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Romix
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Quote: Originally posted by Romix  | I should receive 25g of Ammonium Molybdate in the next couple of days.
First I'll test it on K2HPO4 in 3 different test tubes, first test tube K2HPO4 solution as it is not adding nothing to it, other 2 I'll acidify, one
with HNO3 and other with strong Acetic acid.
Then if any yellow precipitate will form, I'll test Alkali Acetates with it and what is dissolved in bones. |
Bullshit reaction from youtube, no precipitate in neither of a test tubes!!!!!!!!
[Edited on 15-5-2024 by Romix]
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bnull
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That's odd. Either you made a mistake or there is no phosphate at all (!). Or else the ammonum molybdate that came is not real ammonium molybdate.
Very odd.
Precipitation of phosphate as ammonium phosphomolybdate is one of the standard tests.
An alternative is given on pages 471-472 of Hamilton & Simpson's "Quantitative Chemical Analysis" (https://archive.org/details/quantitativechem00hami; you need an account to borrow). It uses hydrochloric and nitric acids, ammonium hydroxide, and
magnesium chloride.
If you want to try the molybdate test again, it is on pages 469-470 of the same book, with the preparation of the ammonium molybdate solution
described in the Appendix. As a control, use Coca-Cola, it has phosphoric acid.
Edit: Here's the link to the reference at the bottom of page 472 of the book: James I. Hoffman and G. E. F. Lundell, "Determination of phosphoric anhydride in phosphate rock, superphosphate, and 'metaphosphate'".
[Edited on 15-5-2024 by bnull]
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Romix
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| Quote: Originally posted by bnull |
That's odd. Either you made a mistake or there is no phosphate at all (!). Or else the ammonum molybdate that came is not real ammonium molybdate.
Very odd.
Precipitation of phosphate as ammonium phosphomolybdate is one of the standard tests.
An alternative is given on pages 471-472 of Hamilton & Simpson's "Quantitative Chemical Analysis" (https://archive.org/details/quantitativechem00hami; you need an account to borrow). It uses hydrochloric and nitric acids, ammonium hydroxide, and
magnesium chloride.
If you want to try the molybdate test again, it is on pages 469-470 of the same book, with the preparation of the ammonium molybdate solution
described in the Appendix. As a control, use Coca-Cola, it has phosphoric acid. |
K2HPO4 and Ammonium Molybdate both are bought from APC pure.
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EF2000
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| Quote: Originally posted by Romix | | Quote: Originally posted by Romix | I should receive 25g of Ammonium Molybdate in the next couple of days.
First I'll test it on K2HPO4 in 3 different test tubes, first test tube K2HPO4 solution as it is not adding nothing to it, other 2 I'll acidify, one
with HNO3 and other with strong Acetic acid.
Then if any yellow precipitate will form, I'll test Alkali Acetates with it and what is dissolved in bones. |
Bullshit reaction from youtube, no precipitate in neither of a test tubes!!!!!!!!
[Edited on 15-5-2024 by Romix] |
It's not a bullshit reaction. It is widely used as test on phosphates.
You are, most likely doing it wrong. See Vogel's Qualitative Inorganic Analysis, pages 200-201 in 6th edition: https://archive.org/details/vogelsqualitativ0000voge/page/20....
Reaction involves 12 molybdate ions per one phosphate, and large complex molecule is formed (with interesting structure). It also involve 23 H+ ions. So the molybdate reagent should be added in excess and should be
strongly acidic. Vogel says 2-3 ml to 0.5 ml of phosphate solution. Lab manual in our university says 5-6 drops of "molybdenum liquid"Note
to 1-2 drops of phosphate solution, with heating. I, an absolute dummy, peformed that reaction during lab practice and got the precipitate.
Note: "molybdenum liquid" (literal translation from Russian) is a solution of ammonium molybdate, ammonium nitrate and 6 M nitric acid (~40% w/w).
Vogel also says that ammonium nitrate accelerates the precipitation of phosphomolybdate complex.
[Edited on 15-5-2024 by EF2000]
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Romix
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Yes, did something wrong the first time I did it, probably not put enough of Ammonium Molybdate in it.
Test works with pure phosphates, will it work with phosphates in less then 10% of mass with Calcium Nitrate or Alkali Acetates being the rest?
[Edited on 18-5-2024 by Romix]
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