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Author: Subject: Best way to check for active content of old borohydride?
myr
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[*] posted on 2-1-2022 at 13:10
Best way to check for active content of old borohydride?


I have a bottle of about 50g of sodium borohydride (from Russia fwiw) that has been sitting around for a few years since I bought it, and presumably before I bought it too. What's the best way to determine how much borohydride is actually in it? I would expect some decomposition into boric oxides and other crap since it was produced.
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Texium
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[*] posted on 2-1-2022 at 14:53


Run a reaction with it. Something like benzophenone or acetophenone would be an ideal substrate. Run the reaction with just 1 equivalent of borohydride, follow it by TLC, see how much more you have to use to get it to go to completion.



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Bedlasky
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[*] posted on 2-1-2022 at 18:31


Practically any oxidimetric titration (cerimetry, manganometry, dichromatometry, bromatometry, iodometry). Argentometry (Fajans method) is also way to go, but oxidimetric methods are cheaper. Bromatometry is the least problematic method - KBrO3 is primary standard, so you don't need to standardize solution. And you also don't need a indicator, first excess of bromate will react with bromide to form bromine, which is well visible.



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tyro
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[*] posted on 2-1-2022 at 21:44


This may be the same as Bedlasky referenced, but his was mentioned in another thread on borohydride:

https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
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[*] posted on 5-1-2022 at 07:18


Direct Volumetric Assay of Sodium Borohydride and Potassium Borohydride
10.1021/ac60077a054

Analytical monitoring of sodium borohydride
10.1039/c2ay26077h

"Methods for monitoring NaBH4
Numerous applications of NaBH4 have urged the need for
development of a simple, fast and accurate method for its
qualitative and quantitative determination. Still, finding a
simple and reliable analytical method for NaBH4 monitoring
represents something of a challenge. The amount of NaBH4 can
be determined gasometrically, by the most commonly used
hydrogen evolution method,23,24 or volumetrically. 25,26...."

23. W. D. Davis, L. S. Mason and G. Stegeman, J. Am. Chem. Soc.,
1949, 71, 2775. <-Analysis,purification

24. J. A. Krynitsky, J. E. Johnson and H. W. Carhart, Anal. Chem.,
1948, 20, 311.

25. D. A. Lyttle, E. H. Jensen and W. A. Struck, Anal. Chem., 1952,
24 1843.

26. S. W. Chaikin, Anal. Chem., 1953, 25, 831.

Attachment: Analytical monitoring of sodium borohydride_c2ay26077h.pdf (526kB)
This file has been downloaded 52 times

Attachment: Direct Volumetric Assay of Sodium Borohydride and Potassium Borohydride_ac60077a054.pdf (275kB)
This file has been downloaded 50 times

Attachment: davis1949.pdf (850kB)
This file has been downloaded 54 times

Attachment: krynitsky1948.pdf (255kB)
This file has been downloaded 46 times

Attachment: lyttle1952.pdf (254kB)
This file has been downloaded 45 times

Book:
Hydrides of metals and metalloids :
a literature search /
Tufts University. 1960
https://catalog.hathitrust.org/Record/100961039


[Edited on 5-1-2022 by Mush]
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