Megamarko94
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expiring dates on chemicals.?
some of my chemicals have expiring date on them.like i have potassium hydroxide from chemical company bought,and it has expiring date on it.. does
that mean it degrades or what???
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not_important
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Absorbs water, CO2, and other acidic gases from the air. Unless you have a really air-tight container it will slowly become wet and contaminated with
the salts formed from the acids.
However it's also a CYA action by the supplier so as to avoid complaints from someone who lets a bottle sit on the shelf for a quarter century and
then expects it to be in perfect condition.
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ScienceSquirrel
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You have to be sensible about these things.
For instance, something like sodium chloride is usable indefinitely if kept dry.
If it is a white free flowing powder or crystals when you open the container then it is fine.
Potassium hydroxide that is going off due to absorption of moisture and carbon dioxide from the air will form clumps and there will be powdery
potassium carbonate sticking the pellets or flakes together.
As an aside we like our cheese a bit on the ripe side so we buy it when it is cheap because it is close to the best before date and then keep it for a
few weeks longer. A good Brie is soft but not overly runny in our opinion, the cat will still snack on it when it is really manky and that can be two
months over the generous French use by date!
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peach
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There's a use by date on jars on honey.
Honey does not go off.
It's biologically impossible for things to grow in it due to the lack of water and the high osmotic pressure caused by the sugars.
Philadelphia cream cheese spread however... that is the item, by far, that I most commonly open planning to enjoy a tasty sandwich to discover an
impressive garden of fuzz has grown. The colours are quite varied, from greens and blacks to orange. I doubt even the squirrels kitty would eat it,
mine won't.
But as the others say, it's partly to get you off their case and partly that some things do degrade over time.
KOH, I included a graph of that in the make potassium thread. I'd simply poured some out onto the balance and measured the weight change over time.
Whether or not it's important is a different thing. My tub of KOH was years old and I'd taken not a lot of care of it. I used it to do the washing up,
so it'd be sat open on the side with the steam from the tap blowing past for half an hour.
I'd sometimes see visible droplets of moisture collecting on the surface. Eventually, I spilt some pineapple and coconut fruit juice in there too. So
it clearly wasn't technically dry or clean any more. But concentrated solutions would still rip through aluminium in a few tens of seconds. It was
fine for anything not particularly important.
The most common source of things going bad is their contact with the atmosphere (moisture and oxygen especially), light and heat.
The most practical way to get a completely air tight seal on something, that is still usable, is to crimp rubber seals over the tops, which then get
punctured with syringes to withdraw the product. Sigma do this on things that need to remain anhydrous and call it 'Sure Seal'. This means the bottles
don't need opening in a super expensive, outer space glove box.
They are also kind, and honest, enough to publish graphs showing the leak rate of the seal, because they do leak.
The only way to hermetically seal something for good is to put it in an ampoule (vial) and melt the glass closed (under pure argon). This is why ultra
pure samples come in little ampoules like something out of Resident Evil. Similar thinking is applied to injectable drugs, which must remain in their
gamma sterilised state for years before going directly into someone's bloodstream.
To solve the light problem, the glass is made actinic (amber, brown) so it doesn't transmit much IR or UV. Both of those tend to be absorbed by
orbiting and bonding electrons.
Temperature, that's up to you to deal with. Absolute zero will do fine. In practice, we've got to be a bit more realistic than that and live with the
knowledge that yes... the molecules probably are vibrating.
The only remaining problem is that everything in the universe is technically unstable. Eventually, everything will decompose back towards a uniform
grey goo, and then probably explode again.
H. G. Wells thought about this and describes it beautifully in The Time Machine, as the protagonist travels more and more ridiculous jumps into the
future and sees the world falling apart at a base level - he visits an abondoned library, far in the future, and the glass has run out of the windows
on the cabinets.
Phillip K. Dick described it as kipple in Do Andriods Dream of Electric Sheep (more commonly known as Blade Runner). The horrible, dirty environment
Deckard lives in is representative of the world decaying once the active upkeep is given up by the humans.
In the same sense, you need to provide upkeep for the more rapidly decaying chemicals. As they would not normally exist in those forms in nature, if
at all; you won't find many lumps of pure caesium digging up the garden. A human has been involved in disrupting the flow of things to produce the
KOH, and put lots of energy into doing it. The KOH now wants to return to the way it was before the human upset the course of events; it will try
turning it's self back into a solution and back into a salt, where it's more stable.
This is called entropy and the uncertainty principle in science.
Similarly, when you accelerate the decay of something, you can get energy back out; a nuclear reactor is a good example of fundamental, artificially
accelerated, nuclear decay.
Some of the more recently discovered elements exist for less than second after their creation, despite them being made in the most ideal conditions
science can manage. Their nuclei are just too fat and bubblery to be bothered staying in one piece. Predictions have been made that stability will
return after progressing to even fatter ones. Those elements unstable now will likely be stable in a few million or billion years, as the universe
changes. The elements we have now would not have been stable towards to the start of the universe, when only things like hydrogen were simple enough
to exist.
What we consider common on the periodic table now is not a universal constant. The table is scanning through the elements as the universe ages.
Hydrogen is being fused down into heavier elements, depleting it's abundance and increasing the others.
Physics has an even harder time with this, because some of the subatomic particles last for such short periods of time it's hard to even tell they
were there to begin with; nano, pico, femto and atto second events.
For some things, like the salts used to dry solvents out, you can simply give them a roast on the hotplate, in the oven or in a frying pan (never
tried the shake and bake in a pan method myself though). This is even done in some impressive journal papers to make sure the drying agents are as dry
as possible before use.
Other things, like light sensitive organic compounds, you'll actually see going brown over the hours, and it's usually easier to start again or try to
separate the polymers and gunk than to undo the damage.
If it exists normally in nature, it will probably store well. At the same time, it's probably not something you're all that interested in storing;
water stores okay. The salts do as well, because there's over a billion kilos of them floating around in the ocean; so they're happy with being in the
open environment (the more simple alkaline earth metals and halogens that they are composed of are not).
Another point, kind of related to the use by dates, is the purity grades. Some of the stuff on eBay is not only not pure, it's cut with bulking agent.
Conversely, there is some stuff you can buy that's as pure, or more so, than what you'll get as CP grade from the suppliers, but quite a bit cheaper
if it's just bought over the counter in a hardware shop.
Always put the lid back on a container immediately after use if you want to keep it pure.
Tape the threads shut with PTFE tape if it's very sensitive - use gas rated tape and more turns than you would for a pipe.
If you won't be using it for months, run some sticky tape over the cap as well.
[Edited on 12-6-2011 by peach]
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Megamarko94
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thats sort of what i tought because its hygroscopic absorbs water..
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The WiZard is In
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By-guess and By-gosh
I would suspect this method is used for both drugs
and chemicals.
Extracted from
Many Medicines Are Potent
Years Past Expiration Dates
By LAURIE P. COHEN Staff Reporter of THE WALL STREET JOURNAL
Do drugs really stop working after the date stamped on the bottle?
Fifteen years ago, the U. S. military decided to find out. Sitting on
a $1 billion stockpile of drugs and facing the daunting process of
destroying and replacing its supply every two to three years, the
military began a testing program to see if it could extend the life of
its inventory.
The testing, conducted by the U. S. Food and Drug Administration,
ultimately covered more than 100 drugs, prescription and over-
the-counter. The results, never before reported, show that about
90% of them were safe and effective far past their original
expiration date, at least one for 15 years past it.
In light of these results, a former director of the testing program,
Francis Flaherty, says he has concluded that expiration dates put
on by manufacturers typically have no bearing on whether a drug is
usable for longer.
Mr. Flaherty notes that a drug maker is required to prove only that
a drug is still good on whatever expiration date the company
chooses to set. The expiration date doesn't mean, or even suggest,
that the drug will stop being effective after that, nor that it will
become harmful.........
continued at —
http://www.terrierman.com/antibiotics-WSJ.htm
djh
----
The average women would rather have
beauty than brains because the average
man can see better than he can think.
Anon.
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BromicAcid
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Quote: Originally posted by not_important  | | However it's also a CYA action by the supplier so as to avoid complaints from someone who lets a bottle sit on the shelf for a quarter century and
then expects it to be in perfect condition. |
That's it in a nutshell, unless we have a stability study that says otherwise a company will only guarantee it's product so long. I've always been
fond of the steadfast expiration dates on some things, n-hexane usually has a bright sticker on it that warns it's already on it's way to the more
random 'hexanes' grade before it was even sent to you. Also I got a unit of AIBN once that had a warning "Product may become unstable and explode on
prolonged storage", apparently there was no helping it.
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woelen
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I think that for many chemicals the expiry date on the bottle is just a method of suppliers to cover themselves in case something goes wrong with the
chemicals (e.g. inconsistent analysis results, bad yields in syntheses). In practice, however, for the big majority of chemicals the expiry date is
total nonsense.
This expiry date thing, however, also has a sunny side for amateur chemists 
In the UK, but also in Germany, The Netherlands, Poland there are labs who get rid of their 'expired' chemicals to people who then sell these
chemicals again but for only 10% to 20% of their normal price. In this way I obtained 'expired' chemicals for outrageous prices:
- 1 kg of (NH4)2Cr2O7 for only EUR 5
- 500 g of KBrO3 for EUR 6
- 8 g of H2PtCl6 for EUR 50 (still in glass ampoule!)
- 100 g of oxalyl chloride for EUR 5
- and many more
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ScienceSquirrel
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Nous avons une chatte français!
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condennnsa
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I for one find it impossible to completely stop my 35% H2O2's decomposition. I once tried to store it in a tightly capped glass bottle that I washed
the best I could. I saw that it was still decomposing , but i thought that the increasing pressure will stop the decomposition.
Big mistake, the bottle eventually shattered to hundreds of pieces. I left it in my room, so I could've been hurt when it went off, but luckily I was
out at the time.
I now keep my H2O2 in a HDPE bottle with the lid partly unscrewed. It's always bubbling very slowly, but it seems to be happier in plastic than glass.
So I think that H2O2 is one item that does degrade over time.
Has anyone come up with a method to stop the decomposition of H2O2, or keep it very low?
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spong
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H2O2 is definitely a chemical with an expiry date, I had a bottle of 50% peroxide, I should test it and see what it's at now after sitting around in
the garage for years, probably 30 or so, it still stings if I get it on my skin. They have chemicals added to slow the decomposition but none will
completely stop it. It's an equilibrium reaction so you want the oxygen concentration above the liquid to be as high as possible to push the
equilibrium to the left so try and keep a cap on it reasonably tight. My cap has a little hole covered with a film which I think just keeps most of
the oxygen from diffusing out.
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unionised
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It is dangerous nonsense to say that sealing a bottle of H2O2 to keep the O2 in will make it last (measurably) longer.
The equilibrium is massively in favour of decomposition. The pressure would need to be astronomical to force the reaction to slow down.
All you have posted is a tacit recipe for a time bomb.
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ChemSwede
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| Quote: Originally posted by woelen | I think that for many chemicals the expiry date on the bottle is just a method of suppliers to cover themselves in case something goes wrong with the
chemicals (e.g. inconsistent analysis results, bad yields in syntheses). In practice, however, for the big majority of chemicals the expiry date is
total nonsense.
This expiry date thing, however, also has a sunny side for amateur chemists
In the UK, but also in Germany, The Netherlands, Poland there are labs who get rid of their 'expired' chemicals to people who then sell these
chemicals again but for only 10% to 20% of their normal price. In this way I obtained 'expired' chemicals for outrageous prices:
- 1 kg of (NH4)2Cr2O7 for only EUR 5
- 500 g of KBrO3 for EUR 6
- 8 g of H2PtCl6 for EUR 50 (still in glass ampoule!)
- 100 g of oxalyl chloride for EUR 5
- and many more |
An old, but very interesting post. I know I'm new here on the forum, and I also know that people don't really want to out sources where they can get
precious chemicals.
Advise on how to obtain chemicals this way would, however, be greatly appreciated (forum or U2U), since it's an expensive hobby. Do you find expired
chemicals via connections or just on Ebay?
Judging from your website and posts here it seems you're able to get almost every reagent you need. The Netherlands is a much better country to be a
hobby chemist in, than Sweden 
I'm mostly relying on, not always dependable, polish suppliers. OK prices, varying quality.
Here in Sweden I've never heard of labs getting rid of chemicals to people who sell them cheaper.
The price for the chemicals you mention in the post ARE outrageous!
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woelen
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Many of the chemicals I obtained are from personal contacts. I have been in this hobby for 10 years or so with a clearly visible presence on internet
(website, forums) and that has given me the most contacts. People contacted me and I had exchanges with such people, who had interesting contacts.
These are mostly people from the Netherlands and Belgium, but also a few from other countries.
I also have good contacts with a few suppliers in the Netherlands. Sometimes they have big boxes with all kinds of chemicals and I visit them, just
picking out the old stuff and paying only a small amount of money for these.
I do not want to brag, but I really think that my website has helped me quite a lot with obtaining chemicals. I even have had donations of special
chemicals, which I otherwise never could have afforded (e.g. osmium, thallium, beryllium sulfate, a lot of exotic organics). These chemicals were
donated to me, because these people saw my website and were confident that these chemicals were put at good use when I used them for experiments.
At the moment I also use eBay for suppliers in the UK or Poland. Sometimes there are nice chemicals, but the really rare stuff is not on eBay, because
eBay is quite restrictive to what is allowed and what is not allowed.
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kristofvagyok
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I do most (+90%) of my experiments with expired chemicals, mostly 30-40 years expired and they usually work well.
Some, like anilines and sensitive chemicals e.g.: pyrroles, indoles, thiophenes, furanes have to be purified before use but they do not degrade as
much, that it would be worth to buy a new bottle.
I have a blog where I post my pictures from my work: http://labphoto.tumblr.com/
-Pictures from chemistry, check it out(:
"You can’t become a chemist and expect to live forever." |
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phlogiston
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Expiration dates are often taken with a grain of salt also in professional labs, unless they absolutely must conform to a quality system which insists
that they are respected.
I myself have learned to make an exception for cell culture medium though, for which the expiration date really does matter. Also, enzymes definately
do degrade noticeably (although the expiration date is typically very conservative).
All labs every now and then clean up their chemical storage and throw out very interesting and useful chemicals, mainly because there is no need for
them in the forseeable future and storing them all indefinately eventually just fills up the storage with a mess of (sometimes hazardous) chemicals.
Most labs just discard them though (by appropiate means), not sell them or give them away. To individuals it might seem like a huge waste, but the
cost of chemicals, even very expensive ones, is completely negligable compared to the cost of labour/instruments etc. If, at work, I don't trust an
expired chemical, I would order it fresh without any hesitation if it possibly saves me the time of repeating an experiment.
[Edited on 18-10-2013 by phlogiston]
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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