Electrolysis of Hard Water

Which base indicator?

Try it, and let us know.

• Do your own homework. CR4 is not a homework cheat site. While some here might relish the opportunity to sharpen up old rusty skills by working the homework problem, consider the following and consider it well. If you cheat on your homework by using someone else's answers, you are only cheating yourself, because the purpose of any homework or other academic assignments is to help you learn - by practice, repetition, and self-discovery.

What is the chemistry of the 'hard water' to begin with?

Is this city water of some sort? Does it contain iodine, fluoride, chlorine, chloramine?

What indicator are you using?

There is no water in the text book.

Also unknown is the polarity of the 9 VDC that is attached to the copper probes.

And the material of construction of those probes is not important, as long as they conduct.

Could this be homework??? Surly not.

When direct current at some voltage is applied to a solution of salts in water (what hard water is) electrolysis takes place, with the metal ion collecting at the cathode and the acidic ion at the anode. If the anion is a reactive metal like Sodium or potassium, it would react with water releasing hydrogen and oxygen. In other words, hard water will not become soft (If that was the intention of the question)' but this electrolysis would go on till all the salts from solution come out as solids.

The intention is not to make hard water soft. the intent is to distinguish a salty water(NaCl) from a hard water which contain Ca and Mg bicarbonates and Chlorides. I would like to distinguish them through a simple test, without using the conventional soap treatment, as shown in Yuo Tube. the indicator i have used is phenopthalein.

Taste it.

When you dont understand the question, it is better not to comment. I am surprised by your frivolous comments.

"Frivolous comments"???? Oh, please.

You come here asking us for help, then admonish a respected member of the forum for a comment that is not uncommon here.

You don't get to stipulate the type of answer you get, unless you start your own forum.

Your question sounds like that of a school child trying to get help with an "exp." they do not understand, or don't want to do.

It is poorly worded and makes little, or no, sense.

By the way, exp. is not a proper abbreviation for experiment.

I will take leave of you now, and remind you that these are the rules here: CR4 Rules of Conduct.

I suggest that you also read: CR4 FAQ

Goodbye. Good luck.

I thought this forum is a scientific community whose ultimate aim is to propagate science. but i found that some of the members think that they have a superior knowledge and as such can be judgemental.

May God help them.

Goodbye.

No this is: The Engineer's Place for News and Discussion®

It is an engineering community with a somehow different and more down to Earth tone in its language. Engineers embrace the idea of science but furthermore we turn science into useful solutions. We discuss science on a regular bases as it helps us finding the solutions but we are far off from being a science forum.

The difference is quite obvious: in Science you think about putting the electrodes into hard water to check what happens. An engineer would have done so and reported voltage, amperes and tables and graphs to discuss the results.

The reason why we might be seen as "superior" is that we do not understand how someone can ask a questions without doing his homework first. Its not comprehensible for hands on guys that something that can be checked with a little effort is being posed as a question following a denunciation as being "frivolous". Did it occur to you that salt water can be easily found by tasting it?

Since you have not told us if this is for a chemical process or industrial usage the comment was more than appropriate and good (scientific) thinking.

Remember the better the question the better the answer!

What you see as a critical flaw, others may see as an important strength.

.

People and ideas are not to be treated the same.

Some ideas are superior to others.

Understanding of these ideas may allow development of knowledge that is superior to what it could have been without those ideas.

Propagating such knowledge and ideas requires judgements about what it superior and what is inferior.

.

Be as tolerant of people you safely can. Contrarily, be extremely judgemental of ideas; be an elitist acting with extreme prejudice toward ideas.

....and perhaps save any god from being overwhelmed by continuous requests for help.

"I would like to distinguish them through a simple test, ..."

Then why didn't you ask that in your original post? The original does indeed sound like a request for homework help, to avoid actually doing the experiment.

Subha, it is not possible to identify hard water from salt water by electrolysis as the process only dissociates water in an open cell.

@Randall was right in suggesting you taste the water.

Quite often you do have water with NaCl and Ca and Mg salts together.

You may be better off using chemical identification of the ions.

You get a cup of tea?

Stop trying to "re-invent" the wheel, my friend. It is easy to purchase on the free market ion-specific electrodes for Calcium, and as far as I know this is almost always included in hard water. There are also color indicators for hard water titration. Also, most natural waters contain hardness and chloride salts, including sodium and potassium. Under no circumstance will "all the dissolved solids deposit from the water".

It would be wise to search the web for answers before you come in here with something so ridiculously sophormoric as to attract such comments as you have.

Could you throw some light on 'Ion specific electrodes ? Could one get them for each metallic radical ? Where do we get them ?

Paste 'Ion specific electrodes' into the Google search field (in my case, of Firefox), and I get:

Clicking on any one of those will bring up lots more, including people quite willing to sell them...

It will be quite similar in any other browser.

try www.hach.com

Hach Company has international sales as I understand it.

Surely, even if you are not in the United States, there are scientific supply houses that will be happy to accomodate you with what is precisely needed. You might also opt for taking samples to a certified laboratory.

I know this was posted quite awhile ago, but had to laugh when I saw it. Mostly because someone wrote that if you were a real engineer, you would have already done the experiment. And also because when I found this, I had just done the experiment. Except that I used 12 volts, from a battery charger.

Try it with a larger aquarium, say 10 to 20 gallons, it's very interesting, at least in hard water. One of the copper wires get's a lot of copper oxide on it, the other one generates gas, probably hydrogen.

While the water started out completely clear, it became very cloudy, and blue/green, I'm assuming from the copper oxide.

And yes, a little data, though not much. About 35 ma, 12 volts, 24 hours. Filtered the liquid and residue, but the residue did not weigh enough to change the scale by 1 gram (after being dried), so it is pretty light. Wires were at the two ends of the aquarium (10 gallon). Ground end was probably generating the hydrogen, and bubbles went up rapidly in a thin stream. Other end didn't bubble as much.

May try it again.

The things is that with DC applied potential, one electrode is always the anode and will be oxidized to some extent, and will also be a local anion "sink" (anions drift toward the anode in these experiments, build up concentration, and usually precipitate unstable metal ions from solution as hydrous oxides), the other electrode will be a cathode where protons drift to (and other cations), except that protons adsorb to the cathode, become reduced to atomic hydrogen, which desorbs as hydrogen (H2 molecular gas).

In some cases oxygen can also be produced at the anode (by oxidation of hydroxide ion), in which case the gases emitted above the electrolysis bath will be a dangerous mixture of hydrogen and oxygen.

You could also try this with iron electrodes, and even AC potential applied, and the result will still be hydrogen, but in this special case, all or nearly all of the oxygen will be tied up in iron corrosion product (iron oxides) that drop out of solution, and make the product hydrogen safer to use. By the way, I think this process is already patented, as a means of producing hydrogen on demand (without the intrinsic danger of flash-back) for introduction with air into the engines that are fuel-injected as a means of improving fuel economy up to 30%.

My goal in the experiment was more to see if I could get calcium to either form on one of the electrodes, or else to form at the electrodes and then fall off. The ultimate goal being to have a water softener that uses less salt, or no salt.

I considered using another material than copper, but first wanted to see what copper could do. If it looked promising, and my interest was high, I would then have continued either with a stainless steel powder, or something else.

However, salt cells, which are used in some swimming pools, do a similar thing. They have a charge between two plates, and have a problem with calcium buildup, which means their 'problem' is part of what I was hoping to accomplish. The challenge then would be to remove the built up calcium. This could possibly be done by changing polarities, forming hydrogen on the calcium coated plates, and then flushing them with water.

Unfortunately, salt cells apparently have specific coatings, because of corrosion. At this point, I had to think about how far I wanted to pursue this. Maybe I could get calcium to form on a bed of stainless steel powder. But if even that has a problem with corrosion (which it must, or the salt cell people would have used stainless steel), then I need specially coated powder or plates. At this point, I may be out of my realm of interest.

Also, if we get the calcium to form on a bed of stainless steel powder, how do we flush it, and how much water can we purify in what amount of time? Obviously, this has gone beyond being someone's homework problem.

Anyway, not sure if I'll get back to this. If I run into a free supply of stainless steel (or other) powder, maybe I'll pursue it...

Believe it or not, there is actually a company out there that attempts to control calcium/magnesium scaling potential in cooling tower water by introducing a side-stream (bypass) with a calcium sink in this loop. The calcium sink consists of a specialty anode (probably titanium oxide on stainless steel), a stainless steel mesh cathode, and an applied DC potential. The cells are replaced when the differential pressure across them increases to the point of plugging. They increase in weight by a huge amount during this process. The "calcium sink" works by keeping the scaling potential just under the limits where scale would form at the heat exchanger tubes.