 Today's old textbook is this one, the International Correspondents' School's inorganic chemistry reference book. So if we open the book, you don't often get inlays like this anymore, very Victorian slash Edwardian. And that's because the International Correspondents' School was founded in the 1880s and it was a distance learning college. Which basically is very similar to the Open University but predates it by the best part of the 1880s. Let's check the date. It is originally 1898 by the Coloury Engineer Company. So this was printed in the UK, incorporated here, not America. And this printing in 1915. So this is a very interesting time for chemistry between about 1898 to 1915. Because what was definitely known, well, atomic theory is pretty much sorted. The elements were listed and tabulated and more complete than they had ever been. But things were about to change. We didn't really know about the proton, the electron. We didn't know about the atomic structure. So 1914 roughly was when Marsden and Geiger and Rutherford were doing their experiments to show that the atom is a solid, very dense nuclear surrounded by a much less dense cloud of electrons. So what you don't find in this, because any reference to that, there is no mention of electrons and protons. They weren't really known to be part of the atom, or at least where they were known to be part of the atom. It was a bit hazy how that all fitted together. So let's have a just a flick through and see what we can look at. So this is basic chemistry? No. This is what we might call general chemistry if you're in the US system rather than necessarily in organic chemistry. But when you flick around, it is more inorganic. So it really just lists elements and kind of what they do when we flick through it. Compounds of oxygen with hydrogen. That's usually age 20, isn't it? Lots of preparations. Preparation of water occurs so plentifully in nature that, except when required for chemical purposes, no special processes of preparation are necessarily true, although we might want to deionise it occasionally. But most of this is just lists and lists of materials. Now, rather interestingly, we are at the stage where we do know that the atoms exist and that those are the best way of describing things. But these aren't really structures as we would normally recognise them. They are talking about connectivity certainly, but we probably wouldn't draw a linear water these days. And the structure of ammonia is sort of there. But it is, you know, this is not like it's an atom with three bonds coming up to it. It's sort of just showing connectivity. So this is still a little bit early. In early times there were two views held in regard to the constitution of matter. One of these was that all matter was continuous and therefore capable of infinite subdivision. Now, that is continuous matter. It's a theory that's been rejected for a long time, but it was still kind of controversial through most of the 19th century. Even when Mendelier was assembling his periodic table, he kind of rejected the idea of atoms for at least over a decade or two after he got famous in 1869. But by this point in 1915-ish atoms are pretty much solid. Now, this theory is incapable of direct proof, but all the observed facts fit in. We do have more direct proof of atoms now. Famously people credit one of Einstein's calculations with Brownian motion, two particles of atoms. We have spectroscopic evidence, we have atomic force microscopy that can actually image individual atoms. And then once we've got the idea of one element is or an atom, we start trying to figure out what a molecule is. There will finally be obtained an extremely minute particle that cannot be further subdivided by mechanical means, and this is known as a molecule. So that's the older definition of a molecule. We wouldn't necessarily use that now. IUPAC's definition, it's got two. It's got molecular entity, which is something involving more than one atom and molecule, which involves more than one atom as well, but is a bit broader in scope. And its broader scope is that it's got to be more than two or more atoms that are bound together tightly enough to host a vibrational state, which is an odd sampling definition if you don't know chemistry, but if you're into the chemical physics or physical chemistry, that's actually a really interesting definition of a molecule because if it doesn't vibrate, they're not bound tightly enough. So a molecule may therefore be defined as the smallest portion of matter obtainable by mechanical or physical subdivision, or the smallest particle of matter having the properties of the original substance. Now that's an interesting definition because that is kind of not correct because properties of substances do depend on their scale. So for instance, gold, you would say a property of gold is that it is, or gold is yellow and it is shiny, but that's a property of the substance being in bulk. If you cut gold down to gold nanoparticles, they're actually red or purple depending on their size, and that red or purple that are in lateral flow tests, they're gold nanoparticles and two antigens. The word atom means indivisible, and divided in use this term is applied to the smallest divisions of matter that can be obtained by most refined methods at present known to the chemist. So an atom is the smallest particle of an element which can be obtained by chemical subdivision. And that's useful because around about this time we are entering the age of our nuclear physics existing. We know that the atoms can be radioactive, they can break apart and maybe change. This is a really transitional moment in science where we are trying to figure out can the atom be split. So this is kind of hinting that maybe the atom can be split because we're using chemical subdivision as the definition. So let's have a look. This is interesting. Glass rods, glass blowing is in this. We don't do much of our own glass blowing anymore. You get dedicated glass blowers who know what they are doing to do this. Generally speaking, we don't because it's difficult, it's time consuming, and you can hurt yourself if you don't know what you're doing. So becoming a properly experienced glass blower takes a decade at least. What else, earlier? The balance. This is really interesting because I actually have a balance that looks like this in this office just over there in the corner. It's a very old school, it's very hard to use. The bottom is quite good. Every chemist should keep his balance and weight sacred and should treat them with the greatest care and consideration. Now it is, we just throw it onto a single pan balance and a digital readout tells us how much it weighs. Other practical stuff, decantation. Well, I don't think I've ever said that out loud. Filtration is kind of separating. A couple of really nice diagrams of some purification and gas purification, which is really nice. Here we have this. Sulfur and chlorine. So we've got sulfuric acid here. And we're getting kind of a hinted structure appearing. Right, so sulfur in the middle. Two double bonds to oxygen, a single bond to the acidic OH groups there. That's kind of how we draw it now. It feels like the limitation is what kind of technology of the time do to show these structures. So you have to remember that we got these structures without any kind of spectroscopy or X-ray diffraction at this time. Rather interesting, it doesn't go into any theory that unifies this. There's very, there aren't really mentions of oxidation state in here. We probably would not talk about inorganic chemistry without talking about oxidation states and how things can combine together. And that's kind of a side effect of the fact that the periodic table was still kind of in its infancy. And we didn't really know atomic structure at all and that all informs how these things put together. We've at least got some organization here. So this is family two group B. It consists of the metals zinc, cadmium and mercury. So we will flip back and find what I think is the most interesting part of this. The big table here, I'll just click to paste it, has to be pulled out. And here it is. That's the periodic table of 1898 to 1915 inch. But you can see it doesn't look anything like a modern periodic table at all. And I have done an animation file. This works to separate them out because you can see that this is mostly P block elements, mostly, but then interleaved between them or the D block elements. And that is sort of a consequence of not really knowing electronic structure. If you don't know the electrons, if you don't know atomic orbitals, if you don't know quantum mechanics, you can't make sense of that. The periodic table reflects kind of the electronic structure of an atom according to quantum theory and the spherical harmonics that the electrons follow. And if all you've got to go on is their reactivity and their mass, this is how you make sense of that. Any of the discrepancies within the groups are solved by pushing them from group A to group B. So for instance, here on the right, we've got fluorine, chlorine, bromine, iodine, and still in group 7 manganese, big red flag that something is wrong there. And then group 8 all these other metals. And over here, you can tell this is a bit later than Mendeleev because it has group 0. Here we are, helium, neon, argon with just an A rather than AR, krypton, xenon. The noble gases, they have all been found by this point. So when the periodic table was first assembled in 1869, 1871-ish, the noble gases weren't around. They were about a decade or two away from being observed. So there was an assumption that 1% of air was something else and then it was identified as argon after that. And then the rest fell into place quite quickly. A helium being the interesting one because it was observed in the solar spectra before it was discovered on Earth. So we knew that helium existed from spectroscopic evidence before we knew, well, before we could isolate it. So this is in here. Now in a modern layout, this is no longer group 0, it is group 8 slash 18 all the way on the right. And there were various assumptions about what group 0 could mean at the time. Before these were even discovered, group 0 was kind of hypothesized as something that is lighter than hydrogen. In fact, Mendeleev left a space on the left for something lighter than hydrogen. I made that assumption. Because of course Mendeleev didn't believe in atoms at the time, he thought, well, there's going to be something even lighter, even lighter than that and put it in group 0. Maybe there's another row on top of this. Now what is really interesting here? Turn the page over. I looked at this a little bit earlier. Do you mention Mendeleev? Written anglicized a different way to how we normally do it without the V. They also credit Lothar Meyer a lot. In fact, this is Meyer's table not Mendeleev's. So the book seems to be more happy with crediting the German scientists rather than the Russian scientists. They kind of independently stumbled on the same idea. Arranged slightly differently, but kind of once you took away the formatting, they had the same idea roughly at the same time. This is really on the cusp of modern chemistry forming. So this is kind of the end of the original chemical era. Here, in atomic weights, this is interesting. It would be obviously be out of place at the time of the method of the atomic weights. And a little reflection will show that the atoms are much too small to have their absolute weights determined and consequently a standard is selected. And this is really interesting because this was not standardized at the time. How do you measure an atom's mass? It's too light to stick it on a balance. It's like 10 to the minus 27 kilograms. You can't weigh that. But you can measure it relative to something else. And do you measure it relative to hydrogen or carbon? And in this case, they're measuring it relative to hydrogen. Now, if you don't score chemistry, you will know that we measure it relative to carbon and specifically carbon 12. And this predates isotopes and it predates knowing the exact masses of hydrogen various precisely. So this is the interesting bit of calculation. Hydrogen is taken as one and says down here quite recently a long series of painstaking experiments have shown that oxygen is 15.88 times as heavy as hydrogen instead of 16 times. Now 15.88 is not the atomic mass of oxygen. That's actually 15.9994. Yeah, that's right. But that is 15.88 times the actual atomic mass of hydrogen. So the atomic mass of hydrogen is 1.0079. Multiply that by 15.88. Within any reasonable error, you're on the actual atomic mass currently accepted for oxygen. So that is a consequence of those masses being measured relative to carbon and carbon 12 specifically. And now we define them kind of by definition, by setting avogados constant to be a set number instead of empirical. There aren't really any glaring errors throughout this. We haven't fundamentally upset chemistry since here. Just how we talk about it has changed. How we do the practicals has changed. How we teach it has changed certainly. So let's look to the back and look at the examination questions. So name three materials in which hydrogen occurs. I probably wouldn't phrase a question like that anymore. That's very weird. Give some of the properties of oxygen. Where does oxygen occur? Where does water occur? Give some properties of those. Some of these questions are very vague and we definitely would not set questions like this at a higher education level for a couple of reasons. One, this is a correspondence course textbook. You just flick to the book and you copy the answer out. And two, they're incredibly vague. Where does water occur? What's that even mean? Do you want to talk about where it forms in the universe? Is it found in clouds? Does it occur in oceans? Does it occur in cells? I don't know. This is really hard to actually interpret what the questions mean. Here we go. What? Define matter? That's one for the physicists to talk about right now. If you can do it in terms of what we knew in 1915 and what we knew in 2022, that would be really interesting to compare. How many cubic centimetres are contained in one litre? I mean, I don't know modern undergraduates. Can't figure that one out very easily. Define a molecule or an atom. Which definition? Because actually you have several of them. These questions are very vague. You either have to memorise the entire book to answer these questions or you look it up in the book. Which is kind of weird because these days we would address problem solving. It would be here is a reaction that you haven't seen before. Use the rules that you have learned from the previous examples to kind of tell me about it. And that is more the question that we'd use at degree level now. So mail your work on this lesson as soon as you have finished it and looked it over carefully. Do not hold it until another lesson is ready. Now, the International Correspondent School is still going and the Penn Career School is still going. So will they accept the 106 years late submission? That's the question.