Sciencemadness Discussion Board - Distilled, De-ionised or Tap water?

Distilled, De-ionised or Tap water?

RedDwarf - 24-10-2019 at 01:33

I'm lucky enough to live in a country with good water quality in an area with soft water and I wonder whether there is much point in me buying and using distilled or de-ionised water instead of tapwater, and if so for what?
My water comes directly from the mains and doesn't go into a storage tank and the utility company analysis of the water in my specific area is as follows:
Parameter Min Average Max Units
Aluminium 6.20 12.2 27.5 µg Al/l
Ammonium (ammonia and ammonium ions) <0.0077 <0.0078 0.0103 mg NH4/l
Antimony <0.140 <0.141 0.150 µg Sb/l
Arsenic 0.130 0.164 0.200 µg As/l
Benzene <0.0471 <0.0471 <0.0471 µg/l
Boron 0.0083 0.0168 0.0371 mg B/l
Bromate <0.0910 <0.0996 0.160 µg BrO3/l
Cadmium <0.0300 <0.0300 <0.0300 µg Cd/l
Calcium 4.88 9.71 13.5 mg Ca/l
Chloride 11.0 17.8 24.2 mg Cl/l
Chromium <0.0400 <0.0938 0.120 µg Cr/l
Residual chlorine - Total 0.64 1.01 1.46 mg/l
Residual chlorine - Free 0.59 0.94 1.21 mg/l
Conductivity 76.1 114 147 uS/cm at 20oC
Copper 0.0015 0.0173 0.0575 mg Cu/l
Cyanide <0.698 <1.05 1.33 µg CN/l
1,2-dichloroethane <0.138 <0.138 <0.138 µg/l
Fluoride <0.0233 <0.0474 0.0900 mg F/l
Hardness Total as CaCO3 19 32 45 mg CaCO3/l
Iron 3.03 6.91 14.6 µg Fe/l
Lead <0.290 <0.338 0.510 µg Pb/l
Magnesium 1.20 1.92 2.98 mg Mg/l
Manganese 0.570 1.19 1.65 µg Mn/l
Mercury <0.0150 <0.0174 <0.0200 µg Hg/l
Nickel 0.420 0.634 1.11 µg Ni/l
Nitrite <0.0016 <0.0016 <0.0016 mg NO2/l
Nitrate 0.974 1.57 3.06 mg NO3/l
Total organic carbon 0.670 1.21 1.65 mg C/l
Hydrogen ion (pH) 6.97 7.18 7.39 pH value
Selenium <0.0500 <0.0513 0.0600 µg Se/l
Sodium 7.44 12.7 17.5 mg Na/l
Sulphate 8.95 35.1 95.0 mg SO4/l
Tetrachloromethane <0.0187 <0.0232 0.0300 µg/l
Trihalomethanes - Total 26.4 30.8 35.5 µg/l

(I apologise for the formatting - if anyone can tell me how to paste a table in here without losing all the formatting I'd be grateful)

So where would you use my tap water and where would you use de-ionised instead?

artemov - 24-10-2019 at 02:19

I washed my glassware with tapwater, then do a final rinse with distilled water twice or thrice.
For reactions, I use distilled water, since the quantity required is never large.

I dun have (cheap & easy) access to deionised water.

Boffis - 24-10-2019 at 03:13

I see you have water very similar to ours and don't live too far away! I use tap water only to wash equipment and then, as artemov suggests, rinse it in deionised water. I buy deionised and distilled water for critical work because when I am working with silver and barium salt (which I do quite a lot) the chloride and sulphate contents are too high and cause cloudiness. For general work and organic work preparations I use the water from two dehumidifiers in my out building/office. These generate about 1.5 L of water a day which is more than enough. I put it throught a fine 1.8micron filter but thats all. I keep the two dehumidifiers scrupulously clean though and clean with homebrew bottle cleaner periodically. Because the latter seems to contains chloride and or borate I discard the first batch of water after a thorough clean.

DavidJR - 24-10-2019 at 04:18

Go on eBay at get yourself one of the cheap reverse osmosis / DI units. Cost is around £50 iirc and it can just connect to a garden tap. Output water is as good as if not better than distilled.

Edit: I have something resembling this: https://www.ebay.co.uk/itm/4-Stage-RO-DI-Reverse-Osmosis-Wat...

[Edited on 24-10-2019 by DavidJR]

mayko - 24-10-2019 at 04:57

Quote: Originally posted by RedDwarf

(I apologise for the formatting - if anyone can tell me how to paste a table in here without losing all the formatting I'd be grateful)

use the [ code ] and [ / code ] tags:

Code:


[b]Parameter	Min	Average	Max	Units[/b]
Aluminium	6.20	12.2	27.5	µg Al/l
Ammonium (ammonia and ammonium ions)	<0.0077	<0.0078	0.0103	mg NH4/l
Antimony	<0.140	<0.141	0.150	µg Sb/l
Arsenic	0.130	0.164	0.200	µg As/l
Benzene	<0.0471	<0.0471	<0.0471	µg/l
Boron	0.0083	0.0168	0.0371	mg B/l

RedDwarf - 24-10-2019 at 06:51

Thank you all for your replies.

David, I'll probably go this route as it's much cheaper (and more convenient) than buying and storing de-ionised. Do you have any idea how long (time or volume based) the filters last before needing renewal?

Boffis, I hadn't thought of dehumidifier water, but it makes sense and I might look at using mine. I had also wondered about collecting some of the copious rain water that we are blessed with in this area but it would still need filtration at least and I'm not sure if there are any/sufficient atmospheric contaminants that I should be worried about (although I'm on the edge of the urban sprawl).

Artemov, Yes I'd probably choose to use de-ionised for reactions and processing, but I'm still not convinced that I'd need to rinse glassware in de-ionised post a tap water wash. I did a quick test on a clean 150ml flask and after washing in hot water and emptying and shaking I was only left with 1.05 g difference from it's pre-wash weight. Some of this would drain out while upside down and the 1.05g also includes any remaining water film on the exterior which wouldn't be a contamination issue.

Herr Haber - 24-10-2019 at 08:18

I cant say I enjoyed using reverse osmosis.
First, it's slow. Second, it's wasteful. Third, I had carbon contamination !

My tap water is pretty good for most things and for the rest de-ionised water from the store isnt that expensive.

Boffis - 24-10-2019 at 09:40

Hi RedDwarf, sorry I got confused between you and artemov's posts. Here in the NW of England there is a tendency for the rain to be high in sea spray so carries lots of chloride and sulphate so would require de-ionising anyway.

AJKOER - 25-10-2019 at 07:47

If you are running a chlorine bleach based task/experiment, for example, I would actually advise tap water rich in transition metals, oxygen, CO2 and dissolved organics. Consider even adding diffused sunlight.

Case in point, you have two water sources that have been filtered with say carbon: a barrel of rainwater and a tap water source. If caution suggests adding NaOCl to disinfect the water sources, followed by aeration and sunlight treatment, which is likely safer following chlorine bleach treatment?

I would suspect it is the tap water source based on my understanding of the underlying chemistry, which in my assessment, involves fenton-type (and photo-Fenton) reactions based on HOCl liberated by CO2 reacting in the presence of transition metals (like Fe and Mn) commonly available in tap water (assuming a pH > 5, see my comment and cited references at https://www.sciencemadness.org/whisper/viewthread.php?tid=15... ). Dissolved oxygen would likely further add to reactive oxygen species (ROS) formation further liberating radicals with hypochlorous acid. Lastly, dissolved organics may contribute to solvated electron presence.

On further thought, the level of dissolved CO2 pre-bleach treatment, is likely a key factor, as it creates the more powerful disinfecting HOCl (actually nearly a 100 times, see comments at, for example, http://www.aerosia.com/popup_article.php?link=article_6.htm ) than NaOCl. If hypochlorite treated tap water is at a lower temperature than the corresponding rainwater, it could be richer in CO2 (and also dissolved O2), and perhaps correspondingly safer. Not sure on CO2 levels? I would add some citrus juice especially if you are using sunlight treatment (rich in Vitamin C, see http://www.sciencemadness.org/talk/viewthread.php?tid=77977 and, if you have a B-complex vitamin on hand, add it during a sunlight treatment as B-2 and B-12 are photocatalysis).

[Edited on 25-10-2019 by AJKOER]

Heptylene - 25-10-2019 at 12:50

It depends on your tap water. I know mine contains a lot of calcium salts. Just heating the water to boiling causes what looks like a lot of white solids to precipitate (from reduced solubility at high temperature). It's unsightly and leaves ugly white residue on glassware.

If you are doing a crystallization, or reducing the volume of an aqueous solution by evaporation, you can end up with a significant impurity in the product.

For me distilled water is used for almost everything except cleaning (final rinse with distilled water tho). I buy it for about 50 cents per liter and I estimate I go through 50-100 liters per year.

If you really want to know whether it's important, just try evaporating your tap water to dryness and weigh the residue.

Sulaiman - 25-10-2019 at 21:28

Walsall (UK) water analysis by the supplier indicates 68 mg/l chloride and 1 mg/l fluoride,
a drop or two of silver nitrate solution in a beaker of my tap water causes cloudiness.

I use distilled water (£0.72 per litre including delivery, 18 MOhm/cm) for almost all of my experiments,
especially to make up 'standard' solutions.

The cost per experiment is low compared to reactants etc. used.

I wash and rinse my glassware using tap water and very often that is all,
after draining there is so little water that I've not noticed any significant problems due to residues from the tap water,
even when using silver salts.

I used to wash and rinse with tap water, drain, rinse two or three times with a little distilled water,
then rinse with acetone for quick drying
... lately I rarely rinse with distilled water and never rinse with acetone.

You could set up a still to produce your own distilled water
at a significantly lower cost per litre,
such a still has been on my to-do list for years.

My new Lab will be in a rural area of Malaysia, where tap water is more highly chlorinated,
so the water still may be promoted up the list
as costs for distilled water will be more than I am used to in the UK
unless I literally buy a tonne of it.

unionised - 26-10-2019 at 04:15

Quote: Originally posted by AJKOER

If you are running a chlorine bleach based task/experiment, for example, I would actually advise tap water rich in transition metals, oxygen, CO2 and dissolved organics. Consider even adding diffused sunlight.

[Edited on 25-10-2019 by AJKOER]

Most of us prefer to have some consistent control of the parameters of experiments.
However, if you don't care about reproducibility...

AJKOER - 26-10-2019 at 07:13

To all, Unionised apparently does not approve of my use of electrochemical cell based paths to synthesis, which provide great prep for CuO (see https://www.sciencemadness.org/whisper/viewthread.php?tid=84... and even ZnO/Zn(OH)2).

Fortunately (and confusingly, for those imbued in the realm of standard chemical reactions), an electrochemical reaction has only a binary concern with concentration, as a parameter. Either the most anodic metal/alloy/compound is consumed first until its concentration is zero, followed by the next. But, there still can be a more limited dependence on temperature!

Reactions based on NaOCl or HOCl, in the current context of my above comment, in the present of electropositive element, like from an Iron or Aluminum alloy vessel, can be the basis of so-called 'bleach battery' (see more details at https://www.sciencemadness.org/whisper/viewthread.php?tid=27... ).

Relatedly some may even be more acquainted by the electrochemical action of O2 with an acid source on Iron metal (where the formation of rust appears consistent to me) or a ferrous salt. There also is the action of O2 (or H2O2) on Copper metal in the presence of NH3, which is actually the basis of commercial leaching of copper ore (with excellent reproducibility).

Now, actually a harder question relative to disinfecting a suspect water source (with a largely unknown composition) with NaOCl, is how much to use to be safe? The legally safe answer is to read the label on the bleach bottle. However, the real answer, in my opinion, is much harder as it depends, for example, on the level of dissolved organics (and not undissolved as I suggested carbon filtering) present in the water source which may consume NaOCl/HOCl before a transition metal interaction liberating powerful disinfecting radicals. Also, the tap water must have some non-zero concentration of Fe or Mn!

Note, my cited use of aeration is likely much more a temperature-sensitive process as very warm water may have a limited content of dissolved oxygen.

Further, I recommend sunlight and even the addition of Ascorbic acid, so an insufficient HOCl concentration issue may be somewhat alleviated as sunlight and Vitamin C can contribute to an albeit limited recycling of Fenton-type reaction radical products.

Prior testing treated samples of the water source in question with varying doses of NaOCl, over various time frames and light conditions, is advisable.

[Edited on 26-10-2019 by AJKOER]

unionised - 26-10-2019 at 08:09

Quote: Originally posted by AJKOER

To all, Unionised apparently does not approve of my use of electrochemical cell based paths to synthesis, which provide great prep for CuO (see https://www.sciencemadness.org/whisper/viewthread.php?tid=84... and even ZnO/Zn(OH)2).

...
Now, actually a harder question relative to disinfecting a suspect water source (with a largely unknown composition) with NaOCl, is how much to use to be safe? The legally safe answer is to read the label on the bleach bottle.

...

[Edited on 26-10-2019 by AJKOER]

you have no basis for that first comment.
And you haven't addressed my point concerning reproducibility of experiments.

The actual answer to how much bleach (or chlorine) do you add is well known to those who actually know about it.
The simple answer is that you add enough oxidant to destroy all the reductants.
In effect, it is a titration- so the idea is well understood by chemists (except AJKOER).

https://blog.orendatech.com/breakpoint-chlorination-explaine...

AJKOER - 26-10-2019 at 08:53

Wow Unionised, you may not realize what you just said, but to quote your source link:

"The oxidant demand in these cases can be chloramines, non-living organics, or any combination of both."

Which agrees, in part ('dissolved organics') with my generally suggested 'testing' of dissolved organics in water.

Now, what you do NOT apparently understand is that breakpoint chlorination relates to the use of excess chlorine to breakdown NH2Cl completely into N2, a step beyond problematic NCl3. The process assumes that some of the starting chlorine is lost due to the unknown amount of the problematic non-living organics and existing, if any, NH2Cl.

But, what if your water does NOT have any NH2Cl in your water source, and you do not want to add ammonia (more like pollute, in my opinion, with the creation of the much weaker disinfectant NH2Cl compared to HOCl). Then other testing is required!

Perhaps, per your reference, take a small sample, add a known amount of ammonia and note the amount of chlorine (a source of HOCl or just HOCl) that is needed from N2 evolution. Use this information to decide on the amount of NaOCl in your non-NH2Cl water source.

[Edited on 26-10-2019 by AJKOER]

RedDwarf - 11-11-2019 at 08:21

Quote: Originally posted by Boffis

Hi RedDwarf, sorry I got confused between you and artemov's posts. Here in the NW of England there is a tendency for the rain to be high in sea spray so carries lots of chloride and sulphate so would require de-ionising anyway.

Out of interest Boffis, do you know how far inland that effect reaches and at what levels?

DavidJR - 11-11-2019 at 19:57

Quote: Originally posted by RedDwarf

David, I'll probably go this route as it's much cheaper (and more convenient) than buying and storing de-ionised. Do you have any idea how long (time or volume based) the filters last before needing renewal?

Sorry, didn't notice the replies in this thread until now.

I'm not sure how long it will last. Mine has been going fine for a couple of years. I live in an area with exceptionally soft water so that probably helps, though the reverse osmosis membrane will get rid of the bulk of the inorganic contaminants anyway, and that is not a consumable part. The mixed-bed DI resin and activated carbon, are, of course, consumables though.

woelen - 11-11-2019 at 23:36

I use distilled water for nearly all experiments I do. Rinsing and cleaning I do with tap water, in many cases, followed by a final rinse with a little distilled water.

Sometimes I give demos, involving somewhat larger volumes. In those cases, it depends on the demo whether I use tap water or distilled water. E.g. a color change of oxidation state for chromium or vanadium can be done perfectly fine with tap water, the same is true for many precipitation reactions and also for reactions in which gases are produced. However, demos involving silver salts I always do with distilled water. With tap water I get quite some cloudiness with silver salts.

I buy distilled water in jerrycans of 10 liter, one such a jerrycan costs 6 euros or so. I need appr. one of these per year.

Sulaiman - 12-11-2019 at 06:47

Quote: Originally posted by RedDwarf

Quote: Originally posted by Boffis

Out of interest Boffis, do you know how far inland that effect reaches and at what levels?

I have no data but there is an affliction called 'Derbyshire neck' which is goitre caused by lack of iodine,
as iodine bearing sea spray does not reach Derbyshire soil.