draculic acid69
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Sodium silicate and boric oxide together.good idea or not?
Has anyone ever added boric oxide into water glass in attempt to make borosilicate water glass? I want to join a pyrex tube to a soda glass vial but
I'm not sure whether ordinary water glass will handle the temps I want to get it to.surprisingly these glass vials can take the kind of heating I want
to do just not sure about the join between the two? I need it to be gastight and teflon tape won't handle it and can't just melt pyrex to soda glass
so I was thinking sodium silicate might make a good deal if fused between the two but sodium borosilicate might be better.if anyone knows about
whether I'm on the right track or I'm wasting my time any comments would help.
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DraconicAcid
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I've thought about it, but never actually done it.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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rockyit98
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how much temperature? silicone adhesive sealant can handle up to 200C some special can go up to 250C. water glass might not work. i once used powder
of broken borosilicate glassware (it was so fine like flour .i used a Ball mill) and silicone adhesive mixed together for 400C application.the
silicone burned off but its ash kept the joint steady.
"A mind is a terrible thing to lose"-Meisner
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unionised
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Quote: Originally posted by draculic acid69  | | I want to join a pyrex tube to a soda glass vial but I'm not sure whether ordinary water glass will handle the temps I want to get it to.
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Almost any sort of joint between borosilicate and normal glass will break if you heat it because of the different rates of thermal expansion.
It's possible, using a graded seal.
For what it's worth, adding boric acid to water glass will make borax and silica. That's not going to help.
The interesting thing about borosilicate is that borate and silicate glasses don't mix (well).
You get something like an emulsion of one in the other.
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draculic acid69
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Quite stupidly I now realize that I should have recognised borax as the product of sodium silicate and boric acid.damm.what about making water glass
by boiling borosilicate glass powder in concentrated NaOH? Will that be any different? I might just give it a go anyway.
A graded seal is what I aim to create but without the cost.and doable in my garage.
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WGTR
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Is there an actual need for having two dissimilar glass pieces and joining them together? A regular air/propane torch could be used to pull a point
on a borosilicate glass tube, although it may take a big flame, and only work well on small tubing. That way you would have a boro tube that is
sealed on one end.
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draculic acid69
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Not what I'm trying to do.the idea was to use water glass as a seal that can handle the heat/ or will fuse the two parts together like sodium
hydroxide in a ground glass joint
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unionised
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Unless you make a graded joint, it's still going to break when the temperature changes.
What are you actually trying to do?
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WGTR
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| Quote: Originally posted by unionised | Unless you make a graded joint, it's still going to break when the temperature changes.
What are you actually trying to do? |
I second the question. It sounds like you want to develop a homemade cement that is "gas tight", can handle large temperature swings, and can be used
to join two dissimilar glass tubes together without breaking. That is a lot to ask for a weekend project. At the very least you would need to
research glass compositions and select one that matches the expansion coefficient that you need, and is compatible with both glasses that you are
trying to join.
"Gas tight" is relative. Does this need to work above or below ambient pressures? If under vacuum, under what absolute pressure? Are the reactants
air or moisture sensitive? How much? Is this intended to be a permanent seal, or rather one that can be easily broken after a reaction so that
products can be removed from the test tube?
Sometimes there are easier ways to work around problems like this, using creative methods. Kapton tape is good to around 300°C or so, depending on
your particular application, and it is easy to tear off a new piece if the old one overheated. Sometimes it is possible to look at how you are
heating things. Perhaps you can add a heat susceptor inside of the test tube, and use inductive heating with the test tube under water. This not
only keeps the tube cool, but also the joint. I have thought of this for small-scale white phosphorus production. Or, water cool around the joint
and just seal with epoxy or rubber O-rings. Or, add secondary containment around the entire hot test-tube/boro tube assembly, and pressurize it
slightly, to maintain a slight positive airflow into your boro tubing.
So yes, what are you trying to do?
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draculic acid69
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Nevermind I've scrapped the idea for now.im going to rethink it.
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