BromicAcid - 12-10-2004 at 17:32
Most of the glassware I have worked with in my lab experience is hydrophilic. It will attract water and keep it close. Good examples of the
hydrophilic effect are seen in burettes and such from the water climbing the sides and forming the meniscus. It is usually more pronounced the
smaller the diameter container you are using.
Being that most glassware starts out hydrophilic, what are some of the advantages and disadvantages of converting to hydrophobic? So far most of the
pros of hydrophobic glassware come from the biology field, keeping proteins and such from collecting on walls of containers and other things pertinent
to that field. But what about chemistry in general?
Another thing, distilling potassium metal in glassware supposedly causes the potassium to displace a large percentage of the sodium in the glassware
(>40%) does anyone know how, or if, this would affect the properties of the glassware?
Very interesting page on glass in general and additives in making it.
The beginning sectoin on this PDF points out that glass is hydrophilic and what to expect.
Details how to make your glassware hydrophobic.
S.C. Wack - 12-10-2004 at 20:09
On surface potassium substitution:
http://www.google.com/search?hl=en&lr=&q=potassium+s...
It is very resistant to damage, I have seen this done. I was told that the glass dipped in K would lose this property due to the fluid nature of
glass, as this layer is very thin. Dunno about the 40% - glass made by distillation of K - a different animal.
Organikum - 12-10-2004 at 23:25
Working in basic environment makes glassware "slimy" - hydrophilic.
Cleaning with acids makes it hydrophobid again. Mostly citric acid suffices, H2SO4/H2O2 is the ultimate weapon of course, just unnecessary in most
cases, like using a "Hummer" for shopping.
Anyways, the final cleaning step with glassware should be acidic and if the glassware is not hydrophobic afterwards its not clean.
Altering the properties of glass is interesting though, but I admit I am happy as long my glassware maintains its most important property of staying
in one piece. 
neutrino - 13-10-2004 at 15:43
The only salts I see mentioned for tempering are nitrates. Is there any reason chlorides wouldn't work? How well would this work on borosilicate
glass which usually has only ~4% alkali oxides, as opposed to the more common soda-lime glass with 15%?
My main concern with hydrophilic glass is unwanted reactions with the added substance. For example, Bromic's third link talks about
dimethyldichlorosilane (used for making the glass hydrophobic by being coated onto it) hydrolysizing in contact with water.
Does the acid method have something to do with removing the alkali oxides on the surface of glass? If it does, this would be a kind of anti-tempering:
It would cause the atoms on the surface to become more 'relaxed', reversing any tempering and it would prevent glass's tempering
afterward.
BromicAcid - 13-10-2004 at 16:10
Interesting S.C. Wack, nice to know there is a name for it. Distilling potassium though a vessle might be one way to do it, but putting the glassware
in a bath of molten KNO3 for 17 hours sounds somewhat safer.
The sites that I looked though said this increases the glass strength significantly, I think I may treat a beaker in this manner, or something else, I
have some broken beakers that I could experiment on pieces of.
Glass
MadHatter - 16-10-2004 at 20:14
I'd be more interested in the attack on glass by more common compounds - excepting HF
of course. More specifically, hydroxides and hydrazine(hydrated or not). Although wearing
out glass in the short term is generally not a problem, the long term exposure could pose
significant hazards in vacuum applications.
neutrino - 17-10-2004 at 05:18
Anhydrous hydrazine does not attack glass. The traditional way of protecting glass from attack by bases is to silver the inside of the vessel.