exchemist

OK, I didn't expect you to be able to follow all the methods. I just wanted to indicate we have standard ways of identifying these compounds, so that is how it would be done if the question were to arise today with an unknown sample. But if what you are after is how these elements and compounds were identified historically, i.e. before modern day analytical chemistry was available, that's a lot trickier. I think I would have to try to explain that by examples. I gave you one example previously, of what Lavoiser deduced from burning phosphorus. He got a lot out of that: - 2 components of air: azote and oxygene - A compound (ash) in which phophorus was combined with oxygen (we would call that an oxide, though I'm unsure if the term existed in his time) - this compound produced an acid when dissolved in water - a phosphorus acid. Silver, gold and copper were obviously known in the Ancient world for coinage and jewellery and alloys of them. Zinc and tin were also known. Bronze is an alloy of copper with tin (e.g. the Bronze Age) and copper and zinc produced brass. Mineral acids, including nitric acid, were known to Medieval alchemists (though not under their modern names): https://en.wikipedia.org/wiki/Nitric_acid So someone in Lavoisier's time could dissolve a piece of silver in nitric acid and realise they had a compound - which today we call silver nitrate. It's obviously not possible to trace all the stages by which all these elements, reactions and compounds gradually became characterised. It would take a book to do that and even then there would still be plenty of uncertainty about how many of the steps became known. The historical record is patchy and some of thee unknown alchemists guarded their knowledge. But I hope from this you get an idea of the sort of things they did and so how the early chemists were able to piece together some rules for elements and compounds. In fact, Lavoisier was the first to make a real list of elements and he still got some things wrong. Here's a quote from the relevant Wiki page: QUOTE The book contains 33 elements, only 23 of which are elements in the modern sense.[5] The elements given by Lavoisier are: light, caloric, oxygen, azote (nitrogen), hydrogen, sulphur, phosphorous (phosphorus), charcoal, muriatic radical (chloride), fluoric radical (fluoride), boracic radical, antimony, arsenic, bismuth, cobalt, copper, gold, iron, lead, manganese, mercury, molybdena (molybdenite), nickel, platina (platinum), silver, tin, tungstein (tungsten), zinc, lime, magnesia (magnesium), barytes (baryte), argill (clay or earth of alum), and silex.[6] UNQUOTE From: https://en.wikipedia.org/wiki/Traité_Élémentaire_de_Chimie It was a long and painful process that was only really sorted out in the latter half of the c.19th with Mendele'ev.

Good question. I have no idea. That would be a good one for Suzie Dent, our charming TV lexicographer. 🙂

I'm still baffled by your question. You know it's silver nitrate because that's what it says on the bottle and you bought it from a reputable supplier. But if, for instance, some idiot transfers it to an unlabelled bottle, you can confirm it is silver nitrate by carrying out some characteristic reactions with a small sample of it: https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Qualitative_Analysis/Characteristic_Reactions_of_Select_Metal_Ions/Characteristic_Reactions_of_Silver_Ions_(Ag) You can also confirm nitrate by infra red spectroscopy and silver by its visible/UV spectrum: https://www.atomtrace.com/elements-database/element/47 Is that OK as an answer? I have the feeling I may not quite have grasped the significance of your question.

What makes you think you will have a new administration in 4 years? 😄

Right, now I feel I'm starting to grasp this. I've now found this very informative link, which explains a lot of what we have been discussing: https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Introduction_to_Inorganic_Chemistry_(Wikibook)/10%3A_Electronic_Properties_of_Materials_-_Superconductors_and_Semiconductors/10.05%3A_Semiconductors-_Band_Gaps_Colors_Conductivity_and_Doping So indeed the conductivity is orders of magnitude lower than for a typical metal, consistent with the idea that thermal population of the conduction band is due to just the very tail end of the Boltzmann distribution. There's also a discussion of colours, which touches on what you were saying about photon absorption - and the link to how LEDs work which, thinking about it, is obviously the converse process. Anyway I think, subject to any further comments either of you may have, that I have the answer to my original question about metallic lustre of non-metallic compounds. I see for instance that iron pyrite, "fool's gold" has a band gap of 0.95eV, and in fact it is a semiconductor being studied for photovoltaic applications! My undergraduate chemistry focused on the populated bonding orbitals , i.e. the valence band, without giving much attention to the (nominally) empty antibonding orbitals, which merge to form the conduction band in an extended solid array. We didn't study solid state physics at all really. But when you think about it, as one descends a Group in the Periodic Table and the principal quantum number goes up, the orbital overlap between a pair of atoms gets less efficient, so the splitting in energy between bonding and antibonding orbitals grows less. And so we get a narrower band gap and start to see semimetallic properties, due to start of thermal population of the conduction band - bingo! Cool stuff.

Hmm. As I understand it, near IR ~1eV, mid IR ~0.1eV and far IR ~ 0.01eV. I recall from the specific heat of diatomic gases that vibrations - which give rise to near IR absorption bands - are not appreciably excited at 300K, which fits with what you say. Whereas rotational spectra are in the far IR. Nevertheless it is clear that in semiconductors there must be some thermal excitation of electrons across a band gap ~1eV, to account for the increase in electrical conductivity of these materials with temperature - and to account for their metallic sheen, which is what sparked my original interest. Perhaps the issue is that we are seeing the effect of the tail of the Boltzmann distribution, i.e. we should be thinking of this on a logarithmic scale. One may not need too many charge carriers to see an increase in conductivity on a logarithmic scale - and the development of a superficially metallic appearance. I suppose one has to look at the distribution of phonon energies in a solid and see if the high energy tail end of these can reach ~1eV at 300K.

I think there is an awful lot of hype and hot air around the whole subject. One day maybe but at present, whilst machine learning focused on specific applications clearly has vast potential, a lot of generative AI seems to be crap. So much so that any self-developing AI would produce a sort of village idiot.

Hmm. How would photon absorption work in this case? I presume if thermal excitation can work then the equivalent photon absorption would be in the IR rather than the visible. Whereas reflection presumably is elastic, with no energy absorption. So perhaps there is an IR absorption band which pumps the conduction band and then the resulting population of the conduction band produces reflection in the visible. By the way I’ve now found something that says that, in semiconductors, valence band electrons can absorb a phonon and be thereby excited to the conduction band. So this would be the thermal excitation mechanism.

One thing I’m missing in all this is to what extent the Trump voters simply thought he would be better than Harris for the economy and their standard of living, and to what extent they had really had it with the current democratic system and really wanted to try Trumpy autocracy. The signs of autocracy were there obviously, for anyone politically conscious, but did the voters perceive it and if so did they just not care? Has there been any opinion research on this? I guess it’s not easy to ask people if they meant to vote for autocracy.

Aha. I wasn’t sure if the band gap was small enough to be bridged by thermal effects, but if it is, that would account for it. I suppose that should mean the metallic sheen on these materials should disappear at cryogenic temperatures. I wonder if anyone has observed that.

On my recent trip to the London Natural History Museum I was struck by the number of minerals that, while not metals, nevertheless have a metallic sheen or lustre. Iron Pyrite (FeS₂), "Fool's Gold" is a classic example. Semiconductor metalloid elements also have this property. I'm aware that metals have this lustre due to the freedom of movement of electrons in the conduction band, which are (in simplistic terms) set into sympathetic oscillation by incident light. However in these non-metals and metalloids, the bonding electrons should by rights be in the valence band and thus not available to move freely in the way necessary to reflect incident light. Hence to my question: in semiconductors, i.e. materials with a relatively narrow band gap, is there some degree of thermal population of the conduction band, by promotion of electrons from the valence band? This is the only way I could think of to explain the metallic surface appearance of these non-metal compounds. Grateful for a physicist's advice.

Just seen this. The only sculptor O’Neill I found online seems to be based near Sodding Chipbury in the Cotswolds and works with a chainsaw. Is that the same bloke?

True, far harder to capture the processes at state level. But it is only the swing states they have to focus on. And for presidential elections they can have fun and games with the electoral college. But yes, in principle the mid term elections seem to be the best hope. If Congress ceases to be in Trump’s pocket I suppose there are things it can do to stymie him. So long as Trump listens to Congress at all by that stage.

Don’t be so touchy. On the internet we don’t know who we are dealing with and I’ve got burnt in the past by timewasters, as have many others here.It takes a while to develop a rapport and trust with someone new. That’s what I mean by bona fides. It was a peculiar question for you ask so I became a bit suspicious, that’s all. But up to you if you prefer to continue with someone else, of course.

Quite, though may be hard to do if you still want the military to be effective and professionally led. Fox presenters as top generals?

Well, there are funny people about, as those of us who have spent time on these forums know, to our cost. Establishing the bona fides of a new poster takes a bit of time, so you will have to excuse me for being cautious. It was a very odd question for you to ask, that’s all. Why did you ask it? Did you really not realise that chemicals can be bought from commercial suppliers?

I doubt he’ll do that though, since that’s the reaction he might get. The model is Orban’s Hungary. So the electoral process will continue, in some form, but rigged to ensure he or his successor is the next president and Repubican waxworks remain in control of Congress, with the aid of @CharonY’s cult votes, cultivated via social media. The idea will be to allow people to think if things go “too far” they would step in, but then carefully nudge along just below that threshold, while acclimatising people so that their threshold moves beyond the situation at any given moment - frog-boiling, if you will. I think civil - or military - rebellion, or at least mass demonstrations, may ultimately be needed, but the problem will be to identify a trigger point that motivates enough people.

You don’t need military force for the kind of soft coup that is now in progress, though. All you need is for the army not to get involved to stop you. Once you have ensured all institutions of the state are under your control and that future elections, if any, are sure to return your party, the job is done.

How would this work? From the little I have read, it does not seem there are reliable predictive signs that can be detected before a patient starts to experience seizures. But I'm not expert. I presume you have studied this. What types of sign would your IT system use as input?

OK. You start.😀

All good info, save that this is not what a "functional group" is in chemistry. That term is used in organic chemistry, to denote groups of atoms which are part of an organic molecule, conferring specific types of behaviour, or functionality. Examples would be amine groups or carboxylate groups. Acid/base and redox classifications would not be described as functional groups. More here: https://en.wikipedia.org/wiki/Functional_group I don't understand your question about silver nitrate. This video does not relate to the dawn of chemistry in the c.18th, when there were real issues with correctly identifying the substances they worked with. For the last 100 years at least, people have been able to obtain chemical compounds from commercial suppliers. Are you serious or are you messing us about?

Exactly. The whole point of an authoritarian coup, a textbook example of which we have here, is that it is irreversible. Part of the programme is to snuff out democracy, or turn its procedures into a merely decorative ornament, as it is in Russia. Once the courts are ignored, as Vance advocates, the way is open for vote suppression, bribery of voters - which Musk has already piloted - and/or intimidation at the polls. It will be interesting to see how they do that but I have no doubt there will be a plan. But the cult aspect that you draw attention to will make the task easier, given the influence of Musk et al over social media and the cowing of regular media that is already occurring through lawfare and selective exclusions from briefings.

Yup very hard to reverse if indeed all the military are loyal to Trump instead of to the Constitution. But are they?

It's good for quite a few metals but doesn't help for everything. And there's also the problem of colours that look similar. But it is a useful thing. As @studiot says, it can be thought of as a very basic kind of spectroscopy. On the mole/Avogadro's number stuff, yes it is a lot to take in but we've covered quite a lot of ground already, thanks to your questions. Let's review it: - the periodic table and why it is structured the way it is, with similar properties among elements in each of the groups (columns) - protons, neutrons and electrons and what makes a element an element - Atomic number and atomic weight, and isotopes - atoms versus ions. - Avogadro's Number and moles, and their importance for the ratios in which substances react together. - Plus some history of the start of chemistry with Lavoisier's studies of combustion That's quite a lot already. This would have been several weeks of school study for my son, for instance. I realise I have not come back to you yet on how we know ions are ions. There is probably a missing piece on the history of how the concept of atoms and molecules was validated, considering they are far too small to see directly (the wavelength of visible light is of the order of 500nm, whereas an atom is of the order of 0.5nm across, so 1000 times smaller.) Ions are just electrically charged atoms, so if you accept the existence of atoms and find that certain solutions conduct electricity, there must be charge carriers of some kind, so it's not a huge leap to think there are atoms with electric charge.The substance produced at the electrodes are also an indication of what is happening, e.g. chlorine is evolved at the +ve electrode when a current is passed through a salt solution. The Cl- ions give up their extra electron to the electrode and make chlorine gas.

Take a look at the periodic table link I gave you and read up the physical and chemical properties of phosphorus. It's a bit complicated because there are different "allotropes" of phosphorus (from the Greek for other forms), but you can get an idea of what its characteristic features would have been, for someone of Lavoisier's time. I don't know which form of phosphorus he was dealing with, I'm afraid. But these guys were not mugs. Elements like sulphur or mercury, were known to them, from all the experiments the old alchemists used to do, in the course of their fruitless quest to turn lead into gold.