I stumbled across a rust remover that claimed to contain hydrofluoric acid. Now don't get me wrong, HF scares the daylights out of me, the way it eats
your bones and all. However, after an internet search on the product name, I found that it's only a very dilute solution (3%) and I have some pretty
good safety gear, so I decided to check it out.
I poured 50 mL into a polypropylene cylinder, transferred to polypropylene beaker, and added the stoichiometric amount of NaHCO3 bits at a time.
Vigorous bubbling occurred. When done reacting, I transferred to glass beaker, boiled solution to near dryness and let evaporate.
2 days later, I got my beaker off of the shelf. I transferred crystals to vial. 3.00g of pure sodium fluoride. It looks perfectly white like snow. It
has a little piece of black dust in it, but other than that it looks awesome. After labeling it as NaF and Poison it is being kept in my closet.
Something I really don't want to do is mix with sulfuric acid :O mr.crow - 31-8-2011 at 18:57
Nice! Nothing like having a little demon in a vialBolt - 31-8-2011 at 20:05
How do you know it's pure?jamit - 31-8-2011 at 20:21
I know the rust remover you're talking about... you can buy it at menards and yes its 3% Hydrofluoric acid.
It's a pain to work with as it leave a permanent damage on any glassware even if you pour it in and out right away. I learned the hard way and now
several of my beakers are ruined forever. O well.
I'm in the process of making copper II fluoride with it... add it to copper carbonate... however its very hard to make crystals out of it. Mildronate - 1-9-2011 at 08:27
What are there so cool?Bot0nist - 1-9-2011 at 10:21
Are you asking why NaF is cool Mildronate? Some of us (including myself) are easily entertained. 3 grams of a fluoride salt has some fun potential for
small scale but very interesting reactions.
[Edited on 1-9-2011 by Bot0nist]mr.crow - 1-9-2011 at 11:54
Calcium Fluoride is insoluble in water, you could make a safe sample this way
Dissolve enough CaCl2 in distilled water then add your acid solution directly to this. Get a nice white precipitate. Put it in a buchner funnel and
wash with water.
Boiling the solution down gives you all the impurities tooAcetic Acid - 1-9-2011 at 14:50
If I changed my whole bottle of rust remover into NaF, I could get around 55 grams worth. I don't feel like it though Panache - 1-9-2011 at 18:17
Whats the product called? Bot0nist - 1-9-2011 at 18:35
There is a glimpse of it in his video http://www.youtube.com/watch?v=DoLvNbjd2ks time = 1:02-1:18 . It is so shaky though I cant make out the brand. I imagine most 'rust
removers'/'rust stain removers' are dilute HF(aq.) Acetic Acid - 2-9-2011 at 05:30
Whink Rust Stain Remover. You can get it at most supermarketsAthiril - 2-9-2011 at 10:32
Hmm that is interesting. How difficult would it be to get a thin fluoride coating (such as calcium or magnesium fluoride) onto the surface of glass?
The original process iirc was done in a vacuum glass jar under high heat with magnesium fluoride that was sprayed on after being vapourised.
I don't think it was done in a true vacuum.
Quoting a popular science magazine which I managed to find on google that shows the process, has this to say.
"Measurement of the film thinckness, microscopic though it is, can be done easily by factory workers so long as they ar not color-blind. The color of
light reflected from the lens surface undergoes a change as the film grows in thickness. When it arrives at a certain shade of purple the process is
stopped for that means the film thickness is one fourth the length of the yellow-green light wave."
It seems pretty straight forward as long as you could set up an apparatus for it..
[Edited on 2-9-2011 by Athiril]Endimion17 - 2-9-2011 at 10:51
There is a glimpse of it in his video http://www.youtube.com/watch?v=DoLvNbjd2ks time = 1:02-1:18 . It is so shaky though I cant make out the brand. I imagine most 'rust
removers'/'rust stain removers' are dilute HF(aq.)
Aren't most rust removers supposed to be mixtures of phosphoric acid and methanol?Acetic Acid - 2-9-2011 at 13:13
This one is HFScienceHideout - 4-9-2011 at 17:06
I use that stuff to clean glassware... the small amount of HF isn't too scary, and doesn't bother me. It sparkles like new.
BUT: If you check the MSDS for stuff like that there is a huge amount of oxalic acid in addition to the 3% HF- so wouldn't your NaF be mostly sodium
oxalate?Acetic Acid - 4-9-2011 at 17:27
Is this the MSDS you looked at? It doesn't mention the existence of oxalic acid.woelen - 5-9-2011 at 01:55
You can easily test for presence of oxalic acid. Take a small spatula of your supposed NaF and add this to 2 ml or so of 10% H2SO4 and let dissolve.
Add a very small amount of KMnO4. If there is no oxalic acid, then the liquid turns deep purple and remains so. If there is some oxalic acid, then the
color of the permanganate quickly disappears.
A similar test is possible with dichromate. A small quantity of oxalic acid will lead to change of the orange color to a kind of deep purple color
(chromium(III) complex with oxalate).blogfast25 - 5-9-2011 at 04:15
@woelen:
Good point! I use twice recrystallised anhydrous oxalic acid as a standard for KMnO4 titrant solutions. Some use disodium oxalate (here a suspect)
instead which has a larger gravitational lever...
[Edited on 5-9-2011 by blogfast25]ScienceHideout - 5-9-2011 at 09:30
Ooh, the HF I use isn't whink- but it's verrrrrry similar...
