exchemist

Hmm, if it has 2g/l of dissolved substances, that does not look to me like anything one could derive from tap water alone. This all feels a bit scammy to me.

You need a salt (NaCl) solution for that, as you are making hypochlorous acid (HOCl).

I'm a bit mystified by all this. Surely the chloralkali process yields NaOH, not acid, doesn't it? And when you speak of carboxylic acids, which ones are you talking about and what are you digesting anaerobically to produce them? And what are you using mother of vinegar with, to convert it to acetic acid? Sorry for so many questions.

Piezoelectric crystals. But this is off-topic for this thread so I'll shut up.

No, that's wrong. You can, if you know the dissociation constant as well. (A dissociation constant is just the equilibrium constant for a dissociation reaction.) You can't know the pH just from the chemical equation for the dissociation, since that does not tell you where the equilibrium lies between the left hand side and the right hand side. That's the missing piece of information that the dissociation constant (or the ionic product in the case of water) tells you. To make life easier for you, if you have a strong acid, such as HCl or HNO3, you can assume that it is fully dissociated (unless you are dealing with very high concentrations). So for these, if you know the concentration of acid from the amount you added, you can set [H+] equal to that, since every molecule of acid gives you one H+ ion in solution. So knowing the acid concentration you can just work out the pH from that. If you have a weak acid, like acetic acid, then you need to look up Ka for the acid and work out [H+] using that, knowing the concentration of acid you have added. If you have a more complex mixture, involving and acid and a base together, then if it is a strong acid with a strong base, you can assume full neutralisation occurs and that the pH will be determined just by what is left over. If you have a weak acid, or a weak base, then you will need to know the equilibrium constant for the neutralisation reaction involved. So it is doable in all these cases, so long as you know the molecular concentrations AND the relevant equilibrium constant.

OK, you still have the same confusion as originally, it seems. In my original reply to you, I mentioned that you seemed to be treating water as fully ionised, when it is in fact barely ionised at all. It looks as if we need to go back and revisit what dissociation into ions involves. (Forgive me if you know all this, but it looks from your posts as if you may not.) Water consists of H-O-H molecules, right? H is bonded to O, by means of a covalent bond. You do not have lots of free "H" and "OH" floating around. However, what happens to a tiny fraction of the molecules is that they split, or dissociate, into ions. The covalent bond involves two electrons, one from H and one from O, being shared between the two atoms. In the dissociation of a water molecule, both electrons go to the O atom, leaving H without an electron. So you get H+, because it is one electron short and OH-, because it has one extra. In bulk water, there is a dynamic equilibrium, in which molecules are continually dissociating into ions and ions are continually recombining into neutral molecules again. But, and this is important to understand, the dissociated state requires more energy than the neutral state, so only a tiny fraction of the molecules are dissociated into ions at any given moment. Whereas what you have been doing, in effect, is counting all the H atoms present, bonded or not, towards your "[H]" figure. That's why it's wrong. You need to know the proportion of the molecules that is ionised at any given moment. This is extra information. You can't calculate it just from the chemical formula You get this from Kw, which is an experimentally determined figure.

There's a rather perfunctory entry in Wiki about this: https://en.wikipedia.org/wiki/Extinction_threshold It's not very good, but possibly some of the links and references could be informative.

If you know the concentration of H+ or H3O+, you are home and dry. You take the log of the value and take the negative of what you get (the logs are almost invariably -ve, so this procedure gives you a +ve value for the pH.) If you want to find the pH without knowing the concentration of H+ (or H3O+), you need to know the dissociation constant for the species present. For pure water we know this, of course. For other solutions, it depends what you've got. They are documented for many molecules. For example you can find values of Ka for all the commonly encountered acids. It is also possible to calculate equilibrium constants, in principle including dissociation constants, from the thermodynamics of the species involved: ΔG = -RT lnK, where ΔG is the change in Gibbs free energy for the dissociation.

That's a fair point, certainly.

From measurement, [H3O+] and [OH-] are each 10⁻⁷ mol/l in pure water at room temp, hence you get a pH of 7 and an ionic product, Kw of 10⁻¹⁴. It looks as if you have calculated the number of moles of pure H3O+and OH- you would have in a litre, if water were 100% ionised. But, as it is only very slightly ionised, so you will get wrong numbers that way. At least, this is how it looks to me at first glance.

Aha, that's interesting. But this must be a universal issue, then, in cooking with stainless steel vessels, since salt is an essential ingredient in cooking almost anything. Why are we not all poisoned?

We have a stainless steel cooking pot, some salt and some water. Where would ferricyanide come from?

No. I've had with you, pal. You're a timewaster.

To me, this has the hallmarks of someone with an idée fixe who is trying to preserve it by deliberate misunderstanding, i.e. arguing in bad faith. I don't see the point in carrying on with this, now.

Well we can rule out the latter in this context, but some MgCO₃ could be present in hard water I suppose. Does that mean you discount the reassurance given in the link in my first post on this thread?

A vibrating object is just the same as your body, just doing it faster.

Well, still a bit wrong, but you seem at least to be accepting that internal forces within the body (of the muscles acting on the bones of the skeleton) cause the centre of gravity of the body to move up and down, in reaction to contact with the floor. Do we agree on that?

Yeah but how are you going to get Cr (0) up to Cr(+6) without a strong oxidising agent? Salt water and a bit of atmospheric oxygen is never going to do that, surely, is it?

A yellowish tinge would be consistent with iron, certainly. I would not expect any health concerns. Iron itself is not a problem and I would have thought the makers of cooking pans would avoid any alloy components that might give health issues if they were to leach out through corrosion. The main other constituent of stainless steel is Cr. It seems to be Cr +6 that is hazardous, but the product of any corrosion due to salt (NaCl) will be lower oxidation states that are apparently not a problem. I found this link which may provide some reassurance: https://bssa.org.uk/bssa_articles/does-the-chromium-in-stainless-steel-contain-chrome-6-cr6-and-is-this-a-potential-health-hazard/

A "jar of pure electrons" would mean an accumulation of -ve charge. You can do this to some degree with something like a Leyden Jar, in other words a capacitor. And you can use those to produce an electric discharge, which involves an arc. But you would not use the photoelectric effect for that, I don't think. You would need something that can "push" the electrons together, against their mutual repulsion, in other words a high voltage. You won't get that from the photoelectric effect.

Not hydrogen atoms. You want a conducting solid material, such as a metal plate, because the idea - at least as I recall it - is that with light above a certain frequency a current flows in a circuit, due to the emitted electrons, whereas below that frequency it doesn't. The experimental setup to "catch" the emitted electrons is shown in this diagram from the Wiki page: https://en.wikipedia.org/wiki/Photoelectric_effect#/media/File:Photoelectric_effect_measurement_apparatus_-_microscopic_picture.svg You can certainly ionise hydrogen or other gases with light with energy above the ionisation energy for the gas, but this is not what people mean when they talk about the photoelectric effect. As for capturing and containing them, you will struggle because they will repel one another and a bulk -ve charge will accumulate.

There is a useful article here about the care needed when interpreting raw numbers from VAERS: https://www.ibtimes.com/over-900-died-after-receiving-covid-19-vaccine-experts-say-data-misinterpreted-3153820 So the answer I think is no, they have not been investigated for possible causality, nor are there necessarily grounds for doing so. By the look of it, it may be the old post hoc ergo propter hoc trap. It seems quite hard to find the data you are looking for viz. the risk of fatal side effects of the vaccine in fit and healthy under 30yr olds. I have been able to find the relative risk due to the virus of death, hospitalisation by age bands in the US, but this does not filter out the fit and healthy from the others: https://www.cdc.gov/coronavirus/2019-ncov/covid-data/investigations-discovery/hospitalization-death-by-age.html I suspect that, for the cohort you are interested in, the main issues will be (i) the risk to them of Long Covid from the virus, and (ii) the increased spreading of the virus in the population by this group if they are not vaccinated - and hence the potential for further variants to arise. I also suspect we simply do not have data on all this, given that the disease has only been with us for 18 months and given the huge number of variables, e.g. there are more than 5 vaccines in widespread use, there are half a dozen variants of the virus, all with their own characteristics, etc. The only further thing I can contribute is that, in the UK, people under 30 are recommended not to have the Astra/Zeneca vaccine but one of the others, due to the low but finite risk of blood clots. I would think the same applies to the Johnson & Johnson one, as that, I gather, uses similar technology. So Pfizer and Moderna seem to be fine for younger people. And by being vaccinated you do your bit for society by stopping the spread and reducing the chance of further lockdowns due to new variants. Plus you avoid the risk of long Covid, like my 25yr old nephew, and which I myself have had a brush with, as a fittish 65yr old.

Unaccountably, this film does not seem to been reviewed in Nature.😁 I did find this: https://www.imdb.com/title/tt2124189/?ref_=fn_al_tt_1

Can you provide a reference to somebody authoritative who says this? It is not my understanding of how this machine works.

Why do you think they should have been carried out in theory? In theory, surely, a Wimshurst machine will work perfectly well in a vacuum, won't it? I can't see that it relies on the atmosphere in order to function. Or do you see it differently?