The Wikipedia article on purified water contains a subsection on methods, with a sub-subsection on distillation, where it is claimed that distilled water may have some non-zero level of dissolved solids, and that the process leaves “most” solid contaminants behind.
Question:
Why would distilled water have any dissolved solids or solid contaminants in it? I thought the whole point was that you boil the water into steam (water vapor), the steam travels to a condenser where it condense back into liquid water, and presto, you’re all set; everything else gets left behind in the boiler. I can see how liquids with a boiling point close to that of water might make the trip, but how can dissolved or suspended solids possibly reach the condenser to contaminate the still’s output?
My speculation is that the breaking of the water’s surface by steam bubbles in the boiler produces an aerosol of tiny [contaminant-laden] water droplets which then evaporate, leaving airborne solid particulates that migrate to every other surface[sup]*[/sup] in the still, including the condenser. Is this an accurate guess, or is there some other transport mechanism involved?
[sup]*[/sup]BTW, this is why I hate ultrasonic “cool mist” humidifers.
By my day job I am a chemical engineer, and I’m in charge of 5 distillation columns.
First of all, Wikipedia isn’t always perfect and it’s pretty lacking in the chemistry department in my opinion.
Where do the solids come from?:
[ul]
[li]The bottle they put the water in isn’t PERFECTLY clean. Nothing is.[/li][li]Inhibitors or other chemicals are many times added during or at the end of a distillation process[/li][li]Every part of the distillation apparatus will add trace amounts of its material to the product. This includes the column itself, the tubes on the condenser, bits stuck in the valves, the flowmeter, etc. This is why liquor distillers say a copper still “imbues” a special flavor to a spirit.[/li][/ul]
Also, if you plan on drinking distilled water because it is clean, do not do so in large amounts. You would risk hyponatremia.
Then I hope you’ll forgive me then for referencing Wikipedia a second time here.
On the same page, the sub-subsection on double-distillation claims this is how the historical “gold standard” for purified water is produced, implying that double-distilled water is more pure than single-distilled water. I would think this could only be the case if the contaminants in the end product were coming from the source fluid in the boiler, i.e. each distillation step removes 99.9% of contaminants, so double-distillation removes 99.9999% of contaminants.
If what you’re saying is true - that the contaminants come from the still itself - then the distillation process would result in a fixed contamination level of the end product, regardless of how many times it’s repeated.
So does double-distillation result in a further reduced contaminant level, or the same contaminant level as single-distillation?
I have a different understanding of it. First, the breaking of droplets does fling solid particles around and carry them across the distillation process, as you speculated. Second, there are some processes that start with water and air and wind up with solids (maybe things that are volatile in the right degree to codistill with water participate, too). I think I remember that carbon dioxide and carbonates are participants, but don’t really know. Third, the water can leach things out of the still and other containers, yes, which would result in a fixed level during subsequent distillations, yes. I don’t know what else is up. I remember hearing these things related to water that is used to aerosolize droplets that dry and leave airborne condensation nuclei, though it’s a bit out of my area any more.
While I’ve heard this many times before, I’m not convinced it is likely. Perhaps if you drank a LOT of distilled water, (more than normal?). But I think the 300ppm or so of calcium and magnesium salts in undistilled water is comparitively small, I wouldn’t be suprised if simply spitting in a glass of distilled water would add enough solutes to counter any osmotic imbalance.
Your body fluids are much more concentrated than 300ppm, I doubt any great difference in osmosis or diffusion is going to be seen between distilled water and non-distilled.
Now the biggest problem I would see from such water is biological contamination post distillation, since it doesn’t have chlorine in it.
So if you have a reputable site to back up your claim of hyponatremia, I’d like to see it. (I’m easily swayed!)
I ran low pressure evaps both solo shell and double shell. Solo effect and double effect. Low pressure flash stills. Vapor compression stills. and high presssure stills. Very few things work perfectally. There will be a small amount of carry over depending on design and the operator.
Pure water is DI water. It has to be handled carefully because the water will absorb a lot of materials. And if drunk will remove minerals from the body. It is like a spong. I have no links for this sorry.
As for drink distilled water being unhealthful? On the ranch the drinking water ran about 1 to 2 micro mos. At my home I have a RO system and when tested it is usually below 10 micro mos. SF water from the Hetch Hetch water system runs normaly below 10 micro mos.
My experience as well. If someone wants to spend the time and money to make “the perfect still” they may do a lot better than I have, but it is usually probably cheaper and easier to simply double-still. I recently distilled red wine. The first distillation was very-ever-so-slightly yellow, with a wonderful aroma and taste. I’m no master, and this was no vodka. By the third distillation it was very much like a good vodka (with very high proof).
I’m sorry, I just can’t let this go unchallenged. I just don’t think distilled water will remove minerals from the body to any greater harmful effect than ‘normal’ water. Maybe it does, but I don’t think its enough of an issue to claim drinking distilled water in normal amounts is harmful. I’ll need a good scientifically peer reviewed study to be able to accept this.
Until some good study is presented, I’ll have to respectfully ask that we consider this claim unfounded.
In chemistry during college, we were asked not to drink the DI water. Not because of health risks, but because it was expensive. (At least, compared to normal water). For people, it is safer than just about anything else in a biochemistry lab (including the glass beakers if you’re as prone to dropping things as I am).
However, the “removing minerals” part can be true in regards to non-human things. For example, if you filled a pool with DI water, you’d see the water leach minerals from the siding, grout and metal components, possibly damaging the pool. But this can be a risk even with non-purified tap water too, and is a reason that calcium hardness is tested for during pool maintenance.
When I was in school, I worked as the chemistry lab assistant for work-study. The tap water in that town was horrible. I always brought home a few jugs of distilled, and that’s all I drank (except for the usual college student’s quota of beer & booze ). I never noticed the slightest ill effects.
The solids are boiled off at the same time as the water, just in lesser quantities.
Dissolved solids are not solids; they have been disassembled by the solvent (water) into individual atoms/molecules/ions. Heat the solvent up enough, and some of the solute (the dissolved molecules) may change phase for the same reason the solvent does: some molecules at the surface get enough kinetic energy to break free of the intermolecular forces that hold the liquid together. While far fewer molecules of the solute will evaporate in this manner, and significant numbers will be pushed back into the solution, the number that escape in the same way as the water vapor will be non-zero if you start with a typical water sample. Distill it enough times in a contaminant-free still and you end up with fewer and fewer non-water molecules in the distillate. Obtaining a contaminant-free still is difficult, so there’s a limit to how good this process can be.
). I never noticed the slightest ill effects.