Sciencemadness Discussion Board - Titanium Dioxide Solution

Titanium Dioxide Solution

HgDinis25 - 22-10-2014 at 13:00

Hey,

So, some time ago I saw two 1L bottles being sold for 30 cents marketed as a 4% Solution of Titanium Dioxide. They were plastic bottles and seemed quite old and dusty. Inside there's a yellow liquid and a lot of white precipitate (TiO2 I guess). Anyway, for their price I just bought them.

Today I decided to open one and see what the liquid was and if the precipitate was indeed Titanium Dioxide.

Some propreties of the liquid:
-->The liquid is yellow (photo below) and has a faint smell of paint (organic solvent maybe?);
-->It is more viscous than water.;
-->It won't burn (not even with a blow torch);
-->I measured a density of about 0,996 g/cm3 give it or take it a few miligrams;
--> It's alkaline (turned litmus paper green);
-->I pippeted some of it into a watch glass and evaporated the liquid. What remained was some black stuff, carbon like (photo below);

I'm puzzled towards the identity of the liquid. Any thouhts? Has anyone ever come across such Titanium Dioxide solutions? Tomorrow I'll try to identify the white precipitate (Titanium Dioxide I hope).

--------------------------------------------
Picture of the liquid:
https://www.dropbox.com/sc/ndp6wzcjxj1y0pu/AACZqV_DPs2UZ5JSD...

Pictures of the black stuff:
https://www.dropbox.com/sc/axeem1ascb5h8rt/AAAQg7ZxAYFVMign1...
https://www.dropbox.com/sc/phqm5tmqpg519fr/AAAAjLmX4Ybfd0V-_...

DrMario - 22-10-2014 at 13:53

TiO2 is completely insoluble in water. It is also one of the least reactive chemicals in nature... and in the lab.

What you might have is some kind of suspension in water, using a surfactant (which would explain why it's a bit more viscous than water). It's also possible that you bought a bottle of what is technically called "snake oil".

Could you snap a picture of the bottle/label on the bottle? That could prove very enlightening.

HgDinis25 - 22-10-2014 at 14:05

The label is in portuguese so it be useless to you, I think. It simply says Titanium Dioxide in big letters and in smaller ones 4% solution. But yes it seems to be a suspension of it. The surfactant idea seems plausible, might also explain the black residue left from boiling it (most of it boiled away).

What compound might it be anyway? I'll check for miscibility with water tomorrow.

DrMario - 22-10-2014 at 16:05

Quote: Originally posted by HgDinis25

The label is in portuguese so it be useless to you, I think. It simply says Titanium Dioxide in big letters and in smaller ones 4% solution. But yes it seems to be a suspension of it. The surfactant idea seems plausible, might also explain the black residue left from boiling it (most of it boiled away).

What compound might it be anyway? I'll check for miscibility with water tomorrow.

I do speak 6 languages, actually, and Portuguese is in the family of languages that I at least understand rather well.

What could the surfactant be? Polysorbate 20, sodium stearate, PEG 2000... something cheap, in any case, considering you paid 30 cents for one liter of the goop.

HgDinis25 - 23-10-2014 at 11:41

My strange liquid doesn't form a layer when mixed with water.

Does anyone know tests for specific sufactants?

PEG200 is probably out because my liquid doesn't seem to have a flash point. Sodium Stearate would need a solvent that would make a layer with water (I think). Any thoughts?

blogfast25 - 23-10-2014 at 13:38

Quote: Originally posted by HgDinis25

Tomorrow I'll try to identify the white precipitate (Titanium Dioxide I hope).

You'll probably have to fuse (dry it thoroughly first) it with sodium bisulphate, that's how insoluble and inert it is. It's reactivity does depend on grade to grade.

My food grade Anatase TiO2 doesn't even respond slightly to 200 C 98 % H2SO4.

Once dissolved (if you manage it), dilute the solution and add aluminium foil or zinc (in a test tube!). That causes any TiO2+ (titanyl cations, Ti(IV)) to be reduced to purple/deep blue Ti3+.

Adding hydrogen peroxide then causes a deep red peroxo titanium (IV) complex to form.

[Edited on 23-10-2014 by blogfast25]

HgDinis25 - 23-10-2014 at 13:48

Quote: Originally posted by blogfast25

Quote: Originally posted by HgDinis25

Tomorrow I'll try to identify the white precipitate (Titanium Dioxide I hope).

Last time I worked with TiO2, pigment grade (is that even IUPAC aproved?), it dissolved in 300ºC Sulfuric Acid (near the decomp. temp.). Adition of H2O2 formed an redish orangish solution, IIRC, not a deep red one. I guess the colour of the complex may vary depending on purity.

I was more interested in finding out the liquid it came in...

DrMario - 23-10-2014 at 13:51

Quote: Originally posted by blogfast25

Quote: Originally posted by HgDinis25

Tomorrow I'll try to identify the white precipitate (Titanium Dioxide I hope).

That's a nice experiment. I'd rather use concentrated sulfuric acid instead of melting sodium bisulfate. Melted sodium bisulfate seems a bit too unstable. Maybe I'm just getting old, but boiling concentrated sulfuric acid is as far as I'm willing to go

[Edited on 24-10-2014 by DrMario]

blogfast25 - 24-10-2014 at 04:20

Quote: Originally posted by DrMario

That's a nice experiment. I'd rather use concentrated phosphoric acid instead of melting sodium bisulfate. Melted sodium bisulfate seems a bit too unstable. Maybe I'm just getting old, but boiling concentrated sulfuric acid is as far as I'm willing to go

Phosphoric acid is unlikely to do it.

You can also fuse with NaOH or KOH: that forms titanate. With water that immediately hydrolyses to Ti(OH)4, which is much more responsive to acids when freshly prepared.

Sodium bisulphate does decompose: it sheds SO3 and forms pyrosulphate. But it's not particularly dangerous.

Metacelsus - 24-10-2014 at 08:31

A while ago I dissolved crude titanium dioxide (from scrap titanium) in molten sodium bisulfate as part of a purification. It takes time, and a lot of heat, but it is feasible.

DrMario - 24-10-2014 at 09:07

Quote: Originally posted by blogfast25

Quote: Originally posted by DrMario

Phosphoric acid? I never mentioned phosphoric acid - where'd you get that???

The reaction with fused hydroxides seems quite interesting, and one I'd feel reasonably safe to try. Thanks a bunch for the tip!

WGTR - 24-10-2014 at 11:09

Dissolving TiO₂ into molten NaHSO₄ is not a big deal, as long as you have either a fume hood, or a decent fan outdoors. The bisulfate salt is available readily from hardware and pool supply stores. More importantly, it can be melted in a test tube without destroying the tube. That is more than can be said for molten hydroxides, which will quickly dissolve glass.

As part of some solar cell experiments, I dissolved TiO₂ into NaHSO₄. Details are in this thread:
https://www.sciencemadness.org/whisper/viewthread.php?tid=27...

There is some SO₃ that is given off, hence the need for ventilation. Also, an excess of bisulfate is needed, to ensure that the mixture remains molten. A clear orange melt should result once all the TiO₂ is dissolved.