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Author: Subject: White growth on unopened container of chlorotrimethylsilane
DReed123
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[*] posted on 26-2-2021 at 12:28
White growth on unopened container of chlorotrimethylsilane


I have a white, moldy-like substance that has been growing nearing the cap of an unopened glass container filled with TMSCL. It has spread to form a thin, powdery coating on all of the other containers of organic reagents it is stored with. This substance appears to have a corrosive effect on glass, but leaves plastic containers and metal containers unaffected. I'd like to know what it is before I go about cleaning it up.
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njl
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[*] posted on 26-2-2021 at 12:53


I envy your access to silanes. Pictures would help more experienced members help you. My first guess would be either very fine silica or an intermediate in the decomposition of TMSCL to silica. Hydrolysis of TMSCL would yield HCl which would likely react with metals, so not really sure.



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DReed123
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[*] posted on 26-2-2021 at 13:50


I got this answer on stackexchange. Seems to make sense. I just wrapped the cap with PTFE tape and Parafilm and noted trace liquid on the green adhesive wrapping the manufacturer had used. So I definitely think there was a leak:

"Chlorotrimethylsilane, like other organosilicon compounds, is easily attacked by nucleophiles and readily hydrolyzes in air yielding hydrogen chloride:

2Me3SiCl(l)+H2O(l)⟶Me3Si−O−SiMe3(l)+2HCl(g)

Hydrogen chloride reacting with traces of ammonia NH3 in the air builds up white solid ammonium chloride NH4Cl depositing on the nearby surfaces.

Also, the final product of hydrolysis for the majority of organosilicon compounds is silicon dioxide SiO2 (sol-gel process similar to olation). Fine powder of silicon dioxide is white as well."

[Edited on 26-2-2021 by DReed123]
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[*] posted on 27-2-2021 at 03:37


Thanks for that . The word "olation" is a new one to me.

A mixture of silica, silicones and NH4Cl seems to be the most likely nature of the white fluff.
Does it dissolve in water?
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njl
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[*] posted on 27-2-2021 at 14:18


Only the NH4Cl will, but everything else is harmless and can be wiped off with paper.



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Amos
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[*] posted on 27-2-2021 at 16:26


Anything that produces HCl produces a white fume on glass that rubs away, I've noticed a filmy texture on the outside of some plastics too.
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