I wanted to have some gold colloids in my element collection, but the aquatic solutions are always at least somewhat unstable. After some research I
found out about cranberry glass, in which the particles are embedded in glass, making them very stable.
I only wanted a small fragment, but the only form I could find it was sold in was expensive decorative glassware, and apparently most glass sold as
"cranberry" is just imitations and fakes.
So I had made my own: I bought a gram of gold, dissolved some of it in HCL/Na(NO3) solution to make a potassium tetrachloroaurate solution and then
heated it with some glass fragments using a propane/butane torch.
The resulting color was uneven, but clearly red/pink.
Sorry if this is the wrong section, would "Miscellanous" have been better than "General"?
[Edited on 10-10-2017 by CaCl2]woelen - 10-10-2017 at 02:53
General is OK for this post.
Interesting experiment. I also want colloidal gold in my element collection and I have the same issue. After some time, the nice pink/purple colloidal
solution precipitates and a dirty brown/black precipitate is formed with a clear solution above it.
Could you please elaborate on the details of your preparation? Did you really purify the gold-compound, or did you just add some solution to the glass
and then heat it? Did you crumble the glass and heat that, mixed with the gold-containing solution?CaCl2 - 10-10-2017 at 03:23
I didn't purify it in any way, just used a dessicator to concentrate the solution a bit. It's possible using pure material would give a better result.
I attached a small glass fragment to the soldering holder thing you can see on the background in one of the images, and then placed a small drop of
the solution on it with a pipette.
Then I heated it, starting gently to evaporate the water, then moving the flame closer to melt the glass. The torch I used seemed to only barely
reach the required temperature.
It's surprisingly simple to get some color, getting an even, strong red is apparently much harder.
I also tried adding some tin (II) chloride to reduce the gold, and using a less concentrated gold solution, but neither gave good results.
The tin chloride resulted in a brown color, indicating the formation of too large particles, the dilute solution gave no color at all.
My collection is very small scale, so I think I will use the tiny fragment with even color for it.
[Edited on 10-10-2017 by CaCl2]
[Edited on 10-10-2017 by CaCl2]j_sum1 - 10-10-2017 at 03:36
Nice. I am impressed. I had sort of given up on the idea of having colloidal gold in my element collection but I hadn't really considered glass. I
might need to rethink although I will probably have the same heating issues as you had since I am using similar heating equipment.Chemetix - 10-10-2017 at 14:09
It's actually not that hard to do by metal spray on glass
If you just melt the glass with the gold spray it goes a nice even red, a little bit goes a long way for colour effect. CaCl2 - 29-10-2017 at 10:52
