chemkid
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Sodium Hydroxide Glass Etching
I was heating sodium hydroxide and sodium acetate in a test tube to obtain some methane. The sodium hydroxide eventually melted and when i cleaned out
the test tube of harden sodium hydroxide/sodium acetate a strange water insoluble rough spot was on the inside of the test tube. What would sodium
hydroxide etched glass look like? Are these circumstances sufficient to etch glass with molten sodium hydroxide?
Chemkid
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Fleaker
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Absolutely, and that is what happened. It is much worse with KOH, and worse yet with CsOH which attacks at little above room temperature.
Molten hydroxide+ borosilicate = etched glass.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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chemkid
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thanks
chemkid
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chemrox
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How concentrated a solution can one use to clean one's glassware? Fleaker, does KOH etch at cleaning strength ? I got a cheap supply of KOH ..
virtually free.. I have my sidearm flask vacuum filter/controller loaded with KOH flakes. Am I nuking the flask? Will it implode on me?
system: pump -> manostat -> KOH acid filter/controller -> trap -> boiling flask
Thanks all
CRX
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JohnWW
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Commercial glass etching is usually done with HF (see the PTFE thread in this section of the forum). If a design is desired to be left as an unetched
part of the glass, this is firstly put on as a paraffin wax mask on the glass.
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not_important
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| Quote: | Originally posted by chemrox
How concentrated a solution can one use to clean one's glassware? Fleaker, does KOH etch at cleaning strength ? |
Yes, the "last resort" cleaning mixture of KOH in alcohol comes with the warning not to use it on volumetric glassware as it will throw off the
calibration. Repeated use or prolonged contact will cause obvious etching.
| Quote: | | I got a cheap supply of KOH .. virtually free.. I have my sidearm flask vacuum filter/controller loaded with KOH flakes. Am I nuking the flask?
Will it implode on me? |
Can't be good. I use heavy walled HDPE tubing for such applications, slam a stopper in each end and you've got a drying tube that can't take much
heat but is pretty resistant to acids and bases.
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chemkid
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So paraffin wax is inert to hydrofluoric acid? how about sodium hydroxide?
Chemkid
[Edited on 4-10-2007 by chemkid]
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chromium
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Alkali metal hydroxides are not good for practical glass etching. Reaction product is nontransparent white substance which sticks to the glass and can
not be removed.
When all think alike, then no one is thinking. - Walter Lippmann
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chemkid
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that would be sodium silicate i believe
chemkid
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chemrox
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@not_important - I should have thought of that, thanks! I will make the tube and put it between the sidearm flask and the vacuum adapter. I will put
glass wool in both ends to catch dust before it all gets to the trap. I could put some in the sidearm as well... wouldn't hurt.
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chemkid
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OK then, if sodium hydroxide ruins glass what won't it ruin? I am trying to make some sodium silicate (since i succeeded with my previous methane
experiment) and am a little short on cash, so disposable glass isn't an option. any ideas?
Chemkid
[Edited on 4-10-2007 by chemkid]
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12AX7
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Well obviously whatever you're going to react with the lye is going to react about the same as the silica laced with sodium and calcium or boron ions
(soda-lime or borosilicate glass, as the case may be) containing it.
A nice hearty fusion of soda (ash, lye, etc.) with clean white sand in a high refractory crucible (lots of alumina content, like mullite, or if you
weren't so strapped for cash, zirconia) is the way to go. But gee, something tells me you can spare the five bucks for a tub of TSP substitute at the
hardware store.
Tim
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not_important
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| Quote: | Originally posted by chemkid
OK then, if sodium hydroxide ruins glass what won't it ruin? I am trying to make some sodium silicate (since i succeeded with my previous methane
experiment) and am a little short on cash, so disposable glass isn't an option. any ideas?
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The usually method of making sodium silicate is to fuse soda ash with quartz sand, much too hot to do in glass.
The "group 8" metals, now groups 8, 9, 10, are resistant to molten alkali hydroxides and carbonates, as are silver and gold.
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chemkid
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How would TSP (trisodium phosphate i presume) substitute help me?
Chemkid
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12AX7
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Do you read any labels? TSP substitute is sodium metasilicate, potentially what you asked for. Naturally, there are two popular sodium silicates,
one of which does not bond (which happens to be the metasilicate; the orthosilicate is found in "water glass", which does bond).
Tim
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chemkid
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I am looking for orthosilicate "water glass." Yes, i do read many labels however i have not read every label.
Chemkid
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Antwain
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I expect that sodium silicate is one of the few chems left that you can buy from a chem supplier w/o leading to suspicion that you are a drug cook/
terrorist. I bought 500mL for $25AU which was cheap compared to the other chems I bought. Of course, an OTC source would be cheaper, but since it
isn't used for so much these days that may be hard.
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