Post by thread:[EE] Resistivity of Water

> Now, I'm not sure, but I would not think that water alone > would "short" the wires. Actualy, distilled water is close > to an isolator, I think. Heavily salted water will be a less > of an isolator, but "shorted" and "massive currents", well, > I don't know... Quoted from a reply by Jan-Erik, buried within a [PIC] thread... Where I work, we have a NanoPure filtration system which is fed deionized water. The little gauge for water quality is given in MOhms of resistance; we get worried if it drops below 18 MOhms. Of course, I don't know what that means- if it's a reference to "resistance per centimeter of a 1 cm diameter column", or what, but I'd imagine it's over a pretty small distance. Anyone else have any input on this? It's a good thing for people like us to know more about. Perhaps I'll do some experiments... Mike H.

Mike Hord <spam_OUTmike.hordTakeThisOuTgmail.com> > Where I work, we have a NanoPure filtration system which > is fed deionized water. The little gauge for water quality is > given in MOhms of resistance; we get worried if it drops > below 18 MOhms. > > Of course, I don't know what that means- if it's a reference > to "resistance per centimeter of a 1 cm diameter column", > or what, but I'd imagine it's over a pretty small distance. Check this out, questions #1 and #2: http://www.circuitcellar.com/library/eq/165/index.htm It's possible that the units really are Mohm-cm or something, corrected for the area and spacing of the electrodes, or it may simply be the total resistance, with an unknown scaling factor with respect to the actual bulk resistivity of the water. -- Dave Tweed

From: "Mike Hord" Subject: [EE] Resistivity of Water > Quoted from a reply by Jan-Erik, buried within a [PIC] > thread... > > Where I work, we have a NanoPure filtration system which > is fed deionized water. The little gauge for water quality is > given in MOhms of resistance; we get worried if it drops > below 18 MOhms. > > Of course, I don't know what that means- if it's a reference > to "resistance per centimeter of a 1 cm diameter column", > or what, but I'd imagine it's over a pretty small distance. > > Anyone else have any input on this? It's a good thing for > people like us to know more about. Perhaps I'll do some > experiments... Water is an insulator. Impurities make it conduct to greater or lesser extents. Where I work we buy our de-ionised water from a local power station, which is a far cheeper alternative than making our own and it is far better quality than off the shelf stuff. We don't talk about resistance, we measure conductivity in micro Seimens (Seimens is (are?) the reciprocal of Ohms). We buy the stuff at a purity they reject theirs at, which is 0.1 uS. By the time it has spent a few months in the plastic containers (we re-cycle them to reduce this effect) the conductivity has usually risen to about 2-3 uS. We reject it from our plant at 20uS. I think the stuff the power stations use in their boilers is better than 0.01 uS. Makes the mind boggle. By the way, water this pure is considered by us to be a toxin. If drunk in sufficient quantities it leaches all the salts out of your system and makes you very ill (dead eventually) indead. Even handling it is a problem, because it washes all the oils from your hands and makes the skin very dry. Cheers...Mike.

> By the way, water this pure is considered by us to be a toxin. If drunk in > sufficient quantities it leaches all the salts out of your system and makes > you very ill (dead eventually) indead. Even handling it is a problem, > because it washes all the oils from your hands and makes the skin very dry. Sure. The same way drinking salt water causes water to move into your intercellular space to attempt to balance the salt content. See "microdialysis" for interesting applications of this tendency to deliver drugs/obtain samples from intracelluar space in the brain. My extremely poorly designed experiment is showing me a resistance of about 59 kOhms for a column of water 14.2cm in length by 1.1cm in diameter. I say poorly designed because I have a piece of 7/16" Tygon hose capped with 1/2" brass plugs, which I bored a hole in for a banana plug, filled with tap water. The above figure takes no accounting for the resistance of the brass plugs or the leads to the meter. I'd be surprised if it's more than 1% accurate. OTOH, I'd also be surprised if it's less than 5-10%. Of course, I haven't tested the hose's resistance... :-( Okay, meter shows infinite resistance across Tygon. Whew. Opinions? Next I'll test the filtered de-ionized. Mike H.

> Opinions? Next I'll test the filtered de-ionized. The filtered, de-ionized water comes back at approximately 1.6 MOhm for the same configuration. It's falling fast, too; after 2 minutes or so, it's now down to 1.2 MOhm. The reading on the filtration system is 18.2 MOhm*cm. I suspect the difference is due to the fact that I didn't flush the system with the "purer" water, coupled with the fact that I flushed it through brass fittings, might have something to do with that...again, this is a pretty crude experiment. Mike H.

Mike Hawkshaw wrote: > By the way, water this pure is considered by us to be a toxin. If > drunk in sufficient quantities it leaches all the salts out of your > system and makes you very ill (dead eventually) indead. Even handling > it is a problem, because it washes all the oils from your hands and > makes the skin very dry. But are there really *that* many more impurities in "drinking water" to make a difference. Drinking water is essentially salt free compared to urine. I can't see how the extra tiny amount of salt in drinking water has any impact at all to the overall salt ballance compared to taking in water that has none. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com

On Mar 24, 2005, at 3:22 PM, Olin Lathrop wrote: >> By the way, water this pure is considered by us to be a toxin. If >> drunk in sufficient quantities it leaches all the salts out of your >> system and makes you very ill (dead eventually) > But are there really *that* many more impurities in "drinking water" > to make a difference. I don't think so. Some fraternity recently managed to kill a pledge in an initiation stunt by making them drink vast quantities of water, and I think it was ordinary tap water. Plain (not specially purified) water makes a fine toxin in quantity as well. It's just that the quantity is quite large... The "ultra pure water is deadly" theory is (I believe) something of an urban legend... BillW

>By the way, water this pure is considered by us to be a toxin. If drunk in >sufficient quantities it leaches all the salts out of your system and makes >you very ill (dead eventually) indead. Even handling it is a problem, >because it washes all the oils from your hands and makes the skin very dry. > >Cheers...Mike. > >-- This is a fallacy as far as i know. The principle of osmosis says that a solution will move from a low concentration to a high one. In other words, split a tank with a semi-permeable membrane. Salt water one side pure water the other. The pure water will move towards the salt water, diluting it. So the same happens if you drink pure water, it simply gets absorbed into your system. I can't see any harm in that. Good stuff;) The priciple of osmosis is best considered in the extraction of fresh water from salt water. Reverse osmosis is required because of the natural gradient. Also, the body has to go to great lengths to extract and isolate pee, a higher salt salt solution, for disposal because of this gradient. Regards Roland Jollivet

William ChopsWestfield wrote: >>> By the way, water this pure is considered by us to be a toxin. If >>> drunk in sufficient quantities it leaches all the salts out of your >>> system and makes you very ill (dead eventually) > >> But are there really *that* many more impurities in "drinking water" >> to make a difference. > > I don't think so. [...] The "ultra pure water is deadly" theory > is (I believe) something of an urban legend... Can't be immediately deadly: www.herbsfirst.com/discriptions/drinkdistilled.html http://www.ecclesia.org/truth/water.html (IIRC, it is sold in US supermarkets as drinking water, too. Even with the FDA being what it is, one can assume that this means it is at least not immediately deadly... :) OTOH: http://chetday.com/distilledwater.htm And something more balanced: http://www.cyber-nook.com/water/distilledwater.htm Seems one of the major (long-term) problems with drinking "pure" water is that it has a much higher potential to get contaminated on the way to your mouth. Gerhard

On Thu, 24 Mar 2005, Mike Hord wrote: > Where I work, we have a NanoPure filtration system which > is fed deionized water. The little gauge for water quality is > given in MOhms of resistance; we get worried if it drops > below 18 MOhms. > > Of course, I don't know what that means- if it's a reference > to "resistance per centimeter of a 1 cm diameter column", > or what, but I'd imagine it's over a pretty small distance. > > Anyone else have any input on this? It's a good thing for > people like us to know more about. Perhaps I'll do some > experiments... Tap water varies from more than 200kOhm to 3kOhm (1 cm between two plates 1cm^2 each). It is much more reliable to measure its capacitance (water has epsilon-r 80). Some kinds of mineral water can appear as a dead short in the same measuring arrangement (under 50ohms). Fortunately most kinds of 'dirty' water (what is likely to flood a basement) will read low R. Peter

On Thu, 24 Mar 2005, Mike Hord wrote: {Quote hidden}>> Opinions? Next I'll test the filtered de-ionized. > > The filtered, de-ionized water comes back at approximately 1.6 MOhm > for the same configuration. It's falling fast, too; after 2 minutes or so, > it's now down to 1.2 MOhm. > > The reading on the filtration system is 18.2 MOhm*cm. I suspect the > difference is due to the fact that I didn't flush the system with the > "purer" water, coupled with the fact that I flushed it through brass > fittings, might have something to do with that...again, this is a pretty > crude experiment. You may be seeing polarization. Conduction in an electrolyte is covered in basic university physics. In general one does not measure an electrolyte with a dc current, one swaps the polarity all the time to prevent electroplating and other effects. Peter

On Fri, 25 Mar 2005, Gerhard Fiedler wrote: {Quote hidden}> Can't be immediately deadly: > www.herbsfirst.com/discriptions/drinkdistilled.html > http://www.ecclesia.org/truth/water.html > (IIRC, it is sold in US supermarkets as drinking water, too. Even with the > FDA being what it is, one can assume that this means it is at least not > immediately deadly... :) > > OTOH: > http://chetday.com/distilledwater.htm > > And something more balanced: > http://www.cyber-nook.com/water/distilledwater.htm MSDS sheet of destilled water: http://www.scottecatalog.com/msds.nsf/0/f40a583d237124f285256a0a004e34f8?OpenDocument "IN EVENT OF EXPOSURE CONSULT A PHYSICIAN" <grin> Peter

>By the way, water this pure is considered by us to be a toxin. > Who is "us"? One of the fundamental rules of toxicology is that the dose makes the poison. >If drunk in sufficient quantities it leaches all the salts out of your system and makes >you very ill (dead eventually) indead. > "All" is a bit extreme. Tap water will do the job too in virtually identical quantities. >Even handling it is a problem, because it washes all the oils from your hands and makes the skin very dry. > Tap water will do the same. Soap enhances the process. Let's think about this. Tap water varies in its content all over the world as does water from streams, wells, lakes and other potential sources. The one thing that is consistent everywhere is that any water which is considered drinkable is mostly water with very little (by comparison) dissolved solids. Even water taken directly from turbulent flow in a stream is well below one percent in non-water content. The US EPA limit for total dissolved solids is 500 mg/L, or 0.05% ( http://www.epa.gov/safewater/mcl.html at the bottom of the page). This is a worst case in the US with most water containing substantially less dissolved solids. I'd guess that drinking water standards in places that have such are similar (certainly not an order of magnitude different) in most parts of the world. The specific content of what is in the water also varies wildly (so, is almost certainly irrelevant to the discussion at hand). Let's assume a two liter per day intake of drinking water. At EPA limits that works out to a maximum of a gram of dissolved solids per day. I just ate a package of peanuts which weighs in at a mere 57g. It looks to me like a few peanuts would replace all of the dissolved solids that I could get from drinking a days worth of tap water if I were inclined to drink ultra pure water instead. Anybody who is eating any food at all places from hundreds to thousands of times more solids into their digestive system than they get from tap water in a day. Dave

> Seems one of the major (long-term) problems with drinking "pure" > water is that it has a much higher potential to get contaminated on > the way to your mouth Yeah, and you know what fish do in it. Maybe WC Fields was right all along - "lost my corkscrew, and we were forced to live on nothing but food and water" A survey on bottled was done here a while ago. Much of it came out more contaminated than fresh tap water. Sits on the shelf in the light and has dissolved plasticisers (from the bottle) and sometimes high bacteria counts. And you pay over the odds for that privilege. Those people who can't go 5 minutes without sucking on a water bottle teat could be doing themselves more harm than good by over-hydrating and not compensating dietarily for the extraordinary urine production

On Mar 25, 2005, at 9:34 AM, Peter wrote: > It is much more reliable to measure its capacitance > (water has epsilon-r 80). Does water still have such a high dielectric constant when impurities have rendered it moderately conductive? A material that is simultaneously conductive and dielectric strains my memories of college physics, but I don't see why it couldn't work as long as steps are taken to prevent actual conduction... BillW

> > It is much more reliable to measure its capacitance > > (water has epsilon-r 80). > > Does water still have such a high dielectric constant when impurities > have rendered it moderately conductive? A material that is > simultaneously conductive and dielectric strains my memories of > college physics, but I don't see why it couldn't work as long as > steps are taken to prevent actual conduction... *Everything* is both dielectric and conductive. The degree to which an object is either varies. My question is how closely are the two related? Does the dielectric constant of a material directly relate to its conductivity? Questions easily answered upon perusal of a college level physics text, of course, and I'm not looking for an answer here. Mike H.

From: "Peter" Subject: Re: [EE] Resistivity of Water > "IN EVENT OF EXPOSURE CONSULT A PHYSICIAN" <grin> I can only relate the story, from my BBC transmitter group days, which I think came from our overseas world service relay on Ascension island. The BBC built the transmitter site and (like a few other overseas sites) the local power supply was either inadiquate or non-existant, so they built an on-site power station, which also had an assiciated de-salination plant to provide drinking water. The power station used vast quantities of very pure water, as did the transmitting station for cooling high power valves. But I think it was the power station chaps who decided that they didn't like the taste of the de-salinated water, and thought they would try the pure stuff. I think it took a few weeks, but after a while they had all become very ill. (Ill enough for Health and Saftey to have to get involved.) Personally, whenever I handle the stuff it makes my hands feel absolutely terrible. I'd say a similar feeling to having used de-greasing agents, but probably not as bad an effect. Cheers..Mike.

>> "IN EVENT OF EXPOSURE CONSULT A PHYSICIAN" <grin> > > the de-salinated water, and thought they would try the pure stuff. I > think it took a few weeks, but after a while they had all become very > ill. (Ill enough for Health and Saftey to have to get involved.) I have read somewhere that drinking water contains salts of essential minerals in forms that do not occur in food. i.e. the body cannot synthesize them without drinking normal water and it runs out after a while. The same text mentioned that drinking water should be done before or after meals. I am not sure about this. > Personally, whenever I handle the stuff it makes my hands feel absolutely > terrible. I'd say a similar feeling to having used de-greasing agents, but > probably not as bad an effect. Distilled water is known to cause 'laundry hands' very quickly (puckered skin on fingers etc). Peter

On Fri, 25 Mar 2005, William Chops Westfield wrote: {Quote hidden}> > On Mar 25, 2005, at 9:34 AM, Peter wrote: > >> It is much more reliable to measure its capacitance >> (water has epsilon-r 80). > > Does water still have such a high dielectric constant when impurities > have rendered it moderately conductive? A material that is > simultaneously conductive and dielectric strains my memories of > college physics, but I don't see why it couldn't work as long as > steps are taken to prevent actual conduction... Afaik the epsilon-r does not change but the equivalent schematic now involves a lossy capacitor (modeled with series or parallel r). Usually this can be neglected if the measuring frequency is high enough, but by using a proper C bridge (Hey ?) one can remove the r accurately and measure c. That is not the problem, the problem is that the capacitive nature of the device gets altered by polarization and other electrolytic effects. The cheap way to get around this is to use insulated electrodes (thin paint, ptfe etc). If there is no water the capacitance is low, if there is water the capacitance is higher, if there is conductive water then the capacitance is very high (the highly conductive water causes the paint sheets to be the actual measured capacitors). For drop-formation reasons the electrodes need to be 12mm apart (or more), and because the capacitance to be measured is low the best configuration is the coaxial one. Afaik the only *reliable* way to measure water is using microwaves at one of the resonant frequencies of the *liquid* water molecule (2.4GHz is supposed to be one of them) while at the same time also looking at the nearby frequencies for non-absorption. E.g. scanning an oscillator around 2.4GHz and measuring absorption should work for this. But for determining a flooded cellar two stainless electrodes with ac as a measuring current using the water resistance should be enough ;-) Peter

The long answer, We live in a world of rules. Always walk with a leash, don't stick your head out the car window, don't bite the mail man. So many! As I plan to work my way up the Darwin Scale, I felt the need to have my own rules. I stole the rule about playing pool, as being a dog, I can't play pool> But it does help me to remember that as great as I think I am, I should never play someone else's game. "Never eat nor drink anything blue" is a rule that I think I can follow. So far I have only failed when it came to some M&M's on the floor. Pookie (the dog) http://princesspookie.com {Original Message removed}

> "Never eat nor drink anything blue" is a rule that I think I can > follow. So > far I have only failed when it came to some M&M's on the floor. > Pookie (the dog) > http://princesspookie.com "Never wearing anything blue" may be a rule you could consider adding. Any substantive (or other) replies to this missive should probably be tagged [OT] so James can have a less stressful life. I usually just write gibberish using this keyboard, and open random web pages, partially for fun and partially in order to annoy. On this occasion a meaningful response seemed in order. Davon Laufen