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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 15 May 2022 14:18 
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Volodymyr wrote:
Попадание внутрь, вдыхание аэрозоля или паров хромового ангидрида.

То есть его можно спокойно держать в руках без вреда?

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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 15 May 2022 15:27 
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Контакт с кожей не допускается. К другим реактивам это тоже относится.

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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 15 May 2022 15:41 
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Volodymyr wrote:
Контакт с кожей не допускается. К другим реактивам это тоже относится.

Как нам сказали на лекции: "да бензол немного канцерогенен, но мы руки в нем мыли и ничего не случилось"
Так и здесь - если попадет на руки смыть и не париться.

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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 21 Jun 2022 11:52 
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Ammonium trichromate - (NH4)2Cr3O10.


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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 07 Jul 2022 14:49 
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kind of molybdenum blue. made from reducing MoO3 with atomic hydrogen. contains for example Mo8O23·xH2O Mo4O11·xH2O.


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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 07 Jul 2022 22:17 
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vano34 wrote:
kind of molybdenum blue. made from reducing MoO3 with atomic hydrogen. contains for example Mo8O23·xH2O Mo4O11·xH2O.

Now it is believed that the reducing agent is the surface of the metal (for example, zinc), not atomic hydrogen.

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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 08 Jul 2022 09:13 
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I have never researched this topic. and what is it?


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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 08 Jul 2022 09:26 
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https://en.wikipedia.org/wiki/Nascent_hydrogen

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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 08 Jul 2022 11:53 
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I know about it. but I never understand what is different.


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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 08 Jul 2022 12:09 
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Old conception:
1) Zn + 2H+ = Zn2+ +2H
2) Mo(VI) + H = Mo(V) + H+

New conception:
Zn + 2Mo(VI) = 2Mo(V) + Zn2+

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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 09 Jul 2022 09:23 
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so its zinc issue not hydrogen?


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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 09 Jul 2022 11:20 
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The reducing agent is zinc (or other metals), not hydrogen.

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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 21 Jul 2022 21:49 
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Hello! weeks ago I made molybdenum metal from trioxide thermite. I washed the metal with hydrochloric acid, there was some aluminum. then maybe a week ago I made powder from larger pieces. it was easy to crack them. when I made powder again I washed it with hydrochloric acid. I am just interested in the valence of molybdenum in this green solution. it's hard to see the color in a beaker because it's opaque, it has a very dark green almost black color.

the second photo is just this molybdenum, I just added a few drops of 1,10-phenanthroline solution and made a complex.


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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 21 Jul 2022 22:36 
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vano34 wrote:
I am just interested in the valence of molybdenum in this green solution.

Compounds of Mo(III) may be green.

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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 21 Jul 2022 23:23 
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thank! I have never worked with trivalent molybdenum, I always thought that it is hard to make solid trivalent salt. what do you think can I make any trivalent salt easily?


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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 22 Jul 2022 11:57 
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I think that it will not be possible to precipitate threevalent molybdenum salts from an aqueous solution. Threevalent molybdenum is a very good reduction agent.

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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 22 Jul 2022 12:04 
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Yes, I thought that. it's very hard. Today I made a more concentrated solution of the phenanthroline complex. a small amount of dark red powder precipitate. do you think maybe it is a trivalent complex?


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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 22 Jul 2022 12:30 
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It's possible, but I don't think so. Most likely red powder is Mo(V) or Mo(VI) complexes.

I read a monograph on the analytical chemistry of molybdenum. There was no information about Mo(III)-complexes with phenanthroline in the book (in russian language http://chemistry-chemists.com/book5/him ... ov/Mo.djvu).

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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 22 Jul 2022 12:40 
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I was wrong:

Extractive spectrophotometry of the molybdenum (III) 1,10-phenanthroline thiocyanate and 2,2'-bipyridyl thiocyanate complexes // Talanta. 1973 Mar;20(3):342-6
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 Post subject: Re: Хром, Молибден, Вольфрам и их соединения
PostPosted: 22 Jul 2022 12:43 
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thanks! I also dissolved molybdenum powder in an HF-HNO3 mixture, the solution was dark pink, I've never seen molybdenum with this color in the solution. very strange and also interesting element.

I'm just thinking about molybdenum III in heteropolymetalate, I mean as heterometal not in polyoxometalate anion, like cobalt III. I've read that polyoxometalates can stabilize heterometal in an unstable oxidation state, for example, Nickel IV. unfortunately very poor information. I have old soviet books, the best inorganic books, but it's also hard to find such information here.

thanks for the research! As far as I can see you are finding good researches, do you have any tips? I personally use sci-hub, but it's still difficult to get the information I need.


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