Mad Scientist pool chemistry

[Aqua Lab Rat]

This is a more than a bit absurd, and I'm not 100% sure it belongs in The Deep End (if not, please correct me). It also give insight into how my brain connects things.

Suppose you had a swimming pool where your source water tended to be low in alkalinity, and your pH tended to run a bit low. The usual remedy would simply be to add some carbonate / bicarbonate. But what if instead of that, you added some heavy water? (This is water that instead of the regular "H" which is just a proton, it also has a neutron so the mass is nearly double). Heavy water has a higher pH than the more common kind.

It's also probably waaaayyyy more expensive than tap water, but that doesn't bother mad scientists since they also tend to be criminal masterminds.

As an extra bonus, the increased water density would make you more buoyant, so it is both "pH Up" and an auxiliary "water enhancer" all in one. And it slows down any radioactive reactions going on in your pool - makes you feel all tingly.

 

[JoyfulNoise]

Putting aside all of the technical and financial difficulties with the idea as well as the long term health concerns with possible heavy water ingestion (it is toxic to cellular life), I think you've got the wrong idea when it comes to pH.

While it is true that the equilibrium pH of heavy water is slightly higher than light water (about 7.4 for heavy water), using it as a source of pH increaser would be somewhat pointless. The pH effects of dissolved inorganic carbon (bicarbonate/carbonate chemistry) would completely overwhelm the naturally higher pH of heavy water. In other words, the scale of the additions would be so large that you'd essentially have to replace huge volumes of water to see any appreciable effect. Then, once your pool water is completely composed of heavy water, adding fill water would that is low pH/low TA would simply start to drop your pH again.

As for buoyancy differences, most of the density of water is related to the atomic weight of oxygen not hydrogen. So the density difference is only about 10%. That's better than salt water versus fresh water (about a 3% difference) but not nearly as noticeable as the Dead Sea (about a 24% difference).

The more interesting effect is melting/freezing differences. A heavy water ice cube would sink in ice cold fresh water and not melt because the melting point of heavy water is about 4 deg Celsius. So if light water is held at a temp of less than 4C but above 0C, then a heavy water ice cube would simply sink to the bottom and stay there.


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[pooldv]

Putting aside all of the technical and financial difficulties with the idea as well as the long term health concerns with possible heavy water ingestion (it is toxic to cellular life), I think you've got the wrong idea when it comes to pH.

While it is true that the equilibrium pH of heavy water is slightly higher than light water (about 7.4 for heavy water), using it as a source of pH increaser would be somewhat pointless. The pH effects of dissolved inorganic carbon (bicarbonate/carbonate chemistry) would completely overwhelm the naturally higher pH of heavy water. In other words, the scale of the additions would be so large that you'd essentially have to replace huge volumes of water to see any appreciable effect. Then, once your pool water is completely composed of heavy water, adding fill water would that is low pH/low TA would simply start to drop your pH again.

As for buoyancy differences, most of the density of water is related to the atomic weight of oxygen not hydrogen. So the density difference is only about 10%. That's better than salt water versus fresh water (about a 3% difference) but not nearly as noticeable as the Dead Sea (about a 24% difference).

The more interesting effect is melting/freezing differences. A heavy water ice cube would sink in ice cold fresh water and not melt because the melting point of heavy water is about 4 deg Celsius. So if light water is held at a temp of less than 4C but above 0C, then a heavy water ice cube would simply sink to the bottom and stay there.


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^^^^^^^ that's what I was thinking.

 

[needsajet]

^^^^^^^ that's what I was thinking.

rofl

Hopefully no one ends up on the no-fly list as a result of this thread

 

[JoyfulNoise]

I just did my own "mad science" - a package arrived with about 5lbs of dry ice in it. So I dumped the dry ice in my spa and ran the spa jets while it all bubbled. I measured the pH of my pool and spa -

pH (pool) = 7.7

pH (spa) = 7.2

The pool/spillover is set to run in a hour so the pH imbalance won't last long but it was kind of fun to turn the spa into my own personal human-size SodaStream maker....now I just need to add some cherry-cola flavoring and red/brown food dye and we'll be all set....

 

[needsajet]

I hope you took a picture or video before the dollop of ice cream

 

[JoyfulNoise]

I hope you took a picture or video before the dollop of ice cream

Sadly no. I was running around a bit between the pool and my crying daughter. She's 9 months and refuses to be put down for a nap under any circumstances...mommy was away for the day and she was not at all happy with her "customer care representative". I suspect my year-end performance evaluation will get a pretty big ding...

 

[needsajet]

This needs to be on your Christmas list... Baby backpack, Storage spaces and Diaper bags on Pinterest

You'll get a 5-star review in no time!

 

[Aqua Lab Rat]

You guys are waaaaay too serious. Mad scientists don't mind replacing 75% of the water as long as it shows those pedants who "da man" is. :queen:

More seriously, though, it does show how things like this usually are defeated due to a misunderstanding of the scale of things. Like putting a smaller bulb in the fridge to reduce the electric bill.

 

[Donldson]

rofl

Hopefully no one ends up on the no-fly list as a result of this thread

Nah, it isn't the heavy water that gets you put on the no-fly list. It's the order for 50,000 smoke detectors that does that.

And heavy water costs upwards of $700 a liter. So, you know, there's that.

 

[bdavis466]

Sadly no. I was running around a bit between the pool and my crying daughter. She's 9 months and refuses to be put down for a nap under any circumstances...mommy was away for the day and she was not at all happy with her "customer care representative". I suspect my year-end performance evaluation will get a pretty big ding...

If you get fired I'll gladly bring you on board...you'll need to drive your own vehicle though because I can only handle so much head-banging to Flock of Seagulls locked on repeat.

At $700 per liter I'd be more apt to fill the pool with Jello!

 

[JamesW]

You could add some super heavy water (Tritiated water). Then, if the pool is deep enough, maybe some of the duterium and tritium will fuse and release heat. That way, you get free pool heating.

 

[JoyfulNoise]

More dry ice arrived today so I decided to put it in the waterfall -

It was a bit windy out today so the "mist" was blowing around instead of traveling down the waterfall path. Normally when I add dry ice on a still day it looks like fog rolling down the waterfall.

 

[needsajet]

That looks great I wonder if anyone here is working on a DIY dry ice dispenser!

 

[JoyfulNoise]

That looks great I wonder if anyone here is working on a DIY dry ice dispenser!

That would be fun...

 

[Saturn94]

Cool!

 

[JamesW]

Maybe try liquid nitrogen.

Molten salt makes a nice reaction when poured into water.

Molten salt teaser video - full video in a day - YouTube

The heat from the salt cooling provides some of the energy. A lot of heat is also released as the salt phase changes from liquid to solid. This provides a lot of energy that phase changes water from liquid to gas.

Get a 40 lb bag of salt, heat it up to about 2,500 f and then pour the liquid into the pool.

Note: Be careful when handling large quantities of molten salt. Wear goggles and gloves.

 

[JoyfulNoise]

Maybe try liquid nitrogen.

Molten salt makes a nice reaction when poured into water.

Molten salt teaser video - full video in a day - YouTube

The heat from the salt cooling provides some of the energy. A lot of heat is also released as the salt phase changes from liquid to solid. This provides a lot of energy that phase changes water from liquid to gas.

Get a 40 lb bag of salt, heat it up to about 2,500 f and then pour the liquid into the pool.

Note: Be careful when handling large quantities of molten salt. Wear goggles and gloves.

I liked the nitrogen tornado he created when he lit the diethyl ether on fire in his pool and then doused it with LN2. Fun times, fun times....

I'm still not buying his explanation for the molten salt explosion being "purely physical". It only takes a small amount of hydrogen gas to create a very powerful explosion. Having worked with liquid nitrogen, liquid helium (both ⁴He and ³He) and hydrogen gas, I can't tell you how many cryogenic and explosive safety videos I have had to sit through. My gut feeling is that the molten salt (being highly reactive) splits a small fraction of the water into hydrogen and oxygen gas but it in itself does not react to form separate sodium metal or chlorine gas. The remaining heat then ignites the hydrogen/oxygen mixture and causes the explosion. That kind of reaction can easily happen without shifting the pH of the solution since the molten salt would likely create chemically balanced amounts -

2•H₂O ---salt---> 2•H_2(g) + O_2(g)

That's a pH neutral reaction. Sodium metal is a completely different reaction in that the sodium reacts directly with the water to split it into hydroxide and hydrogen gas.

2•Na_(m) + 2•H₂O -----> 2•NaOH + H_2(g)

That is most definitely not a pH-neutral reaction. I think my position is also bolstered by looking at the standard enthalpies of formation for water and sodium chloride -

H2O(l) -285.8 kJ/mol

NaCl(s) -411.0 kJ/mol

So it would take 1.4 times as much energy to split salt into it's components than it does to split water. I'm pretty sure one can achieve the necessary ∆H_f of water with a large volume of hot molten salt especially given the fact that smaller and cooler quantities of the salt he threw in did not really result in an explosion.

- - - Updated - - -

Oh, and the doofus is really lucky he did not get impaled with glass fish tank shrapnel....

 

[JamesW]

I don’t think that any hydrogen or oxygen gas would be produced. That would require some sort of chemical reaction or electrolysis. The molten salt should not be chemically reactive.

Even if hydrogen were produced, I don’t think that there would be enough temperature left to ignite it.

I think that it’s just a heat transfer thing. The salt cools down rapidly and as it converts from liquid to solid, it dumps a lot of heat in a short time causing some of the water to boil and convert into steam.

520 joules per gram x 50 grams = 26,000 Joules of energy are released as salt converts from liquid to solid.

26,000 joules / 2,260 jouls per gram for water = 11.5 grams of water converted to steam.

11.5 ml of water will convert into about 20 liters of steam.

I suspect that initially the salt has low surface area in contact with the water. However, when the water begins to boil, I suspect that it disperses the salt enough to greatly increase the surface area in contact with the water resulting in a big heat transfer from the salt to the water.

 

[JoyfulNoise]

Suddenly have a burning desire to tee of my natural gas line and make my own liquid-salt furnace....don't think the PB covers molten salt explosions as part of the warranty on the gunite shell though