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