Distilled Ignorance

[electrosys]

How to make 'de-ionised' water, without a pH meter ...

First, collect water from a dehumidifier - this will undoubtedly contain many dust particles, as well as being ever-so-slightly acidic from the absorption of carbon-dioxide from the large volume of air which has passed through the machine.

So, pass this water through a paper filter (a couple of paper towels would be ideal) into a plastic or similar unbreakable vessel.

Then, place the vessel containing the filtered water in a freezer, and when approximately 50% of the water has turned to ice, remove the ice and allow it to melt in a clean container. This water will then probably be near enough pH7 for most purposes - however, if you want to be absolutely sure, then recover the ice at 75% instead, melt and re-freeze, recovering again at 75%.
This process is known as fractional freezing, which is a parallel process to fractional distillation - with each pass through the process, the recovered product becomes increasing purer.

Of course, I couldn't possibly comment as to whether fractional freezing is an equally viable (and perfectly legal) method of extracting alcohol from hooch ...

 

[lw395]

Well, I've only got a first degree in chemistry, so I'll happily bow to anyone more qualified to comment, but ....

THERE'S NO SUCH THING AS DE-IONISED WATER. It just doesn't exist - it can't.

When people talk of 'de-ionised water', what they are referring to is water with a pH of exactly 7.00 (at 25 °C (77 °F)) a number, which as many people know, represents exact neutrality on the Acid-Base continuum (i.e. on the pH scale - which is a logarithmic scale of hydrogen ion concentration).

But - water described as having a pH of 7 has both a hydrogen ion (H+) concentration of 1 x 10-7, and a hydroxyl ion (OH-) concentration of 1 x 10-7, and thus may be considered as either a very, very weak acid, or a very, very weak base. But it will remain ionised to that small degree (i.e. 1 x 10-7) - it will NEVER become completely de-ionised, for that's impossible.

However, terming water with pH7 as 'de-ionised' (and not simply distilled) creates a certain mystique about it which impresses those without chemical knowledge, as well as enabling a higher price to be charged. Perhaps this matter should be referred to Trading Standards for misleading advertising ?

I think what most useful people mean by 'de-ionised' is the removal of all or most of the other ions such as sodium, calcium, carbonate etc.
The reason that it is not referred to as 'distilled' is that de-ionising is a much cheaper process, it would be fraudulent to refer to it as distilled when it hasn't been.
PH7 is of course the lowest possible total concentration of OH- and H30+ ions, around 2 millionths of the number of ions in PH1 or PH13.
You can also have a PH7 solution with a high ion content which you would not want in your battery or steam iron.

 

[prv]

Of course, I couldn't possibly comment as to whether fractional freezing is an equally viable (and perfectly legal) method of extracting alcohol from hooch ...

I hear it's viable, I'm surprised to hear it's legal. I wouldn't have thought the law would specify how spirits had to be produced for a license to be required.

Someone once asked me to build him a still to convert his home-brew into some kind of approximation of whisky. I suggested he freeze-distill it instead; don't know if he ever did or what the result was like.

Pete

 

[AntarcticPilot]

I hear it's viable, I'm surprised to hear it's legal. I wouldn't have thought the law would specify how spirits had to be produced for a license to be required.

Someone once asked me to build him a still to convert his home-brew into some kind of approximation of whisky. I suggested he freeze-distill it instead; don't know if he ever did or what the result was like.

Pete

Fractional crystallization as a means of producing extremely high proof hooch is a well known bit of polar legend! Various explorers are reputed to have carried out freeze distillation of low alcohol drinks such as beer to produce firewater. I have been unable to verify any of them - they all remain apocryphal - but Shackleton's name is linked to one such experiment. It would be easy in the polar regions - leave a barrel of beer outside, and keep fishing the ice out. You would readily get to about 96% alcohol, in a much less difficult process than distillation.

It is the traditional way of making applejack; a sort of apple brandy, and as far as I know is completely legal in the UK - it really is distillation that is taxed, NOT fractional crystallization. Of course, sustained low temperatures that would make this a viable means of producing quantities of rocket-fuel are not usual in the UK. Doing it in the freezer would only work for small quantities, and the temperature wouldn't be low enough for higher concentrations to be reached - you need sustained temperatures of (say) -20C. I forget what the minimum freezing point (reached at maximum alcohol) is, but I guess less than -50C.

Very many years ago, while still in my teens, I worked for a while in a laboratory that had a large semi-industrial fractional crystallization rig. I was told that a few years before my time, they had bought a barrel of beer and run it through the rig, and got some extremely potent stuff out of the other end. H&S was not a factor of laboratory life in those days!

 

[VicS]

THERE'S NO SUCH THING AS DE-IONISED WATER. It just doesn't exist - it can't........................

Good heavens.

I am amazed to read all that, especailly as one of my responsibilities for a number of years was overseeing the operation of a de-ionisation plant capable of producing 10,000 gallons of de-ionised water per hour!

The exact details of the process varies but basically involves passing the water through beds of ion exchange resins to remove the dissolved salts.
Typically the process can consist of the following stages.

• Passing the water through a bed of cation excahnge resin in the hydrogen form to remove most of the dissolved cations, replacing them with hydrogen ions
• Scrubbing the carbon dioxide, produced from dissolved bicarbonates, from the water with a current of air.
• Passing the water through a bed of anion exchange resin in the hydroxide form to remove most of the remaining anions, replacing them with hydroxide ions (which combine with the hydrogen ions produced in the first stage to produce water).
• Finally passing the water through a mixed bed, consisting of a cation resin in the hydrogen form and anion exchange resin in the hydroxide form, to remove practically all the remaining cations and anions.

That in a nutshell is the basics of the de-ionsation process ... so called because it removes the ions that make up the dissolved salts.

The process is often also called demineralisation.

 

[prv]

Doing it in the freezer would only work for small quantities, and the temperature wouldn't be low enough for higher concentrations to be reached - you need sustained temperatures of (say) -20C.

If I took all the shelves out of my freezer and filled the space with a suitably-shaped container of beer, I think that would be quite enough quantity for me

And ok, I guess it makes sense that you need colder temperatures the more alcoholic the liquid you're dealing with, but I think a domestic freezer ought to reach -20 ok. Mine has a little LCD readout on the front which normally says -22 or -23. I have a bottle of vodka in there which is just on the cusp of forming ice crystals in its water content (just as it should be ). So I assume I could get applejack to a similar point - 40% cider would be quite enough for me, thanks, no need for 96% bonce-blower at -50C

Pete

 

[electrosys]

Good heavens.


That in a nutshell is the basics of the de-ionsation process ... so called because it removes the ions that make up the dissolved salts.

The process is often also called demineralisation.

I would call that purification, by the removal of dissolved ionic compounds (or demineralisation) - sure - but to call it 'de-ionised water' is the wrong use of the english language.

I repeat - you cannot 'de-ionise' water. It's impossible. It will always remain ionised, if only to a small degree.

But - rather than pedantically argue points of chemical terminology - I think a far more important question to raise is why companies who engage in this process do not simply describe their product as 'de-mineralised water', which is a perfectly satisfactory term to describe it.
Certainly in the case of outlets such as Halfords, and garages up and down the country I would suggest that the principle reason NOT to describe it simply as 'de-mineralised' is that ordinary users such as the OP would quickly make the connection between water from dehumidifiers and ice, and the virtual absence of minerals within water originating from those sources, and begin to question the logic of paying £3.50 a pop (or whatever it costs) for water with which to top-up a battery.

 

[VicS]

I would call that purification, by the removal of dissolved ionic compounds (or demineralisation) - sure - but to call it 'de-ionised water' is the wrong use of the english language.

I repeat - you cannot 'de-ionise' water. It's impossible. It will always remain ionised, if only to a small degree.

What you would call it is up to you.

In practice it is called de-ionisation or de-mineralisation and anybody in the water treatment industry would, I am sure, recognise those terms.

Chambers Dictionary of Science and Technology defines de-ionised water as, "water from which ionic impurities have been removed by passing it through cation and anion exchange columns".

.

 

[Stu Jackson]

Am I right in thinking that my condensing tumble dryer makes a ready supply of distilled water?

Wasn't the OP question about DISTILLED water? How'd we get to de-ionized water?

I've been using the more expensive non-toxic antifreeze and distilled water for years, with a cleanout every year or two.

 

[lw395]

Wasn't the OP question about DISTILLED water? How'd we get to de-ionized water?

I've been using the more expensive non-toxic antifreeze and distilled water for years, with a cleanout every year or two.

You don't often see distilled water for sale, de-ionised does what's needed, but some people loosely call it distilled water anyway. It's essentially the same stuff, it's just been through a different process.

Some people use the frost scraped from the freezer BTW. All right if you only need a bit to top up a motorbike battery.

 

[VicS]

Wasn't the OP question about DISTILLED water? How'd we get to de-ionized water?

I've been using the more expensive non-toxic antifreeze and distilled water for years, with a cleanout every year or two.

Actually it was about condensate from a tumble drier

 

[Martin_J]

now another word has crept in ... 'condensate'

I guess that's what drips out from the car air conditioning when I park up... that I assume is cleaner than that collected from the tumbler drier..

OK.. best not go there

 

[macd]

..condensate...de-mineralised...de-ionized...that chemist has missed a trick. Surely you can't de-mineralise water. There's only water in it. The stuff that comes through the tap (or even falls from the sky) is summat else.

 

[Seajet]

The Harrier aircraft uses water injection to cool the engine and give a denser charge, wringing the maximum power out of the engine for hovering etc.

When my father was in charge of the Sea Harrier at a Paris air show and sorting out the logistics beforehand, his request for 50 gallons of demineralised water a day was met with incredulity, " Sacre Bleu, the thing runs on water ! "

 

[Blueboatman]

Delete

 

[Blueboatman]

Deleted. Wrong thread!

 

[Vara]

Deleted. Wrong thread!

Oh that's a shame that was the best bit of Fred drift for ages.

Any way, to summarise, distilled, demineralised and deionised in terms of battery refilling, are synonymous , so bung it in with gay abandon.

The jury is out with respect to water from tumble driers or dehumidifiers.

I have placed some water from my dehumidifier on a slide to evaporate and it left no residue, that proves nothing.