Unknown Substance

[Guest abcdefg]

Hey...

Well tonight I distilled some water by boiling it for a few minutes. I had 4 D sized batteries hooked together to form a battery pack. I then had 2 stainless steel screws, hooked to wires, which were hooked to the battery terminals. I was trying to separate the water into hydrogen and oxygen, not sure why though. Well, I read online somewhere that salt makes water conduct electricity better, some I threw in about 5 tablespoons of salt. (yes that is A LOT) Then, I plopped the screws in the water. The positive side bubbled fast (oxygen) and the negative slow (hydrogen). I had a glue stick cap at the top of the hydrogen screw because that is what I wanted to collect. Well, I got pretty bored waiting for this to make a good amount of hydrogen, so I took out the lighter. I lit some oxygen bubbles to see if they would pop, and they did.. (very little, little pops). Then, this rust started to form on the top of the water. (at least that is what I think it was). Then, I decided to stop lighting the buubles so I went to put the lighter away. When I came back, this green- pulp like substance was swirling around in the water. The water kept getting greener and greener, and a slimy green substances formed on the top of the water. Soo, after a few I pulled the screws out of the water, and the green substance stopped forming. I scooped some of the stuff of the top and put it in a conatainer, and then I filltered the water to get the green pulp and put that in a container. It is a very, very dark green substance, that is quite thick. It leaves a brownesh greenish residue on my finger when I touch it. Does any one know what I stumbled apon?

Thanks,

Mike

[Tetrahedrite]

With that much salt, chlorine gas was probably formed during the reaction. I have seen the same green gunk using graphite electrodes. I really don't know what it could be, but i'm sure someone here will.

[calbiterol]

It's much more efficient to use graphite electrodes... Well, efficient isn't the right word, but it's a lot faster in the long run than nails, because the nails will corrode. Just carve the wood off of a pencil with an XACTO knife, or any other sharp knife. The core (in other words, the lead) is really graphite, which makes for a fine electrode. The lead tubes are actually surprisingly strong.

 

My best guess would be that it's some form of corrosion of the nail, but that would go against getting that result with graphite electrodes.

 

I've never had that problem with my nice graphite rods (out of a pencil, true to form) and have been bubbling away hydrogen when I feel like amusement. My next project with hydrogen is to create a solar "hookup" that will keep it running without batteries, "producing" clean, free (aside from water bills) hydrogen for... "experimentation..." (Insert evil laugh) Yes, I said create, as in, from scratch.

 

There's another problem here that I see though - there should be much more bubbling on the negative electrode (the anode, the one bubbling hydrogen) because water is, quite simply, H₂O, two parts hydrogen to one part oxygen. Perhaps you are forming a diluted form of an acid (like, hydrochloric... something with H and Cl).

[BenSon]

I dont know about that green sludge your probably forming some chloride compound but i don't know what. Also if you want to speed up you electrolysis add some sulfuric acid instead of a salt. Plus graphite electrodes like calbiterol suggested is also a good idea

 

~Scott

[Dak]

Lol, this reminds me of the aqua detoxifyer machine. it was a foot spa that was loaded with brine, and an eletrical current passed through the water and your feet, allegedly driving all the nasty toxins out of your body through the pores in your feet. As 'evidence' for the detoxifying effects of the miraculouse aqua detoxyfier, patients attention was drawn to the layer of brown scum of 'toxins' that magically formed at the top of the water.

 

in your case, just as in the aqua detoxifyer, the brown scum is ferrouse oxide ie rust, caused by the H2O, NaCl and eletricity rapidly oxidising the ferrouse eletrodes.

 

see here for more info.

 

(the funny thing is, as the conductivity of salt-water is significantly greater than the conductivity of your feet, very little (if any) electrisity is actually passed through the feet)

 

as for the green stuff. umm...

 

well stainless steel has more metals than Fe in it, chromium, nickel and myobium mainly, so maybe the oxidised forms of one of these metals is green.

 

what containter is the water kept in? if it is made with copper, then i suppose the green stuff could be copper oxide.

 

it leaves a brownesh greenish residue on my finger when I touch it.

 

as a biochemist i feel obliged to advise you not to poke unknown substances with your finger. also, you might want to do the experiment outside or in a well ventelated place (the extracter fan above some cooking hobs will do) incase chlorine gas is created from the salt -- even small quantities of chlorine are VERY unplesant to inhale. im talking bleeding lungs here.

[BenSon]

"well stainless steel has more metals than Fe in it, chromium, nickel and myobium mainly, so maybe the oxidised forms of one of these metals is green."

 

I though about this but wouldn't iron oxidise first due to reduction potentials therefore the other metals (chromium nickel) wouldn't oxidise untill all the iron was gone. Which would be most of the pan!

 

~Scott

[Dak]

hmm, interesting. but i guess if the Fe oxidises, then the structural integrity of the alloy will be disrupted, bits of the other metals will fall away from the alloy and float away from the stainless steel, allowing it to oxidise away from the Fe.

 

or if oxygen is being produced in abundance at one of the eletrodes, aslong as the ratio of O:Fe is greater than 1.5 O2 : 1Fe, then the Fe would be oxidised to Fe2O3 and there would still be sum O2 left over for the other metals.

 

(umm, just read that last bit and dont know whether it makes sense. its been a long time since i did non-bio-chemistry)

 

actualy, thinking about it how dus the stainless steal rust in the first place? i thought the whole point of stainless steel is that the chrom layer prevents oxidisation?

[BenSon]

I think that the small amounts of other metals that may fall away from the screws would be minimal and would hardly make a measurable amount of substance. Stainless steel can oxidise but it takes a bit of work i dont think that the screws were very high quality. I thought steel was just an alloy with iron and other metals, dont know about a chrome layer though?. Galvanised steel is coated in zinc i believe maybe thats what your thining of...

 

~Scott

[YT2095]

this may or may not be the answer, but I`ve noticed the same thing occur on many occasions also, here`s what I put it down to...

 

during the "Fizz" part of the reaction, tiny droplets like a mist bounce around and gather on the wire that you used to hook up with (copper) this then drips a little and creates copper chloride and hydroxide, that`s the light green "scum" that floats.

 

you avoid this I always dip the electrode where the hookup wire connects to, in some hot wax, it`s stops it dead

 

edit: Nickel salts are all green too!