I have to prepare a demo for my chemistry class, and while I hear lots of people talking about blowing things up, I'm settling for something
controlable and slow, yet striking and bold.
There's a demo about ligands I like a lot, where potassium (or sodium) thiocyanate and iron sulphate are mixed to give a blood red iron complex.
I was wondering if the same ligand reaction would work with sodium cyanate (not cyanide) instead of thiocyanate, and what colour will it yield.
I know I can also use sodium cyanide to make a blue ferricyanide complex, but I don't feel like doing a demo that requires the use of a nasty poison.
Has anyone worked with cyanate? I can't find much info about them, other than they exist. Do they yield nice colours?
[Edited on 1-10-2012 by White Yeti]plante1999 - 9-1-2012 at 15:34
I worked with Thiocyanate ligan and I was realy amazed of wath I can get(complex) for the price of the chemicals(My favorite section of chemistry is
coordination chemistry). If you reduce sodium cyanate with carbon You will get sodium cyanide , filtering the sol and adding a base like Na2CO3 and
boiling the solution with exess sulfur will give thiocyanate than filtration and acidification will give you a sol. of sodium thiocyanate.
Each ligant have there own proprety , cyanate should not give same effect.
[Edited on 9-1-2012 by plante1999]kavu - 9-1-2012 at 15:39
Just to get the terms right. Ligand is a molecule or an ion that binds to the metal ion. The formed species is called a coordination complex or
complex for short. Aqueous coordination chemistry of iron is quite restricted as many basic ligands form iron hydroxides. A blue color can be achieved
by mixing aqueous solutions of potassium hexacyanoferrate(II) and Fe³⁺. Formation of KFe[Fe(CN)6] will colour the solution deep blue. The
colour is thought to be due to charge transfer between iron(II) and (III) in the complex. I don't recall seeing iron cyanate complexes mentioned to be
particularly colorful. Rather more joyful coordination compounds can be made from nickel(II) and copper(II). A good demo would be to form iron(III)
thiocyanate as you described and then make the color vanish by adding in sol. of F⁻ or PO4³⁻. They form a more stable coordination
compound with iron and the -SCN ligands are exchanged for -F⁻.
[Edited on 9-1-2012 by kavu]plante1999 - 9-1-2012 at 16:28
I prefer cobalt III chloride amine complex. The coordination valence of Cobalt which is 6 make a realy large coordination chemistry. Chromium III have
also a great coordination chemistry.
[Edited on 10-1-2012 by plante1999]ScienceSquirrel - 9-1-2012 at 17:20
Iron is a lot less toxic than cobalt which is a lot less toxic than chromium.
Safety can be a big issue in chemistry demonstrations by non staff members or at science fairs, etc.
No hazard issues, spills can be just mopped up, waste can be put in the trash or poured down the drain are big pluses.White Yeti - 9-1-2012 at 18:13
Iron is a lot less toxic than cobalt which is a lot less toxic than chromium.
Safety can be a big issue in chemistry demonstrations by non staff members or at science fairs, etc.
No hazard issues, spills can be just mopped up, waste can be put in the trash or poured down the drain are big pluses.
Yep, that's why I don't want to use those other transition metals even though I could. Copper is also one I can use, but unless someone can convince
me otherwise, I think copper is a little dull, only changing from one shade of blue to another.
I wanted to perform the chameleon reaction with permanganate, but the colour changes are not dramatic enough to capture the attention of some pretty
distracted chemistry students. I don't think there's anything worse than performing a demo and have people lose interest and start to talk amongst
each other.plante1999 - 9-1-2012 at 18:18
Make thiocyanate complex of iron , simple and effective.White Yeti - 9-1-2012 at 18:30
Make thiocyanate complex of iron , simple and effective.
I don't have thiocyanate, I'm curious if cyanate works as well, curiosity is the driving force behind scientific inquiry and experimentation. If you
stay within the bounds of the things you know, you will never try anything new.
I'm going to buy some urea in a few days, whereas I will make my own sodium cyanate and see what happens when a solution of iron ions is added. Enough
armchair speculation, has anyone tried this or not? Does anyone have a textbook or PDF that clearly states that this has been done before, and the
outcome?plante1999 - 9-1-2012 at 18:41
. Enough armchair speculation, has anyone tried this or not? Does anyone have a textbook or PDF that clearly states that this has been done before,
and the outcome?
Wath does you want to know? Sodium cyanate is easy to make from Na2CO3 an Urea , but I reacomend to make thiocyanate from it.Magpie - 9-1-2012 at 18:45
There is a color test for cyanate using Co++. The positive test gives a blue color.
Wath does you want to know? Sodium cyanate is easy to make from Na2CO3 an Urea , but I reacomend to make thiocyanate from it.
How would you go about converting cyanate to thiocyanate? I have not seen any literature on the subject. I saw that I could convert cyanide to
thiocyanate by reacting with elemental sulfur, but nothing on cyanate to thiocyanate.plante1999 - 9-1-2012 at 19:02
If you reduce sodium cyanate with carbon You will get sodium cyanide , filtering the sol and adding a base like Na2CO3 and boiling the solution with
exess sulfur will give thiocyanate than filtration and acidification will give you a sol. of sodium thiocyanate.
[Edited on 9-1-2012 by plante1999]
BromicAcid - 9-1-2012 at 19:49
Believe it or now you can not only work out on paper if a coordination complex will form, but what color it will be. When I was freshly learned of
coordination chemistry it wasn't all that hard using the 'back of the envelope' method as my teacher called it which gave surprisingly good accuracy
for reducing so many variables down to just a few numbers to crunch. Unfortunately that information has left me sometime in the last 6 years...
