...although I haven't found any explanation online why it works. This method has probably been known for over a century, so I suspect it may be in some old physics books.

If you have a salted potato (rescued from a salad perhaps), I would not do the experiment indoors, nor would I stick my face close to it.

There are ways to kill someone with potatoes, but they don't involve electrolysis.

How, without breaking the skin?

I suppose you could burn yourself if you deliberately wrapped the wires around an appendage and immersed it in the salt water. It'd take a lot of current, and whether that would do more harm than just drinking the salt water is questionable.

The cathode reduces H+ to H2. Hydrogen gas is mostly harmless if breathed, but if you collect it, it’s explosive.

Water minus that H+ that turned into hydrogen gas leaves OH- behind. Concentrate that enough and you have a base that will dissolve your skin.

The anode can oxidize water to oxygen, which can be a fire or explosion hazard but is otherwise fine. (A stoichiometric mixture of hydrogen and oxygen is Bad News.) But this is not the major reaction because…

The anode can also oxidize Cl- (the chloride in your salt) to Cl2: chlorine gas. In the absence of considerable care (which you don’t have in this hypothetical potato salad or glass of saltwater), that chlorine gas will bubble right out of your little reaction, where it will end up in your eyes or your airways. And it will dissolve into your tears or the fluids in your airways and chlorinate you. You do not want do this. NIOSH says that chlorine gas is immediately dangerous to life and heath at 10 ppm, and you can easily achieve that in a cup with a little power supply. (Like I said, a hundred watts or so can chlorinate an entire swimming pool. Chlorinating your cornea is trivial in comparison.)

This is a major industrial process, which you should not do in your house:

https://en.m.wikipedia.org/wiki/Chloralkali_process

I came upon this which I think is a similar (if not the same) reaction as is occurring in OP.

https://thehappyscientist.com/content/simple-electrolysis

And in the final paragraph states that, and I'm loosely plagiarizing here, the negative ions created in an electrolysis reaction are attracted to the positive/live terminal*, and in the presence of chlorine (as in salts found in the potato) the copper (wiring) react to form green copper chloride.

Edit: not battery, but positive/live terminal

At the copper wire of the positive electrode the chlorine reacts with the copper to make green hydrated copper(II) chloride - CuCl2·2H2O - https://en.m.wikipedia.org/wiki/Copper(II)_chloride

So one wire will lose material into the potato.

Assuming the wire is copper (much wire is) it will appear green in similar vein to how the statue of liberty is green.

>An engineer draws a random sample of electron tubes and measures their voltage. The measurements range from 75 to 99 volts. A statistician computes the sample mean and a confidence interval for the true mean. Later the statistician discovers that the voltmeter reads only as far as 100, so the population appears to be 'censored'. This necessitates a new analysis, if the statistician is orthodox. However, the engineer says he has another meter reading to 1000 volts, which he would have used if any voltage had been over 100. This is a relief to the statistician, because it means the population was effectively uncensored after all. But, the next day the engineer informs the statistician that this second meter was not working at the time of the measuring. The statistician ascertains that the engineer would not have held up the measurements until the meter was fixed, and informs him that new measurements are required. The engineer is astounded. "Next you'll be asking about my oscilloscope".

> https://en.wikipedia.org/wiki/Likelihood_principle#The_voltm...

Specifically if you read the "Example 2" section above that blurb, and then read the "throwback" bit at the end after the voltmeter story, it makes more sense.

PS this story doesn't make sense because you can tell when a voltmeter is out of range.

It's also a bit sloppy with the bounds. To me, "reads only as far as 100" includes 100V, whereas the measured voltages only go as high as 99V.

Good job MTA @ diy.stackexchange.com for recommening this and jasonhansel @ HN for posting it.

[1] https://www.youtube.com/watch?v=QwQJ-3pZfwc

For those who don't know, on a slightly related nugget, you can also use any sort of fat as a lighter fluid as well. Cook up some bacon (for instance), collect the fat/oil from the pan, and next time you're grilling - a few napkins (or other sort of kindling) rubbed around in the bacon fat is more than enough to heat your wood/coal to burning.

Now to set those napkins on fire with a water bottle!

> watter

I was working at some other factory where rats would "cut" data cables occasionally.

I think a lot of us have similar experiences with European (grand)parents born around the era of the two wars. Honestly think that them being born in horrible times yet living during (comparatively) great times helped form a generation of people that stood out.

I miss them.

> The potato was originally believed to have been domesticated by Native Americans independently in multiple locations, but later genetic studies traced a single origin, in the area of present-day southern Peru and extreme northwestern Bolivia.

[0] https://en.wikipedia.org/wiki/Chu%C3%B1o

But wet skin, especially if there's salt involved, is considerably more conductive. As a kid I had applied a mere 12V to some slightly salty water, when some small object fell into the soup. Thinking "it's just 12V" and thinking it harmless, I went to fish the offending object out with my fingers. This was a rather unforgettably unpleasant experience, I will attest.

So, cautionary tale there - even with low voltage, watch out if your hands are wet!

Plugging two (hopefully pretty equal resistance) incandescent lights in series, each lamp should have a 110v potential difference... say:

A ----(60W lamp)-- B --(60W lamp)----- C

By plugging A and C "cables" to a 220V electrical outlet, one should be able to grab 110V from either A-B or B-C :-) (assuming both lamps have about the same resistance). Most electronic devices work with a wide range of input voltage any way, so it doesn't have to be extremely precise.

Why does this matter? Let's put two of these bulbs in series, one of them hot and the other cold, and run 220V through them. The total resistance will be 384Ω, so the current will be V/R, or 0.57A. The hot bulb will have IR volts across it, or 206V; the cold bulb will have 14V. Bingo: your voltage divider is way, way off. Even better, putting 200+ volts across a 110V bulb will blow it (power would be IV, or 117W), and you've got either nothing or 220V.

Now, you won't be starting with one bulb hot and the other cold, but the two bulbs won't be exactly equal. The one with the higher resistance will be hotter than the other one; can you be sure that the imbalance won't slowly get larger and larger?

[0]: https://electronics.stackexchange.com/questions/571836/why-d...

I actually _had_ to do this once, when I forgot a 220v to 110v adapter for a wireless microphone, for a wedding, in an hard to access location [1], and there was just no time to go get a transformer from anywhere else :-) Luckily, the whole "setup" did not turn into fire for the 30 minutes or so that the mic was needed and the wedding speech could actually happen without anyone needing to scream :-)

1: https://en.wikipedia.org/wiki/Tigre,_Buenos_Aires

What happens if they touch? Note that this is while the adapter is unplugged, before sticking the wires into the potato, so shorting them isn't a concern. I can't really imagine that some kind of contamination is a problem since both wires are (probably) copper, nor would I expect any kind of reaction as long as it is unplugged.

Just put the wires at some distance in the salt water and look. The wire emitting the blueish fog (chlorine) is the positive, and the one emitting bubbles (hydrogen) is the negative.

Meaning there's Sodium chloride (NaCl) in solution which not only makes the solution (more) conductive but also in combination with the application of electric current should electrolyze the solution into gaseous O2, H2 and Cl2.

Would that not be copper oxide?

Source: did that as a teenager and did not die (trying to synthesize hydrogen as any normally constituted teenager would do), and the copper wires just ended up being entirely corroded until the immerged part disappeared. No hydrogen as I did not seal the apparatus properly. But I had a nice blueish precipitate instead. I absolutely had no idea it could have generated chlorine. I did sleep in the same room as the experiment for a full week. So I guess either my bedroom was well ventilated or it did not produce enough chlorine, or that it was just copper oxide.

Even if it did make chlorine, as long as your power wasn't too high it might not hurt you (much) due to ventilation. It is also very reactive, so it tends to get used up reacting with whatever random crap is near it.

Chlorine is more yellow/green, so that's unlikely to be chlorine, I'd think.