Making salt water the very hard way.

When I was in High School Chemistry it came to my attention that if you mixed Red Devil Lye (NaOH) with Hydrochloric (muriatic) Acid (HCl) you would end up with NaCl.H20. Common everyday salt water… and drinkable. Maybe too salty, but still drinkable. I really thought I understood the process back then and checked and rechecked my hypothesis with the text book as well as my father’s chemistry books. He was a chemist but I never asked him. I really though I was right. I had fantasies of mixing up lye and hydrochloric acid in class, then drinking from the beaker. I could never get the nerve up to try it though, since both NaOH and HCl are highly caustic. Was I off base? Should I be really really glad that I didn’t try this experiment, or at least drink it?

Best not to try it. Unless you get the proportions just right, you’ll end up with NaOH or HCl in the solution.

Sodium hydroxide (NaOH) is a base, and hydrochloric acid (HCl) is an acid (obviously). When acids and bases react, they creat water plus a metal salt, in the case, NaCl – common table salt. So, yes, if you mixed equal amounts of them, you’d end up with very salty water. More practically, you’d mix equal amounts of solutions of them with the same molarity.

I imagine there would be a rather “exciting” reaction too. Probably messy as well.

I my memory serves, this is one of those demonstrations teachers used to do in the old days before they realized that it was, well, really stupid. Kind of like mouth pipetting. It could be done, but you’d have to be very careful to mix exactly the right amounts.

Not really. Acid-base reactions are pretty dull. They’re weakly exothermic, and there’s no products other than water and a metal salt, no gas production or anything like that.

My eigth grade chem teacher performed this experiment, and drank the result without ill effect. If you want to try it at home, be sure to dilute the acid and base before mixing them, else you’ll end up with an extremely concentrated and boiling hot, salt solution. It’s also important to mix exactly equal amounts of the acid with the base. Any error would leave you drinking a solution with a lot of acid or base still left. Liquids with pH’s of <1 or >10 not only taste terrible, they can give you chemical burns.

Well, now I’m so totally pissed off. I could have done it! I probably WOULD have diluted them first, as Squink recommended. I probably would have ended up in detention anyway, even if the Chemistry teacher did think I was a genius. Probably for the best. I might have mixed them inequally.
Now I can’t wait to have kids so I can really impress (scare) them. :slight_smile: Or give them stupid ideas. :slight_smile: My Dad used to do science experiments for my sister and me, by making fireworks and such. It’s rubbing off.

Thanks for the info.

Eh, don’t listen to them; if you dilute it enough you might as well drink the acid right away, and where’s the fun in that? :wink:

On a more practical note, does anyone know if anyplace still sells those chemistry kits that used to be advertised in old magazines & such? I think they disappeared before I was even born due to the realization that an exploding consumer base isn’t good. Or lawsuits, I dunno. Science experiments (even at school) seem to be getting safer and safer at the expense of any useful output.

(I once attended a science fair where our team lost marks on the chemistry section when myself and my friend neglected to wear the safety goggles. Our protests that we already had regular glasses, and in any case were experimenting only with the fairly-stable liquids of water and green tea (both cold) failed to sway the judges.)

More complete answer.

Fully possible. You’d use some kind of indicator that shows when the solution becomes acidic, such as Phenolphthalein, then add HCl from a burette into a fixed amount of NaOH, and note roughly the point at which a pink tint occurs. Then you could rerun this, probably several times, slowing down as you approach the indicator change point, and eventually, as you got a more precise measure of quantity to add, you could omit the indicator, and thus do a perfect netrualisation. This is titration.

However, I wouldn’t trust the purity of solutions found in school, nor the cleanliness of the equipment.

QED- whaddabout that bakingsoda and vinegar thing? That’s somewhat gassy*

*messy too- whooooo!

I would not drink any mixture of lye and muriatic acid, even if mixed exactly. The purity on these (store bought) chemicals tends to be very low, and they probably will contain some contaminants that are likely to be harmful if ingested. After all neither of these products were intended to be consumed.

I think Q.E.D may have been referring in general to the reaction of strong acids with strong bases. Acetic acid and sodium bicarbonate are not included in these categories (HCl and NaOH are).

Correct. Experiments involving ingestion should only be performed with laboratory-grade chemicals to insure purity, unless you have a data sheet specifying exactly what impurities are to be found and in what amounts.

I realize that this probably took place years ago, but this still has to be the stupidest demonstration I’ve ever heard of. Any teacher that ever performed such a demo in front of impressionable students should permanently lose their job and teaching certificate.

What happens if a student tries to replicate the demo, and doesn’t get the proportions quite right? (Or they use a polyprotic acid? Or they use a Group 2 hydroxide?)

Answer 1: potential severe chemical burns to the mouth and esophagus, possibly resulting in death.

Answer 2: a lawsuit that could bankrupt the school district.

One of the strongest admonitions given to chemistry students is to NEVER taste anything.

Anyway, all of that being said, there is a neat demo that can be done, in the laboratory, involving the neutralization of a strong acid with a strong base:

Titrate 50 mL of 1.0 M NaOH (aq) into 50 mL of 1.0 M HCl (aq). The resulting volume can be most easily seen if the HCl is contained in a 100 mL buret. What happens?

Answer: in such a neutralization, not only is NaCl (aq) formed, water is as well. The proportions specified above will produce nearly 1 mL of water. In other words, the resulting volume will not be 100 mL, but will be nearly 101 mL.

For some reason, students have to see this to believe it.

BTW, the concentrations involved are high enough that this is best done as a demo, rather than by students themselves. Of course, less concentrated solutions can be used, but there is correspondingly less water produced.