 Okay, well, it's a real pleasure welcoming Sarah Hems today here in Louvain de Neuve. For those who may not know Sarah, Sarah is a historian of chemistry, specializing in 19th-century chemistry, I would say mostly. She recently finished her PhD in teleprotoisphère in Paris, under the supervision of Jean-Pierre Nordet. And the thesis was on the discovery of the elements from Lavoisier to Mendeleev. Was that the line here? And of course Lavoisier, with his operational definition of the element as the endpoint of chemical analysis, really helped the field of chemistry and the discovery of the elements. But at the same time, the instrumental means at that time were not always sufficient to really reach this endpoint of chemical analysis. Yet chemists were somehow convinced they discovered elements. So you looked into the different kinds of argumentation chemists used for the existence of chemical analysis, even though they were made to prove it as a simple substance. And analogy, I think, played a very important role in all of these harnesses by 19th-century chemists. And I think this is becoming some kind of a threat in your research, the role of analogy. So today's talk will be on the role of chemical analogy with respect to the case of ammonia. So before it's yours, you have one hour short break and then we'll have one hour of Q&A. Yeah, thank you so much. And thank you all for coming, all of you. I'm very happy to meet you and to be here and to discuss. So indeed, this is a case study, which I did as part of my PhD, but it's the one chapter that's still sort of unfinished, where I'm thinking there's still a lot actually to add and to sort of rethink, because it's quite a complex case. So my next project is also my new project at the Technical University. It's also about ammonia. And yeah, thinking about the role of analogy in this case. So for most of you, I'm assuming that the idea of ammonium being a metal probably sounds quite new. So I thought I would start with expanding what I mean by that. So I want to start with, so I also opened with this in my abstract. There's this very curious, surprising experiment from 1888, when the Swedish chemist Jonseco Brzevis and his colleague Magnus Martin Pontin found that they were able to produce an amalgam from ammonia with mercury. So that's a metallic alloy. Here you can see an image on the side of a very recent reproduction, kind of using a different experimental method, but we can assume that it may have looked something like this. So as you can already see, it looks very metallic and it kind of is a metallic alloy of mercury and what then later would become ammonium. So as Brzevis and Pontin also said, they described it as a miracle. So we saw the known constituents of ammonium means at the negative pole, so of the battery they used electricity to produce this amalgam, and form a metallic body and in affirming that a metal was composed under our eyes from a fluid of which the constituents are perfectly known to us, we relate a miracle. So they really describe this sense of just being completely astounded that they were dealing with a gas, ammonia, which was already known by then to be composed of nitrogen and hydrogen, which during this reaction seemed to transform into a metallic substance. So that's of course completely surprising because only metals form these kinds of compounds. So they communicated this to Humphrey Davie in England who had reproduced experiment, had the same reaction and concluded that it is scarcely possible to conceive that a substance which forms of mercury so perfect in an amalgam should not be metallic in its own nature. So what that means is ammonia has to contain the metal, even though we think it might be this gas composed of nitrogen and hydrogen, actually there just has to be a metal in there because it's not possible to imagine that it would have this kind of reaction otherwise. So how should this metal be called? Ammonium in analogy also to potassium, magnesium, calcium etc. So meaning kind of the metal from ammonium. Brazilian then again was completely convinced by this idea so much so that he included ammonium in this 1811 classification of chemical elements where you can see it all the way at the bottom right, ammonium. And then the 14 that's in parentheses there refers to a footnote where he said that under the conviction that chemists will sooner or later agree with me I have placed ammonium among the metals. So he was really aware that it was still a kind of controversial idea but pretty sure that sooner or later everyone would be convinced of the existence of this metal. So despite all of this and despite these two people being really more or less the most famous chemists that were alive during that time in Europe this history of ammonium is actually not so well known and the reason is of course as I mean I assume that most of you realize is that nowadays we don't recognize a metal called ammonium or this is not seen as a metallic substance and especially not a metallic element and so it has been mostly kind of either ignored by historians or if they do mention it then it's usually mentioned as a failure mistake or some kind of weird sidetracking of chemical research around that time where they were going the wrong way and then eventually ended up thankfully finding the right answer. So it's usually seen as something that's not super interesting to research because it's not like an exciting discovery basically. Nevertheless I think that it's exactly because it's such a complicated and strange and kind of contradictory case that it that's what makes it really interesting. So yeah that's why I said why should we care and also why should we care at a philosophy seminar not just for the history of the fact that these people were actually really working really hard on this question is that I think that these kind of complex cases can tell us a lot more about scientific practice because practitioners and so in this case chemists have to be more explicit about why they think something when there are different kinds of evidence contradicting each other or when they have to convince other people that don't agree with them. So a lot of things that are kind of implicitly assumed when everyone agrees a lot of things remain implicit but when the controversy arises is when they have to really justify these kinds of arguments of why do we actually think that this metal might exist. And secondly, specifically in this case analogical reasoning played a really big role so I think it's also an interesting case as an example of what the use of analogical reasoning might look like specifically in chemistry in the early 19th century but maybe also more generally. And the reason why analogical reasoning was so central here is because there was kind of this direct access to a metallic substance that would be ammonium was impossible so it remained impossible to isolate this metal and the only way to sort of access its composition was indirectly through analogical reasoning but I'll say more about this later. Yeah, so using this as a kind of integrated history of philosophy of science and of chemistry in this case study I want to use this to argue that analogical reasoning could function as a guide in the establishment of chemical knowledge and kind of helping chemists dealing with this kind of uncertainty when there was a lot of contradiction happening. Yes, so that's what I just said. It's a case study for analogical reasoning in identifying chemical composition. So the outline basically I will have two main parts. The second part will be more detailed about the story of ammonium between the first two decades of the 19th century but I'll mostly focus on these years 1877 to 1813 because that's when really the metallic ammonium was pursued as a possible hypothesis. But before then I will explain a little bit more about chemical analogy and its link to chemical composition in the 19th century. Yes, so depending on what type of topics you all work on you might be asking yourself different kinds of questions specifically I think for the people working on the concept of chemical element or questions related to that or who have been reading about this already might possibly be a little bit surprised that these very famous chemists would think that it was possible that metallic ammonium existed because it's relatively well known that the general definition of chemical element around this time was that of an indie composable chemical substance. So I first want to reflect a little bit on this point of what chemical elements were around this time, how they were viewed and what the relation to analogy there was and I'll show that actually chemists quite regularly relied on this type of analogical reasoning in their identification of chemical elements so Peter already referred to this a little bit but let me just explain a little bit more. So chemical elements right after what is usually called the chemical revolution so in the late 18th century the view of what chemical elements were changed and the most accepted definition around this time so from the late 18th almost all the way to the end of the 19th century was based on the definition formulated by Lavoisier who said that we must admit as elements all the substances into which we are capable by any means to reduce bodies by decomposition not that we are entitled to affirm that these substances we consider as simple may not be compounded but we ought never to suppose them compounded until experiment and observation has proven them to be so. What it means is any substance that cannot be decomposed by experimental means should be seen as a simple substance or chemical element even if it's possible that those substances might be decomposed in the future there's no way of knowing that they're truly simple because yeah there's no way of knowing until one day we actually decompose them even with all that uncertainty the best thing is just to stick purely to experimental operations and to never speculate about what their internal nature might actually be so the idea of adding something like ammonium to a list of elements even though it has never been isolated completely goes against this definition so indeed in that sense it's relatively surprising but the reason why it's less surprising than it may seem is that in practice actually views of chemical elements were much more complicated than this so this is exemplified actually in the definition of chemical elements that is listed in Brazilians' textbook so the same chemist who also put ammonium on the list who added a third category so he had simple bodies or chemical elements compound bodies, any body that's composed of multiple elements that is known to be decomposed and recomposed etc and there was a third category called undecompounded bodies so he said we call undecompounded those bodies which we have valid reasons not to regard as simple but which we have not yet been able to decompose into simpler elements and whose constituent parts in case these bodies were composed are still completely unknown to us so these are the substances that are actually indecomposable and yet still are not seen as chemical elements so chemists were completely aware of this issue that there might be multiple reasons that the substance cannot be decomposed and very often it might just be due to the fact that the means of decomposition are not strong enough and so they had this, so in Brazilians' case it's quite explicit listed at the beginning of his textbook but many other chemists were also dealing with this idea of undecompounded bodies that were actually, yeah, these bodies that were indecomposable but for different reasons and the role of chemical analogy here was kind of straightforwardly to distinguish between which are the bodies that are actually simple or probably simple and which are the ones that are indecomposable yet still composed and what might they be composed of so what do I mean by chemical analogy? Chemical analogy, so it's a term that was used by the chemists themselves at this time by it I mean a set of relevant similarities in chemical properties so similarly to how an analogy doesn't really work if it's just similarities the similarities that from the base trigonological argument have to be relevant so in this case this often came down to similarities in chemical behavior so if two bodies react in the same way with another set of bodies they might be seen as chemical, chemically analogous so for example we might say chlorine and iodine are analogous because they form acids with hydrogen in a similar way they react in a similar way with potassium and sodium to produce similar kinds of salts etc so this is what I mean by similarities in chemical behavior and these similarities are relevant enough to say that chlorine and iodine are the same kind of substance they're chemically analogous and they are both halogens and that means also that chemical analogy was primarily a principle or at least very very strongly linked to chemical classification when there were these relevant similarities it meant that substances could be placed in the same kind or the same class and there was a whole debate about which similarities were relevant enough to determine whether or not substances could fit into a class together but there was at least this really close link between classification and chemical analogy both classification and analogy also had a strong link to composition so I would say that chemical classifications were actually based on composition and analogy so different levels of composition around this time at least within each level of composition so simple, composed and then more complex bodies were classified according to these similarities in chemical properties there was also the idea that analogous bodies generally had the same composition so analogy in properties was kind of like an indicator for the fact that they would have the same composition this was at first just kind of a general observation it just happened to be that most often these bodies were composed in the same way but it also was a kind of rule almost or a guide as I already later that so for example already for Lavoisaiso in the late 18th century the observation that a few kind of the most paradigmatic acids all contain oxygen was reason enough to say well probably all acids contain oxygen and that's just a property of the group of acids is that they are composed of oxygen and this kind of reasoning was very normal happening all the time during in chemistry around 1800 and this idea this link, the idea that similar bodies contain similar elements could be used in the study of chemical composition and helped identify what that composition was so what did that look like? like I said analogy could be used to distinguish between simple and merely un-decompounded substances so this meant that on the one hand once a new indigaposable substance was produced chemical analogy could be used to establish the plausibility of its simplicity so in other words that if a new simple substance or indigaposable substance was produced and it was analogous to other substances that were already known to be simple then it was very possible to say well this is probably also a simple substance or at least even if that doesn't mean that it might be absolutely simple because that's impossible to prove that it might not be decomposed in the future at least it will be as simple as all the other simple substances because it fits into a classification that makes sense this is what happened for example in the case of sodium and potassium when Davey first isolated these new substances he really insisted very heavily on their analogy to the metals so they had some strange new properties such as the fact that they were very light but Davey really insisted no no they have to be simple substances because they have all these other metallic properties which means that they are similar enough to the metals to be classified as such and therefore if they're metals then they're simple on the other hand there are other examples of substances that didn't have such analogies and therefore were really problematic so chlorine is a quite famous example where there was this probably indigaposable simple substance chlorine it didn't fit into any classification of simple substances it was different from other simple substances and it was contested for a while like six years more or less it depended on individuals but there was a whole debate and most chemists were actually first opposed to this new element because it just didn't fit into classifications with analogies and other simple substances that changed when iodine was discovered and it was just so clearly analogous to chlorine that you had this new family of simple substances that could then be sort of coherently accommodated so you have the possibility of simplicity but on the other hand if a substance was analogous to other substances that were known to be compounds this meant that it was probably one of those undecompounded substances so chlorine was seen like that for a while but there was a whole list actually so Thomas Thompson is a chemist from that time who had the most explicit list of undecompounded substances where he said so this is my list of simple substances and then there are about 10 or so more that are technically also impossible but they don't fit into any of the simple substances and actually there are a lot more analogies to some of the compounds so I'm going to place them with the compounds in the expectation that they will be decomposed basically in anticipation of what will happen later and I will come back to some of those examples later but that was a reason to say ok probably in this case the fact that we're unable to decompose these bodies is probably due to some other issue that's not related to their simplicity yes so that's on the distinction between simple and undecompounded but then once a body was identified as undecompounded then an analogy could also be used to predict what it might be composed of so an example of that is alumina which is one of the earths as they were called in the early 19th century so alumina was very similar to the alkalines and alkaline earths so potash, soda, magnesium, lime all these other substances that were decomposed by Humphry Davey between 186 and 188 and shown all to be metallic oxides he then predicted well the earths are so similar to all these newly found metallic oxides that they are probably also metallic oxides but was unable to actually confirm this by decomposing them what he then said was actually this similarity in itself is justification enough to take alumina and the other ones as undecompounded and to predict that they will also contain new metals and so on the basis of this analogical inference he also predicted that alumina would contain a metal that he named aluminium it took almost 20 years from that prediction onwards before it was actually isolated aluminium as a metal but despite that fact it was also already accepted almost immediately so if we look back at Bruselius's classification you also see aluminium there right between beryllium and magnesium listed as one of the elements and you also notice that on the contrary to ammonium aluminium doesn't even have a footnote after it because it was just already so consensual everyone was listing aluminium as an element already because you know this analogical inference just made sense yes the reason why I kind of already anticipated this but the reason why it just made sense to believe these predictions was not really because analogical arguments in themselves were so perfectly logically justified it was more of a pragmatic justification of in kind of common sense reasoning it makes more sense to just take a whole family, move it to the group of compounds rather than to make this really sort of artificial separation between different substances in the same group just because you can decompose them or not and like I said the substance might be decomposable for a variety of reasons so chemical analogy helps identify the most likely explanation so now I've hopefully explained a bit more clearly what I mean by this link between analogy and composition so just to recap the most important idea is that chemical analogy so by which I mean relevant similarities in chemical properties was taken to be correlated with chemical composition similar bodies have similar composition and this idea could be the basis for analogical inferences regarding substances composition so distinguish between simple and the compounded but also predicts the composition of the compounded bodies so now it's hopefully also clear that in itself it was not so exceptional to assume that there would be an autocollumonia at least initially to make this inference was kind of normal but there is a sense in which this case does stand out from the other ones which is that ammonia was not an only compounded body because it had already been decomposed and they knew already that it was that the decomposition produced only nitrogen and hydrogen so there was no metal there and that's what makes this case so complex and also for chemists at the time you really really see that they're really struggling with this idea of how can this be it's just not possible that this is the only exception to this correlation between properties and composition there has to be some other explanation and that's why this case I think is particularly interesting because we can kind of see how different types of arguments different types of evidence weigh up against each other so you have the decomposition evidence but then there's the reasoning from analogy they contradict each other so there has to be some kind of strategy to go about making all of this work and that's where the role of chemical analogy becomes even more clear in my view so that takes me to the second part where I will zoom in on some of the different hypotheses that Davie and Prasadius went through the different ideas that they explored in order to make sense of this contradiction so Davie only worked on ammonium for this short period of time so 1877 to 1813 and then he kind of abandoned the question for Prasadius it actually remained a super important substance it remained super important in his work almost really until the end of his life he went through a lot of different views of what it might be but at least he also abandoned ammonium as a metal around 1813 as well they were really really close in contact during the beginning until about 1889 and then really started to drift apart and completely have divergent views on the issue but at each stage they were both of them really attached to this link between analogy and composition which Prasadius himself summarized this way in a letter to Bertelet it would be very inconsistent to believe that only ammonia provides phenomena that are externally so analogous to those of the fixed alkalis, the earths and the metallic oxides and yet internally of an entirely different nature so just to decipher kind of this citation the fixed alkalis are potassium soda which I already mentioned the oxide of potassium and sodium newly discovered by Davy the earths are substances such as alumina which were very similar to the alkalis in which were also most of them decomposed by Humphry Davy around 1888 and they were shown to be metallic oxides so ammonia behaved very very similarly externally analogously to all these substances that were all metallic oxides and yet somehow it would not be a metallic oxide that's just very inconsistent to believe that so these substances behave similarly therefore ammonia should also be a metallic oxide so in the next few slides I just have summarized the different analogical arguments that they made or schematized is maybe a better word so Paul Bartha has this way of schematizing analogical arguments which I find really helpful to just really see the property that they inferred in this case so the horizontal relations are from the source to the target there's some relation of similarity between P and P star and the vertical relations are then from the known similarities to a further feature which is known to hold in the source and therefore predicted to also hold in the target so yeah, I hope that's clear and this is the first analogical argument that was made regarding ammonia which was actually also predated at Davy's work on the question because that was made a similar one which is that like I said ammonia, this gas was known to be composed of nitrogen and hydrogen therefore it was thought that probably these very similar substances the three alkydides they were known as together were probably also composed of nitrogen so this is actually how in 186 Davy said about decomposing the fixed alkydides thinking well they're very similar to ammonia so they will probably be compounds of nitrogen as well he wasn't the first to make this inference but he wasn't the first to actually decompose them and what he found was that they weren't compounds of nitrogen they were compounds of these new metals potassium and sodium with oxygen so what he did was reverse his previous argument and doubt the knowledge that we had of the composition of ammonia saying that even though previous experience on ammonia left no doubt of its nature in the mind of the most enlightened chemists all new facts must be accompanied by a train of analogies and often by suspicions with regard to the accuracy of formal conclusions so basically this new knowledge made him think oh wait a minute then there's probably an error somewhere in the studies that we did of ammonia and we can reverse the previous analogical argument taking ammonia as the target knowing with this new knowledge of potassium and sodium thinking that probably this oxygen must also be somewhere in ammonia so probably instead of being all compounds of nitrogen all the alkalizers are probably all compounds of oxygen which in early 19th century chemistry would have been a super amazing success because oxygen was already linked to acidity so if it could also be linked to alkalinity then that was just beautiful as a theory kind of around the importance of oxygen and this actually seemed to work out at first because David for a while thought that he was able to confirm that ammonia contained oxygen then actually through repetition it turns out that he was not but he did really keep on to this idea that ammonia contained oxygen then I already referred to this happening a few times in 1808 he was able to decompose all these other cellifiable substances that were really similar to potassium soda so the ones I already referred to the earths and alkaline earths so all these substances that were really similar to potassium soda lime magnesium, barites etc among which was also alumina and showed that they were all composed of oxygen and of a metal so now we have a whole family that has a similar composition except for ammonia or at least that's not clear so he slightly adjusted the argument and now said that they all contained oxygen and a metal so ammonia also has to contain oxygen and a metal this metal will be called ammonia the additional evidence of course for this was this really amazing experiment of ammonia forming an amalgam so that's added even more evidence that all these other substances not only reacted in the same way but also formed an amalgam ammonia also formed an amalgam so this added even more likeness to the conclusion that ammonia would also contain a metal called ammonium however there was still this other evidence that really went in the opposite direction so even the fact that there was an amalgam didn't solve the fact that there were various contradictions the attempts to isolate this metal from the amalgam all failed so no amalgam could be taken from the amalgam repeated attempts to confirm the oxygen content of ammonia also failed and repeated decomposition of ammonia continued to produce only nitrogen and hydrogen so this wasn't just daily working on it but multiple chemists in France and in the UK were working on this question and just repeating the decomposition of ammonia and all they could find was just nitrogen and hydrogen so they kept running into this contradiction so how might that be solved? actually David's suggestion was maybe the oxygen of ammonia is not free oxygen that we can just take out maybe it's contained within one of the elements that compose ammonia so he said probably nitrogen itself is a metallic oxide and it just seems to be an element but the oxygen of ammonia has to be contained within nitrogen so in other words it was more willing to question the elementary nature of nitrogen and hydrogen than to admit that maybe there was just this really curious exception that one substance just did not follow this rule so by 1899 he was strongly inclined to suspect that there was this whole series of oxides of ammonium so hydrogen would be the first oxide, ammonia the second one and then nitrogen trioxide and very complex reasoning also going on here but this was his suggestion here this was really taken on by Brazilian so he has stayed a little bit at first and then 1810 was just really running with this so here is an example from a paper from 1811 where he just has all these calculations about how it might be calculated how much oxygen is in nitrogen how much oxygen is in ammonia and all these different so he had a very very complex system yeah based on sort of patterns of composition between different substances where he could use those to then calculate the exact composition of substances composed or which could be decomposed but didn't really follow the other pattern so it's yeah like I said there were a lot of really complex rules but the basic idea is that nitrogen could only fit into these patterns of composition if it was considered to be a compound containing oxygen so for him that was like proof also that yeah nitrogen was an oxide of ammonium and ammonia was then a higher oxide yeah even though it seemed to behave like an element that was just sort of superficial and so we also really see that Bersalius takes this idea of analogy and composition to a whole new level making the composition really down to the exact proportions and yeah a sign of an analogy between different substances so yeah I have a whole other slide about Bersalius' work but it's basically he also kept changing his mind about nitrogen first being the oxide of ammonium and then in 1813 said no actually it's not the oxide of ammonium it's the oxide of this other radical sort of not yet an isolated element called nitric changing his mind again about what ammonium was and then only in 1820 did he actually accept that nitrogen might be a chemical element which then again changed his view of what ammonium was and then even later in his work ammonium started to play a role in his views of organic substances so all of this yeah all of Bersalius' work is very complex and even people around that time write to him saying actually your view of composition is so complex it's really hard to understand so I won't really go into it much more but the the basic idea is that he kept sort of adjusting on this based on this rule that all the similar substances should be composed similarly while all of this was happening actually Humphry Davey was also again changing his mind so actually only a few months after he had suggested to Bersalius that nitrogen was an oxide he again completely reversed his argument and said no actually I will accept that ammonium is compounds so it seems it appears to be a compound of so hydrogen and nitrogen as well yet it's also still metallic so he took it to be a compound metal and then used that as the basis for an analogous analogical inference to say that probably all metals are compounds so like he said here in late 1889 he suggested that a phenomena perhaps might be more easily explained on the notion of nitrogen being a basis which became alkaline by combining with one portion of hydrogen and metallic by combining with the greater portion so it first forms ammonia an alkaline substance and then when ammonia combines with even more hydrogen it becomes a metal the argument then becomes you know we have this one example of a metal that has been decomposed that's evidence for all metals being compounds so he very explicitly states this in his textbook saying as far as our knowledge of the nature of compound bodies has extended an energy of properties is connected with an energy of composition so yeah kind of explicitly saying what I have been saying and then if if one of the inflammable solids or metals is proved to be compounds there would be strong evidence for supposing that the others were likewise compounded we have one compound metal all of them will be composed and so he stuck with this actually for relatively long time until about 1812-1813 and then after that gave up on the idea altogether he just stopped publishing on it he referred to ammonia in almost all of his papers during this time and then all of a sudden just did not refer to it anymore in one of his letters he said that he was deceived by the analogies and that he was resolved to trust nothing but facts so it seems that he was just like okay I give up like I don't know how to make sense of this thing no but I'm actually yeah going to do some more research on that soon to find out if something specific happened yeah it's hard to know why he just stopped but I think he just couldn't make sense of this these contradictory facts yes so I just went through like a whole series of arguments just to summarize them of what I said in the second part in one side these different arguments ammonia contains nitrogen therefore potassium soda contained nitrogen was the first argument that turned out to be false instead it was potassium soda contained oxygen therefore the inference was ammonia contains oxygen ammonia forms an amalgam therefore it has to contain metal if oxygen and the metal cannot be detected in the ammonia directly then it has to be somewhere else so probably nitrogen must be a metallic oxide and then lastly Davey's argument was ammonium is a compound of hydrogen therefore all metals are compounds of hydrogen so in all of these arguments the premise is again analogous substances are similarly composed and even though they keep running into contradictions they stick with this idea instead of just saying well it's just an exception it's remarkable to say at least and you can really see that it's disturbing to them this whole like contradiction so even though the importance I think that they attach individually to this kind of rule can vary so someone like was extremely attached to it there were other people who were willing to give you seconds and now for example in France they actually did admit that ammonia was just an exception so there was variation but despite all that I think that it can tell us something about the use of analogy in chemistry and specifically in the study of chemical composition around this time so let's talk about that in the last part so yeah what can we actually maybe learn from this case so as I see it in the literature on analogical reasoning there are kind of two main questions it's either the question of justification is this a good analogical argument or the question of the different functions of analogical reasoning in scientific practice we can talk about it more in the discussion but I will say already for now that I'm I don't think that this case is the best one to answer the first question so it's not really a question that these chemists were asking themselves they're not really discussing about like is this argument valid they're not really looking for a logical justification or a valid argument it's just a very messy situation and they're using everything that they can use in that sense I don't know if logical validity is really the the most important point here but I do think that we can use this to say something about the different functions of analogical reasoning in scientific practice also because it kind of brings all of the functions or what I would like to do is bring all of the functions together so energy has been set to help with discovery, formulate new hypotheses but also with justification yeah obviously justifying, establishing possibility with experimental design and in some cases also as complementary evidence and I think if we interpreted as kind of a guide in the process of laboratory reasoning it can sort of bring together all of these functions so what I mean by that so that's also why initially my the title I had for this presentation was the role of analogy in the process of epistemic iteration thinking about it a bit more so I still think that that could work but I actually also want to combine it with this notion of laboratory reasoning which comes from Katherine Jackson Jackson's recent book on organic chemistry in the 19th century so just to specify both of these terms iteration comes from Hassab Chang's book on the history of temperature scales and he describes the development of these scales as an iterative process through which the correct values were gradually established so at each stage corrections are made to the previous knowledge and it's not necessarily the approaching of some pre-existing correct value it's just well you know these scientists are working in a context where they just have a specific knowledge that's all they have they need to build on that to get as far as they can get and then they end up to this point where actually the things that they're finding out are contradicting their previous knowledge so they're adjusting it and they're like going through this iterative process in that sense that is similar I think to what's happening in the ammonium case where there is a certain type of knowledge available to Dave and Brasilias they build on that as best as they can then they realize that probably what they're finding is contradicting their previous knowledge and they're adjusting it every time so a similar process like I said is described by Katherine Jackson but less so the iterative aspect of it she talks about laboratory reasoning as the way in which experiments stabilize concepts and yeah basically leads to the development of new knowledge so it's kind of about the relation between experiment and theory and I think in both of these cases so the important thing is that it's a gradual process and it's a lot of just correcting things as they're going on gradually approaching something that feels coherent operational etc and I think that analogy can really play a role in these kinds of processes so kind of guiding at least in this case Dave and Brasilias guiding in which direction they could move which hypotheses might be plausible how they might adjust their previous knowledge and the analogy is not really something to my knowledge that Chang and Jackson really take into account in that process so I think in that way it might be a useful example likewise like I said so there are a lot of different ideas of how an analogy helps scientists how it facilitates research but it seems to me like often it's just the arguments are analyzed as if they're just arguments and then that's it kind of and I want to say more of like this is a whole process so everything is always functioning together with the experimental design then the interpretation of the results and then the adjustment so it's I want to sort of integrate analogical reasoning into this more process of scientific practice few rather than just analyzing them as arguments in themselves even though they can be helpful I think this might be a new way of looking at it based on the ammonium story but I would be very open to other suggestions or interpretations for you so that's kind of where I am now in this project there's still also a lot of primary research research that I want to do and then ideally for the future I would also really like to continue looking at what happens with ammonium after that once it's abandoned as a metal how it gets taken up in organic chemistry and then also as an ion in electrochemistry and then even all the way until the 20th and the 21st century it just continues to be a super surprising thing it just does not behave in a way that makes perfect sense or at least like it goes against some of the other ideas so there are still papers of does metallic ammonium exist or can we see it as a pseudo alkali metal so just leads to interesting questions I think and I actually don't know a lot about this work yet so but it's something that I would like to explore further yeah here are some references to literature that I didn't really explicitly cite and thank you so much Franklin and Brink yeah a few questions and comments do you want me to start here let's see okay just a couple of comments from Cameron Restrepo who says first the iterative process of scientific discovery has a myriological background when it starts with a hole performs an operation on it and it comes up with new holes that are now parts of the old hole it would be nice to explore the story of metallic ammonium from that kind of a perspective so that's just a comment okay thank you and the second one and maybe if you want to riff on responding to the comments well there's questions related to the last slide on slide on current chemistry on ammonia and its metallic character a classic book of inorganic chemistry in the 2000s included ammonium as an alkali metal the book is by Jeff Reiner a common descriptive inorganic chemistry okay yeah that's good yeah that's very cool um it's a good book it's a good book yeah I mean it makes a lot of sense I guess to do that and it's similar there also ammonium is not the only substance in that sense because there's also cyanogen is that how you pronounce it which is like a pseudo-hanogen but also Garrett Hamsen actually mentioned that during the talk there were some comments in the chat saying that yeah that's another case where it wasn't sometimes is considered to be halogen yeah exactly because it behaves very similarly so there just are these strange kind of compound particles that behave as if they're simple and this also has a whole history in so I'm more familiar with the 19th century part where again in the 1830s, 1840s um the idea that there could be compounds that behave as if they're elements then was reason to say well maybe all elements are the compounds because maybe they're just behaving as if they're elements but they're not simple at all uh also see the same author's book on the periodic table which looks at many unknown analogies in the periodic system descriptive and got Jeff G-O-F-F Rainer R-A-Y-N-E-R dash common C-A-N-H-A-N okay okay just noted chat thank you that's very interesting yeah that's okay for now I can look back there's some other smaller comments if we have yeah thanks that was super interesting I'm a logician so I look at that analogical reasoning from that point of view and I was wondering how they came to I mean so what kind of so this is partly the distinction between discovery and justification I guess but I would like to know to what extent these guys believed the results of their analogical reasoning or did they treat it as research hypotheses of which they were quite confident or something but did they actually believe it would they say this is true because I had this analogical reasoning by the way I'm completely I think really we should see analogical reasoning as part of a bigger process I think that's a very nice observation that I completely agree with but if you do take them apart the results that were really demanding on this analogical reasoning would you say that these guys believed in virtue of that analogical reasoning then it's hard to give one general reply to this so it depends on the individual someone like Brazilians was super super convinced that analogy was always true I guess it's not really a valid reason even to question experimental results so he was completely unwilling to admit any exceptions and just saying like well I calculated the composition of this substance based on analogy and so I know it's or like even his thing of saying I placed a man ammonium with the metals assuming that everyone will see that I'm right and he was also the last person to admit that chlorine was an element or one of the last he was very very attached to this kind of general rules someone like Davey is just really hard to know because something that he said in 18.7 will be completely different or like his views fundamental views of nature and elements and matter they completely changed it just very he will say like anything and the contrary within one article so it's hard to know what is actually his belief or like how and that was also really hard to kind of establish this chronology of what is he even thinking because he just says a lot of stuff but in general I think it just seems very very plausible to them and that could be said for most of the 19th century for as far as I know and probably even before then also maybe also after that I don't know but yeah this rule of an analogy being correlated to composition comes back all the time and there are for example a lot of discoveries that are established based on them also in mineral analysis metals that were identified that were never isolated but everyone was accepting them anyway because it just yeah worked really well really often and that's reason enough to think that it will probably also work this time so that's my understanding so and nowadays chemistry do you think there are still parts of it that's where are most likely beliefs are actually just based on a lot of general reasoning I think so yeah yeah I mean I'm not really deep into the current chemical literature but I have met probably no more about this I mean I have met people at conferences for example who were working on completely like current day chemical questions where they still yeah they still search for analogs or they do this completely analogical reasoning if I could just help when I did the research of the paper you kindly remind that I wrote on an analogy it's not in the paper but I did that research and they're sociologists of science that study how people discuss in lab the lab meeting about the next experiment and in biochemistry at least they do analogy all the time most planning of new oh we should we know that we should do that why because it looks like this it's like that but they use the techniques but this are like common knowledge and chemistry based on it that's your job I don't know but analogical reasoning is used all the time I still wanted to push it a little bit but I don't know if it's an energy field cosmology of relation between level is analogical in chemistry a direct follow-up coming from Guillermo it's also of course the center of all the current machine learning and AI in chemistry are all analogy based as well so I I've got two I'm going to first I have one from online and then I'm going to ask but I have we're getting Gary we're kind of riffing on each other it gets sort of simultaneous discovery in the comments so first if you want to say I want to comment on the fact that from the historiographical point of view your study of ammonia demonstrates how the chemical the chemical reasoning in this at this time is still deeply pre-levelized the oxygen or hydrogen tightly contained within nitrogen is a very caloric kind of argument isn't it and simultaneously Gary was typing in the chat Lavoisy is partly responsible for this this oxygen was a principle not an element and so that's kind of there are none that pre-levelized I think so it was very impressive yeah I mean but she falls up and says you know on one perspective you mentioned for further research on this fascinating topic or a topic that you may be fascinating again do you intend to also look at the practice sorry which practice is that actually I am not entirely positive and how which practice practice is surrounding worse research on ammonia perhaps there's like a 10 second delay so we'll take her a moment to okay yeah in that sense I can already maybe comment on the pre-levelized so yeah firstly Lavoisy himself was very bad Lavoisy and in that sense I think a lot of the people in the 19th century were like Lavoisy because they were still yeah also making a lot of exceptions dealing with a lot of so Lavoisy's definition is really good, really simple and gives a clear criterion seemingly but in practice it's just more complicated so they were making these distinctions not all indecomposable substances are elements and I think for Lavoisy that was also the case I have the second half of the question now I hadn't come in when I first saw it so practice in the sense that how mere manipulation of substances in the laboratory might seem to rest on a very primitive kind of technological reasoning that's slightly different from the philosophically pure concept of analogy so many different senses of analogy a practical one and a theoretical one yes yeah so a lot of this I have been kind of wondering also to how to make sense of it sometimes because I think so all of these chemists very clearly use the term analogy and throughout the most of the things that I've looked at in the most first half of the 19th century but it's what they mean by it and what they mean by similarity is changing and depending on the stuff that they are able to actually do with these substances and then on top of that a lot of it is also tacit knowledge almost or qualitative like embodied so in the mineral chemistry work a lot of them will just say oh it's so obviously analogous to this other substance and they don't specify it's just anyone who's dealing with these two substances will see or will feel or will sometimes even smell that they are analogous but it's hard to really characterize that as a like clearly defined sort of account of what an analogy is it's just it's very it's just very obvious to the people who are dealing with the actual substances but not so much a very explicit account of like here is my argument this and this are the explicit like the positive similarities therefore I deduce that and that is just yeah so a lot of it is I think I necessarily have to do with a lot of this more practice stuff because that's just what's happened like that's the only way that I can study these arguments so I hope that yeah that's an answer to the question then I have one of my own so for someone who I know a bit of the 19th century stuff but most of my chemistry knowledge is from high school college my gut reaction to this I just wonder if anybody at the same time had the same reaction so from a contemporary perspective you look at that experiment and you go oh yeah of course they teach us that I feel like I was taught this in whatever 11th grade chemistry class mercury is weird amalgamation is super strange and so was anybody did any what was the thoughts at the time about if you will picking up the problem from the other end from the mercury end instead of from the ammonium end because from a like I said from a 2024 perspective like that would be like my gut reaction would be yeah mercury is really weird like it does really strange stuff when you mix it with things so what was the thinking on mercury in this period um so at least arguments that I know from that side are that even if mercury is weird it doesn't form amalgams with non-metals otherwise if you look at other examples like um cinnabar I think yeah it's not metallic or like yeah that's like one of the examples that it comes up a lot which is a compound of mercury with a non-metal I want to say sulfur but I'm not 100% sure but like with the other like as they would say inflammable bodies or metallic substances it doesn't form um these amalgams um so in that sense it had been pretty useful as a test yeah and even then also I think at least for Davey and Brasilius the argument of it's just really weird was kind of unsatisfactory because like I said it's another exception it's just oh this substance doesn't do what we want but then but how like that that's just not acceptable so because they could have also said well ammonia is just really weird and I mean it kind of is but that's not really an explanation of what's really happening in the sense that they were looking for I think um because yeah so gain a second scenario the only ones that say we just have to accept that it's not doing any of the stuff that substances are usually doing it's very weird um and that's it but I think I don't know I also have some like maybe more historical arguments about why they specifically were willing to accept it in that way like it's it's it's hard to always know why people are doing things of course but they were also in different contexts Bertolet who was the one of the people who first colonized ammonia and showed that it was a compound of nitrogen hydrogen was like more or less their direct superior so it I don't know to me also seems like risky to question his previous analysis of the substance things like that yeah maybe they also just had different styles or yeah um but even from today's perspective I for as far as I know this is this is really exceptional that you can make this exceptional enough so that people are still doing it and still citing it in course textbooks and things like that yeah it is really cool or at least I don't know okay so there's the thank you it's a very interesting talking really you found a case where you use an allergy after the other all the time but in your talk it was not clear to me the difference when they are conscious to use an analogy so the square this is to this this is to this and it seems to very strong guiding principle correlation between behavior and composition because they could use analogy without that without this principle they could use this principle and develop it without analogy so what is the why do they believe that composition and behavior are so correlated at that time because they don't have an atomic notion yet they have why do they think that this principle it seems to be a guiding principle beyond analogy why do they think it's probably true um yeah I've wondered about this and my sort of hypothesis is that maybe it becomes a kind of goal in itself in order to be able to explain chemical reactions or explain properties on the basis of composition this correlation needs to be there because otherwise there can't really be an explanation so that expresses itself in different ways for different people again but for Brazilis for example his goal during this time was to really establish a system where the properties of substances can be explained based on their composition so this and then specifically in relation to oxygen which for him was a really central substance element so depending on if something is protexide or dioxide or trioxide or how much oxygen it contains that will modify its properties and then based on the element that is combined with the oxygen the properties are modified so he really tried to establish this system where he could correlate or at least have a kind of general system for yeah explaining properties on the basis or at least correlating them in a way probably for teaching I don't want to misinterpret you because at the beginning of the answer you almost said something like it's almost a transcendental principle because they needed to build that new science so if they believe it was false they would not even begin to do that kind of practice they are doing so they presume it's true on the other hand they would like to know for real is it something like that because that's much more than as a Chang approach it's really a fundamental principle that if it's not true or most of your time we would not engage in this scientific practice at all we would do something else and try to become both stuff on the other hand probably they don't have much data to be sure it's true which is interesting at that time yeah and there's no explanation really for why I spoke about this analogy between the micro world and the macro world probably they don't believe it anymore in the middle ages they would be quite comfortable with that of course there's a structural and there's correlation between the micro and the micro so it must work but do they share that I spoke not that's plus Newton plus yeah for as far as I know not really yeah so there at least I know of one paper that's from different context of 1840s a chemist who completely was working just on mineral analysis of any theoretical stuff let's say just very concrete questions of how is this mineral composed was this minerals composition show identifying chemical formula from beginning to end all his papers are just that and then he has one paper where he makes one very short remark on some theoretical system of atomic weights and he just says it has to conform to the fundamental rule of chemistry that similar bodies are composed similarly and he doesn't comment on it at all but that was one of the papers where I really thought oh okay so decades later this is first of all still there and then second of all seen as just a rule like it that has to be the fundamental principle of chemistry and but yeah for these earlier years it a lot of it is still so they're still really setting things up I think in terms of chemistry and how does it work what are the what is the fundamental rule of chemistry really like it's not so clear I think always but yeah it's I have to think about it it's a really good I want to insist the case you presented it seems pretty clear it's a powerful principle so they seem convinced maybe it's not absolutely true but we use it like it was so it must be follows on exactly this point from online actually this is like the most active chat I think ever in seminar history so bravo both you and everyone but so I just roll back up to get it all hang on so first and this is all been unfolding during this discussion so so so again by saying the interplay between experiment and analogy is nicely exemplified by the expansion of the chemical space there are results showing that hydrogen was similar to alkali metals in the early years the 19th century but then with the surge of organic chemistry it becomes more like the halogens and then Gary adds well then of course it plays all kinds of chemical roles at high pressures and temperatures it's a metal and then Brigitte adds because they still live in this is because they still live in the conception of principles as bearers of properties that these principles carry into the composition in other words being inflammable is explained by the presence of a principle of inflammability we've disconnected simple substances from principles and bearers of properties but that comes back in organic chemistry later on so maybe that's a helpful that gets right at these kinds of questions about where the what's doing the causal power in here what's is it just what's this connection between this ability to do things yeah for Davey there's definitely at least so perseus I have to say I'm not so sure how he feels about this principle idea but maybe it does yeah I have to say I don't know that much about the organic context but for Davey it's sure that that's one of the things that he's really thinking about at least until but again like I said earlier like his views really really changed her also during this period so at first he was really looking for principles the principle of alkalinity at first it would be nitrogen and then that turns out to be probably oxygen which then is the principle of both acidity and alkalinity then he has this idea of hydrogen as the principle of metals metallic nature in sort of phlogiston like reasoning so he was really really thinking about it that way as a causal relation between composition and properties but I don't know if it would work the same way since he had this really complex system where oxygen I don't know that also is really complex there's definitely a lot of principle like thinking going on still in the 19th century even though they don't they don't like to explicitly say that that's what they're doing but it comes up you already showed it very clearly with Davey okay thanks for all these remarks this is really super helpful different question I guess when you talk about this belief between composition and properties would you say that this is still like present today modern philosophers they believe that there is at least correlation between composition and properties of substances that seems like a safe assumption yeah I think composition became a lot more complicated as a concept over the course of the 19th century because now there's things like molecular structure yeah okay so if we take this into account I was just thinking about platinum and D 2 in earth experiments with the water H2O and XYZ and then we have philosophers that have this you know intuition apparently yeah that's completely fine that we have these two substances with completely the same superficial properties but completely different microstructure and then I read like a philosopher of chemistry he said this is just insane it's just complete pure fantasy so I was just wondering as a philosopher of chemistry in these circles what do they think about the thought experiments like that you know examples yeah I think most would agree that it doesn't really work for at least the twin earth like yeah I guess it will be interesting also to hear like the chat anyway a few on this but I mean for me it's kind of inconceivable to just imagine that there would be a substance that behaves the same as water and it doesn't have the same composition because that composition is established based on its chemical behavior that's how we know that it's composed that way so how like I just don't really understand how it's possible yeah with ammonia we have like just some properties you know that obviously shares with scientists correctly and even that's like you know what's going on here right if we actually had two substances that were completely different and had all of their properties the same that would be like an insane scientific factor I mean but superficially heavy water and water behave almost the same come superficially heavy water and water they're pretty close you know physically difference but chemically pretty close yeah but they're composed of the same elements I mean I guess we get this yeah yeah because if I would include in behavior things like if I electrolyze it it produces hydrogen and oxygen that's part of chemical behavior or if I I don't know so the distinction is okay so the distinction is between chemical properties and physical one it's what seems to aim at yes but heavy water is physically different than water but chemically really really close so it depends what you mean by composition like the putnam example yeah but then again I mean it's close but it's not the same oh it's not the same as the putnam example yeah but it always seems you have a neutral and more the small differences always somehow translate to the larger differences that wasn't the case scientists would be really baffled if this happens that you have just some small differences on the physical or chemical level there are no differences up there it would be like what's happening something's not right but just based on already the fact that the knowledge of the microscopic comes from the microscopic just his story so it's I find it a it microscopically it's different but it doesn't mean then how do we know it's microscopically different I don't know maybe that's a yeah that's how I thought kind of reading about this water example yeah so I guess I agree with you probably on this point yeah another question so you analyze all these things as analogical arguments and that makes a lot of sense obviously but the focus on exceptions towards the end makes me think that they could maybe also be read as induction arguments because all these the reasons why they become problematic is it all has to do with some kind of uniformity which is typically what justifies induction arguments and I'm not even sure what you can make a real distinction between induction and an analogy but I wonder whether these cases you were open to analyze them otherwise or whether they are really like clear analogy arguments and you can't read it otherwise I think they can be seen as induction arguments but yeah, analogies also a kind of induction right or at least the distinction is not always to some extent I guess it depends on author to author how we just agreed about that once how it is because analogy for me is an inductive reasoning what you call induction is the generalization everything is blah blah blah which is a cabinet for me that's an inductive reasoning also it's the special cases of a general category and we disagree about that but it's true it's not obvious because I like your question there's a uniformity principle hidden in the reasoning of Davey and all these guys that that looks like a generalization it's a strong attachment that seems to be the idea of a world that's uniform and that's the last thing we want to give up while I guess you can apply an analogy arguments also in a non uniform world especially if it's just a guide in research if you really want to have your beliefs based on it the world better be uniform I guess but if it's just like oh we want to have a model for this other situation then we can start from this first thing that we already know very well and analyze this and then maybe get carried out over the properties to this other thing even if there is no metaphysical basis to assume that they have anything in common just like they might have something in common and gives us tools to study this stuff and so that's also I guess the origin of my first question that seems to be a very big difference if you just say well let's test let's just like let a thousand flowers bloom or how do you say that and let's use it as a way to give us tools to analyze new stuff and to find new hypotheses or when you really say I use this as a basis for my beliefs you need much more uniformity and so on I don't know this is not much of a question yeah but it's a good point yes I think so a lot of it is yeah could be reforminated as substance A is part of this and this kind this and this kind has that composition therefore substance A has this composition but I do think later on so first of all I mean they themselves use the word analogy a lot which is how I took this as an analogy in part but also in later forms it doesn't always pass through the kind formation so there's when there are crystal shapes for example then there's a lot of comparison these crystals have the same shape therefore they have analogous composition and then it's not necessarily something of passing through therefore they are of the same kind of it's really just well we observe that usually crystals like I guess there is an explanation in terms of atoms I guess later on but even yeah we observe that usually crystals that have the same shapes have the same composition therefore once you have two crystals with the same shape you can infer the composition so I don't know yeah I guess it's not really a reply I'm just thinking at last yeah but it's a good point but then again some people also argue that all analogical inferences can be reforminated as induction so that's the point on the media I know that I'm but willing to accept it but there seems to be interesting differences if it comes to a scientific method because all of science is based on induction and analogies typically seen as more suspicious or something we have these very good statistical tools for doing induction about kind of general induction while analogies it's more not to finger work but to say I'm sorry for the exception I couldn't translate that wet finger work is still translation people use their intuitions to do analogies while we have very good inductive tools so that's why I like to make a distinction even if you can read analyze phenomena in many ways of course yes one more round from online Rujides, can you spot a difference between decomposing a mineral and a chemical compound because analogimation analogies could as well not be seen as chemical reactions apparently that was seen as chemical reaction at the time but could there be different sorts of decomposition between a mineral and a compound and analogimation would then fall under a compound so yes I do see a difference but actually I wouldn't place the difference at the decomposition part it's just that more in terms of like analysis so analysis or what is generally referred to as analysis of compounds in general around this time so the beginning of the 19th century was very often decomposing things and then recomposing them using things like electricity using things like sparks to burn substances or all these kind of any means that could be used to decompose mineral substances specifically were often studied with this specific set of tools that that's now known as classical analysis in the case of ammonia the amalgam for me would fit in the compounds section but I don't know maybe could you read the question because I'm not sure I 100% understood that sorry the second because amalgamation could as well not be seen as chemical reaction apparently it was seen as chemical reaction at that time okay so here I have to say I don't know about the views of amalgamation in general here specifically the practice was to produce an amalgam from a compound so it is in itself already kind of decomposition in that sense for example if you produce an amalgam of potash then it's only the potassium entering sort of in the amalgam so it requires the reaction altogether is a decomposition of potash after which or during which potash then combines with the mercury and then you can evaporate away the mercury and leave behind potassium so in that sense it would be a chemical reaction maybe that's right so here the idea would be or a mixture or a mixture of the metals but you would need to decompose potash also so that's the chemical reaction I think okay the question of Peter another question so the analogy you showed us is A to B what C is to D which is the classical analogy and usually it's related to a certain conception of new formative nature or relation between level and nature but did you see in your literature an analogy of like you were describing structural analogy I have some model, some relation between stuff here maybe it's more than two and I project on the target because this analogy to my knowledge appeared in physics later and I would be very curious to see if Ken has invented it before the structural analogy historian says it's Lord Kelvin that invented if made an analogy between electromagnetic phenomenon and heat phenomenon saying it's different but it's related to the same therefore you can project an equation there on this field and it will work which is A to D much more complicated what is C to D is there more complex analogy and I'm always mostly A to D what is C to D it would be it would be cool that a chemist invented before physicists because they are really proud of that I think there isn't it's all very just A to B is C to D there's no I can't think of any example that's more but it's possible because they believe some principle of uniformity or analogy in nature that justify the specific form of arguments that's possible that's why they have so much confidence in it and especially this kind of I guess mathematical or formal analogy that's not happening at all it's all just properties yeah you should probably need to go at some point we have one week true so it's a social since we had a historian and not a philosopher I can ask a social historian so I know that the Napoleonic War were important at that time for the Karyon, Fridaides and all these guys and it's mysterious that your debate is 1807 to 1830 is there some influence of the war on the debate about Imonia an external effect not that I know of or at least not really the one you would expect so Davey was actually really a Francophile so in good relation with Napoleon almost himself so he was invited to France he received a prize from Napoleon for his work with the battery he was also the inspiration to build a battery in Paris so yes, it wouldn't at least be something of the British versus the French but there is, I am wondering if there's not something because Gailesac and him were just having debates all the time about everything they disagreed about everything and even in the textbook of Gailesac and Ténare from 1811 so in French they have a whole table that goes on for multiple pages where they list their own views in opposition to Davey's views we think this, Davey thinks that we think this, Davey thinks that and then rarely but sometimes you find actually here we agree and then they go on so there's something but I think they were kind of as you would say today frenemies like happy to debate each other all the time because there had to be some kind of benefit or something yeah at least in presenting it that obviously in a textbook it seems surprising to me yeah and so they also agreed on ammonia disagreed sorry on the nature of ammonia and on the discovery of iodine and on a lot of things but yeah that's the only sort of Franco-English thing that I found even though Davey was also invited into their own group in Arcaille like doing discussing with them for example what was the debate of ammonia in the British not Davey because maybe the fact that Davey was considered almost a traitor to go to get that class physically crossing the channel during the war it doesn't create inside of a society something where this subject oh it's Davey so it must be wrong or we don't work on that there I'm not so sure I only know of Thompson Thompson mostly agreed with Davey he was really also convinced by this analogy and the other the other things I found were kind of where it's just stated that it's a debate it's like some people think this and other people think that and we don't really know I have a hard time finding kind of an expression of what the chemical community was thinking or even in England it's hard to actually know for sure yeah but one one sort of concrete influence was that sometimes it was difficult to get correspondence across actually mostly with France like at the beginning Brazilians and Bertonew and they were writing to each other sometimes you really see in the ledgers that they tried to send things which didn't go through and they had difficulty getting information across yeah maybe just a quick question on a little a little analogy I guess you mentioned at some point but I think you want to mention one is that relevant similarities did they ever discuss you know which similarities are actually relevant or not because you could make the case that everything is similar to everything so was this ever part of the discussion and kind of costier I guess yes but strangely not of the same in the same places so there was generally either discussion on classification or discussion on the composition of a specific substance but then they wouldn't in the cases that I've studied they wouldn't question the relevance of the similarities of the substances that they were working on maybe it's possible that I've looked at cases where that were very consensual things like the alkalis those are never questioned in these debates it's never like no one for example says maybe ammonia is not an alkaline or maybe just the similarities that we see are actually not that relevant at all but there are in at the same time debates going on about how should chemical classification be organized for example one approach was to only focus on the reaction that an element specifically would have with oxygen to organize families on the basis of is it inflammable is it acidifiable by through oxygen or is it like non-reactive with oxygen just kind of just this one property was seen as extremely relevant by one camp and then others were criticizing this approach and saying actually you're just reducing it down to the super artificial characteristic and you should take into account all the analogies between these substances like the actually relevant similarities so this was a debate yeah definitely in the most in with regards to teaching how to represent all of this in textbooks because I mentioned the oxygen classification thing were they aware I mean they explicitly say okay this is like for pragmatic purposes or okay yeah it was it was literally called artificial classification or maybe that was also kind of a criticism point but out of sort of yeah pragmatic purposes of like sometimes we just don't there's so much information to take into account that we'll just take oxygen oxygen was also very important substance for a lot of views of a composition because the debate is also like similar to the debate in biology for classification in classification and then classification now and you also have like these competing systems where it's not clear whether you know they're all equally valid or not yeah well this is the same period so this is where we're all busy fighting about what classifications are natural and what classifications are artificial this is like a huge preoccupation of this whole early 19th so I mean it's not surprising that it's I'm not stunned at all that it shows in chemistry too yeah yeah the natural yeah yeah definitely yeah but in a different or at least in different so same people with different publications than the ones actually study conversation so maybe if I can just one short question to this discussion the one thing that struck me during the talk and I wonder what would happen historically is when you present the case I mean the fact that you get this amalgam is you know I can see how strongly evidence this must have been for them to claim that ammonia must contain a metal what makes the case interesting is the fact that they knew ammonia only contained hydrogen and hydrogen but what I missed was was some quantitative reasoning because it's stronger than that if you start from 100 grams of ammonia and you decompose it you will end up with 100 grams of hydrogen and hydrogen there simply is no room for any metal to be present in ammonia unless of course you argue that well no it's the nitrogen and hydrogen themselves that are composed of a metal and then whatever else but that seems to be something they were willing to entertain but that seemed to come much later into this whole debate whereas at first they seemed to be perfectly willing to accept the presence of an unknown metal in ammonia even though quantitatively there was no room so did these quantitative reasoning lay any role in those discussions where they pushed aside I mean yeah I'm wondering yeah it's a really good question I can only see yes the importance of that so yes but also there it's at least at the time was slightly easier said than done so the first reaction of Davey was he first said ok there's probably oxygen in ammonia the first reaction was to look at the quantitative stuff and to look for discrepancies there he found that actually in his analysis one eleventh of ammonia was unaccounted for and then he said oh that's probably oxygen one eleventh ok that's where at least the oxygen would fit in and relatively soon when it couldn't be detected was or isolated so first reaction was ok we have this amalgam usually from an amalgam you can relatively easily isolate the two metals because mercury evaporates quite easily they tried that, didn't work couldn't isolate it any other way so then it must be in these other elements there was also another type of experiment where Davey was convinced that he had decomposed nitrogen for a while because he had made a compound from ammonia and potassium and then decomposed the compound and the weight relations were off so there is a different a whole explanation for why that was so he was looking at these things but actually really often it's difficult so yes it is a really important factor but it's difficult from the weights alone to know which substances are actually simple because a lot of different explanations are still possible even even when you have the conservation of weights but yeah but it's totally completely true that they were they were looking for quantities of things because you can just add another constituent and then it doesn't work so it all had to fit together yeah