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Question Fresh Solutions

5 months 3 weeks ago #41402 by Cerberus
Hi all,

Am setting up the Testing for Cations with sodium hydroxide expereiment and flame test experiments (Splints type) and one of the teachers is pracctically demanding that all the chemicals are made up fresh.
Said to teacher that I'm testing the older stock to see if they'll work but they still want the chemicals made up fresh.
Just wanted to know if someone with better chemistry knowledge than me can tell if its really worth making up all the solutions fresh for all the lessons.

Thanks C.

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5 months 3 weeks ago #41406 by SteveKeys
What defines "Fresh"?

Made an hour ago? Made that morning? Made the same day? Made 3 months ago?

If they haven't specified what 'Fresh' means then it's left up to you to interpret as you see fit.

Personally I would say Fresh in this case would mean fresh enough to work safely and satisfactorily - so once you've tested them, like you said you were going to, then you will have your answer as to whether they are 'Fresh' or not.
The following user(s) said Thank You: Cerberus

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5 months 3 weeks ago #41407 by Cerberus
Thank you, that was what i was thinking, you comfired what was in my head already and will have to remember that responce for the next time that the teachers ask this :)

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5 months 3 weeks ago #41410 by Baldilocks
The only problem that I can see with this is that "yesterday's samples" may have had a previously used splint shoved into it, thus giving spurious results.

The solution to this is to organise the work-flow so that it cannot happen or to issue tiny amounts of each solution so that yesterday's solutions are discarded and ''fresh" solutions (ie, not previously issued) are used.

Ian

“Do not believe everything you read on the Internet.” -Abraham Lincoln

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5 months 2 weeks ago - 5 months 2 weeks ago #41411 by bsimmo
they don't need to know. Just clean the bottles up a bit ;-)

If they look off ("moulds"), or the Iron(II) or Iron(III) looks pale, then you may need to redo them or filter/sieve the "growths" out.
Ours can be over a year old otherwise and still be perfectly fine.


That's if I've remembered the right practical, it's Monday morning!

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5 months 2 weeks ago #41412 by AndyG
Isn't "fresh" when it is insisted you have to fill and label 16 60ml bottles so that 5 can be returned unused, 8 with only a few ml used and 4 cross contaminated with a "made up wrong, don't work" note ... when the entire class only really needed 60ml between them?
Or am I misinterpreting some requests for "fresh" solutions? :-(

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5 months 2 weeks ago #41413 by Kasey
I'm with bsimmo on this!

Clean the bottles up, inspect for contaminants and send them out as fresh.

As long as they work, fresh is what you say it is!
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3 months 3 days ago #41456 by DavidS
What i used to do many moon's ago was just make enough for each occasion then remake but use the same bottles each time

It is best to remember that when you are up to your waist in Alligators that your original intention was to drain the swamp!

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