Subject: Can someone please explain?
Posted by: Mixamatosis
Date: Jan 21 17
I've read that it's dangerous to mix ammonia and bleach. Variously I've read that it can produce deadly cyanide gas, chlorine gas (which is said to be bad for you) and even explosions.
However swimming pools are kept fit for use with chlorine, and our urine contains ammonia but then we may clean toilets with bleach. Also many cleaning products contain either ammonia or bleach and it would be easy to use them unthinkingly in combination.
How is it that people aren't generally harmed by these dangers when swimming in swimming pools or doing daily cleaning, or are we being harmed at low level and is the harm cumulative?
Posted by: Mixamatosis
Date: Jan 21 17
I've read that it's dangerous to mix ammonia and bleach. Variously I've read that it can produce deadly cyanide gas, chlorine gas (which is said to be bad for you) and even explosions.
However swimming pools are kept fit for use with chlorine, and our urine contains ammonia but then we may clean toilets with bleach. Also many cleaning products contain either ammonia or bleach and it would be easy to use them unthinkingly in combination.
How is it that people aren't generally harmed by these dangers when swimming in swimming pools or doing daily cleaning, or are we being harmed at low level and is the harm cumulative?
526 replies. On page 15 of 27 pages. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
brm50diboll 
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My view of technology is that you do not want to be the first person to use a new technology but you don't want to be the last person, either. Some people make jokes about their lack of tech savvy - "Haha! I never did understand those thingamajigs." I don't believe in being ashamed of your own ignorance, but you certainly shouldn't proudly be blurting it out, either. There is nothing to be proud of in not knowing things, even if you don't consider it important. You may be wrong. I am not a Luddite. Society does not benefit by trying to protect the jobs of buggy makers, telegraph operators, steamboat pilots, or anyone whose job is in the process of becoming obsolete by developments in technology. That said, I recognize it is difficult to teach old dogs new tricks. Retraining people is useful for the young, but not so much the post-50 crowd. Downsizing is necessary, but it is best accomplished at a somewhat deliberate pace, with some foresight. Never liked hostile takeovers followed by running up huge debts, declaring bankruptcy, and liquidating companies. That doesn't improve market efficiency, it just disrupts lives and makes a few "vultures" spectacularly wealthy. There are already laws and regulations on the books to curb that sort of thing, it's too bad we have too many cases of foxes guarding henhouses. The revolving door between government and the private sector should be at least slowed down, if not stopped altogether. I don't think having hedge fund executives (euphemism: "investment bankers") serving in the Treasury Department is a good idea, but the reverse process is even worse. We should be ready for massive changes in timescales of decades, but not so much in timescales of weeks or months. Anyone who thinks they know where technology is headed in 50 years should be investing in their views now in the private sector, not in government trying to pick winners and losers. Reply #281. Jun 19 18, 6:07 PM |
Mixamatosis
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When I was at work, I could see over time how everything is speeded up and expectations constantly rise at the same time that jobs are cut. This puts enormous pressure on those still in place and many simply can't keep up or burn out. It's not so much the speed and amount of work but the lack of clear vision and direction too and the constant chopping and changing of policy. It leads to a certain amount of chaos which is never admitted and 'initiatives' which are poorly thought out and untested. I worked in the public sector. Such pressures are undoubtedly high in the private sector too but mostly people know why they are there and what they have to achieve. It comes down to the baseline - make money - make a profit. I agree with you about the 'revolving door' issue between private and public sectors. Reply #282. Jun 20 18, 12:29 AM |
| Mixamatosis
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Here's a science question. Does air weigh anything? We all carry some gas or air around inside us and expel it at times. Would we weigh less after expelling air or does it make no difference, and if so, why not? Reply #283. Jun 20 18, 2:51 AM |
| brm50diboll
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Air definitely does have weight. All gases have weight, even hydrogen, the least dense gas. But ordinary scales cannot measure that weight because air weight is responsible for pressure and air gets below the scale to exert an equal pressure to that on top, cancelling out any measurement. Weighing gases requires very, very carefully designed experimental apparatus. Weight different from mass (gases, being matter, have both) in that weight is a force that depends on the gravitational accelerational constant g, which on Earth is 9.8 m/s^2. The relevant physics formula, derived directly from Newton's Second Law (F=ma, force equals mass times acceleration) is w=mg (weight equals mass times the gravitational accelerational constant.) But weight, being a force, exerts pressure according to the definition of pressure, P=F/A (Pressure equals force divided by area.) The reason we have atmospheric pressure is actually due to the weight of all the air above us. Using standard SI (official metric) units, standard atmospheric pressure is 101,325 Pa (pascals), which corresponds to 760 torr (760 mmHg) or 14.7 psi (14.7 pounds per square inch). That last form may be most helpful in understanding air pressure. That means the combined weight of all the air above us is enough to exert 14.7 pounds on *every* square inch of our bodies. That is actually a very high pressure. The only reason we don't feel this pressure is that the pressure inside our bodies equals the pressure outside our bodies. There is a famous experiment I do for both chemistry and physics classes (as air pressure is an area where the two fields overlap) that shows us the true nature of how powerful air pressure really is. A can, mostly empty, has a small amount of water placed in it. With the cap to the can off, the can is heated to bring the water inside to a full boil, so that visible steam is seen exiting the top of the can. This drives the air out of the can and replaces it with steam. The cap is screwed tightly back onto the top of the can and the heating quickly stopped. Then the can is quickly cooled by immersing it in ice water. This causes the steam inside the can to condense back into water. But liquid water, as it is not a gas, does not exert pressure, and since the air that was in the can was driven out, the pressure inside the can drops dramatically when the can is cooled. But the pressure outside the can remains at 14.7 psi, and the result is that the can is crushed by atmospheric pressure since the interior and exterior pressures are no longer equal. This demonstrates just how powerful atmospheric pressure actually is. There are YouTube videos of this experiment where 55 gallon steel drums are crushed with this little experiment. Very impressive. In order to actually weigh air or any gas for that matter, the measuring apparatus must be so designed (using vacuums) to eliminate the pressure effect I've been describing. Then the true weight of the air (or any gas) can be accurately measured. University physics labs do have such equipment. Air weighs 1.225 grams per liter, on average. (It varies slightly with changes in atmospheric pressure, which are also related to changes in temperature.) Here's basically how that would work: A glass jar containing a vacuum (with a sealed cap) is placed on a scale inside a vacuum. Let's say the glass jar has a volume of 1 liter (1000 cubic centimeter). Let's say the scale reads 235 grams. The glass jar is removed and filled with air (cap on) and then reweighed in the vacuum scale. The scale now reads 236 grams. The first weight was the weight of the jar itself. The second weight is the weight of the jar plus the air inside it. The weight of the air is therefore the difference between the two weights, which is 236-235=1 gram. Since the volume was 1 liter, the density of the air is 1 g/l, which is close to to standard value I quoted above. A finer scale measurement (to the thousandth of a gram, rather than just to the gram) would yield a more accurate weight for the air. Not just any glass jar could be placed inside this apparatus, though. The glass has to be thick enough so that when it is filled with air it does not shatter in the vacuum (or, alternatively, when it is originally made a vacuum *inside*, it does not shatter from the air pressure outside.) I actually oversimplified the description of this apparatus to help in visualizing how it works, but the real mechanism does involve vacuums and vacuum pumps and is considerably more complex than just described. Air *does* have weight. Gases have weight. It is just very difficult to measure the weight, as common scales don't work in measuring weights of gases. As a practical matter, in fact, chemists generally don't bother with going to the trouble of trying to weigh gases. They calculate what the weights of the gases *should be* by using the ideal gas law and other, more conveniently measured, parameters like volume and temperature. Reply #284. Jun 20 18, 11:27 AM |
| brm50diboll
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https://www.youtube.com/watch?v=j0TQxYemrgg Reply #285. Jun 20 18, 11:38 AM |
| Mixamatosis
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You are bringing back some vague memories of physics and chemistry lessons. The video demonstration was impressive. I remember our teacher, when I was 11 or 12 doing a sort of opposite experiment where she heated up a tin with its lid on until the lid blew off. I think she was demonstrating that temperature changes the pressure of air ( and gases in general?), but my memory is vague on that. Pressure of air on them is the way that barometers predict the weather isn't it? How is air pressure linked to the weather and/or how is the weather explained by air pressure? Reply #286. Jun 20 18, 12:23 PM |
| Mixamatosis
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I know that high pressure means good weather and low pressure means bad weather because air pressure is always trying to equalise so air moves from high to low pressure areas in the form of winds. I hope I've got this right. Is that the answer? Reply #287. Jun 20 18, 12:26 PM |
| Mixamatosis
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How do parachutes create resistance and slow down a person's descent because surely the air above the parachute is the same pressure as the air below it? Reply #288. Jun 20 18, 12:28 PM |
| Mixamatosis
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I don't think I'd make a scientist because even if I worked things out and understood the explanations, I'd soon forget them. Maybe if you're steeped in science and using it on a daily basis you don't forget these explanations. I'm quite good with technical things and fixing them because I always apply logic and never end up in frustration mode resorting to kicking the television (or whatever is malfunctioning) and the like, or forcing things. I'm good at following manuals and maps. Reply #289. Jun 20 18, 12:34 PM |
| Mixamatosis
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At school you have to choose between subjects (at the age of 14 here) so some abilities never get developed or used in life. I like the idea of Renaissance Man (or woman) like Leonardo Da Vinci who used all his abilities and just followed his interests. There were no subject boundaries for him and no channelling of his development into subject areas with defined borders or parameters. Reply #290. Jun 20 18, 12:39 PM |
| brm50diboll
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Air provides resistance to *acceleration*, not to speed. A falling body will fall at an acceleration (g=9.8 m/s^2) in a vacuum. In air, as it falls, air resistance slows the acceleration. If the body was high enough to begin with when it started falling, it will stop accelerating and continue to fall at some *terminal velocity*. What a parachute does is slow the acceleration faster, causing the terminal velocity to be lower. A parachutist still falls, but at a rate that is now survivable. Reply #291. Jun 20 18, 12:48 PM |
| brm50diboll
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Regardless of what schooling channels you into, the great thing about FT is that if you want to learn about something, no matter how unrelated it may be to your previous training, career, or life experience, you have the opportunity to do so. Ask and search for whatever question you're interested in. I have had students say "I don't understand any of this." That is not a question. It is a statement, and a useless hyperbolic one at that. If you don't understand something, ask a question. If you don't understand the explanation, ask about whatever terms you didn't understand. It is true that you will not have the level of understanding a person trained in the area has. But you can always get a better understanding of something than you had before you aked a question. Reply #292. Jun 20 18, 12:54 PM |
| brm50diboll
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Asked, not aked. Reply #293. Jun 20 18, 12:56 PM |
| brm50diboll
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Your explanation in #287 is basically correct. What causes the pressure differences in the first place is temperature differences. Air pressure generally rises with higher temperatures. Since tropical areas get more direct (and therefore more intense) sunlight than temperate or polar areas, air pressure tends to be higher there, causing winds which flow away from the equator towards higher latitudes. These winds are distorted somewhat by the Coriolis force due to Earth's rotation, but it mixes air at different temperatures, leading to water vapor condensation and storms in areas of lower pressures. Reply #294. Jun 20 18, 1:28 PM |
| Mixamatosis
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I like the term 'terminal velocity' I know what you mean by it, but can't help thinking the person who coined the term might have a sense of humour because velocity certainly is terminal if you fall from a great height without a parachute. What are the thresholds for survivable heights and non -survivable heights to fall from. There is a famous attempted murder case here where a parachute jumper's parachute (and reserve parachute) were both disabled by her huband (Emile Cilliers) yet she survived the fall (4000 feet) and was a witness at his trial. There must have been some resistance from her damaged parachutes I'm guessing because that seems an impossible height to survive without one. She landed in a field of ploughed earth making it softer than a normal field. Reply #295. Jun 21 18, 3:51 AM |
| brm50diboll
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The largest moon of Saturn, Titan, is the only moon a spacecraft has landed on - Huygens. Reply #296. Jun 27 18, 8:08 PM |
| Mixamatosis
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Interesting modern inventions https://www.bbc.co.uk/programmes/p06cnqxp Reply #297. Jul 09 18, 12:38 AM |
| brm50diboll
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I am all for private individuals experimenting with alternative energy production. I am not so much for government's plowing large amounts of money into projects that are clearly not cost-effective or cost-competitive. Both tidal power generation and hydroelectric power generation have been around for decades. Their limitations are that they require abundant sources of water, there are environmental issues associated with the mechanisms in the water, and that power generated from them is not easily stored in low-demand times, nor easily integrated into pre-existing power grids. All that said, more power to the young lady in the video. My own personal favorite type of alternative energy technology I want to see developed further is fuel from algae. Of course such fuel will still generate carbon dioxide, but I see it as becoming very cheap, renewable, and expandable when the technology improves enough, which I think will be in a decade or two. Reply #298. Jul 09 18, 1:22 PM |
| Mixamatosis
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Isn't algae a bad thing to have lots of? I thought it killed other useful organisms by poisoning water or not allowing sunlight through? I may be wrong. I'm sure you'll tell me if so. Some very useful inventions have been small scale especially in poorer parts of the world - inventions like solar powered mini fridges to store vaccines, and wind up radios. These do not require any sophisticated or expensive power sources but are immensely useful in improving lives. Reply #299. Jul 09 18, 4:00 PM |
| brm50diboll
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We're not talking about algae in a natural environment. We're talking about setting up huge tanks of algae in the desert where there is an enormous amount of sunlight where the tanks are designed to extract the fuel they produce from photosynthesis. This is effectively biochemistry. Solar power alone has one *very serious* drawback: it is not easily stored, so much of it goes to waste. But algae power uses photosynthesis (and, by the way, algae are *much* more efficient at photosynthesis than trees, they've been doing it for hundreds of millions more years than trees have and they don't need to divert a big part of their production to massive cellulose formation to support themselves as trees do). Photosynthesis has the added benefit of lowering carbon dioxide, and the fuel the bioengineered algae produce is highly storable, unlike the electricity from photocells or hydrogen gas from fuel cells. So what bioengineered algae do is take otherwise nonproductive desert land and greatly increases its photosynthesis output. The present drawbacks are in avoiding waste of the water required for the tanks (so more water recycling technology is needed) and the bioengineering to create the most easily extractable fuels (instead of sugars, which natural algae produce) is not fully there yet. But, unlike the Luddites, I'm all for genetic modification. We all need glow-in-the-dark cats. If you don't know what I'm talking about, Google it. Glow-in-the-dark kitties are so cute! Reply #300. Jul 09 18, 4:19 PM |
526 replies. On page 15 of 27 pages. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
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