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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Problem of the Week Archive => Topic started by: Borek on March 26, 2012, 08:03:35 AM

Title: Problem of the week - 26/03/2012
Post by: Borek on March 26, 2012, 08:03:35 AM: One of many halogen compounds of a metal known for toxicity of its compounds (high enough to make it a poison of choice in many famous cases, both in fiction and real life) has a molar mass of 1030.3 g/mol.

What is the metal, what is the compound?
Title: Re: Problem of the week - 26/03/2012
Post by: Borek on March 29, 2012, 08:09:38 AM: No one interested in diophantine chemistry?
Title: Re: Problem of the week - 26/03/2012
Post by: fledarmus on March 29, 2012, 09:51:02 AM: You got me. The heaviest metal I can think of that has been deliberately used for poisoning is polonium, and even if PoI₆ existed (which I am not sure of), that only gets to around 972. I'm not an inorganic chemist though - perhaps there is a dimetal halide that fits this description?
Title: Re: Problem of the week - 26/03/2012
Post by: DrCMS on March 29, 2012, 10:45:27 AM: OsAt₄ ?
Title: Re: Problem of the week - 26/03/2012
Post by: Borek on March 29, 2012, 12:21:39 PM: You don't need any fancy elements ;D
Title: Re: Problem of the week - 26/03/2012
Post by: fledarmus on March 29, 2012, 01:33:37 PM: I'm assuming there is nothing in the halogen compound except the halogen and the metal?

Thallium, polonium, mercury, and lead are the metals I know have been used in poisonings. I can't find a sufficiently heavy halide for any of them, however. Cadmium and lead might be added to the list, although I don't know specifically of intentional poisonings with either of these, only accidental ones. Does this jog anybodies thought processes?
Title: Re: Problem of the week - 26/03/2012
Post by: Borek on March 29, 2012, 02:14:45 PM: Quote from: fledarmus on March 29, 2012, 01:33:37 PM
I'm assuming there is nothing in the halogen compound except the halogen and the metal?

Yes, just a metal and halogen.
Title: Re: Problem of the week - 26/03/2012
Post by: DrCMS on March 29, 2012, 08:14:01 PM: Thallium Chloride Tl₄Cl₆ or Tl^I₃Tl^IIICl_₆
Title: Re: Problem of the week - 26/03/2012
Post by: AWK on March 30, 2012, 01:35:06 AM: Journal of Materials Science, vol. 18, issue 10, pp. 3087-3091
Title: Re: Problem of the week - 26/03/2012
Post by: Borek on March 30, 2012, 05:03:52 AM: Quote from: DrCMS on March 29, 2012, 08:14:01 PM
Thallium Chloride Tl₄Cl₆ or Tl^I₃Tl^IIICl_₆

Yes!

When I wrote about "diophantine chemistry" it was a hint - I checked (by brute force) that there are not many compounds fitting the description and having molar mass close to that listed. Of all other Tl_nX_m type formulas the closest one to given molar mass is Tl₃F₂₂ with 1031.11 g/mol, but the formula doesn't look convincing ;) Similarly with other metals, and list of those I checked is very similar to the one posted by fledarmus.

Quote from: AWK on March 30, 2012, 01:35:06 AM
Journal of Materials Science, vol. 18, issue 10, pp. 3087-3091

I found the compound in Physicochemical handbook published in 1962 in Poland by WNT, so it must be known for quite some time. I have a gut feeling it could be easily synthesized in 19^th century.
Title: Re: Problem of the week - 26/03/2012
Post by: fledarmus on March 30, 2012, 07:51:14 AM: I even looked for that one! I missed the subscript when I checked the formula though...

Quote
Tl₂Cl₃
This yellow compound is formulated Tl^I₃ Tl^IIICl₆.^[7]

http://en.wikipedia.org/wiki/Thallium_halides (http://en.wikipedia.org/wiki/Thallium_halides)