Wikipedia:Reference desk/Archives/Science/2010 December 11

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December 11

chlorine dosing

I've been trying to find out the dosing rate for chlorine but I couldn't. Would you please help me on it? The R.O product rate [is?] 2.6GPM, the Chlorine solution strength is 0.1PPM, and I need 1 ppm on the product.

On the other hand, how to adjust the pump speed and stroke? Should i deal with it as a percentage of it's maximum?

Thanks a lot. — Preceding unsigned comment added by Dawoad0a (talk • contribs) 06:58, 11 December 2010 (UTC)

Dose is a function of time, so make sure the surface is exposed for 10 times as long with 0.1 ppm as you are supposed to expose it to a 1 ppm solution. Ginger Conspiracy (talk) 10:55, 11 December 2010 (UTC)

circuit idea

Can I get a circuit or a block diagram for a single port wireless d.c. charger? —Preceding unsigned comment added by 117.207.197.196 (talk) 07:30, 11 December 2010 (UTC)

Yes.[1][2][3][4] Ginger Conspiracy (talk) 11:05, 11 December 2010 (UTC)

Mercury sulfate

Does the dissolving of mercury in concentrated sulfuric acid produce mercury(I) sulfate or mercury(II) sulfate? Thanks, --Chemicalinterest (talk) 12:03, 11 December 2010 (UTC)

It dissolves in hot conc. sulfuric acid forming mercury(II) sulfate. But in water it dissociates forming a yellow solid.

3HgSO₄ + 2H₂O→Hg(SO₄)•2HgO + 2H₂(SO₄).

--Stone (talk) 12:40, 11 December 2010 (UTC)

How is mercury(I) sulfate produced then? Is it a metathesis reaction between a sulfate and another mercury compound like mercury(I) nitrate? Thanks, --Chemicalinterest (talk) 12:57, 11 December 2010 (UTC)

Mercury (I) is pretty exotic stuff. For the one, it's a dimolecular metal ion, which is pretty much a one-of-a-kind thing. If you read Mercury polycations, you'll see that Mercury (I) is essentially metastable in solid form. That's because of the equilibrium in solution Hg₂²⁺<--> Hg⁰ + Hg²⁺. Anything which precipitates Hg²⁺ will, by Le Chatelier's principle, cause the equilibrium to shift rapidly away from the Mercury (I) ion. You can create solutions of Mercury (I) nitrate via reduction from Mercury (II) nitrate; however it doesn't really "exist" except in solution. The solid precipitate has a hydrated cation (see the infobox in the article Mercury(I) nitrate), and any heat applied which would eliminate the water of hydration causes the Mercury (I) to disproportionate. There are other mercury (I) compounds, like calomel (mercury(I) chloride), but calomel isn't an ionic compound, it's molecular in nature; it sublimes at a relatively low temperature and forms gasseous molecules of Cl-Hg-Hg-Cl fairly easily. It's also non-polar, so it isn't much soluble in water. --Jayron32 14:22, 11 December 2010 (UTC)

This is all very interesting. But how is mercury(I) sulfate made? --Chemicalinterest (talk) 14:58, 11 December 2010 (UTC)

There are references in the article Mercury(I) sulfate. If you have access to a library, you could look these up. --Jayron32 15:18, 11 December 2010 (UTC)

Here ya go: this article from 1962 has a procedure. The procedure involves slow addition of sulfuric acid to a mixture of mercury(I) nitrate and nitric acid. And by slow I mean S....L....O....W. The procedure calls for dropwise addition of the sulfuric acid over 67 days... and then the product left to settle for 3 months, then is stored in an airtight, dark, nitrogen atmosphere before being subjected to an elaborate purification procedure. I have no idea how much time and equipment you have, but depending on how desperate you are, you could do this. (I did mention that mercury(I) compounds were exotic, didn't I?) --Jayron32 15:28, 11 December 2010 (UTC)

Is this a joke? People may revert it if I add that to our article... I do not want to do any experiments with mercury as I do not have any mercury or mercury compounds. This is just for Wikipedia article research. --Chemicalinterest (talk) 15:51, 11 December 2010 (UTC)

[5] states three methods:1) precipitation from mercury(I) nitrate solution with sulfuric acid 2) By adding an access of mercury to sulfuric acid 3) electrochemically from mercury(II) sulfate. --Stone (talk) 15:32, 11 December 2010 (UTC)

This sounds a little more practical than the above method, but probably will come out with a more impure product. Anyway, thanks for the answers; I plan to be adding them to my article on simple and your article here. --Chemicalinterest (talk) 15:53, 11 December 2010 (UTC)

I'm pretty sure that the Journal of Physical Chemistry, which published the above article, is not much into publishing "jokes" as peer reviewed articles. On the contrary, the actual practice of chemistry is usually quite tedious; getting a pure compound is not a trivial thing, and actual working chemists are used to doing some pretty long, otherwise tedious procedures to do it. --Jayron32 15:59, 11 December 2010 (UTC)

Gives plenty of "down-time" to edit Wikipedia! DMacks (talk) 20:05, 11 December 2010 (UTC)

..BURNING DIMOND....

I want to know as dimond is purest form of carbon .... would it give any product (ash) if we burn it....? would it burn or not...? I also want to know why table teniss ball, when burnt do not give any product...? —Preceding unsigned comment added by 220.225.96.217 (talk) 14:29, 11 December 2010 (UTC)

If you burned a diamond (and it does burn pretty readily, as you note, it is just carbon) you get some combination of carbon dioxide and carbon monoxide gases, in a proportion depending on how much oxygen is present. If you have enough oxygen, you get essentially carbon dioxide. In low-oxygen environments you get more carbon monoxide. There will be no "ash" left over, unless the diamond has some impurities; for example I believe that so-called "blue" diamonds contain cobalt impurities, if you burn one of those you will get a (very tiny amount) of cobalt oxides as an ash. However, if you have an essentially pure diamond, it will burn completely. --Jayron32 14:46, 11 December 2010 (UTC)

To answer your second question, a table-tennis ball is plastic, probably polyethylene. These sort of plastics are essentially just long hydrocarbon chains. That is, nothing but hydrogen and carbon. The carbon (as noted above) makes the gasses carbon monoxide and carbon dioxide. The hydrogen produces water when burned, and in the heat of a flame, it will be a gas as well. Thus, burning the table tennis ball will ALSO not leave any ash behind. When ash forms, it because burning the substances produces some sort of solid oxides; if the substance contains only elements that have gasseous oxides, you get essentially all gasses. --Jayron32 14:49, 11 December 2010 (UTC)

Most plant ashes (pot ash) are sodium or potassium carbonates and oxides. --Chemicalinterest (talk) 14:56, 11 December 2010 (UTC)

Table tennis ball is Nitrocellulose and the burning is so rapid that the little ash which is produced is going up as little fume.--Stone (talk) 15:14, 11 December 2010 (UTC)

I'm not so sure about that; nitrocellulose is notoriously unstable and flammable, it used to be used early on as a plastic when there were no other alternatives, however I don't think that many modern products that use it. --Jayron32 15:55, 11 December 2010 (UTC)

You are right, but you never have a large amount of table tennis balls at home. The last one I burned 10 years ago was still Nitrocellulose made flexible with Camphor. You smell it sometimes if you rub a table tennis ball.--Stone (talk) 16:11, 11 December 2010 (UTC)

Celluloid is what table tennis balls are. I don't know the relationship and/or difference between that stuff and nitrocellulose. 90.195.179.14 (talk) 17:03, 11 December 2010 (UTC)

The difference is the amount of nitro groups per sugar molecule. The one is soluble in acetone the other not. But in general the difference is small.--Stone (talk) 17:22, 11 December 2010 (UTC)

Another factor in if any "ash" is left is how complete the combustion is. If part of the original is left unburnt, then that will be mixed in with the ash. You might think it would be obvious if part of it is left unburnt, but it's often not. If the material is fractured and blackened, it may look just like the rest of the ash.

What leads to incomplete combustion ? It's usually a result of not enough oxygen getting to the material, such as the pages on the inside of a phone book. Increasing the surface area and air flow will help here, and a table tennis ball (ping-pong ball) has a large surface area relative to it's volume, so complete combustion is likely.

Another reason for incomplete combustion is that the temperature falls below that needed for combustion. This can be a problem for things which burn slowly, as they might not generate enough heat to maintain the fire. A large wooden log can have this problem. But, as noted previously, the table tennis ball burns quickly and generates plenty of heat to maintain combustion. StuRat (talk) 17:51, 11 December 2010 (UTC)

Musical volume

I want to know why do we call the loudness or lessloudness of music "volume" ? why don't we use technical terms such as frequency... or amplitude....? —Preceding unsigned comment added by 220.225.96.217 (talk) 16:15, 11 December 2010 (UTC)

Because loudness (or volume) isn't directly tied to a physical property, it is a perceptive property, that is it's biologically and psychologically-based, not physically-based. The human ear's response to sound is roughly logarithmic with respect to the amplitude of the sound waves, which is why the loudness scale, decibels, is a logarithmic one. For most acoustic applications, its the perception of sounds which is more important than the actual physical properties of the sound. See loudness for more information. --Jayron32 16:42, 11 December 2010 (UTC)

The closest technical term for the intrinsic property of pressure-wave is "intensity" or "power" (and they are derived from frequency and amplitude). But loudless/volume is (as Jayron32 notes) about "how you hear it", not "how it is". The pressure-change of a tornado is enough to shatter your windows, and a dog-whistle is intense enough to anger my the pets the next property over, but neither one is "loud" in the common meaning of that term. Different terms for different situations/effects/properties, even if they are all related concepts. DMacks (talk) 20:05, 11 December 2010 (UTC)

"Volume" has been used to describe the size of a book since 1530, and for other quantities since 1621, but for an amount of space only since 1701 (judging by OED first usages). The first usage in music was in T. Busby's Complete Dictionary of Music in 1786 ("Volume, a word applied to the compass of a voice from grave to acute: also to its tone, or power: as when we say, ‘such a performer possesses an extensive or rich volume of voice’."), with the restriction to loudness or power not occurring until the early 1800s. "Amplitude" has been used for size or width since 1590, but did not gain its modern scientific usage until 1837, by which time the word volume was already in use for music. Dbfirs 00:25, 12 December 2010 (UTC)

On consumer audio equipment, "Volume" controls the amplifier gain equally at all frequencies while a so-called Loudness control alters the frequency response curve to match a human's loudness perception, usually in the crude way of merely boosting low frequencies at low volume. Cuddlyable3 (talk) 11:51, 19 January 2011 (UTC)

Unidentified Mineral

My nephew found some minerals that look like glass but much thicker and not as clear, more whiteish. Does anyone have any idea what it could be or how I could identify the rock or mineral?— Preceding unsigned comment added by 71.137.246.92 (talk • contribs)

If you type "identifying rocks and minerals" into Google, you get several promising websites that do just that. Without a picture of said mineral for people here to look at, it would be VERY hard to identify. --Jayron32 17:08, 11 December 2010 (UTC)

Are you sure that it isn't just quartz? Some good specimens are quite clear. Does it scratch glass (do not try this on a good window)? Then it probably is quartz, one of the most common minerals. --Chemicalinterest (talk) 17:36, 11 December 2010 (UTC)

Depending on how you found it, it might actually be glass. I once found some frosty glass pebbles in a river. Best as I can tell, they came from a broken glass bottle (old glass bottles were often much thicker than window glass) which had been in the river long enough to weather to smoothness (this also explains the frosty color). -- 174.31.218.235 (talk) 19:03, 11 December 2010 (UTC)

Glass doesn't scratch glass, which is why I put that test in there. --Chemicalinterest (talk) 23:44, 11 December 2010 (UTC)

Examples of specific halophiles

I'm looking for specific examples of slight halophiles, moderate halophiles, and extreme halophiles, but can't seem to find any. What are some examples of each? Albacore (talk) 19:41, 11 December 2010 (UTC)

The "Lifestyle" secion of that article gives some specific species (or families, or genus, etc.) as examples of moderate and extreme ones. Might also be useful to find a copy of Dieter Häussinger and Helmut Sies (2007) Osmosensing and Osmosignaling, Academic Press, 579 pages ISBN 0123739217, which is given as the reference for the statement "The extent of halotolerance varies widely amongst different species of bacteria." in the halotolerance article. DMacks (talk) 19:55, 11 December 2010 (UTC)

High pressure = good weather

Why is high pressure associated with good sunny weather, even in winter? Thanks 92.15.28.181 (talk) 19:47, 11 December 2010 (UTC)

Our atmospheric pressure article says "See pressure system for the effects of air pressure variations on weather", but the "Local atmospheric pressure variation" section-title makes it hard to find. The linked page talks in gory detail about how high pressure relates to lack of precipitation, reduced cloud-cover, etc. DMacks (talk) 19:52, 11 December 2010 (UTC)

Think of it this way: Turbulent and potentially turbulent weather fronts travel from high to low pressure regions, along with all the other air, so when you're in a high pressure area the storms and potential storms are moving away from you (on balance; things such as the jet stream might be moving the entire high pressure system away.) Also, the higher pressure differential is caused by atmospheric heating, which occurs more efficiently with little or no cloud cover, so if you're in a high pressure area, you've probably been generally free from clouds and in warm air for hours to days to begin with. Ginger Conspiracy (talk) 02:18, 12 December 2010 (UTC)

Well, that's pretty much completely wrong. There are two main factors. First, high pressure is associated with cold air masses, which are stable, whereas low pressure is associated with warm air which tends to rise and create clouds. Second, in the northern hemisphere high pressure masses spin clockwise, whereas low pressure masses spin counterclockwise. Because weather tends to move from west to east, the result is that when a high pressure center is approaching, the flow of air is from the north, where is a relatively cold and dry. When a low pressure center is approaching, the flow of air is from the south, where it is warm and moist. Looie496 (talk) 05:15, 12 December 2010 (UTC)

What is your source for this information? Pressure system#High-pressure system says high pressure systems are associated with relatively warm air. What does temperature have to do with cloud formation? Ginger Conspiracy (talk) 10:27, 12 December 2010 (UTC)

High pressure in my experience is asociated with warm temperatures and clear sunny skys. The air pressure in my part of the UK was about 1005hPa a few days ago when it was unusually cold with lots of snow, but in the last two or three days has risen to about 1025hPa with milder temperatures and sunny skies. Its winter here. 92.28.246.75 (talk) 15:05, 12 December 2010 (UTC)

The answers above are all confused or plainly wrong. The real reason is that high pressure regions are associated with sinking air. And that sinking warms up the through adiabatic compression leading to smaller relative humidity. 71.101.41.73 (talk) 06:46, 13 December 2010 (UTC)

Lets see if we can lay this out. If the articles at Wikipedia are confusing, ignore them. At the center of a high pressure system (that is, at the peak of the highest pressure) is a mass of cold sinking air. Cold air is more dense than warm air, so it tends to sink. This air, being colder and at a lower pressure than the air below it, has a lower dew point. As the air sinks the pressure and temperature both go up, meaning that the relative humidity of the air is dropping at the center of a high pressure system. This makes high pressure systems have clear, relatively dry and sunny conditions at their center. This sinking air forces some of the air below it outward, and that coupled with the coriolis effect generates an anticyclone. This means that in front of high pressure systems (as measured by their general direction of motion) the air is coming from the poles, and tends to be colder, while behind such systems, the air is moving from the equator, and tends to be warmer. This explains the Bermuda High which effects summer weather in the southeastern United States. The high pressure system parks itself over Bermuda, and the anticyclonic winds around it pulls hot, humid air into the Southeast out of the Atlantic and Gulf of Mexico. It depends on where relative to the high pressure center you are which will determine whether your local weather is warmer, cooler, wetter, or drier. But directly under the high-pressure center, it will be clear and cool. --Jayron32 07:03, 13 December 2010 (UTC)

Mass Energy and Black Hole evaporation

Lets say we have a black hole that has a mass of 225 tons. According to Hawking Radiation, this black hole should decay in about 1 second, and eventually result in a "dissolution of the black hole in a violent burst of gamma rays". Would all the energy given off equal the mass-energy of 225 tons of mass? In what form would this energy manifest itself? Mostly or entirely gamma rays? ScienceApe (talk) 22:35, 11 December 2010 (UTC)

Mass-energy of 225 tons of mass, minus the potential gravitational energy (which can be a significant amount). Probably gamma rays, but not necessarily. I don't believe anyone really knows though. Ariel. (talk) 23:31, 11 December 2010 (UTC)

How much energy is lost to potential gravitational energy? ScienceApe (talk) 04:42, 12 December 2010 (UTC)

I don't know. And anytime I try to do calculations I get nonsense results. Ariel. (talk) 06:01, 12 December 2010 (UTC)

Wonder why.... ScienceApe (talk) 18:28, 12 December 2010 (UTC)

What's that non-sense about lost potential energy? That doesn't happen. 71.101.41.73 (talk) 04:01, 13 December 2010 (UTC)

You've never heard of gravitational redshift? The photos are emitted with the combined energy of 225 tons, but once they escape the gravity they have less. Ariel. (talk) 05:20, 13 December 2010 (UTC)

It seems to me that the total mass has to be conserved; after all, I can't take less than 225 tons of matter, annihilate it, and concentrate the photons to form a 225-ton black hole, can I? I think that any negative gravitational potential is already accounted for when we speak of the hole's mass. --Tardis (talk) 05:02, 14 December 2010 (UTC)

It's complicated to measure mass properly when you also need to account for gravity, but essentially some matter that masses 1 gram relative to earth actually masses far more relative to a black hole (and note I said, and mean, mass, not weight). So you have less than 255 tons of mass that mass 255 tons once you take into account their gravity. Ariel. (talk) 22:30, 14 December 2010 (UTC)

Hawking radiation will look like blackbody thermal radation, with the apparent temperature given by the formula in our article. Neglecting losses to potential energy, the apparent 'temperature' of a 225-ton black hole is on the order of 10¹⁷ kelvin — and it gets hotter as it evaporates. The peak emission wavelength at that temperature is down into some very short gammas — 10^-21 or so meters. TenOfAllTrades(talk) 19:32, 12 December 2010 (UTC)

It doesn't just get hotter as it evaporates, the temperature tends to infinity as it evaporates. It won't actually get there, of course, because the energy is released in quanta, so it goes from 1 photon's worth of mass to zero mass in one jump. Is the wavelength of the last photon well defined? (Or at least the expected wavelength - there is some quantum randomness going on, so you probably can't be certain about it.) --Tango (talk) 00:07, 13 December 2010 (UTC)

Does this have anything to do with why small type Ia supernovae are standard candles? Ginger Conspiracy (talk) 00:00, 13 December 2010 (UTC)

No. Nothing at all to do with it. They are standard candles because there is a fixed mass that the white dwarf has to reach in order to go supernova - the Chandrasekhar limit (the first paragraph of the section you link to explains that). --Tango (talk) 00:07, 13 December 2010 (UTC)

Does the Chandrasekhar limit have anything to do with how small a black hole needs to be before it will evaporate quickly (defined as faster energy out than went in, for example)? At the very least, there must be a linear relationship between the two. Ginger Conspiracy (talk) 13:23, 13 December 2010 (UTC)