Wikipedia:Reference desk/Archives/Science/2013 November 26

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

November 26

Must an element's pth ionization energy be greater than its qth ionization energy if p>q?

I think the issue of 12th ionization energy of Aluminium in Molar ionization energies of the elements has been left there for some years. There is a note saying 12th ionization energy, which is 223366KJmol^-1 "Should be less than the 13th; perhaps 201266." 201266 is the value in Ionization energies of the elements (data page), while 223366 seems unreferenced. By the way, is it possible that 12th ionizaton energy is greater than 13th one?--chao xian de lun zi (talk) 01:45, 26 November 2013 (UTC)

Feel free to change it, I saw a graph of the ionization energies in a book, no exact values given but the 12th was in the region of 200000, and definitely lower than the 13th, so 201266 seems reasonable, certainly better than 223366. Ssscienccce (talk) 15:33, 26 November 2013 (UTC)

Real life transformer

In real life, do they match the primary coil turns with designed input voltage (so 220v means 220 primary coil turns)? Because in science questions I frequently encounter 120v for 240 turn coil 140.0.229.39 (talk) 13:28, 26 November 2013 (UTC)

It's strictly the ratio of the turns of the two coils that matters. The resulting voltage can vary very quickly if the input voltage changes. Hcobb (talk) 13:47, 26 November 2013 (UTC)

The number of turns per volt depends on the core area, the frequency and the maximum flux density of the core (limited by saturation losses) ; the rated power VA determines the core area needed, say for example 10 cm² for 100VA (at 50Hz). The Transformer universal emf equation gives you the E_rms that the maximum flux density will produce: E_rms=4.44.f.a.N.B_peak With a maximum flux density of 1.5 Tesla and a frequency of 50 Hz, you get E_rms/N=333a, a= 0.001m² so E_rms/N=0.333. So a core of 10 cm² will require 3 turns per volt. Ssscienccce (talk) 15:27, 26 November 2013 (UTC)

Numbers in exam/revision questions rarely have anything to do with real life examples. They are chosen more to make it easy for the writer to set, the student to calculate, and the teacher to check. It is frequntly the case that if your answer isn't a whole number or a simple fraction then you have done something wrong in a test question. Conversely, in real life answers are rarely simple or whole numbers. A mains transformer will usually have many more turns on the primary than the number of input volts. SpinningSpark 15:36, 26 November 2013 (UTC)

I have spent a fair amount of time working with transformers and offer an observation (which could be readily backed up by references). I really liked Ssscienccce's response with very specific design information. When the other windings of a transformer are open(unloaded), and you excite the primary winding with its rated voltage at rated frequency, the transformer and the winding should act as an inductor with sufficient inductive reactance to limit the exciting current to a reasonable low value. Thus there will be a minimum number of primary turns for satisfactory operation. If you had too few turns in the winding, excessive exciting current would flow, causing overheating of the winding or blowing a fuse, even if there were no load on other windings. This exciting current has both real (overcoming resistance of the wire) and reactive components. To the extent other windings are then "loaded" by drawing current to a load, the primary current will increase above the exciting current. A caveat: in a large utility transformer the initial inrush of exciting current will vary somewhat depending on the point in the cycle it is energized and the previous recent magnetization history of the transformer. Edison (talk) 17:39, 26 November 2013 (UTC)

Possibility of chromatophore bacteria using complex pigmentation for crypsis

Is there a chemical reason why there could not be chromatophore bacteria that use the right pigments to achieve the same level of crypsis as chameleons, if not better? I'm aware no such species of microorganism is known to exist, however would a living incredibly stealthy pigment goo be as scientifically impossible as something like faster than light speed time travel? I cannot think of a reason such a bacteria would have access to all those pigments in nature without being mobile like higher organisms such as chameleons; so I'm assuming this would have to be made by scientists or be from space. Even an example from science fiction of such a bacteria would be welcomed. CensoredScribe (talk) 22:11, 26 November 2013 (UTC)

Would visual camouflage help a bacterium hide? The only bacteriovores i can think of do not hunt by sight. Someguy1221 (talk) 01:03, 27 November 2013 (UTC)

I agree with you that visual camouflage is largely ineffective against most animals as they rely more on smell; however if the pigments it used were highly poisonous as well, like a lot of commercial paints, that could give the bacteria an additional level of protection against predators. Smell would also not be a factor in anaerobic conditions, like an asteroid; I don't know why it develop camouflage in a cave where there is little if any visible light. Nor would being able to survive on it's own be important where it artificially created in a laboratory environment; where that the case it's only means of survival could well be in forming a symbiotic relationship with humans.

Coincidentally, some of the photorhabdus toxins are bright red, but I don't think that has anything to do with warding off predators, and certainly nothing to do with camouflage. Someguy1221 (talk) 03:04, 27 November 2013 (UTC)

Bacterivores basically hunt by touch, not by sight or smell. As our bacterivore article obscurely points out, the only way for bacteria to camouflage themselves is by altering their cell wall chemistry. Looie496 (talk) 02:21, 27 November 2013 (UTC)

Acid rusted tools

I accidentally exposed some of my sockets in my cheap socket set to very concentrated hydrochloric acid and now they've rusted up. Can they be saved? It's not a fancy set but I'd like to keep them if I can. I'm not sure how they were manufactured/what their composition is. --78.148.107.181 (talk) 22:12, 26 November 2013 (UTC)

A l-o-n-g time since I had a chemistry class, so chemistry experts please be kind. This is not advice, but Hydrochloric acid says the acid is used to remove rust from steel, in a "pickling" process which has as inputs the acid, surface rust, and the iron itself and , with results ferrous chloride and water. There would be some loss of the metal, and perhaps pitting. Perhaps the acid removed a protective chrome layer. An article about mild steel in hydrochloric acid notes pitting and evolution of hydrogen [1]. Have you tried washing it to remove acid residue, drying, wirebrushing to remove rust (while wearing suitable personal protection against eye injury or inhalation of particles and spraying with WD40 to discourage additional rust? If there is significant pitting and loss of metal I'd pitch the damaged sockets, since "cheap" socket sets can be had for a few dollars, and they will be even less useful than they started out, especially the works inside a ratcheting socket wrench. [2] says that while concentrated hydrochloric acid removes rust from steel, a dilution of the acid causes rapid rusting. Edison (talk) 23:57, 26 November 2013 (UTC)

The acid just removed the very thin coat of oil that is applied in the factory, allowing oxidization to precede rapidly. Get some more hydrochloric acid (an excellent rust remover) and diluted down to 5%. Adding acid-to-water. The original strength will be written on the container (use some eye protective goggles). Dunk all sockets in this, until the rust has been removed ( just a few minutes will do). Wash in boiled water and 'immediately' coat in oil. Anything will do, like engine oil but something really tenacious like Wynn’s engine oil additive or STP engine oil additive is even better. Wipe off surplus oil. --Aspro (talk) 00:17, 27 November 2013 (UTC)

If you want to avoid messing around with hydrochloric acid, there are plenty of rust treatments out there that chemically remove the rust - most car parts stores stock many kinds. But (as Aspro points out) - the important thing is that you should wipe your tools with an oily rag afterwards to prevent the rust from coming back. (You should do this periodically with most metal tools anyway.) SteveBaker (talk) 14:56, 27 November 2013 (UTC)

If you choose a propriety rust Rust Treatment, steer clear of a Rust converter. That will just stabilizes the crud and so the sockets may no longer fit over the nut. Hydrochloric Acid based treatments are better. Phosphoric acid is not bad but it tends to leave a coat on the metal and so not so good for high tolerance parts. The advantage of these branded products are that they sold at the most effective dilution strength (but you pay dearly for the added water and product marketing). So they are very expensive. As you appear to already have access to hydrochloric, a little dilution should be a cheaper and a more edifying option. As soon as the sockets are clean, drain and wash in a little acetone to remove the water and drain again. Then heat until they are 100 plus Celsius over an electric cooker ring (acetone is flammable so drain well). That will drive off the last of the moister and make it easier for the oil to thoroughly coat them. Wynns is so tenacious you wont probably need to re-oil in you life time. I think I can say this with a little confidence as I used to de-rust things in an R&D lab. Yet as Steve indicates it is a good habit to get into. Every year, we religiously re-oil our gardening tools before winter and often during use, so that some, have now lasted several generations. This is especially important for tools like scythes (they are far quicker than a modern string trimmer as they give you a wider sweep (they keep you fit too). The razor thin edge is constantly being wiped clean of the protective oils by friction. So they need daily wiping with an oilrag to stop the morning dew coating it with rust. But once rust permeates the blade, that really sharp edge can never be recovered. Linseed oil is recommended for the wooden handles. --Aspro (talk) 18:55, 27 November 2013 (UTC)