Wikipedia:Reference desk/Archives/Science/2014 May 23

= May 23 =

Effect of hydrogen on electrical resistivity of metals
Hydrogen weakly dissolves into pure iron (including iron below 1185 K, therefore solid in alpha phase). The solubility increases with temperature. Same with other metals. I've been trying to find out what effect the dissolved hydrogen has on electrical resistivity. I can find journal articles on the effect of hydrogen forced out between crystal boundaries by fast cooling (super-saturation), but that's not what I am after. Can anyone help on this? Assuming dissolved hydrogen affects resistivity, which it surely must do, by increasing the probability of drift electrons encountering atom interference, is the effect different above and below the Curie point (1043 K)? 139.168.241.56 (talk) 02:28, 23 May 2014 (UTC)


 * It must always increase electrical resistivity. There are three types of metal-hydrogen alloys. In two types, hydrogen exits as either dihydrogen or as atomic hydrogen. In the third type, hydrogen crystalises out by forming a solution of molecular hydrides dispersed in the bulk metal. As any molecular solute will affect, dihydrogen increases the electrical resistance. As a solute, atomic hydrogen does exhibit electronic delocalisation, though only about half as strong as most metals. Thus it should also increase the resistance, but not as severely as dihydrogen. Molecular hydrides should have an effect intermediate of the two, due to the bond polarisability of the M-H bond. I don't know about the Curie point effects. Maybe another user can extrapolate based on what I've said? Plasmic Physics (talk) 04:29, 24 May 2014 (UTC)


 * The question is - by how much does it increase? 124.182.50.125 (talk) 05:09, 24 May 2014 (UTC)


 * I doubt that anyone would know an average figure from the top of their head. So, I assume that you'll have to find a relevant paper, just as what I would have to do. Maybe for a rough guess, you could have a look at how carbon content affects the electrical properties of steel? Plasmic Physics (talk) 07:13, 24 May 2014 (UTC)
 * Plasmic, If you read my question, you would have realised I HAD tried to find a relavent paper, and/or otherwise look it up.  Not everything can be found with Google, but more can be found if you use just the right search key(s), and if you are familiar with the subject. Carbon does not seem relavent, as it either chemically combines with Fe is much larger amounts, or it accumulates as pure carbon in between the Fe crystals.  Iron is a slightly permeable to hydrogen - the hydrogen atom is small enough to difuse through the iron crystal atomic structure.  So, apparently, is the hydrogen molecule, at a slower rate.  Carbon atoms can't do this.  I found quite a few journal articles about hydrogen diffusion, none about the effect on electrical conductivity. 124.182.50.125 (talk) 09:04, 24 May 2014 (UTC)

Dihydrogen monoxide
http://dhmo.org/facts.html lists "Dihydrogen Oxide, Hydrogen Hydroxide, Hydronium Hydroxide, or simply Hydric acid" as alternate names for this horribly destructive compound. Are all of them valid names by IUPAC nomenclature? All four of them are redirects, with three different targets: In particular, I'm left wondering whether "hydric acid" is perhaps an invalid name. I'm tempted to send all of them to WP:RFD, saying that all should go to the same place, and asking people to decide which place. If that's a chemically bad idea, please let me know so I don't waste people's time at RFD. Nyttend (talk) 03:29, 23 May 2014 (UTC)
 * Dihydrogen oxide goes to Properties of water
 * Hydrogen hydroxide also goes to properties of water
 * Hydronium hydroxide goes to Self-ionization of water
 * Hydric acid goes to the DHMO hoax article


 * This nonsense gets 36 hits if one simply checks the archives.  Are we to understand User:Nyttend is unfamiliar with the search function? μηδείς (talk) 03:37, 23 May 2014 (UTC)


 * Did you read the Q ? He's asking which names are valid and if there's any reason they shouldn't all redirect directly to the water article. StuRat (talk) 03:41, 23 May 2014 (UTC)
 * Correct. This search is more relevant.  Nyttend (talk) 04:01, 23 May 2014 (UTC)


 * Another one I've seen is hydroxyl hydride. —Tamfang (talk) 07:16, 23 May 2014 (UTC)
 * I'd send them all to the hoax article as that is the context in which they would most be used. Dmcq (talk) 09:29, 23 May 2014 (UTC)

Relative to heavy water, ordinary water is acidic. Count Iblis (talk) 11:48, 23 May 2014 (UTC)
 * Could you also say that relative to lye, baking soda is acidic? Sagittarian Milky Way (talk) 22:07, 24 May 2014 (UTC)


 * Google searches suggest that "hydrogen hydroxide" in the majority of cases is not used in the DMHO hoax sense, so it probably should redirect to the water article. The others seem almost always to be used in connection with the hoax.  John M Baker (talk) 15:11, 23 May 2014 (UTC)


 * Here is the IUPAC webpage and database, in all it's glory: . I don't know enough chemistry to sort through it. I can find fairly WP:RS for most of your variants (googling e.g. /site:.edu IUPAC water nomenclature/). To my reckoning, this is certainly worth a reconsidering of the redirects by the people who know about such things. SemanticMantis (talk) 15:14, 23 May 2014 (UTC)


 * It's not a hoax, it's just a one-sided presentation. Water promotes both life and death. ←Baseball Bugs What's up, Doc? carrots→ 19:25, 23 May 2014 (UTC)


 * Assuming that all the names are technically valid names for water (I'll leave this decision to others), they should continue to be redirects to articles to what they mean technically, for encyclopaedic reasons. That some play on these words (only possible due to lack of familiarity and their "chemical" sound) is out of scope IMO.  If someone wants to find out what they mean, they should be able to find out in WP, and not be given the impression that they are invalid names by, for example, deleting the redirects or directing them to articles essentially about their abuse.
 * Dihydrogen oxide IMO should be a redirect to Water, not to Properties of water.
 * Hydrogen hydroxide IMO should similarly be a redirect to Water.
 * Hydronium hydroxide refers to ionic components that occur in water, not water per se. That should remain a redirect to Self-ionization of water.
 * Hydric acid may fall into a systematic naming system, in which case it would be valid. If so, it should also be a redirect to Water.  If not, I'd suggest deleting it.
 * —Quondum 20:26, 24 May 2014 (UTC)

Deep red color becomes faint orange in digital camera picture :(
Yesterday I took some pictures of thunderclouds near the horizon which contained very nice deep red colors near the horizon. But whatever I tried with reasonable white balance settings, the colors in the picture were far off from containing that very deep red color. It looks like faint orange. Of course, I can correct that with digital processing of the pictures, but I'm not sure why a reasonable white balance setting wouldn't have led to a result that is at least approximately correct. Or could this have to do with me being red-green color blind? Count Iblis (talk) 12:00, 23 May 2014 (UTC)
 * Have you uploaded the images elsewhere? Color blindness could affect how you view the colors, I think, though I'm surprised at what you mentioned. — Crisco 1492 (talk) 12:20, 23 May 2014 (UTC)

.
 * When this sort of thing happens, it may be due to one or more of three things:-
 * 1 The original colour is highly monochromatic (ie not a spread of wavelengths), and the wavelength does not match the peaks in the RGB sensors of the camera; The read colour in the sky comes from dust/pollutant scattering, it would not be very monochromatic;
 * 2 You are colour blind, and the peak wavelength of your eye's cones do not match the RGB emission from the screen that you are viewing the picture on (You'd need to have quite exceptional colour blindness for this to be significant);
 * -and, perhaps the most important-
 * 3. Many current generation digital cameras have an automatic white balance algorithm. Mine is of this sort.  I don't know the details of the algorithm, but it reliably gets it right when I take outdoor pictures of people and scenery, reliably gets it right when I take pictures of people and everyday things indoors under tungsten light (which is quite yellow compared to sunlight), and, suprisingly, doesn't do a bad job under flourescent lighting, which film photography could never do (due to reason 1 above).  But when I take pictures of more unusual things, like small electronic parts, insides of machines, and the like, it gets the white balance badly wrong.  For these sorts of things, I turn the automatic white balance off by turning a switch to manual program position, for which I have turned auto white balance off in the software menu system.  Perhaps your camera has auto white balance but doesn't know what to do with thunderclouds.  — Preceding unsigned comment added by 124.182.50.125 (talk) 12:36, 23 May 2014 (UTC)
 * No monochromatic colors in the visible range are "missed" by camera or human eye sensors, so your first point doesn't really make sense even if the light source was monochromatic. -- BenRG (talk) 20:45, 25 May 2014 (UTC)


 * If clouds near the horizon look deep red, then it must be near sunset. Light levels at that time are usually very low.  The human eye is much better at compensating for low light levels than digital cameras are, so it is not surprising that you are getting color distortion. Looie496 (talk) 12:53, 23 May 2014 (UTC)


 * What type of digital camera was used? Can you upload the image?  Nimur (talk) 14:33, 23 May 2014 (UTC)


 * Agree with Nimur. Upload this image so we can have a look at it. Methinks that you may have used an algorithm to correct for WB that is not applicable for an image of this type. Even if you do not have a RAW file, upload the jpeg and we will tweak the oranges to  reds. Then, you can decide if the photo, better represents the image you were attempting to capture. If so, then tell  us what camera you are using so we  can than advise you as to how to avoid this color shift.--Aspro (talk) 22:42, 23 May 2014 (UTC)
 * If your camera has a high dynamic range (HDR) setting try it when you next use it in low or unusual light conditions. The linked article explains ways to take and process photos to get the same effect when using a camera that doesn't do it automatically. In that case you need to take three photos - one under-exposed, one "normal" and one over-exposed (or even more than three, each at a different "stop" setting) and then combine them in your photo processing software. Some of the article's sources lead to fuller instructions. Roger (Dodger67) (talk) 12:58, 24 May 2014 (UTC)

I'll see if I can upload the image. I did also take HDR pictures with my Sony SLT-A58. There are two options for this, I think in one it applies a different gamma correction (the raw pictures are 16 bit, so there is plenty of room to increase the dynamic range). In another setting (only available when you are not shooting in RAW), the camera takes 3 pictures and combines them automatically to a HDR picture. But I did not see the deep red in the HDR pictures. Count Iblis (talk) 13:05, 25 May 2014 (UTC)


 * I think the most likely explanation in a case like this is that the image is overexposed. If the reds are starting to get up near the top of the range (255 for example, in 8-bit color) then you can add any amount of red to your image and it won't get any brighter; but the green channel continues to increase linearly with exposure because its value is still low.  And it's really easy to overexpose an image of a sunset because most of the landscape is dimmer than the reflection of the sun off the clouds. Wnt (talk) 13:59, 26 May 2014 (UTC)

Color modeling theory (in particular photographic rendition of colour) is quite a complicated subject. See for example RGB color model and links found therein. One would indeed love a device that perfectly rendered image color as the typical human discerns the object. First there is the issue of "typical": as others have mentioned above color blindness is an extreme example of the variance in human color perception. There are even arguments (I believe) about the correct modeling for human color perception. More mundanely your camera (I suppose it to be digital) is almost certainly using an array of three different color filters in front of the photo-cathode which itself has a wavelength response. Careful design can emulate in the product a "good" rendition of the color in the image that you would have seen in the object (though that will depend also on the image display medium/technology). Here is another extreme example. Your cell phone camera provides decent color rendition under most conditions. But use it to look at the front of your TV remote as you click it. You will see the (near) infrared diode blinking--not a color since we don't see it at all, just due to your cell phone's camera sensitivity to wavelengths of light at which us mere mortals are insensitive to. Juan Riley (talk) 22:01, 26 May 2014 (UTC)