Dissolving salt in de-ionized water

GA

milo

Oh, well... Just blow it out your de-ionizing water pump, why don't you!!!

Can't, its peristaltic!

HAve you tried using a magnetic stirrer?

If you have a means of placing it underneath the tank, it can provide long continuous agitation.

http://www.sciencelab.com/page/S/CTGY/21761

Spare computer parts at home ?

HEres a diy:

http://blog.makezine.com/archive/2006/09/how_to_make_a_magnetic_stirrer.html

You may find it easier to predissolve in smaller batches ...

milo

Have you tried ultra high frequency(ultra sonic) sound generation to dissolve the salt?

I'll try warming the water first and see where that gets me.

No, I haven't heard of mixing with ultrasonic sound waves.

Not mixing, dissolving or creating a liquification of the salts into a lquid state

prior to mixing into the remaining de-ionized water. Very similar to the medical use

of UHF sound for destruction of kidney stones.

Of all those parameters you took into account, I did not see temperature. The water will dissolve more or less salt depending on how warm the water is. At the temperature you are working, you've created a saturated solution - no more salt can be dissolved, so any more add simply sits at the bottom. If you raise the temperature considerably higher, you will be able to dissolve even more salt. When undissolved salt appears in the bottom of the heated mixture, you have created a "supersaturated" solution.

People that grow crystals first create a very warm supersaturated solution. In the center of the container, they hang a small, well-formed crystal of the material in solution - this is called the "seed crystal." This small seed crystal will not dissolve because the solution is supersaturated. However, once the solution is allowed to cool, the degree of saturation passes beyond the state of supersaturation, and rapid crystallization begins about the seed crystal. If lucky, this produces a large, nearly perfect crystal of the salt.

However, the main point of all this is to remember that the amount of something being dissolved is dependent on the temperature of the solvent - in this case DI-water.

So, is there a formula or rule of thumb for how much heated DI water it would take to dissolve 9+ lbs of salt? And, how hot is hot? The hotter the better, right? So, should I try boiling the water? Thanks all, you've been a big help.

Sorry, stochiometric is the wrong word. We are not reacting salt with water to produce different chemical products, we are simply dissolving it.

To dissolve more of the salt into the water you indeed must raise the water temperature. This is because the solubility of salt is increased the warmer the water is. You can look this up in chemical tables so that you can calculate how much salt can be dissovled into how much water at a given temperature. Up to a point, the dissolved salt can still remain in solution even if the water is cooled after the salt is dissolved.

Please emphasize that that was "temperature" and not "heat." Two different things. Right?

Thank you, PhysicsProf! That's what I'm looking for. I've already started looking at circumstantially specific ways to heat the solution. Thank you all for the help. I'm moving in the right direction now.

Yes, the hotter the water, the more will dissolve. And as someone mentioned, dissolving aliquots and adding that to the main tank should make it easier. Stirring or agitation by any means mixes the solution so there are no pockets or clines of saturated solution. Can you estimate the amount of undissolved salt? It may be you are a small amount low on the required quantity of water (say, a gallon short).

I figured out why I had so much solute left over that wouldn't dissolve. The "salt" we ordered is synthetic sea salt, which, in an effort to be representative of real sea water, is composed of about 58% NaCl, and the rest is about a dozen other chemicals in various quantities that may or may not (apparently more the latter) be water soluble. (oops) Mystery solved. We're reordering 99.9% NaCl. We can all go home now. Thanks everyone.

Oh, btw, I did find a source online that said the temperature of the solvent only affects the solubility of some solutes (like sugars), but not others (like salts) (Longman GCSE Chemistry, Jim Clark and Wikipedia - Solubility Table). Something to ponder...

Dunno as how I'd believe that - try an empirical evidentiary method. I use warm salt water as a sore throat gargle, and the warmer the water, the more salt dissolves...

So that's where my margaritas have been disappearing to!!!

I know I'm late into this thread, but was surprised with your challenge as we have been running those fog tests for many years without difficulty.

Thanks for keeping on your own investigations and finding the "real" answer tot he problem.

I was actually surprised that none of the others had gone to the science, looked up solubility of salt and found that you were not even close to saturated.

We mix our solution with a little plastic boat impeller on the end of a shaft driven by a 12 Volt motor scavenged from a radiator cooling fan.

Welcome to the forum. Your thorough process will make you a welcome addition to the "body of knowledge" that is here.