Shelf Life

[dolphinscales]

Hello everyone
Have a question for the group dealing with as the subject line suggests shelf life of chemicals that have been made up – is there a rule of thumb of when to toss and restart?
Is there a bible that gives some ideas on this?
I have been asked by a student and all I could say was in my experience which does not cut it really does it if you are dealing with the idea of if I win lotto and a newbie comes into the position with no experience how are they going to know.

Thanks in advance for you help with this question.

[Robb]

Hi Dolphinscales,

I is a common Sense thing when it comes to the crunch with the shelf life of chemicals

The solid Chemicals don't really have a defined "Life Span", although I would be very watchful on the chemicals that are anhydrous or the chemicals that are subject to being ruined by mositure.

The gaining of any moisture would be the deciding factor as if any water is present then the Chem would then be deemed useless.

Acids, for example: Hydrochloric Acid when exposed to light for prolonged periods discolours to a yellowish colour, this however does not change its concentration.

ON THE OTHER HAND, Chemiclas or Acids that are made up and constantly used should have a shelf life of about two years, this is because opening and closing plus stirrring of the solution every time the bottle is tipped over whilst stirring, will absorb a little CO₂ from the atmosphere, hence changing the concentration. And over the two year period the concentration would have change quite surprisingly. Although the bottle of the acid will have to be used and not refilled with fresh acid for this to occur.

I hope this has cured a few dubious questions.

Cheers,

Robb.....

[Labbie]

Just to help your self, when we have a new chemical arrive, we do put the date on that chemical, 6/07 so I know it arrived at school in June 2007. With solutions, we have a label on the back of the bottle, and put the date in ink on the label, yes sometimes it gets wet, but it does not matter really, it is only a guide line for me. As too when I made it up.

Hope it helps

[Robb]

Hi All,

Just to re-iterate what pommy has mentioned. It is advantageous to keep track on the chemicals by dating them. It offers some time frame for when chemicals arrive, because there may be so many.

Shelf life of most chemicals though will be alright, as I have explained previously..

Cheers,

Robb....

[m]

Hi all

I also record in texta the date chemicals arrive
a) to sort which is new/old and rotate stock accordingly
b) to estimate how long it takes to get around to using it so as to help with reordering quantities next time

I also stick a little date label on the lid of solutions made so I can see how old it is. Occassionaly I find solutions that have been standing there unused for some time. This tells me how much of a solution I should make up, although usually I like to only make up just enough for immediate use. Dont like haveing loads of solutions laying around the place.

maria

[estelle]

Not sure if this helps anyone but when I get new chemicals I put the appropriate usage dots on them and then cover the label with contact because some of the printing seems to wear off so this saves that problem. I also put a purchase date on the container like other lab assistants and on the lid I write what shelf or storage area it comes from so it is easier to return to the right area. Another idea that I find helpful is to write in perm pen on the back of the container some of the measurements that I seem to always use for that particular chemical.
e.g. 100mL 0.1M 0.256gms ect saves me having to work it out each time. It doesnt' take much space or time to do.
Estelle