Wikipedia:Reference desk/Archives/Science/2015 November 20

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November 20

The taste of salt

I understand that when common salt is dissolved in water it dissociates into separate sodium and chloride ions. So when we taste a salty liquid, are we tasting the sodium, the chloride, or a combination of both? --rossb (talk) 00:02, 20 November 2015 (UTC)

Salt substitutes (potassium chloride) and calcium chloride taste salty, but not identical. Calcium chloride is chalky and salty at the same time. Sagittarian Milky Way (talk) 00:09, 20 November 2015 (UTC)

Warning: Do not put large amounts of calcium chloride in the mouth. The article says too much gets hot enough to cause burns. Sagittarian Milky Way (talk) 00:13, 20 November 2015 (UTC)

See Taste#Saltiness. The direct answer is "the sodium ion". --Jayron32 01:13, 20 November 2015 (UTC)

I confirmed thenardite (sodium sulfate) has a salty taste similar to halite. [1] Wnt (talk) 23:44, 20 November 2015 (UTC)

On the other hand ammonium chloride (sal ammoniac) is used to give salty licorice its taste! Wnt (talk) 04:10, 23 November 2015 (UTC)

Candle pot heater

Does a candle pot heater heat a room significantly (that is, you feel it)? A candle pot heater is a DIY heater that is built with a clay pot (or a set of them stapled) upside-down, with a candle (or more) inside it. Some people claim that "Terracotta pots absorb the thermal energy of the candles and convert it into radiant space heat." and "heater works by trapping and concentrating the heat that would normally just rise to the ceiling and quickly dissipate in the surrounding air."

Would the heat of this heater be transmitted differently from the heat of a candle alone? I am just curious about it, but do not intend to build one. There seem to be some safety issues with this thing.--Denidi (talk) 00:56, 20 November 2015 (UTC)

There's a very detailed discussion about these at stack exchange. -- Finlay McWalterᚠTalk 01:04, 20 November 2015 (UTC)

I wonder whether it has an article with another name here in Wikipedia.--Denidi (talk) 01:13, 20 November 2015 (UTC)

The nearest I can find is a Masonry heater, which is basically the candle/terracotta pot heater but for realz. It is functionally the same operation (a burning source first heats ceramic, which then heats the room radiatively). --Jayron32 02:01, 20 November 2015 (UTC)

Yes, the British used flower-pot heaters during the second world war to heat their Anderson shelters. In the scouts we used them too (but that was mainly because Akela somehow managed to take us camping on on the cold and wettest weekends). As the OP says, heat from a candle just goes up but in a flower-pot heater, it gets trapped and radiates. It might seem surprising but considering a average one Candela candle produces about 80 watts of heat, three produces not much short of a ¼ of a kilowatt. So, to answerer OP's question – Yes, you do feel the warmth. The OP may not be intending to make one but here is some easy to follow destructions in case he changes his mind: Candle Powered Air Heater. This came in handy about a decade ago when we had a long winter power cut, which meant the electric central heating pump would not run. Unfortunately, we only had some scented candles which meant the place smelt like some oriental whore house – but at least we were warm.--Aspro (talk) 22:10, 20 November 2015 (UTC)

Ahh, the aroma of oriental whorehouses... Alansplodge (talk) 02:13, 22 November 2015 (UTC)

A typical space heater is 1500 watts, so even the three candle 240 watt setup is less than 1/6th of that. That would only warm a small room slightly. StuRat (talk) 08:54, 21 November 2015 (UTC)

Comment: Both Anderson shelters and tents are very small spaces. I reckon I could fit nine into my lounge (three rows of three) and being lower in hight than the ceiling, they would take up less volume too. So that's about a tenth of what a space heater is expected to warm . Remember too, that a big part of the reason one feels cold in this situation -is that you too- are radiating heat but little heat is being radiated back. It is a bit like putting ones finger close to an ice-lolly. Ones finger on that side feel colder but we know cold does not radiate. It is the diminution of radiated heat blocked by by the ice lolly that gives the subjective imprecision of radiated cold. Flower-pot heaters work just fine in the right environment. Also, they don't produce carbon monoxide (bad in a small space). I entourage the OP to build one, just in case he should need one – but please, do hold a stock of non-scented candles for such emergenticies.--Aspro (talk) 16:21, 22 November 2015 (UTC)

They shouldn't produce a significant amount of carbon monoxide provided they have a sufficient oxygen supply. However, if in a small sealed area, they could indeed reduce the oxygen to a level where they start producing carbon monoxide. Presumably both Anderson shelters and tents have proper ventilation. StuRat (talk) 18:51, 22 November 2015 (UTC)

Good points StuRat. Answer thus: Don’t know about modern tents of synthetic materials and zips, but boyscout tents of that era and Addison shelters were endowed with too much ruddy ventilation! They were cold, damp and draughty (and that was in the summer). Obversely, some common senses had to be drummed in to us, in so much, that one never-ever uses a charcoal stove inside. They do pump out carbon monoxide. The Japanese and other orientals, use this method of charcoal in tents and enclosed spaces to commit Charcoal-burning suicide. Candles, on the other hand pose no such issue as the CO is combusted in the outer flame mantle. One would start cough on the build up of CO₂ before CO was produced. And as I sit here typing, it must be true, for me to be able to sit here today still typing.--Aspro (talk) 16:52, 23 November 2015 (UTC)

Contamination by hammering

Seen today in Edgerton, Ohio on the side of a slowly-moving rail car:

Hammering on side of car will contaminate product.

What kind of product could this be, and how would it be contaminable? The car in question looked like a grain hopper, but I'm not sure that it wasn't something else. Google reveals nothing except for a few pages (example) commenting on this kind of inscription. This page doesn't seem to make much sense, because aren't grain hoppers emptied by gravity through trapdoors in the bottom of the car? Nyttend (talk) 01:33, 20 November 2015 (UTC)

I suppose hammering could damage some coating, which could contaminate the product. --Denidi (talk) 01:42, 20 November 2015 (UTC)

• Here's a quote from a company that leases hopper cars:

Car body damage caused by a derailment, sideswiping or hammering of side sheets can cause failure of the interior lining and subsequent product contamination from chips or flakes of lining material.

It may have been a pressurized hopper car, which uses air pressure rather than gravity to dispense the product. The company talks about transporting plastic resins, which are very prone to contamination (since even a tiny amount could change the resin's properties or gum up the machinery). Smurrayinchester 08:44, 20 November 2015 (UTC)

What's considered as biggest or smallest skull bones?

I mean according to those that count 22 parts (rather than 28) 92.249.70.153 (talk) 02:54, 20 November 2015 (UTC)

The two Parietal bones are the largest bones in the skull. Of the 22 named in the Wikipedia article Human skull, the smallest is the Vomer, a small portion of the nasal septum. --Jayron32 03:05, 20 November 2015 (UTC)

Thank you. In our article about "lacrimal" bone, I saw that the lacrimal bone is the smallest bone. What's true? 92.249.70.153 (talk) 03:23, 20 November 2015 (UTC)

Sorry, yes, I believe you're correct. I misremembered which bone in the nose was the smallest. It looks like each of the two lacrimal bones are smaller than the vomer. FWIW, if you consider the ears to be part of the skull, the stapes is much smaller than any of those, but that is not one of the 22 listed at the Human skull article. --Jayron32 04:03, 20 November 2015 (UTC)

About the largest bone I heard about two: Frontal and occipital, and this is the first time that I hear about the parietal. Someone has a relabel source about this topic? (I have Gray's anatomy book and Moor anatomy book and I didn't find) 92.249.70.153 (talk) 05:56, 20 November 2015 (UTC)

The Parietal bones form the largest part of the top and sides of the cranium, The parietal bones are two of the largest bones of the skull --Jayron32 13:50, 20 November 2015 (UTC)

Are the parietals always the largest, even across species? This might refer only to humans. DRosenbach ^{(Talk | Contribs)} 15:45, 20 November 2015 (UTC)

Context established by the OP "...22 parts (rather than 28)..." has already made it clear we're talking about the human skull. --Jayron32 16:04, 20 November 2015 (UTC)

Oddly enough, we just had this question on the science desk a little while ago. The material above notwithstanding, our article on mandible says it is the most massive bone "in the face" (which is obviously not synonymous with skull). The frontal and parietal bones are wide, but quite thin (the frontal bones appears thick at the front, but is mostly hollow there to accommodate the frontal sinus whereas the jawbone, especially in males, is much more robust. 99.235.223.170 (talk) 13:47, 21 November 2015 (UTC)

Perpetual motion

I was changing the water in my fish tank last night, and while removing water from the tank via a pump action siphon tube (starts off by hand pumping, but then runs by itself), I noticed that I was able to have the water exit the tube up to 3 inches higher than the water enter the tube inside the tank. So it got me wondering why we're not able to create perpetual motion machines using such technology. Sure, the amount of power we could generate with a gallon of water dropping 3 inches per, I don't know, a minute, is not much. But couldn't this be built on such a tremendous scale, and by having a million tubes set up like this, couldn't it then generate endless power? Obviously I'm missing something, because I'm no physicist and I'm sure this would have been something discovered a while ago. But just curious as to what the issue is here. Thanks! DRosenbach ^{(Talk | Contribs)} 15:43, 20 November 2015 (UTC)

Friction is a mean bitch. --Jayron32 16:05, 20 November 2015 (UTC)

Rule #1: If you think you have perpetual motion - you don't.

With a syphon, the water can't possibly exit higher than the surface of the water from which it's fed. It doesn't matter where the BOTTOM of the intake tube is. Lower the water level until it's below the height of the output of the syphon and it stops working - no matter how deep the input end is beneath the water. The syphon doesn't do anything magical that simply drilling a hole in the side of the tank at the same height wouldn't have done. Hence, you don't have perpetual motion here and you can't gain any 'free' energy.

So there is always an error in your assumptions. The only (somewhat) interesting thing is figuring out where you went wrong.

SteveBaker (talk) 16:59, 20 November 2015 (UTC)

I should be completing mine within the next few days. :-) --Modocc (talk) 17:21, 20 November 2015 (UTC)

Such a device was designed by Robert Boyle in 1660, so the idea is not original. Tevildo (talk) 19:18, 20 November 2015 (UTC)

Yep, and for further info we have articles about perpetual motion and thermodynamics. And I may as well post here in a couple a days to let you know whether my own twist on a 2nd thermodynamic law violating machine actually works or not.. -Modocc (talk) 19:38, 20 November 2015 (UTC)

(EC)You need to ignore the submerged portion of the tube because its irrelevant. Next time you siphon you should notice that the flow stops when you raise the free end of the tube higher than the level of the water in the tank so only the water's gravitational potential can be tapped from the setup. -Modocc (talk) 17:16, 20 November 2015 (UTC)

It is relevant, since once the water level drops below the submerged portion, the process stops. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:55, 21 November 2015 (UTC)

Being submerged certainly matters, but I didn't think I be misunderstood and needed to state the obvious and said only to ignore the submerged portion, that is with a depth greater than 0. --Modocc (talk) 17:25, 21 November 2015 (UTC)

If water is in constant motion between the two tanks, the part of the tube in the source tank has to stay submerged. For it to be perpetual motion, the tube has to be long enough so that it will never not be submerged. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:42, 23 November 2015 (UTC)

When you say "...long enough so that it will never 'not be' submerged" doesn't seem to make sense in this context.[I suppose you meant an infinite tube within an infinite tank of water.. not that that is practical.. :-)] Normally, for a fish tank, one needs a siphon tube which is long enough to make it over the tank side and the flow rate is fastest if the tube is run to the ground or bathtub due to the greater distance in its fall. The length needed in the tank however depends on how much you want to drain but unlike the other end the depth to which it is submerged in the tank has little effect on the flow rate although excess length adds friction. Of course, there is no perpetual motion to be had with this setup no matter what length of tube is being used. BTW, it's taking a day or two longer than I expected to complete my novel contraption and the cold weather is aggravating my sinuses. I'm hoping to complete it tomorrow though. --Modocc (talk) 17:43, 23 November 2015 (UTC)

The above comments are true, but I'll go a step further: consider capillary action, where the water is drawn above the surface of the body of water the tube is placed into. Well, the problem is, the force of attraction between water and wetted surface that brings the water into the tube ... also resists it being removed from it. So you can draw water up but it won't drip out from that height. You (or plants) can manipulate the system via transpiration, but that relies on a difference in humidity that is gradually being used up to power the system, essentially a sort of "wind power" you might say.

The bottom line is path independence. However you get to a region of low potential energy, you are always going to have trouble going back up again. Wnt (talk) 18:05, 20 November 2015 (UTC)

Notwithstanding all the assertions by learned Users here, it is possible to create a device to which water is added, and then the water flows to a height above the level of the water pool! One example is known as Heron's fountain. It provides a useful exercise to explain why it isn't perpetual motion. Dolphin (t) 06:15, 21 November 2015 (UTC)

It looks like it uses the energy produced from lowering most of the water to raise a small portion of it. I suppose you could also do that at any hydroelectric dam, by using the power generated to raise the level of a small portion of that water. StuRat (talk) 06:30, 21 November 2015 (UTC)

Stu, did you mean to, and forget to, link to Pumped-storage hydroelectricity? --Jayron32 06:35, 21 November 2015 (UTC)

To be clear - we're talking here about a simple syphon. In that case, the water that emerges from the syphon can't end up higher than the surface of the water in the reservoir supplying it. Nobody is saying that you can't build some other kind of contraption (such as Heron's fountain) which is powered by the gravitational potential energy of water in one place to raise a smaller quantity of water to a greater elevation in some other place. Clearly that's possible so long as the net energy of the system didn't increase as a result. That restriction means that you can't extract 'free' energy from such contraptions, and because of friction, they'll always run down eventually.

Our OP's surprise lies in the fact that the height of the inlet side of the siphon can be lower than the outlet...but it turns out that this doesn't matter. What matters is the relative height of the surface of the water on the inlet and outlet sides. SteveBaker (talk) 13:29, 21 November 2015 (UTC)

Thermodynamics explained in four simple rules (by C. P. Snow):

Zeroth - You must play the game.

First - You can't win.

Second - You can't break even.

Third - You can't quit the game.

Roger (Dodger67) (talk) 08:36, 22 November 2015 (UTC)