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iron standard solutions
Posted: 03 Aug 2020, 10:23
by Kathryn
Hi
Hoping someone can help me out with making standard iron solutions. The chem students are going to be doing the Colorimetric analysis of iron in foods (Pearson) and need standard solutions of iron:
0.0050%
0.0025%
0.0013%
0.0010%
0.0005%
Why doesn't the textbook provide instructions on how to make these???
We did the experiment last year but I can not find the instructions and that teacher has recently moved on. It's definitely above my pay scale to figure this out!
Thanks in advance for your help.
Kathryn
Re: iron standard solutions
Posted: 03 Aug 2020, 12:57
by Merilyn1
I think Pearsons provide on-line notes for the labbie. I've just never worked out how to access them!
Re: iron standard solutions
Posted: 04 Aug 2020, 08:02
by Marama T
Hi Kathryn. I think you work this out as follows. I will assume the percentage is weight of solute/weight of solution. Start with your desired volume of solution. If you need 500mL of each, for example, each solution will weigh 500g. Then multiply the weight of the solution by the percentage required.
0.0050 x 500 = 2.5. In this case, add 2.5g of your iron compound to 497.5mL water.
I don't know which Pearson book to look in - it might help if I could read the prac.
Also, if the percentage is of iron alone then that complicates matters. Get back to me if you need help.
Re: iron standard solutions
Posted: 04 Aug 2020, 12:03
by Wayne
0.0050% is 0.0050g made up to 100mL, so would be 0.025g for 500mL. I am fairly sure if you making standard solutions of iron the percentage will have to be of the iron not of, for example, iron chloride (or whatever other iron salt you are using).
Re: iron standard solutions
Posted: 04 Aug 2020, 12:52
by Marama T
Oh yes! My mistake. It should be 0.0050 x 5, not 500. Thank you, Wayne. That'll teach me for doing calculations first thing in the morning.
Re: iron standard solutions
Posted: 04 Aug 2020, 13:20
by Kathryn
Managed to find the calculations from last year - it is more complicated than just weighing out a percentage as they have to be made from combining potassium thiocyanate and iron nitrate. If anyone is interested I will put up what I am doing.
Re: iron standard solutions
Posted: 06 Aug 2020, 10:51
by doconnor
this is what we did last year
make up a fresh solution of FeCl3 (iron 111 chloride) 5%
0.5g 10ml H2O This is solution A
1ml solution A in 999ml H20 = 0.005% = solution B
then dilute solution B
0.0025% 50/50
0.0013% 25/75
0.0010% 20/80
0.0005% 10/90
hope this makes sense
Delma