is part of the cocktail. Does every lab have such a fridge or is the one I work in just grotty? ;)

Mind you, it's not all grotty, the floor was exceedingly clean after I accidentally flooded it on friday morning. I thought the piss taking was bad enough until I refused to learn from my mistakes and did exactly the same thing again in the afternoon! :rolleyes:

At least the management were away at a conference, I'm sure they would have wanted to know why they were splashing around in a good half inch of water... :D

Heh, there is a Fridge of Doom in just about every lab :) You know your supposed to immerse ethylamine, or any low BP solvent, in an ice bath before opening it right?

I say stick a stopper in the hole of the test apparatus. Pressure will affect breakthrough times, but so will not having any material to breakthrough. The closest result you would likely get is by refrigerating the test cell to keep the ethylamine below the BP.

Your going to have to sacrifice something unless you wish to attach a reflux condenser to the test setup. You would need a refrigerated recirculation bath connected to the condenser to keep it cold enough, but not so cold you affect your results. A condenser may at least delay the evaporation of the solvent. Otherwise you may have to continually add more from time to time.

Thanks for the info Mega. I think the solution will be either a bung or maintaining a surplus level of chem. Unfortunately that's going to mean yours truly keeping a near constant eye on it. I hope the gloves fail after 5mins and don't go the full 8hrs :(

There is a large chest freezer that goes down to -50*C (I was freezing pens in it on friday) that the test could be run in, but I'm pretty sure the standard calls for controlled temp/humidity. Also the lack of fume extraction might bother someone.

I wasn't aware of the practice of ice bathing low BP solvents, but then I've had no formal general chem handling/lab pratice training. Except a 30 min presentation from an industrial chem spill handler at the Fisher Science Expo, who explained the fallacy of storing benzene in a whiskey bottle and how you should phone the fire department if a fork lift truck crashes into a pallet of H2SO4 drums...

I have supervision though (on the occasions that she's there) from the chemical engineer from the Motherland itself :) Not that I should divulge that it took her 20 minutes, an A4 sheet of scribbles and some furious calculator bashing to produce a 5% HCl solution from the 37% stock!

Producing a 25% NaOCl solution required a phone call to Aldrich... "I'm pretty sure the stock is ~100%" said I. "But it says 10-13% Cl content on the label, we can work out its concentration from that. What's the molar mass of NaOCl?"

Buggered if I knew, so I picked a general chem tome form the shelf and read her the defintion of a mole: "The amount of a substance that contains as many atoms, molecules, ions, or other elementary units as the number of atoms in 0.012 kilogram of carbon 12"

At which point she went for the phone...

Of course, Aldrich said the obvious - mix it 25:75 with water for a 25% solution...

Oh dear, I seem to have gone off on a rant :D

Not as bad as the director who covers out department. They're expanding the site with two new buildings, one being built now and the other built after the completion of the first. The first new building is going to be kitted out with big new lab which will include a 6 figure balance so that some poor sod can have fun weighing dust on filters...

Both new buildings require pile driving for the foundations, and you *know* when they're doing it because the whole bloody building shakes. The director wanted to know if these "vibrations" might upset his shiney new balance...

Lets see... Balance needs protecting from normally unoticable air conditioning currents, pile driving sometimes makes employees nearly fall over. Hmmmmmm!

One of the other challenge chems for this particular test seemed familiar - Aniline, which seemed familiar for a reason I can't recall. I've just looked up an MSDS for it and I think it's one of those chems where you need to wear gloves all the time, instead of most of the time :)

I'm sure this rant has given faith to everyone concerning UK and EU standard testing for protective lab wear ;)

BTW, anyone know how benzene compares to toluene for cleaning off sticky tape residue? We're out of Toluene, but have plenty of benzene...

EDIT: typo

Odd, I thought 100% NaOCl was unstable and decomposed upon concentration?

Anyway, if you have the possibility conduct the experiment in a sealed box and saturate the air with ethylamine before you start the experiment. That way there will be no vaporization of ethylamine out of the solution :)

Ofcourse you must make sure that the ethylamine vapours can NOT reach the other cell half.

Oh, no, pile driving won't affect a balance. You don't really need a two ton block of marble to isolate it from someone walking down the hall next to it or a radioactive ionizer to cancel static attraction... I jest of course.

Benzene is a better solvent (slightly) than toluene accross the board. Due to its toxicity nobody uses it anymore.

I know this is waaaay off topic, but you did ask about stickytape residue. Best thing I've found for that job is a product called Desolv-it. It contains citrus oil so it smells rather nice, it also works wonders for getting all kinds of shit off things e.g. Blutack, masking tape, tar, plasticene, sticky labels ...

What about running a refrigeration coil through the cell holding the Et amine? Keep it liquid at just below its boiling point.

No sense in testing for liquid penetration at a temp/pressure above that which it could actually exist while human hands are in the glove being tested, now is there?

Something you soon realise is that a lot of PPE standards don't make sense...