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Topic: Sodium Borohydride getting stuck to weigh paper  (Read 486 times)

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Offline tusk

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Sodium Borohydride getting stuck to weigh paper
« on: February 09, 2024, 09:17:56 PM »
Does anyone know how to handle sodium borohydride (or any chemical for that matter) getting stuck to the weigh paper? I have a very small amount I want to add to my reaction, and the powder is sticking to the weigh paper screwing up the amount I tried to add.

I guess I want to know if there is a specific type of weigh paper that things stick less to or something I could do to prevent the sodium borohydride from sticking to it in the first place NOT a workaround like pouring solvent down the weigh paper.

Online Borek

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Re: Sodium Borohydride getting stuck to weigh paper
« Reply #1 on: February 10, 2024, 05:26:48 AM »
There are several types of weighing glass, have you considered using them?
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Offline Babcock_Hall

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Re: Sodium Borohydride getting stuck to weigh paper
« Reply #2 on: February 10, 2024, 02:19:23 PM »
We sometimes weigh a reagent into a small, oven-dried flask and dissolve in an appropriate solvent.  Then we add the solution via a syringe to a dropping funnel or right into the reaction flask.  That may not be applicable in your case.

Offline rolnor

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Re: Sodium Borohydride getting stuck to weigh paper
« Reply #3 on: February 11, 2024, 04:15:46 AM »
These type of questions are important, org chem is very practical, you need both theoretical and practical skills or you will fail. paper is not good for this purpose as pointed out

Offline tusk

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Re: Sodium Borohydride getting stuck to weigh paper
« Reply #4 on: February 11, 2024, 02:38:41 PM »
Hello, I am trying to reply to people that posted back, but don't know how to do that, so Im just writing a reply to my topic in hopes everyone who posted will see it.

@Borek: I looked up "weighing glass" and found "glass weighing boats" and "glass weighing funnels." I dug through the glassware drawers in our community lab and I actually found one of them. And used it! The sodium borohydride did not stick very much, and I was able to tap the glass funnel against the neck of the reaction flask, which helped dislodge most of any stuck pieces. Then I sprayed just a tiny bit of water on it to get remainder. So easy and so satisfying to have a good solution! Thank you!

@Babcock_Hall - I was thinking I was going to do this if I didn't find another way...I was nervous about dissolving it in water before it got inside the reaction flask. Also didn't want to get residue stuck in pipet or have to wash pipet and add more water to the reaction flask. But it probably would have served just fine. Thank you for the idea.

@Rolnor - Thanks for your kind note about importance of practical skills. I definitely want to know as many as I can!

Online Borek

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Re: Sodium Borohydride getting stuck to weigh paper
« Reply #5 on: February 11, 2024, 04:14:29 PM »
Hello, I am trying to reply to people that posted back, but don't know how to do that, so Im just writing a reply to my topic in hopes everyone who posted will see it.

Just click "quote" instead of "replay".
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Offline rolnor

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Re: Sodium Borohydride getting stuck to weigh paper
« Reply #6 on: February 12, 2024, 12:30:36 AM »
Hello, I am trying to reply to people that posted back, but don't know how to do that, so Im just writing a reply to my topic in hopes everyone who posted will see it.

@Borek: I looked up "weighing glass" and found "glass weighing boats" and "glass weighing funnels." I dug through the glassware drawers in our community lab and I actually found one of them. And used it! The sodium borohydride did not stick very much, and I was able to tap the glass funnel against the neck of the reaction flask, which helped dislodge most of any stuck pieces. Then I sprayed just a tiny bit of water on it to get remainder. So easy and so satisfying to have a good solution! Thank you!

@Babcock_Hall - I was thinking I was going to do this if I didn't find another way...I was nervous about dissolving it in water before it got inside the reaction flask. Also didn't want to get residue stuck in pipet or have to wash pipet and add more water to the reaction flask. But it probably would have served just fine. Thank you for the idea.

@Rolnor - Thanks for your kind note about importance of practical skills. I definitely want to know as many as I can!

You know that water will react with sodium borohydride? THF can be better to wash the weighing funnel. Nice that you found the glassware you needen!

Offline Babcock_Hall

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Re: Sodium Borohydride getting stuck to weigh paper
« Reply #7 on: February 12, 2024, 10:41:04 AM »
tusk,

Rolnor probably has much more experience than I do with sodium borohydride, but this reagent sometimes prepared in ethanol and used promptly.  IIUC the rate of decomposition varies with the choice of which alcohol is used.  We have one weighing funnel with a flat side and a 19/22 joint.  The idea is to weigh out a reagent on the flat side and then add the compound to a reaction flask.  One could then use a spatula to push or use a solvent  to rinse sticky material into the reaction flask.  I don't see this particular piece of glassware in all laboratories, however. 

Offline Babcock_Hall

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Re: Sodium Borohydride getting stuck to weigh paper
« Reply #8 on: February 12, 2024, 10:58:46 PM »
https://pubs.acs.org/doi/pdf/10.1021/ja01628a044 (from the laboratory of Herbert C. Brown)

Within this paper is some data on decomposition rates of sodium borohydride.

Offline rolnor

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Re: Sodium Borohydride getting stuck to weigh paper
« Reply #9 on: February 13, 2024, 04:23:06 PM »
Nice paper, after 100min ca 10% of NaBH4 in ethanol is hydrolyzed. I can remember wrong, but in water its less stable.

Offline wildfyr

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Re: Sodium Borohydride getting stuck to weigh paper
« Reply #10 on: February 13, 2024, 07:45:35 PM »
Much less stable in water. Using alcohols is a great choice

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