• Blog Stats

    • 77,682 hits
  • Archives

  • Enter your email address to subscribe to this blog and receive notifications of new posts by email.

    Join 157 other followers

  • Copyright notice

    This blog entry and all other text on this blog is copyrighted, you are free to read it, discuss it with friends, co-workers and anyone else who will pay attention.

    If you want to cite this blog article or quote from it in a not for profit website or blog then please feel free to do so as long as you provide a link back to this blog article.

    If as a school teacher or university teacher you wish to use content from my blog for the education of students then you may do so as long as the teaching materials produced from my blogged writings are not distributed for profit to others. Also at University level I ask that you provide a link to my blog to the students.

    If you want to quote from this blog in an academic paper published in an academic journal then please contact me before you submit your paper to enable us to discuss the matter.

    If you wish to reuse my text in a way where you will be making a profit (however small) please contact me before you do so, and we can discuss the licensing of the content.

    If you want to contact me then please do so by e-mailing me at Chalmers University of Technology, I am quite easy to find there as I am the only person with the surname “foreman” working at Chalmers. An alternative method of contacting me is to leave a comment on a blog article. If you do not know which one to comment on then just pick one at random, please include your email in the comment so I can contact you.

What is prussian blue ?

OK you good people out there, I have written a lot about Prussian blue. You might want to see what it is. Now sadly despite the marvels of modern science we do not have a clear picture of the atoms in Prussian blue.

One of the forms of Prussian blue has been crystallised, this cubic solid is very crystalline but very disordered, not good ! It has the empirical formula {Fe2(CN)6(H2O)6}n and the waters and cyanides are arranged in a random manner, which makes things complex. This form is not a true Prussian blue as it has no potassium ions but it is a good model for what Prussian blue is.

Disordered solids, they can make life very hard. A nicer solid exists, it is a 1D coordination polymer with the formula of [Me4N][(Fe(CN)6Mn(H2O)4].H2O.

This solid has linear chains of manganese and iron atoms with waters on the manganese atoms and cyanide groups bonding to the iron through carbon, some of the nitrogen lone pairs bond to the manganese thus giving us a coordination polymer.

Overall the chains have a negative charge, for every iron atom the chain has one additional atomic charge unit. Now as we need to maintain electro neutrality we need one cation for each iron. In the case of Prussian blue it is potassium while in our model it is a tetramethyl ammonium cation.

What the Prussian blue does is to act as an inorganic version of an ion exchange resin, while it is in the gut it exchanges caesium (or thallium(I)) cations for the potassium cations which it gives up.

Here is a picture of one of the repeat units of the Prussian blue; you can see the four waters on the manganese and one extra which just fills up space.

Asymmetric unit of Prussian Blue mimic with iron and manganese in it

There units link together to form long chains which make up the structure of one of the forms of Prussian blue.

1D coordination chain in the Prussian Blue mimic

Advertisements

Go on, Have your say !

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: