This is the general behavior with the Mo wire as a cathode in an electrolyte solution of distilled water with just slight amounts of sodium bicarbonate. When earlier on I started with tap water it seemed too much conductive and the wire would burn very quickly.
It becomes incandescent and relatively bright also as an anode, but it does not start combusting like it seems to do as a cathode.
In an attempt to improve the reaction I tried enclosing the active electrode with the body of a small syringe and an enlarged opening. In this way, the electrolyte solution is able to heat up rapidly and as a result the formation of glow plasma electrolysis is favored even at low power and the 1-mm thick tungsten welding rod I have been using recently. As an additional benefit, noise is also greatly reduced.
The increased impedance of the electrolyte from the longer electrical path also allowed higher voltages on average during the reaction as my high voltage power supply can only output currents in the order of tens of mA at about 750V. This appears to improve the reaction. Here the electrolyte was a KOH solution with a concentration of less than 0.05M in tap water (dirtied by iron oxide from the steel anode). The anode was also enclosed in a semi-open large plastic tube.
After the reaction the tungsten rod appeared cleaned and eroded.
The reaction now also works well for significant lengths as an anode. I find that the enclosed configuration makes it oxidize faster, as well as getting reduced faster; possibly, the oxidizing/reducing species might accumulate more and therefore have a stronger effect (needs confirmation).
Tungsten oxidized like this appears to have a sort of iridescent quality. Thicker oxide layers are more opaque though.
EDIT: here is another video, with slow motion at minute 00:56
Electrolysis was performed with a 15x0.3 mm nickel cathode enclosed by a small plastic tube with an inner aluminium foil, in impure distilled water and 800V across both electrodes (open circuit voltage). This configuration allows water temperature to quickly and easily locally reach the boiling point, which apparently improves the reaction.
When water appears to be fully boiling it seems easier to make the cathode glow from incandescence. Local temperatures visually seem higher than 1000 °C (and can easily exceed the melting point of the wire if allowed to).
However, it appears that this mode of operation makes it oxidize despite being the cathode. The oxidized electrode was dull and had a hint of green nickel oxide color, upon inspection.
In spite of oxidation, the reaction can be applied for a long period of time without significant electrode wear within reasonable periods of testing. I'm wondering if it's just oxidation from steam or if there's a different water decomposition process going on. Tadahiko Mizuno and others have suggested years ago that water pyrolysis can occur under electrolytic glow plasma, although I'm not sure if the conditions I am achieving in these tests are exactly the same. The entire immersed surface of the electrode appears to homogeneously become incandescent however, so there still appears to be some sort of glow plasma process going on.
When forcing the reaction to operate with a lower current density and/or conditions that do not cause the cathode to become incandescent, a punctiform yellow plasma appears on the cathode surface and it instead gets cleaned/reduced from hydrogen (slowly if an oxide layer is already present). The transition between these modes of operation is not abrupt and at times both those "dots" and significant incandescence can be observed at the same time, at least with the thin nickel cathode used here.
can. In an attempt to make colloidal nickel some years ago I used the same method I had employed years before to make colloidal gold. Thin nickel wire just in contact withe the surface of the water, low voltage high current. Nickel being more reactive than gold it stripped oxygen out of the water and made a lovely emerald-green compound with a weak gel structure, probably nickel sesquihydroxide. Maybe you have made some of that too.
I am not obtaining a gel-like green compound. The green color seems located strictly on the surface of the Ni cathode and appears only when the cathode becomes incandescent under the water level (or possibly just when it gets in contact with water in that condition). The color should be clearer in this photo, showing the green Ni cathode together with molten Ni balls (with a surface green NiO layer) that were formed from it in earlier testing. The Ni wire is wrapped around a 1-mm thick tungsten welding rod (somewhat eroded from previous testing).
On the other hand, I'm getting fluffy (cotton-like?) white formation in the solution; it could be in part from the Al foil I used in the plastic tube enclosing the cathode (but it should not participate directly to the electrolytic reaction).
I used distilled water, but I later added some tap water—since it already became partially conductive from residues on the electrodes, at least at the voltages used—and it occurred also with it. I'm trying to use low-conductivity water because I find that for the incandescent cathode effect from electrolytic glow plasma there's no particular need for a high conductivity, and a low one makes it more controllable in several ways, as well as making the reaction more tolerable for my HV power supply.
Not sure why, but the aluminium foil that I previously put inside the plastic cap surrounding the Ni cathode turned brown (only the side exposed to the cathode). To the right a small strip of the pre-reaction material.
Not sure why, but the aluminium foil that I previously put inside the plastic cap surrounding the Ni cathode turned brown (only the side exposed to the cathode). To the right a small strip of the pre-reaction material.
That would be an interesting sample for performing EDS.
The materials are cheap and the same HV power supply available on Amazon, so I encourage those with easy access to EDS equipment to try for themselves. However probably I should try reproducing it with fresh materials first and just using Ni, Al and perhaps a new anode (I used a 6mm graphite rod, but it has prior experimental history).
For what it's worth, I tried again on the other side of the foil (which was dull but still gray) and the change seems reproducible, although after just a few minutes of testing it only acquired a slight gold tinge. I must have previously tested it for about an hour or so. The jagged edge was on the upper side.
I made another test after cleaning the jar, using a new Al foil and Ni wire, but I used the same improvised small plastic enclosure (also washed) and graphite anode (which was previously used only in carbon arc experiments) as earlier. This time I used tap water instead of about 50% distilled water and 50% tap water. I think this made it perform a bit worse as the Ni cathode did not seem to heat up as easily. Still, it could quickly melt with careless operation. This is still a rather crude setup and no attempt has been made at improving the presentation and materials yet.
After about 20 minutes of testing, trying again to make the wire incandescent with the electrolytic plasma, the foil visibly acquired a brown tinge, although not as strong as earlier on (with longer multiple-session testing and possibly better experimental conditions). The nickel cathode was again dark from oxidation, but the green color from NiO isn't apparent as earlier due to the less favorable artificial lighting. As I write this I checked again—it is indeed nickel-green.
One thing I noticed is that after removal from water the Al foil "fizzes" as if it was wetted with a caustic or acid solution. However I just used tap water.
reminds me of dissimilar metal reaction using one side of the foil as a source and a capacitor.
The foil is immersed in the electrolyte (just tap water+distilled water) but it is not directly electrically connected to the electrodes. Even if it was, the color change is puzzling, although perhaps it could be explained with nickel vapor deposition on it (would it show as a gold/brown layer, though?). However it has become dark both below and above the water level.
The photo below shows on the bottom left the latest aluminium foil I used. After some more testing it has acquired about the same color of the previously used one (bottom right). The smaller strip (top center) is an unused foil. The white middle portion on the bottom left foil I think is due to Al2O3 (alumina) formation from the heat of the cathodic plasma.
As a side note, this gif animation shows that the plastic tube with the internal Al foil produces a much stronger reaction than the colder open area closer to the anode (a graphite rod, partially visible in the background).
you know how it is,, someone will just tell everyone your adding argon gas to it.
it is puzzling/interesting..
seems we really should revisit all the rabbit holes in science ~
I'm curios what this is.
Maybe a continuity test inside and outside the foil area will help identify voltage stabilization.
you may have a better ground within the foil continuity to the water then outside the zone.
if I was welding and saw this, I would think of it as a bad ground seeing the spark blow out and I would check my ground strap.
Under cold conditions (in the current setup with just tap water), there is a slightly stronger reaction outside than inside the plastic tube, mainly due to the electrically shorter path to the anode. I should also point out that in my case the cathode is at negative 400V and the anode at positive 400V (difference: 800V); there is no low-impedance connection to ground voltage.
On an unrelated note, a brief test was done after adding 5% weight acetone to the electrolyte solution (i.e. water). It had the effect of making the reaction slightly stronger and easier to trigger (as already pointed out a few days ago), as well as apparently preventing cathode oxidation when it becomes incandescent under water (upon inspection, the cathode was shiny, not dull green). Also, at least for a while, frequent bright white flashes occurred in the same reaction, as seen below. This might have all mostly been from acetone decomposition and its volatility.
Nickel carbonate usually occurs as a light green crystalline solid or a brown powder. It dissolves in ammonia and dilute acids but is insoluble in hot water, easy tests to make. But if it appeared using distilled water, where would the carbonate come from?
Does the brown deposit appear without using the plastic tube? Try substituting a glass tube if you have something suitable.
It was initially distilled water with some impurities from the graphite anode which made it conductive, so I can't rule out that the same impurities brought this brown layer as well. I have repeated the tests more times just using tap water (replacing it a few times) and only 0.3 mm nickel wire as the cathode and a similar discoloration has also appeared with it, but to a lesser extent. I also tried again distilled water, but with this test there were no significant impurities dissolved from the electrodes and the reaction just did not work—too low conductivity even at 800V.
The plastic tube as shown in the previous gif is a sawed off 5 ml syringe, which should be made of polyethylene, nominally (C2H4)n but other compounds may be present. I also tried other clear tubes (plastic caps of various sorts and similar size, modified into cylinders/tubes) obtaining a similar change, but I'm not sure if they were made of the same base material. I would have used a glass tube, but I did not have any at disposal that could be used—the aim initially was just enclosing the cathode to locally heat water much faster than normally and thought that a plastic one would have been fine, even more one made of polyethylene which should be chemically inert.
The latest Al foil I used (from a different, thinner sheet) has also showed a similar discoloration, but this time mostly on the backside in contact with the plastic tube. The top foil in the first photo is the source material.
Yesterday I mentioned that with acetone addition the 0.30 mm nickel cathode became cleaner after the usual reaction where it turns incandescent (temperatures visually in the 1200–1400 °C range) from electrolytic cathodic glow plasma. This is probably because of reduction from excess hydrogen evolution and possibly carbothermic reduction from acetone decomposition products. Below is a photo after one such tests. No nickel oxide-green observed.
Since this seemed interesting/promising, I added some more acetone to the solution (just tap water). This time the Ni cathode surprisingly acquired an iridescent color. I'm not aware if nickel on its own forms iridescent oxides. At the wire temperatures employed I think this is unlikely to be due to some organic compound.
Depending on exposure time and perhaps other parameters the color at the melted tip can change. In this other photo it turned out to be gold-colored.
The aluminium foil (originally intended to be used just as an infrared reflector) this time does not seem to have acquired any particularly strong color. Besides the possibility of contamination mentioned earlier, there's also the chance that the color observed was due to some oxide, perhaps the same that is now giving odd colors to the nickel wire. If following acetone addition there is excess hydrogen in the region, or a decreased amount of oxidation going on, then the same color might not appear anymore. After some testing however the foil still appears dull and somewhat brittle.
EDIT: after replacing the solution with again tap water, the nickel cathode again becomes oxidized with a hint of nickel oxide green color, following a period of incandescent operation. The Al foil, it's not clear yet.
EDIT2: after about 15-20 minutes of testing with the oxidized Ni cathode, I'm not able to obtain the same brown-gold color as earlier. Furthermore the Al foil is not "fizzing" to the same extent as it did earlier, after operation. It's likely that there were other compounds dissolved in the solution earlier on.
I m ravelling the moment, but it hs occured to me that maybe you are sputtering the Al foil with Nickel. I put this thought into the category of 'unlikely but possible
That could have been from the tungsten rod I'm using as a holder for the Nickel wire, since it oxidizes very easily with heat. I'm now going to test this, repeating the same reaction with just the rod (but it won't get as hot as the Ni wire).
EDIT: I would say it is likely to be due to tungsten. I put two foils inside the plastic tube. The smaller one was in front of the larger one. After some testing under various conditions, they both easily acquired a light brown-gold color, and it's likely that it would have become stronger after a longer period of testing or several testing sessions.
I found that the white cotton-like residues that I obtained earlier on were actually due to tungsten oxides coming off the rod when it's heated to bright incandescence. When wetted with such solution, the Al foil also "fizzes" like I observed at the time, probably from the same tungsten oxides. They must be somewhat reactive.
