Sciencemadness Discussion Board

color of ultrapure water

guaguanco - 8-1-2004 at 14:52

Long ago, I remember browsing through a multivolume treatise on Water in the chemistry library. It talked about every conceivable phyiscal and chemical property of H2O. One of the things I vaguely remember is that absolutely pure water is not exactly colorless, but had a very, very slight but measurable blue tint. (Obviously not visible to the casual observer.)
I'd be curious if anyone else had run across this, or is my memory failing me?

blip - 8-1-2004 at 14:58

I have seen that stated many times in many different texts, although my source memory seems to be failing me. You're not going mad, don't worry. :) Did you ask for some specific purpose? Just wondering....

unionised - 8-1-2004 at 15:06

Google gives
http://www.des.ucdavis.edu/courses/est116/116_04.htm
among others.

guaguanco - 8-1-2004 at 15:11

Quote:
Originally posted by unionised
Google gives
http://www.des.ucdavis.edu/courses/est116/116_04.htm
among others.

Thanks, I haven't searched very hard yet. It would be interesting to try to devise an experiment that would allow this effect to be visible to the naked eye, rather that relying on spectrometers.

chemoleo - 8-1-2004 at 17:05

Last year (gosh it's 2004 now) we went down a glacier hole. It was a cloudy day, so no blue sky. Anyway, upon decending into the hole things got from nicely turquoise to deep ocean blue! Amazing colour!! This was the light let through by 100+ meters of ice!
So, go to a glacier, that's an easy experiment :D

Anyway, it's interesting to see that the hydrogen bonds are responsible for this. Presumably, highly pressurised and heated water above its BP would elicit LESS absorption in the infrared/red range, as the duration/strength/quantity of H-bonds would be much less?
Or, vice versa, very cold water or, ice, of course, would absorb more? How about ice at -50 deg C, i.e. in Antartica? this should absorb more red light (and hence have a stronger blue touch to it) than ice that temporarily forms in warmer regions...

Marvin - 9-1-2004 at 02:08

I seem to recall that if you stand inbetween 2 parallel mirrors you see a large number of multiple reflections which get greener and greener becuase of the colour of the glass. Maybe you could arrange mirrors, preferably the other side to the glass, under water so you could see the blue colour. It should be possble to set this up in the bath or with a fishtank though for best results I would think a pin hole in one mirror to look through would be best. Having the mirrors in the water would help also but if your eye is underwater, you wont be able to focus without goggles.

chemoleo - 9-1-2004 at 05:33

Thats a good idea, but then you will definitely need very good mirrors, that do not use common glas (Quartz layered?). Else you will see only green colour, and not blue. Probably, a metal mirror (with no glas covering it) might be better.

By the way, I have measured H2O in a Quartz cuvette against air before, and I never noticed a peak, be it absolutely tiny, in the red region. I suspect that this is because the pathlength of 1 cm is not quite sufficient - a 1000 x greater pathlength might work out better ;)

Purple Haze - 9-1-2004 at 08:14

Actually I've heard of a free floating
SO4 radical within pure spring water.Mainly
imported water.Especially from the volcanic
regions like Hawaii,Iceland,or a spring near
such activity.The spring could be 200 miles
away from the nearest volcano and it will
still contain the SO4 radical.
Generally speaking it is filtered out but
exists in minutes quantities eg:3 ppm

I am a fish - 9-1-2004 at 09:33

Quote:
Originally posted by chemoleo
Thats a good idea, but then you will definitely need very good mirrors, that do not use common glas (Quartz layered?). Else you will see only green colour, and not blue. Probably, a metal mirror (with no glas covering it) might be better.


Even then, I expect the mirrors would reflect some wavelengths preferentially.

I doubt there is any simple way of seeing the instrinsic colour of pure water.

BromicAcid - 9-1-2004 at 09:38

If you could produce a single stream with no turbulence you might be able to discern a specific color. I've seen such a thing done at water parks for display. The water is forced through tiny capillaries and when it comes out the shape of it is so consistent that it doesn't look like its moving. So you could see if there is some intrinsic color to it without any encasement.

unionised - 10-1-2004 at 06:42

There is no way that you could maintain ppm concentrations of an unstablised free radical like SO4 in solution for more than a few seconds.
You could set up 2 mirrors and fill part of the space between them with water. Above the water you would get whatever colour the preferental reflections of the mirrors give. Below the water you would get that plus the effect of the water. You might be able to see the difference.
another problem is that any traces of impurity in the water might swamp the effect you are looking for. (And, unfortunately, this could be a problem with the clacier too.)