exchemist

Then the question becomes a different one, viz. what limits are there to the rate of pressure change the human body can withstand, or something like that. So far as I know, the most sensitive part of the body from the point of view of pressure changes is the ear. The middle ear equalises pressure with the environment via the eustachian tube, which is linked to the nasal sinuses and is very narrow, with a sort of semi non-return valve in it, to encourage the removal of any mucus discharges etc. To pressurise the middle ear, air must go the "wrong way" through this non-return valve, leading to the sensation of deafness, relieved by swallowing, that we are all familiar with in a descending aircraft. Swallowing allows the non-return valve to open and allow air in "the wrong way". If you increases the pressure too fast, you experience deafness, as the eardrum becomes stretched by the pressure difference, followed by pain as it is further stretched. The eardrum can easily rupture if enough time is not allowed for the ears to "pop" and thus transfer the increased pressure via the eustachian tube to the other side of the eardrum. Some people have difficulty equalising the pressure, especially if they have a cold or other inflammation of the sinuses. To you have to go carefully or you can inflict considerable pain and make people go deaf.

OK, then I can't answer that for sure. But seeing as borate is sold as a buffering agent, it looks to me as if using it may make use of HCl unnecessary. But you would need to check with a supplier of borate, I guess.

This is a silly question.

How long is a piece of string? The time will depend on the pressure differential, the size of the valve aperture, the viscosity of the fluid passing through and the size of the space the fluid has to fill.

It has already been patented for that purpose, but unfortunately it is so expensive to make that it has never been commercialised.https://en.wikipedia.org/wiki/L-Glucose

Meaningless question. Unless this "shape" has observable consequences, in the way the photon interacts, it is simply not real as far as QM is concerned. One could just as well hypothesise that there are pixies dancing round it on its way.

Yes, this is how it is possible for divers to go down so far, as long as the gas mixture they breathe is at the pressure of the surrounding water.

Eh? No. A photon is not split in two by a semi-transparent mirror. It is either reflected or transmitted, with 50% probability of each outcome.

If the pressure is equalised throughout the object, i.e. with no spaces at a different pressure, then merely a bit of compression of the materials of which it is made.

Agree. The hearing of these sounds, and the rather improbable persecution scenario, put me in mind of schizophrenia.

This is not so much a question about chemistry as about the shelf life of specific manufactured items. I found this link, which may point you in the direction of an answer: https://electronics.stackexchange.com/questions/8794/do-electrolytic-capacitors-have-a-limited-shelf-life From this it rather looks as though trying to put into service a 30yr old component may not be a good idea.

I don't know about a formula, but this link: https://www.borax.com/BoraxCorp/media/Borax-Main/Resources/Brochures/borates-swimming-pools.pdf seems to contain a lot of information about the use of borates in swimming pools. It seems to act as a buffer, enabling the chlorine to work in its best regime and also to soften the water by binding calcium. If it acts as a buffer, it may be that by using borates you can fully control the pH with them alone and can dispense with the hydrochloric acid entirely, but I stress I am learning all this as I go in response to your queries, so you might want to do some further checking.

It is not strictly true that water is non-compressible. Liquids are about as compressible as solids, which is to say hardly at all by comparison with gases. But they still compress a bit. If you suddenly expose the water in a torpedo tube to 100atm, you exert that pressure on the water inside and thus on the walls of the tube as well. The water will compress a tiny bit and the walls of the tube will stretch and expand a tiny bit as well. (Because it is only a tiny bit, very little work is done, so there will be very little stored energy in the compressed and stretched materials.) Water hammer is a shockwave caused by abruptly blocking the path of a moving mass of water, thereby causing rapid change in momentum. This change of momentum requires a certain impulse (F x t) and because t is so small (because it happens fast), F has to be great. So that means water hammer creates large forces and hence pressures - a pressure wave. When you open a torpedo tube that is full of water, you do not have this, because the water on both sides of the opening is static and no change of momentum occurs. So it won't cause water hammer, just a bit of stretching of the walls of the tube. As for the equalising valve, I suspect that will be because when you flood a torpedo tube in practice you most certainly do have trapped air, which will compress to 1% of its volume, storing a lot of energy and causing water to flood in as it is compressed - with momentum. So there can be large forces and energies created in that scenario, which you do not want for safety reasons. So you flood it progressively rather than instantaneously. At least, that would be my best guess as to what is going on.

Yes I suspect you touch on something important here. I'm halfway through Carlo Rovelli's book "Helgoland" at the moment. He points out that Heisenberg's approach to QM was based on deliberately restricting the model to accounting for the behaviour of systems in interactions - and not making any assumptions about what goes on in between. It is the classical mindset that assumes something goes on in between that can be defined and tracked. QM gives up that assumption. Or so I am led to understand. I feel it is not a coincidence that @Duda Jarek's posts and links continually refer to classical or semi-classical models. I suspect this is all an exercise in semi-classical modelling and should not be taken seriously as the way nature really behaves.

I'm still struggling to see what the "dimensions" of a photon, or even expectation values for a set of dimensions for an ensemble of them, can mean. According to my understanding, QM only describes how quantum objects are expected to interact (usually expressed in terms of probability distributions) and is deliberately silent on what they "do" in between. Do any of these authors suggest that the "shape" or "dimensions" of a photon predict how it will interact with other QM objects? If not, then it seems to me to be just building castles in the air.

My limited, chemist's understanding of QM is that you can't really speak of an "objective" EM field configuration for a single photon. If you could, it seems to me it would be a classical object rather than a QM one. But I think we probably now need a real physicist's input.

I'm sure you can say something about the distribution of probability of detecting the energy.

Ah, so the salt is used to generate chlorine by electrolysis - which I can see makes sense, if you don't mind swimming in salt water and the associated potential for corrosion, I suppose. I didn't know that. Thanks.

To be honest I have trouble seeing how asking what the "shape" of a photon is can possibly be a question with any meaning. One could only define a "shape" if one could find a way to interact with it in a way that did not disturb it, which does not seem possible to me. It also seems to me the uncertainty principle would suggest its extent in space would depend on the degree to which its momentum was defined. This seems to be merely an academic exercise in exploring, for fun, the ramifications of the Bohr model - which was abandoned as a model in the 1920s, due to its obvious inadequacies. I also note the paper is dated 2018, a decade after this George Hunter bloke, whoever he may have been, died. But I'm not a physicist. There are others that can comment more authoritatively, I'm sure.

In space travel, the numbers are awful. (Douglas Adams) These other civilisations may well have decided, quite coolly and rationally, that spending centuries flying through empty space is a pointless exercise. Oh, ninja-ed by @dimreepr, I see.

Those stains look like iron salts to me. You'll have to explain to me why you associate them with salt, as I'm a Brit and we don't have many outdoor swimming pools here. Do you use salt to treat the water in some way? Could it have iron as a contaminant, like the rock salt we put on the road in winter, which always looks a bit pink or brown? Chemically, I would expect ascorbic acid to form a "chelate" with iron Fe³⁺ ions, which is a sort of cage molecule enclosing it. This could serve to dissolve the iron salts off the sides of the pool, if that it what it is.

This looks like a question for someone with experience of the paint or allied industries. I can't answer this myself but I see from this: https://www.crayvalley.com/docs/technical-paper/dispersing-titanium-dioxide-with-sma-resins-(1).pdf that TiO2 is sometimes indeed given a surface coating, in this case involving Al2O3 and something organic. It may be that either Cray Valley or Millenium Inorganic Chemical could advise you further if you contact them.

It certainly looks as if it has pink feldspar, black mica and white quartz, so could be granite. It doesn't look porphyritic to me, in that there is no glassy or microcrystalline matrix. But I'm no mineralogist. It's rather a pretty rock, actually.

This looks like a case for early legislation, mandating that manufacturers take back expired batteries for recycling. From the article, the technology to do it does exist, so there is no need for it to be like nuclear waste that has to be just put in a hole in the ground. But it will be costly and nobody commercial will do it just out of the goodness of their hearts, so legislation must be the way to go, I think.

You're right, it's the empirical formula. Silica (quartz) is a covalent giant structure. As such, there is no molecular formula, since there are no discrete molecules in the structure. You could almost say that an entire crystal is in effect a single "molecule! So for giant structures, the empirical formula is what we use. Here is a picture, in which you can see the SiO4 tetrahedra sharing the O atoms at their vertices with their neighbours: