# The colour of Hydrogen **URL:** \ **Category:** Factual Questions\ **Created:** [March 16, 2010, 2:39pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649 "2010-03-16T14:39:17Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Deflagration](https://avatars.discourse-cdn.com/v4/letter/d/3ab097/32.png) [@Deflagration](https://boards.straightdope.com/u/Deflagration)\ **Post date:** [March 16, 2010, 2:39pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/1 "2010-03-16T14:39:17Z")
What colour is liquid hydrogen? All references to the element, I can see, say it is a colourless gas, but what is it like when it is a liquid? Is it ‘clear’ as in actually colourless or just appears nearly colourless. Eg. Water is light blue, as is liquid oxygen, as is hydrogen peroxide etc. ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [March 16, 2010, 2:59pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/2 "2010-03-16T14:59:16Z")
Hydrogen is a metal, so I’d assume it would look somewhat… metallic? ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [March 16, 2010, 3:08pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/3 "2010-03-16T15:08:51Z")
I’m reasonably certain that Hydrogen is colorless. Oxygen is blue because of electronic transitions in the visible range. Hydrogen will have no electronic transitions in this range. Water is blue due to the fourth harmonic of the O-H stretch in the infrared. Hydrogen will not be infrared active. I can think of no transitions in the visible range for hydrogen. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [March 16, 2010, 3:10pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/4 "2010-03-16T15:10:02Z")
> [@Alessan](#): > > Hydrogen is a metal, so I’d assume it would look somewhat… metallic? Hydrogen is a metal? Not by any standard definition. It is about as far from metallic as you can get. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [March 16, 2010, 3:20pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/5 "2010-03-16T15:20:54Z")
Hydrogen can be metallic, under the appropriate circumstances of temperature and pressure. But if you simply cool it down under atmospheric pressure, it’s a liquid. I think it appears slightly bluish, but like most liquified gases, it’s pretty clear and not obviously colored. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [March 16, 2010, 3:23pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/6 "2010-03-16T15:23:23Z")
Hydrogen is placed on the periodic table as an alkali metal. While it is not considered to be a metal under normal conditions, at high enough pressures it is theorized that it will take on metallic properties. > [@](#): > > Though at the top of the alkali metal column in the periodic table, hydrogen is not, under ordinary conditions, an alkali metal. In 1935 however, physicists Eugene Wigner and Hillard Bell Huntington predicted that under an immense pressure of ~25 GPa (250,000 atm or 3,500,000 psi), hydrogen atoms would display metallic properties, losing hold over their electrons.[1] Since then, metallic hydrogen has been described as “the holy grail of high-pressure physics”.[2] > > The initial prediction about the amount of pressure needed was eventually proven to be too low.[3] Since the first work by Wigner and Huntington the more modern theoretical calculations were pointing toward higher but nonetheless potentially accessible metallization pressures. Techniques are being developed for creating pressures of up to 500 GPa, higher than the pressure at the center of the Earth, in hopes of creating metallic hydrogen.[4] From here: [Metallic hydrogen - Wikipedia](http://en.wikipedia.org/wiki/Metallic_hydrogen) I’ve heard liquid hydrogen described as colorless. I’ve also heard it described as being pale blue, which makes me think it looks a lot like water. I personally don’t just happen to keep a bucket of the stuff handy in case this question comes up though. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [March 16, 2010, 4:30pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/7 "2010-03-16T16:30:31Z")
> [@engineer\_comp\_geek](#): > > Hydrogen is placed on the periodic table as an alkali metal. While it is not considered to be a metal under normal conditions, at high enough pressures it is theorized that it will take on metallic properties. > > From here: [Metallic hydrogen - Wikipedia](http://en.wikipedia.org/wiki/Metallic_hydrogen) > > I’ve heard liquid hydrogen described as colorless. I’ve also heard it described as being pale blue, which makes me think it looks a lot like water. I personally don’t just happen to keep a bucket of the stuff handy in case this question comes up though. I’m well aware of metallic hydrogen. If you compress helium enough then helium will also be metallic. Are you going to claim that helium is a metal too? In fact, I’ll bet if you compress any element to the point that the electron electron repulsion raises the ground state into a conduction band you’ll get the same thing. By calling hydrogen a metal, you are essentially saying that all elements are metals. Hydrogen is not classified as an alkali metal. It is classified on it’s own because it can react in ways that alkali metals cannot react. Any classification scheme that puts hydrogen in the alkali metal category is completely ignoring it’s covalent and hydridic reactivity. That’s not useful. ---
**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\ **Post date:** [March 16, 2010, 4:38pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/8 "2010-03-16T16:38:16Z")
The wiki page on [Liquid hydrogen](http://en.wikipedia.org/wiki/Liquid_hydrogen) lists its appearance as “colorless liquid”. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [March 16, 2010, 5:09pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/9 "2010-03-16T17:09:18Z")
So… if the gas giants in our solar system were pure hydrogen without anything else, they’d be white? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 16, 2010, 5:26pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/10 "2010-03-16T17:26:07Z")
> [@](#): > > If you compress helium enough then helium will also be metallic. Cite? I’ve never heard of metallic helium before. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [March 16, 2010, 6:03pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/11 "2010-03-16T18:03:53Z")
[Here is a cite](http://www.sciencedaily.com/releases/2008/08/080806184907.htm). I’m sure as a physicist, you are better equipped to find better cites. I’m not a physicist, but it makes sense to me that this should eventually happen to any element with enough pressure. I think of the electronic energy surface as a series of hills and valleys. In non metallic elements, the electrons are localized in the valleys, but as you compress them the valleys will rise in energy due to electron electron repulsion. Eventually, I think that the difference between the energy of the hills and the valleys will be small enough that the valence electrons will no longer be localized. Of course the hills will rise to, and this assumes that the hills won’t rise as fast as the valleys. Also, I have no idea if the amount of pressure required to get to this state will be enough to breakdown other barriers like nuclear. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [March 16, 2010, 6:27pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/12 "2010-03-16T18:27:38Z")
> [@WarmNPrickly](#): > > Hydrogen is not classified as an alkali metal. Are you claiming that hydrogen is never ever classified as an alkali metal, anywhere, by anyone, under any circumstances? ---
**Author:** ![Myglaren](https://avatars.discourse-cdn.com/v4/letter/m/f1d935/32.png) [@Myglaren](https://boards.straightdope.com/u/Myglaren)\ **Post date:** [March 16, 2010, 7:03pm UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/13 "2010-03-16T19:03:40Z")
> [@](#): > > In 1973, a group of Russian experimenters may have produced metallic hydrogen at a pressure of 2.8 Mbar. At the transition the density changed from 1.08 to 1.3 g/cm^3. Earlier, in 1972, a Livermore, California, group also reported on a similar experiment in which they observed a pressure-volume point centered at 2 Mbar. Predictions say that metallic hydrogen may be metastable; others have predicted it would be a superconductor at room temperature. From: [Corrosion Source](http://www.corrosionsource.com/handbook/periodic/1.htm) ---
**Author:** ![rbroome](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@rbroome](https://boards.straightdope.com/u/rbroome)\ **Post date:** [March 17, 2010, 12:12am UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/14 "2010-03-17T00:12:58Z")
> [@Deflagration](#): > > What colour is liquid hydrogen? > All references to the element, I can see, say it is a colourless gas, but what is it like when it is a liquid? > Is it ‘clear’ as in actually colourless or just appears nearly colourless. > Eg. Water is light blue, as is liquid oxygen, as is hydrogen peroxide etc. I have seen liquid hydrogen, but frankly there was so much condensation in the air that I can’t say what color the liquid is. Very little if any color though. I can say by direct observation that liquid helium is a clear liquid. No trace of color that I could see. And we were lighting the liquid to observe superfluid behavior. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [March 17, 2010, 3:10am UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/15 "2010-03-17T03:10:46Z")
> [@engineer\_comp\_geek](#): > > Are you claiming that hydrogen is never ever classified as an alkali metal, anywhere, by anyone, under any circumstances? Hydrogen is often categorized as an alkali metal by elementary school teachers, non-chemists and OCD people that look at it’s place in the periodic table and stick their fingers in their ears when you mention hydride just so they can make it fit. Hydrogen is in every respect a unique element and nobody with any sense would classify it as an alkali metal. Hydrogen is not a metal. ---
**Author:** ![Imasquare](https://avatars.discourse-cdn.com/v4/letter/i/5f9b8f/32.png) [@Imasquare](https://boards.straightdope.com/u/Imasquare)\ **Post date:** [March 17, 2010, 4:59am UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/16 "2010-03-17T04:59:34Z")
Is water really blue? I was taught in school that the ocean appeared blue because it was reflecting the blue of the sky. Although now that I think about it, the sky is a much lighter blue than the ocean. ---
**Author:** ![USCDiver](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/uscdiver/32/354_2.png) [@USCDiver](https://boards.straightdope.com/u/USCDiver)\ **Post date:** [March 17, 2010, 5:04am UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/17 "2010-03-17T05:04:58Z")
> [@Imasquare](#): > > Is water really blue? > > I was taught in school that the ocean appeared blue because it was reflecting the blue of the sky. Although now that I think about it, the sky is a much lighter blue than the ocean. Have you ever seen an indoor pool? ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [March 17, 2010, 5:58am UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/18 "2010-03-17T05:58:31Z")
> [@USCDiver](#): > > Have you ever seen an indoor pool? I’ve never seen one that did not color the sides of the pool blue, and the water has never seemed any bluer than the sides. ---
**Author:** ![Imasquare](https://avatars.discourse-cdn.com/v4/letter/i/5f9b8f/32.png) [@Imasquare](https://boards.straightdope.com/u/Imasquare)\ **Post date:** [March 17, 2010, 6:31am UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/19 "2010-03-17T06:31:47Z")
> [@BigT](#): > > I’ve never seen one that did not color the sides of the pool blue, and the water has never seemed any bluer than the sides. I also thought it was due to coloring the surface. I have seen some outdoor pools where the water is green. Not due to algae but because the pool surface is green. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [March 17, 2010, 9:15am UTC](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649/20 "2010-03-17T09:15:37Z")
> [@Imasquare](#): > > I was taught in school that the ocean appeared blue because it was reflecting the blue of the sky. Although now that I think about it, the sky is a much lighter blue than the ocean. They tried to teach me that too, but I never believed them. I find the persistence of this myth quite remarkable, as the sky is blue for probably less than half the time here in England - so we have abundant opportunity to observe the falsity of the claim. [Next page](https://boards.straightdope.com/t/the-colour-of-hydrogen/532649.md?page=2)