# Reducing contaminants in a jar with water:

sonhouse
Posers and Puzzles 16 Dec '10 12:28
1. sonhouse
Fast and Curious
16 Dec '10 12:28
So I am thinking about when you do dishes, you have a jar with some glop in it, you put in say, 1 cc of soap in a liter bottle wash it out then start to rinse. Is there a way to maximize the removal of said soap from the bottle?

For instance, suppose you just run ten liters of water flushing continuously. Would that remove more soap, lower the concentration more, than say, filling 1/2 liter, shaking it up, dumping, refill with another 1/2 liter, and so forth, 20 times so you use the same 10 liters of water. Would there be a difference in the left over concentration of soap (the liquid kind for doing dishes) from either method or would the resultant concentration of left over soap be the same in either case?
2. PBE6
Bananarama
21 Dec '10 21:48
Originally posted by sonhouse
So I am thinking about when you do dishes, you have a jar with some glop in it, you put in say, 1 cc of soap in a liter bottle wash it out then start to rinse. Is there a way to maximize the removal of said soap from the bottle?

For instance, suppose you just run ten liters of water flushing continuously. Would that remove more soap, lower the concentra ...[text shortened]... either method or would the resultant concentration of left over soap be the same in either case?
This is actually a very tricky problem to answer with any precision. The amount of contaminant removal is going to depend on the flow rate, the concentration of the soap solution, degree of mixing, contact with the contaminant, diffusion rates, physical perturbation, bulk transport, etc... It would be an interesting exercise to try and model the situation using some of these parameters. Considering that this is just the type of problem to send me into an OCD-like tailspin, I might even post the results!

As a rule of thumb though, 3 washings with small (relative to the size of the container) clean water aliquots should remove 99%+ of the soap. This is the rule of thumb that we followed back in university when cleaning glassware, and it seems to produce good results.
3. 22 Dec '10 00:234 edits
i can not answer your question, mainly because of what crazy banana has mentioned ...

maybe you like to change the riddle to something seemingly more easily answerable:

given a glass of wine (what a coincidence...), a glass of water and a spoon (volumes x,x and y respectively, with y << x), how many times do you have to take a full spoon from wine galss to water glass and back to mix them both 50:50 ?
4. 22 Dec '10 00:271 edit
Shaking quickly turns the soap/water to foam, making it very tricky to empty out of the bottle.
5. coquette
22 Dec '10 06:01
the mechanical forces of shaking the container would be very important in helping to remove contaminants.

without attempting mathematical modeling, my intuitive guess (presuming a contaminant that is reasonably water soluble - all bets are off for insoluble greases, for instance) is that you could add very little water at first - maybe 1/10th of the volume and shake vigorously and dump it for a lot of "gross" removal. that gets down closer to the "stain" then, you add between 10% and 20% and shake for a few seconds, that gets read of a lot of the stain. next ~ 20% of the volume and a nice swish and you are pretty close to clean.

The real trick goes back to all the earlier factors . . . the stain may NEVER come out.

also, 99% is nowhere near "clean" or "stain removal" for chemistry lab work. So, you are back to flushing and flushing and flushing. the rule of thumb is the same as for mixing paint - do it until you think you are way past the point where you thought you needed to.
6. PBE6
Bananarama
22 Dec '10 14:03
Originally posted by coquette
also, 99% is nowhere near "clean" or "stain removal" for chemistry lab work
That's why I added the "+" at the end! ðŸ˜‰
7. sonhouse
Fast and Curious
22 Dec '10 15:391 edit
Originally posted by coquette
the mechanical forces of shaking the container would be very important in helping to remove contaminants.

without attempting mathematical modeling, my intuitive guess (presuming a contaminant that is reasonably water soluble - all bets are off for insoluble greases, for instance) is that you could add very little water at first - maybe 1/10th of the volu aint - do it until you think you are way past the point where you thought you needed to.
I get down and dirty, so to speak, with contaminants. One of my jobs was maintaining a DI water treatment facility in our cleanroom. Talk about 99%. That would ruin every process that depended on the DI water to clean, such as flushing sulphuric acid from acid baths, the high pressure jet wafer cleaners that used DI water and such. We have sophisticated contamination measurement instrumentation and 5 or so stages of contaminant removal starting with city water. One of which is an electronic ionization exchange that electrically ionized the contaminants in the water then using strong magnetic fields to divert the suckers. We also have to deal with algae growth which for some reason loves DI water, a system of about 8 high powered UV lamps with the water going by that kills most of the bacteria and algae. The weird thing about that was, the particulate counter would show low parts per million but at some of the flow meters (transparent slightly cone shaped tubes with a plumb bob looking thing that would measure the flow by how high it floats in the tube), that instrument STILL had a small amount of algae build up. After all that work to make DI water, some stuff still lived!

I know from experience if the contaminant is insoluble in water, it is a heck of a lot easier to remove by mechanical shaking. The really bad stuff is soluble. We have a water cooling loop that we had to remove all the iron fittings and replace with plastic because we would have devices that was water cooled and unless you take extreme pains you can't use DI water for cooling unless forced by, for instance, high voltage barriers (DI water is a good insulator, we cooled an ion implanter with it, which has 200,000 volt power supplies but it is a pain in the butt to use because there can be no metal at all in the DI water path, DI water eats out SS like acid)
so the cooling loop had some iron piping and it contaminated a molecular sieve vacuum pump ( a very high tech machine) and I had to add a lot of filtering units to keep the crud out of the pump). Contamination was one of my biggest bugaboos in our cleanroom. I guess any cleanroom, and I have seen hundreds of them.
8. Igloo
Fishing
22 Dec '10 18:10
Originally posted by sonhouse
We also have to deal with algae growth which for some reason loves DI water, a system of about 8 high powered UV lamps with the water going by that kills most of the bacteria and algae.
We used to have an algae problem with in the piping (plastic) from the DI unit. Then a new lab-tech was hired and he cleared up the algae problem. We didn't worry too much about how he fixed the problem, we were just grateful that we didn't have algae particles in our experiments anymore.

It took three weeks to trace back the meandering pH readings in the experiments to his acid cleaning of the piping. ðŸ˜•
9. sonhouse
Fast and Curious
22 Dec '10 21:252 edits
Originally posted by Igloo
We used to have an algae problem with in the piping (plastic) from the DI unit. Then a new lab-tech was hired and he cleared up the algae problem. We didn't worry too much about how he fixed the problem, we were just grateful that we didn't have algae particles in our experiments anymore.

It took three weeks to trace back the meandering pH readings in the experiments to his acid cleaning of the piping. ðŸ˜•
Interesting. The DI piping is all teflon with just the occasional glass flow tube like I said. Are you saying the algae built up inside teflon? If so, what acid did he use? I would think that would be a major repair because you would have a major DI water line flush to do. Do you remember how many gallons it took to do that? Our DI water tank is a teflon tub about 500 gallons.

Ah, I read it again and you said the ph readings went nuts for three weeks, which is what I would have expected. When you say fluctuate, do mean from say 7 to 7.2 or were they really nuts like 4 to 15?

What lab do you work at?
10. 23 Dec '10 09:52
Ignoring the soap foam, my thoughts are this:

Shaking does not increase the amount of glop than can be dissolved in a given amount of water, but it probably speeds up the rate of dissolving, saving time because you don't have to wait so long for the glop to dissolve.

An additional effect, if you are rinsing with warm water, is that the shaking lets the glop dissolve into solution whilst the water is nice and warm which means it can hold more glop.
11. coquette
23 Dec '10 17:58
there's more to it than dissolving . . . there's also suspension (mixtures, not dissolved) and suspensions. those factors are increased greatly by stirring (active movement, or churning, of the solvent)
12. 23 Dec '10 22:47
Originally posted by coquette
there's more to it than dissolving . . . there's also suspension (mixtures, not dissolved) and suspensions. those factors are increased greatly by stirring (active movement, or churning, of the solvent)
Agreed, suspensions are also helped. Reactions may also be catalysed if the shaking is very high frequency (e.g ultrasonic)
13. coquette
24 Dec '10 07:10
okay, while we're at it, let's throw in laminar flow and fractals . . . .churing and vigorous shaking all about would be important, especially with mixtures and suspensions, but also for dissolving
14. sonhouse
Fast and Curious
25 Dec '10 00:35
Originally posted by coquette
okay, while we're at it, let's throw in laminar flow and fractals . . . .churing and vigorous shaking all about would be important, especially with mixtures and suspensions, but also for dissolving
If it dissolves. What about stuff that does not dissolve in water?
15. coquette