Wikipedia:Reference desk/Archives/Science/2010 October 6

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October 6

change in ic engine

how we can change petrol ic engine to disel ic engine? —Preceding unsigned comment added by 210.212.170.226 (talk) 09:52, 6 October 2010 (UTC)

Not easily. A Diesel engine has needs higher compression to ignite its fuel instead of using a spark plug. External heating or adding kerosene will be needed to start a diesel engine in cold weather, its power-to-weight ratio is worse, its speed range is low, and it produces unhealthy black smoke particles unless a special filter is fitted. Cuddlyable3 (talk) 10:08, 6 October 2010 (UTC)

On the other hand, the thermodynamic efficiency is higher, practical efficiency is further boosted because the fuel has a higher energy density, the engine is more robust, it delivers more torque at low revs, and the power-to-weight ratio is plenty good enough for e.g. BMW to offer Diesel engines for a wide range of models marketed towards performance-oriented drivers. At least in Germany, Diesel engines are the first choice for people who drive a lot (Diesel models are more expensive, as is vehicle tax, but Diesel fuel is cheaper and mileage is better - there is a cross-over somewhere between 10000 km/year and 30000 km/year). I agree that there is no practical way of reconfiguring standard petrol engines as Diesel engines. However, there are some new engine concepts that essentially amount to a Diesel cycle with petrol as a fuel - see Gasoline direct injection.--Stephan Schulz (talk) 14:44, 6 October 2010 (UTC)

Is there a differential in the tax imposed on the fuels in Germany? In the UK, diesel fuel is more expensive. Dbfirs 23:03, 6 October 2010 (UTC)

Yes. The fuel tax on Diesel is 31.6 cents/l, for gasoline its 50.1 cents/l. --Stephan Schulz (talk) 15:58, 8 October 2010 (UTC)

(edit conflict) It would be very difficult to convert an engine from petrol to diesel, as the two types of engine are very different, despite both being called internal combustion engines. A diesel engine does not use a spark plug to ignite its fuel - it uses the heat created by the compression stroke. As a result, a diesel engine needs to have a much higher compression ratio than a petrol engine. It may also need a mechanism for pre-heating the engine block or the air intake when starting in cold weather. A car can be converted from petrol to diesel, but this involves completely replacing the engine. Gandalf61 (talk) 10:14, 6 October 2010 (UTC)

Could diesel fuel be ignited with the spark plug, thereby reducing the needed compression?Edison (talk) 19:34, 6 October 2010 (UTC)

Not really. Diesel fuel under lower pressures produces MUCH less explosive force than does gasoline. The higher compressions are required not only to ignite the diesel, but also to generate the forces necessary to actually run the engine. If you tried to burn diesel in a gasoline engine, it wouldn't generate enough energy to keep itself going. Part of the genius of diesel engines is the ability to use a wide range of lower-energy fuels. You can make diesel from a wide variety of sources, not just petroleum (see biodiesel) and, with small modifications, you can actually run a diesel engine on straight vegetable oil, like the stuff you buy in the grocery store, see Vegetable oil fuel. In that way, diesel engines are much less "finicky" than gasoline engines, which require a fuel of a very specific burning profile, and require carefully timed sparking system to control the burn just right. With diesel engines, if its a liquid and it burns, you can probably run the engine on it, at least in the short term. Of course, certain substances would produce too much soot, and would gum-up the engine, but you really can run a diesel engine on just about anything. See Diesel_engine#Fuel_and_fluid_characteristics for a bit more. --Jayron32 05:28, 7 October 2010 (UTC)

I have read somewhere that some military vehicles can run on Diesel, gasoline or jet fuel, but I don't recall the vehicle, which country made it or if the capability was limited to emergencies and would shorten the life of the engine. Googlemeister (talk) 13:12, 7 October 2010 (UTC)

Perhaps the military vehicle was this which has a multi-fuel diesel engine, or T-72 whose engine is similarly described [although not in its main article). Cuddlyable3 (talk) 14:08, 8 October 2010 (UTC)

I think it was this guy Chieftain tank, but there appear to be several vehicles that can do this. Googlemeister (talk) 15:50, 8 October 2010 (UTC)

Atlantic halibut

Why is it called hippoglossus ("horse-tongue")? DRosenbach ^{(Talk | Contribs)} 16:51, 6 October 2010 (UTC)

Hippoglossus says "a reference to the shape of the fish". (Why are these separate articles?) 213.122.67.69 (talk) 17:04, 6 October 2010 (UTC)

One is about a species and one is about a genus. --The High Fin Sperm Whale 18:11, 6 October 2010 (UTC)

Planet gravity

If we assume that Gliese 581g is 3 times heavier then Earth, and have same density, what "gravity force"(or whatever it called, excuse my English) would be on the planet? My first estimation would be cubic square from 3, so ~1.45 bigger then on Earth, 9.81 m/s2 * 1.45 = 14.22 m/s2. Am I correct? Or increased volume(*3) would slightly decrease that number? 76.67.8.211 (talk) 19:49, 6 October 2010 (UTC)

Your number is correct, but I'm not sure it is correct for the right reason. Gravity is proportional to M/R². M would increase by a factor of 3, R by a factor of the cube root of 3. Plug these in and you get gravity increasing by a factor of cube root of 3. Looie496 (talk) 20:00, 6 October 2010 (UTC)

The term that OP was looking for is gravitational acceleration. --Wrongfilter (talk) 10:14, 7 October 2010 (UTC)

Cleaning detergents

There are dozens of different brands of detergents for household cleaning. Some are designed to be diluted with hot water, others are sprayed. Are they basically all the same apart from colouring and fragrence, or do some have different ingredients that truely make them better than other brands? In other words, is the supermarket own-label likely to be just as effective as more expensive brands? Thanks 92.29.127.126 (talk) 19:52, 6 October 2010 (UTC)

You'd have to look at the label of each product, and tease out the "active ingredients" from them to know how each worked before deciding to rank cleaning products by effectiveness. It should also be noted that some cleaning products work better in some applications, but not in others, so there is no "one-size-fits-all" detergent. The Wikipedia article Detergent presents an overview, and lots of blue-links to different classes of detergents. Some of these may be used in different proprotions in different products, while sometimes cleaning products are incompatable for safety reasons (never mix ammonia and bleach, for example). --Jayron32 19:59, 6 October 2010 (UTC)

You may also want to invest in the magazine Which? or check out their website. They often do this sort of comparison of products. ny156uk (talk) 21:05, 6 October 2010 (UTC)

The point is that the list of ingredients all look similar or identical across the brands. In the UK you only get one or two things listed. The ingrediants list of two near at hand detergents I have are -

Fairy Liquid: 15-30% anionic surfactants, 5-15% non-ionic surfactants, methylisothiozolinone, phenoxyethanol, perfumes.

Elbow Grease: Less than 5% non-ionic surfactants, cationic surfactants, phosphate, perfume, limonene.

Fairy Liquid is a washing-up liquid. Elbow Grease is a spray on household cleaner. It says "All puropose degreaser" on the bottle, but isnt any detergent a degreaser?

Is Elbow Grease no more than just a very watered down version of Fairy Liquid?

(I got some wet gloss paint on my clothes. I smothered it in neat Fairy Liquid, then rubbed it under a tap - to my surprise it disapeared completely.) 92.24.183.150 (talk) 23:12, 6 October 2010 (UTC)

The challenge is providing an emulsion system for solvation of grease without dissolving or attacking your hands. Quaternary amines are usually seen as powerfully strong, so they are avoided. (Those are cationic surfactants.) They are also capable of penetrating cell membranes, whereas anionic surfactants can't. I wish they had a househould equivalent of acetone (30% concentration maybe) -- I get it on my hands so often in the lab I am sure that if you wash it off immediately it's MUCH more of a convenience than household detergent, and it doesn't oxidise like bleach. John Riemann Soong (talk) 02:31, 7 October 2010 (UTC)

Is there any consumer guide to the different types of household detergents that I could read? Thanks 92.28.245.77 (talk) 12:58, 7 October 2010 (UTC)

My guess is, that own-label washing powder diluted with hot water should be as effective as any other detergent, and a fraction of the cost. 92.15.10.67 (talk) 19:44, 7 October 2010 (UTC)

My experience is, own-label washing-up liquid is a false saving compared to buy (for example) Fairy Liquid, because it is sold in much more dilute form. You are paying for a bottle of mostly water, rather than a small bottle of concentrate, and so pay over the odds. You end up using more, because you need a generous squirt per bowl of water, and it flows more easily from the bottle, because it is less viscous. If you use a more expensive, concentrated washing-up liquid (like Fairy Liquid), you only need a drop in each bowl of water, and it's easy to only release a drop, because it is quite viscous. So (as the ads say) you hardly ever have to buy it, and it works out cheaper. Unless you don't understand that you are buying concentrate, and squirt the stuff out! 109.155.37.180 (talk) 21:37, 9 October 2010 (UTC)

Oh, and this would be your ideal source, if you had a paid account. Or you could seek out a relevant copy of the print magazine. 109.155.37.180 (talk) 21:43, 9 October 2010 (UTC)

Microfibre cloths for cleaning

Are microfibre cloths truely better at cleaning surfaces than rubbing with ordinary cloths, or are they just a gimmick? I've read the article. Thanks. 92.29.127.126 (talk) 19:54, 6 October 2010 (UTC)

What makes microfiber cloths useful is two things: 1) They are less likely to scratch the surface you are cleaning than an ordinary rag. and 2) They have a particular distribution of pore space that makes their absorbant properties useful in holding dirt. Whether these are important factors for you in deciding to spend money on them is, of course, entirely up to you. --Jayron32 20:02, 6 October 2010 (UTC)

"Better" depends on what you're cleaning and how much time and money you have to spend on cleaning it. As Jaron explains, they're not just a gimmick, but neither are they a 'cleaning panacea'. If you need to rub hard, then microfibre cloths are probably no better than the average rag, but that doesn't mean there aren't people who find them useful for lighter cleaning. Physchim62 (talk) 20:26, 6 October 2010 (UTC)

My experience with microfibre cloths is that they are very good because they don't chafe and leave lint. This is particularly attractive for wet cleaning glass such as mirrors and motor vehicle windshields. Dolphin (t) 22:11, 6 October 2010 (UTC)

I can add my anecdotal support. They work well for me! Mattopaedia ^{Say G'Day!} 04:30, 7 October 2010 (UTC)

One way to think about the benefits of microfiber is this: for a cloth of the same macroscopic area, microfiber products have more surface area which can contact the surface. This can result in a more efficient cleaning experience. --SemanticMantis (talk) 14:16, 8 October 2010 (UTC)

The theory of toxic sludge lagoons, re: Hungary's red flood

News stories such as [1] and the article Ajka alumina plant accident state that an aluminum plant pumped waste products into a "sludge reservoir" for 25 years. Eventually the reservoir wall collapsed and the sludge, said to have a pH of 13, and to contain some radioactive metals and toxic heavy metals, leaked over the countryside, killing a number of people. What was the theory behind storing the waste in a reservoir? Was some natural process supposed to eventually detoxify it, such as by lowering the pH? Do chemical plants in some jurisrdictions have to treat the waste products on an ongoing basis, such as by using something acidic to neutralize the waste? Was the idea that someday someone else than the aluminum plant owners would set up some process to detoxify the material? Was it assumed that it could just be stored forever in the reservoir, perhaps by somehow drying it and putting plastic or clay over the top?How would it become dry if it is in an open reservoir? Does some Wikipedia article cover the general topic of sludge reservoirs other than sewage sludge? Edison (talk) 22:26, 6 October 2010 (UTC)

According to this source listed in the red mud article, basically they put it into a reservoir just to serve as a landfill: no theory that it would ever naturally clean up, or even necessarily be cleaned up by the company, just an isolation of waste. Bleck. --Mr.98 (talk) 22:49, 6 October 2010 (UTC)

There is a natural process that lowers the pH: the absorption of carbon dioxide from the atmosphere. The company involved in Monday's accident says that it covers its disused sludge ponds with "soil and plants" (make of that what you want). Otherwise, there's not much theory behind it, it's just something that's been done for the last 130 years in the alumina industry. Physchim62 (talk) 22:54, 6 October 2010 (UTC)

Disposal of carbon dioxide is a major problem in relation to global warming. Is reaction with red mud a way to sequester a lot of carbon dioxide while making the red mud less toxic? How come the book cited above says it is not an environmental hazard? Edison (talk) 23:04, 6 October 2010 (UTC)

The scales are not anywhere near close. It would take upping the production of alumina waste several thousand times before you made a reasonable dent in terms of carbon sequestration. --Jayron32 01:26, 7 October 2010 (UTC)

Back to the OP's question, part of the idea of these sludge ponds is to essentially keep all the wastes and toxins in one location, rather than spreading them around the countryside, rather like any waste dump but with the added threat of toxins getting out. I live near the operations of fairly extensive gold mining from the mid-late 1800s to early 1900s. Large amounts of toxic waste, largely cyanide wastes from the gold cyanidation were initially dumped in the waterways, and then when at some point they realised that wasn't such a good idea, they started collecting them in these sludge ponds. The remains of the ponds are still there - not much grows on them and they are not even fenced off, but there are warning signs. There is a type of crust that has formed on the surface which means they don't blow or wash away or anything, and the general wisdom is that as long as you don't break the crust they're generally pretty safe. There are people that live reasonably close to the most obvious dumps, say within about 1/2 to 1 km, and they don't show any obvious signs of cyanide poisoning or shortened life spans. --jjron (talk) 07:49, 7 October 2010 (UTC)

I suspect what the book means is that as long as it is kept in a pond, it won't spread, leech, or otherwise affect the environment in a major way. Why that would be, I don't know. --Mr.98 (talk) 01:11, 8 October 2010 (UTC)

It may be that the waste is a suspension of particles heavier than water in water. It gets pumped into the reservoir, and the heavy particles settle. The relatively clean water on top gets pumped out. Eventually, the reservoir is full to the top with solids, at which time it could be capped with impermeable clay and stand like a mesa, but not usable for agriculture or building. One problem is that it has the silly 13 pH, more alkaline that ammonia or bleach, since the factory owners did not neutralize it with acid on an ongoing basis. Also, by definition it is more dense than water, thus exerting more pressure per unit area on the aging reservoir walls. The Hungary accident shows that the waste, after 25 years, has not solidified, but is a fluid, able to spread over the surrounding countryside when the walls are breached. Could the waste be mixed with cement or other substances to ensure that it is a rock-like solid unable to flow outside the containment? It all sounds like an "externality," whereby the factory owners make their money and leave a hazard to be dealt with by others. Is there no principal in chemical engineering that a factory should clean up its own mess, and not spew it about like a dog owner who refuses to pick up his dog's poop in the daily dog walk, or a homeowner who disposes of his garbage by throwing it over the fence into the neighbor's yard? Why is the price of alumin(i)um made artificially low by neglecting the disposal or remediation of this "red mud?" How much more would we pay for our aluminum pop cans if the "red mud" were neutralized and solidified? Responsible cost accounting might make recovery of the iron more economical. Edison (talk) 05:00, 8 October 2010 (UTC)

Not to be trite, but the obvious answer is that Hungarian legislation did not require the factory owners to dispose of the waste in a more responsible manner, or allowed them to sell the problem on companies who were not required to dispose of it in a more responsible manner, or did not properly police or enforce the legislation, or the legislation did not allow for significant consequences if it was broken. In Britain, a Chemical Engineer considered responsible for this mess could indeed find themselves knocked out of the IChemE, which is as far as professional punishment can go. Contrast with the situation of landfill in Britain, which has much more stringent legislation, certainly if anyone is setting up a new landfill. As a consequence, we're heading for a crisis in which sending stuff to landfill is expected to become punitively expensive (as one of my lecturers said, you'd have to be mad to take on the legal responsibility for landfill now, since you will be responsible for what happens to it forever) which is probably why most councils actually push recycling now and limit collection for landfill, quite apart from the tax. 109.155.37.180 (talk) 21:31, 9 October 2010 (UTC)