Chemistry

"In the time of Lavoisier, and preeminently through his exertions, this vague and unmeasurable principle phlogiston was eliminated from the laboratory and the textbooks: quantities took the place of indefinable qualities, and numerical determinations increased in frequency and accuracy. The vague phlogistic theory, which contained a germ of truth, but one which at that time could not be put into definite terms, had helped to gather up many valuable facts and observations: these were collected and restated in a new and precise language. It has been said that every science must pass through three periods of development. The first is that of presentiment, or faith; the second is that of sophistry; and the third is that of sober research."

"Even before the appearance of The Sceptical Chemist there was a growing conviction that the old hypotheses as to the essential nature of matter were inadequate and misleading. ...[T]he four "elements" of the Peripatetics had become merged into the tria prima—the "salt," "sulphur," and "mercury"—of the Paracelsians. As the phenomena of chemical action became better known... the conception of the tria prinui, as understood by Paracelsus and his followers, was incapable of being generalised into a theory of chemistry. Becher, while clinging to the conception of three primordial substances as making up all forms of matter, changed the qualities hitherto associated with them. According to the new theory, all matter was composed of a mercurial, a vitreous, and a combustible substance or principle, in varying proportions, depending upon the nature of the particular form of matter. When a body was burnt or a metal calcined, the combustible substance—the terra pinguis of Becher—escaped."

"This attempt to connect the phenomena of combustion and calcination with the general phenomena of chemistry was still further developed by Stahl, and was eventually extended into a comprehensive theory of chemistry, which was fairly satisfactory so long as no effort was made to test its sufficiency by an appeal to the balance."

"The theory of phlogiston was originally broached as a theory of combustion. According to this theory, bodies such as coal, charcoal, wood, oil, fat, etc., burn because they contain a combustible principle, which was assumed to be a material substance and uniform in character. This substance was known as phlogiston."

"All combustible bodies were to be regarded... as compounds, one of their constituents being phlogiston: their different natures depended partly upon the proportion of phlogiston they contain, and partly upon the nature and amount of their other constituents."

"A body, when burning, was parting with its phlogiston; and all the phenomena of combustion—the flame, heat, and light—were caused by the violence of the expulsion of that substance."

"Certain metals—as, for example, —could be caused to burn, and thereby to yield earthy substances, sometimes white in colour, at other times variously coloured. These earthy substances were called calces, from their general resemblance to lime."

"Respiration is a kind of combustion whereby the temperature of the body is maintained. It consists simply in the transference of the phlogiston of the body to the air. If we attempt to breathe in a confined space, the air becomes eventually saturated with the phlogiston, and respiration stops."

"The colour of a substance is connected with the amount of phlogiston it contains. Thus, when lead is heated, it yields a yellow substance (); when still further heated, it yields a red substance (red lead). These differences in colour were supposed to depend upon the varying amount of phlogiston expelled."

"The doctrine of phlogiston was embraced by nearly all Stahl's German contemporaries, notably by Marggraf, Neumann, Eller, and [Johann Heinrich] Pott. It spread into Sweden, and was accepted by Bergman and Scheele; into France, where it was taught by Duhamel, Rouelle, and Macquer; and into Great Britain, where its most influential supporters were Priestley and Cavendish. It continued to be the orthodox faith until the last quarter of the eighteenth century, when, after the discovery of oxygen, it was overturned by Lavoisier."

"During the sway of phlogiston chemistry made many notable advances... in spite of it. ...[U]ntil the time of Lavoisier few if any investigations were made with the express intention of testing it, or of establishing its sufficiency. When new phenomena were observed the attempt was no doubt made to explain them by its aid, frequently with no satisfactory result. Indeed, even in the time of Stahl facts were known which it was difficult or impossible to reconcile with his doctrine; but these were either ignored, or their true import explained away."

"It is commonly stated that the exception is a proof of the rule. The history of science can show many instances whereby the rule has been demolished by the exception. Little facts have killed big "theories, even as a pebble has slain a giant. During the reign of phlogiston a few of such facts were not unknown at least to some of the better informed of Stahl's followers."

"Some of the alchemists had discovered that a metal gained, not lost, weight by . This was known as far back as the sixteenth century. It had been pointed out by Cardan and by Libavius. Sulzbach showed that such was the case with mercury. Boyle proved it in the case of tin, and Rey in that of lead. Moreover, as knowledge increased it became certain that Stahl's original conception of the principle of combustion as a ponderable substance he imagined, with Becher, that it was of the nature of an earth was not tenable. The later phlogistians were disposed to regard it as probably identical with . But even hydrogen has weight, and facts seemed to require that phlogiston, if it existed at all, should be devoid of weight."

"Towards the latter half of the eighteenth century clearer views began to be held concerning the relations of atmospheric air to the phenomena of combustion and of calcination; many half-forgotten facts relating to these phenomena were recalled, and the inconsistencies and insufficiency of phlogiston as a dogma became gradually manifest. Three cardinal facts conspired to bring about its overthrow—the isolation of oxygen by Priestley; the recognition by him of the nature of atmospheric air, and of the fact that one of its constituents is oxygen; and, lastly, the discovery by Cavendish that water is a compound, and that its constituents are oxygen and . The significance of these facts was first clearly grasped by Lavoisier, and to him is due the credit of their true interpretation. By reasoning and experiment he proved conclusively that all ordinary phenomena of burning are so many instances of the combination of the oxygen of the air with the combustible substance; that calcination is a process of combination of the oxygen in the air with the metal, which thereby increases in weight by the amount of oxygen combined. Water no longer a simple substance is formed by the union, weight for weight, of oxygen and hydrogen. ...The phlogiston myth was thus exploded."

"Inspired by Lavoisier, a small band of French chemists Berthollet, Fourcroy, Guyton de Morveau thereupon set to work to remodel the system of chemistry and to recast its nomenclature so as to eliminate all reference to phlogiston. The very names "oxygen," "hydrogen," "nitrogen," corresponding respectively to the "dephlogisticated air," "phlogiston," and "phlogisticated air" of Priestley, were coined by the new French school."

"For a time le principe oxygine was regarded by this school in much the same relation as phlogiston was regarded by Stahl and his followers. The one fetich was exchanged for the other. The combustible principle—phlogiston—was renounced for the acidifying principle—oxygen. The new chemistry for a time centred itself round oxygen, just as the old chemistry had centred itself round phlogiston. The views of the French school met with no immediate acceptance in Germany, the home of phlogistonism, or in Sweden or England, possibly owing, to some extent, to national prejudices. The spirit of revolution, even although it might be an intellectual revolution, had not extended to these countries. Priestley, Cavendish, and Scheele could not be induced to accept the new doctrine. It was, however, accepted by Black, and its principles taught by him in Edinburgh; and before the end of the century it had practically supplanted phlogistonism in this country. Some of those who, like Kirwan, had energetically opposed the new theory ended by enthusiastically embracing it. Its introduction into Germany was mainly due to the influence of Klaproth."

"“There’s been a fair amount of work done in both the U.S. and Canada as well as Europe that documents [pharmaceuticals] in wastewater and in water,” says Joanna Wilson, a biologist at McMaster University in Ontario, Canada. She studies how drugs in the water affect zebrafish, a tiny freshwater fish in the minnow family. More recent data shows that the same types of compounds are in drinking water. One study found several pharmaceuticals in treated tap water, including atenolol (a beta-blocker), carbamazepine (an anticonvulsant), gemfibrozil (an antilipidemic), meprobamate (an antianxiety medication), and phenytoin (an anticonvulsant). The concentrations of these compounds were very low, usually less than 10 nanograms per liter, which is parts per trillion. For reference, one part per trillion is equivalent to about one second in 64 years. “We have an aging demographic, and we have an increased reliance, in North America and Europe in particular, with the treatment of health concerns with pharmaceuticals.” This translates to more medicines making their way into the water system, and we need to determine how to deal with it, she says. “Long-term exposures [to pharmaceuticals] are quite a bit different than short term exposures, and we need to really start testing and figuring out if chronic exposures of low doses are relevant for the health of an individual or population of animals.”"

"“There really have been no studies that have associated the [pharmaceutical] residues in our water with human health problems,” says Ilene Ruhoy, a pediatric neurologist and environmental toxicologist who has studied the issue. That could be a sign that they pose no threat, but like Wilson, Ruhoy stresses how difficult it is to do these types of studies. “You’re talking about exposure to parts per million, parts per billion. And it’s a combination of drugs. It’s not just one drug in the water, it’s multitudes of. It’s exposure to these very, very minute amounts of these drugs, but many drugs over decades—ten, 20, 30, 40, 50, 60 years.”"

"In 1991, Landsat captured the devastating environmental consequences of war. As Iraqi forces withdrew from Kuwait, they set fire to over 650 oil wells and damaged almost 75 more, which then spewed crude oil across the desert and into the Persian Gulf. Fires burned for ten months. According to a 2009 study published in Disaster Prevention and Management, firefighting crews from ten countries, part of a response team that comprised approximately 11,450 workers from 38 countries, used familiar and also never-before-tested technologies to put out the fires. When the last one was extinguished in November, about 300 lakes of oil remained, as well as a layer of soot and oil that fell out of the sky and mixed with sand and gravel to form 'tarcrete' across 5 percent of Kuwait's landscape. An estimated one to 1.5 billion barrels of oil were released into the environment. After most burned, 25 to 40 million barrels ended up spread across the desert and 11 million barrels in the Persian Gulf, according to a 2012 paper published in Remote Sensing of Environment. For comparison, the 2010 Deepwater Horizon spill into the Gulf of Mexico is estimated to have released nearly 5 million barrels of oil. Kuwait's landscape has recovered somewhat. Clean up efforts have removed 21 million barrels of oil from the desert, but an estimated 1 million barrels still remain."

"If we some day choke on the pollution of our own air, there will be little consolation in leaving behind a dying continent ringed with steel."

"The lower spheres are so polluted that one could say without exaggeration that meteoric dust is being oxidized because of the chemical reactions of psychic energy, which first of all act upon metals… Of course, the pollution of the spheres closest to our planet is disastrous. The lower subtle bodies loiter about like swindlers at a bazaar and thereby prevent the successful formation of a spiral of constructive effort. One has to harbor a special aspiration in order to penetrate beyond the bounds of these dreadful deposits. So we should not believe that there might be thoughts without consequences; even the largest cup can be overfilled! This especially applies to rotation, when gravity holds back many particles of lighter weight. So when We speak about the vital need to purify psychic energy through refinement of thought, We have in mind the purification of the lower spheres. To borrow the language of the Church, it is necessary to conquer the infernal hordes."

"Wildfires, heat domes, hurricanes, and extreme weather events are hard to ignore; yet, much to the consternation of environmental activists, a significant segment of the population continues to deny anthropogenic global warming. Even among environmental advocates, there is often a tendency to view the rise in diseases such as cancer, Parkinson’s disease, and heart, liver, and kidney diseases—along with neurological disorders—as merely bad luck or the result of poor genetics. The difficulty in definitively linking these disorders to the increasing presence of chemical toxins and microplastics allows agrochemical, petrochemical, and pharmaceutical companies to continue their practices without accountability. The industrial use of glyphosate and other pesticides, PFAS, heavy metals, dioxins, phthalates, and VOCs continues to accumulate in our environment, creating an ever more toxic planet. Bioaccumulation may be the most dangerous term that people either don’t understand or don’t know. Every person and organism has physiological thresholds for warding off viruses, bacteria, and chemical toxins, which, when exceeded, can lead to illness, disease, or even death. Much to the delight of chemical companies, the greatest threats to our biosphere—chemical toxins and waste—often go unnoticed."

"Continued unrestricted testing by the nuclear powers, joined in time by other nations which may be less adept in limiting pollution, will increasingly contaminate the air that all of us must breathe. Even then, the number of children and grandchildren with cancer in their bones, with leukemia in their blood, or with poison in their lungs might seem statistically small to some, in comparison with natural health hazards. But this is not a natural health hazard -- and it is not a statistical issue. The loss of even one human life, or the malformation of even one baby -- who may be born long after we are gone -- should be of concern to us all. Our children and grandchildren are not merely statistics toward which we can be indifferent."

"The fact that both human sperm count and insect biomass are estimated to be declining at about 2 percent per year may be just a numerical coincidence. Nevertheless, it’s a number that should grab our attention. [...] Unless the chemical load on the environment is radically reduced, and soon, the stakes may be existential. If sexually reproducing animals, including humans, lose the ability to yield offspring, then in the future the biosphere may host a radically reduced roster of higher life forms. Meanwhile, the public should be warned more explicitly and urgently about the perils of chemical exposure, and provided with information about the products most likely implicated. With regard to climate change one often hears the refrain, “We don’t need to ‘save the planet’; the Earth will be fine, it’s just humans that will suffer.” In reality, some environmental trends now in motion, including the widespread release of endocrine-disrupting chemicals, are imperiling all of nature. Are rubber duckies and other plastic crap, overly manicured lawns, throw-away packaging material, and cheap cookware really worth that level of risk?"

"Plastic pollution in the form of small particles (diameter less than 5 mm)—termed "microplastic"—has been observed in many parts of the world ocean. They are known to interact with biota on the individual level, e.g. through ingestion, but their population-level impacts are largely unknown. One potential mechanism for microplastic-induced alteration of pelagic ecosystems is through the introduction of hard-substrate habitat to ecosystems where it is naturally rare. Here, we show that microplastic concentrations in the North Pacific Subtropical Gyre (NPSG) have increased by two orders of magnitude in the past four decades, and that this increase has released the pelagic insect Halobates sericeus from substrate limitation for oviposition. High concentrations of microplastic in the NPSG resulted in a positive correlation between H. sericeus and microplastic, and an overall increase in H. sericeus egg densities. Predation on H. sericeus eggs and recent hatchlings may facilitate the transfer of energy between pelagic- and substrate-associated assemblages. The dynamics of hard-substrate-associated organisms may be important to understanding the ecological impacts of oceanic microplastic pollution."

"Pollution is nothing but resources we're not harvesting. We allow them to disperse because we've been ignorant of their value. But if we got onto a planning planning basis, the government could trap pollutants in the stacks and spillages and get back more money than this would cost out of the stockpiled chemistries they'd be collecting."

"Mr. President, I find it encouraging that you are proposing an initiative for reducing air pollution. Accepting the urgency, it seems clear to me also that climate change is a problem which can no longer be left to a future generation."

"By examining conditions in China and experimenting in a lab, the scientists suggest that a combination of weather patterns and chemistry could have caused London fog to turn into a haze of concentrated sulfuric acid."

"Worldwide, pharmaceutical use has been on the increase for the past century and will continue to increase into the future with the development of new medicines to cure recently discovered diseases as well as previously untreatable conditions. Following use by the patient, active pharmaceutical ingredients (APIs) and their metabolites are excreted to the sewerage system. They are then typically transported to a wastewater treatment works, where, depending on their molecular structure and physicochemical properties, they can be either degraded by biological treatment processes or released to the environment in effluents or sorb to sludge. The soil environment will therefore be exposed to APIs and their metabolites when sludge from treatment processes is applied to land as an agricultural fertilizer or when soil is irrigated with reclaimed wastewater effluent. While only a few studies have explored the occurrence of APIs in the soil environment, available data indicate that a range of API classes, including nonsteroidal anti-inflammatory drugs, antidepressants, anticonvulsants, and antibacterial agents do occur in soils in concentrations up to the low mg/kg level. Because of detection of pharmaceuticals in soils, concerns have been raised over the potential for these substances to be taken up into human food items and to pose a risk to human health. A number of studies have demonstrated the uptake of pharmaceuticals used in human and veterinary medicine into plants. Studies have explored the uptake and translocation of a variety of APIs with a particular focus on the antidepressant drug fluoxetine and antibacterial chemicals including sulfamethazine, sulfamethoxazole, and trimethoprim into numerous plant species including root and shoot crops such as soybean, lettuce, and carrot."

"Waste-water from the houses collected in the gutters running alongside the curbs and emitted a truly fearsome smell. There were no public toilets in the streets or squares. Visitors, especially women, often became desperate when nature called. In the public buildings the sanitary facilities were unbelievably primitive....As a metropolis, Berlin did not emerge from a state of barbarism into civilization until after 1870."

"Plastic pollution free world is not a choice but a commitment to life - a commitment to the next generation."

"Net-based surveys are less subjective than direct observations but are limited regarding the area that can be sampled (net apertures 1–2 m and ships typically have to slow down to deploy nets, requiring dedicated ship's time). The plastic debris sampled is determined by net mesh size, with similar mesh sizes required to make meaningful comparisons among studies. Floating debris typically is sampled with a neuston or manta trawl net lined with 0.33 mm mesh. Given the very high level of spatial clumping in marine litter, large numbers of net tows are required to adequately characterize the average abundance of litter at sea. Long-term changes in plastic meso-litter have been reported using surface net tows: in the North Pacific Subtropical Gyre in 1999, plastic abundance was 335 000 items/km2 and 5.1 kg/km2, roughly an order of magnitude greater than samples collected in the 1980s. Similar dramatic increases in plastic debris have been reported off Japan. However, caution is needed in interpreting such findings, because of the problems of extreme spatial heterogeneity, and the need to compare samples from equivalent water masses, which is to say that, if an examination of the same parcel of water a week apart is conducted, an order of magnitude change in plastic concentration could be observed."

"The wave equation was quickly followed by remarkably similar equations for gravitation, electrostatics, elasticity, and heat flow. Many bore the names of their inventors: Laplace's equation, Poisson's equation. The equation for heat does not; it bears the unimaginative and not entirely accurate name 'heat equation'. It was introduced by Joseph Fourier, and his ideas led to the creation of a new area of mathematics whose ramifications were to spread far beyond its original source."

"Analytical chemistry is extremely important—probably even more important than analytical chemists think. Everything in science requires measurement; analytical chemists are experts in the science of measurement, not just in determining the structures of molecules and the compositions of mixtures of molecules."

"The old mechanical and atomic hypotheses have, during recent years, become so plausible that they have ceased to seem like hypotheses; atoms are no longer just a convenient fiction. It seems almost as if we could see them, now that we know how to count them. ...The kinetic theory of gases has thus received unexpected corroboration. ...The remarkable counting of the number of atoms by Perrin completed the triumph of the atomic theory. ...In the processes used with the Brownian phenomenon, or in those used for the law of radiation, we do not deal directly with the number of atoms, but with their degrees of freedom of movement. In that process where we consider the blue of the sky, the mechanical properties of the atoms come into play; the atoms are looked upon as producing an optical discontinuity. ...The atom of the chemist is now a reality. But that does not mean that we have reached the ultimate limit of the divisibility of matter. When Democritus invented the atom he considered it as the absolutely indivisible element within which there would be nothing further to distinguish. That is what the word meant in Greek. ... the atom of the chemist would not have satisfied him since that is not indivisible; it is not a true element; it is not free from mystery, from secrets. The chemist's atom is a universe. Democritus would have considered, even after so much trouble in finding it, that we were still only at the beginning of our search—these philosophers are never satisfied. ...This atom disintegrates into yet smaller atoms. What we call radioactivity is the perpetual breaking up of atoms. ...Each atom is like a sort of solar system where the small negative electrons play the role of planets revolving around the great... sun. ...the atom of a radioactive body is a universe within itself and a world subject to chance."

"The Atomic Theory and the Periodic Law have been given prominence, since their neglect unfailingly leads to obscurity and triviality."

"The results of a scrutiny of the materials of chemical science from a mathematical standpoint are pronounced in two directions. In the first we observe crude, qualitative notions, such as fire-stuff, or phlogiston, destroyed; and at the same time we perceive definite measurable quantities such as fixed air, or oxygen, taking their place. In the second direction we notice the establishment of generalizations, laws, or theories, in which a mass of quantitative data is reduced to order and made intelligible. Such are the law of conservation of matter, the laws of chemical combination, and the atomic theory."

"And thus Nature will be very conformable to her self and very simple, performing all the great Motions of the heavenly Bodies by the Attraction of Gravity which intercedes those Bodies, and almost all the small ones of their Particles by some other attractive and repelling Powers which intercede the Particles. The Vis inertiæ is a passive Principle by which Bodies persist in their Motion or Rest, receive Motion in proportion to the Force impressing it, and resist as much as they are resisted. By this principle alone there never could have been any Motion in the World. Some other Principle was necessary for putting Bodies into Motion; and now they are in Motion, some other Principle is necessary for conserving the Motion."

"If two plane polish'd Plates of Glass... be laid together, so that their sides be parallel and at a very small distance from one another, and then their lower edges be dipped into Water, the Water will rise up between them. And the less the distance of the Glasses is, the greater will be the height to which the Water will rise. ...And in like manner, Water ascends between two Marbles polish'd plane, when their polished sides are parallel, and at a very little distance from one another. And if slender Pipes of Glass be dipped at one end into stagnating Water, the Water will rife up within the Pipe, and the height to which it rises will be reciprocally proportional to the Diameter of the Cavity of the Pipe, and will equal the height to which it rises between two Planes of Glass, if the Semidiameter of the Cavity of the Pipe be equal to the distance between the Planes, or thereabouts. And these Experiments succeed after the same manner in vacuo as in the open Air, (as hath been tried before the Royal Society,) and therefore are not influenced by the Weight or Pressure of the Atmosphere. ...There are therefore Agents in Nature able to make the Particles of Bodies stick together by very strong Attractions. And it is the Business of experimental Philosophy to find them out."

"The Parts of all homogeneal hard Bodies which fully touch one another, stick together very strongly. And for explaining how this may be, some have invented hooked Atoms, which is begging the Question; and others tell us that Bodies are glued together by rest, that is, by an occult Quality, or rather by nothing; and others, that they stick together by conspiring Motions, that is, by relative rest amongst themselves. I had rather infer from their Cohesion, that their Particles attract one another by some Force, which in immediate Contact is exceeding strong, at small distances performs the chymical Operations above-mention'd, and reaches not far from the Particles with any sensible Effect."

"And is it not from the mutual Attraction of the Ingredients that they stick together for compounding these Minerals... And the same Question may be put concerning all, or almost all the gross Bodies in Nature. For all the Parts of Animals and Vegetables are composed of Substances volatile and fix'd, fluid and solid, as appears by their Analysis; and so are Salts and Minerals, so far as Chymists have been hitherto able to examine their Composition."

"And when Aqua fortis, or Spirit of Vitriol poured upon Filings of Iron, dissolves the Filings with a great Heat and Ebullition, is not this Heat and Ebullition effected by a violent Motion of the Parts, and does not that Motion argue that the acid Parts of the Liquor rush towards the Parts of the Metal with violence, and run forcibly into its Pores till they get between its outmost Particles, and the main Mass of the Metal, and surrounding those Particles loosen them from the main Mass, and set them at liberty to float off into the Water? And when the acid particles, which alone would distil with an easy Heat, will not separate from the Particles of the Metal without a very violent Heat, does not this confirm the Attraction between them?"

"And when Water and Oil of Vitriol poured successively into the same Vessel grow very hot in the mixing, does not this Heat argue a great Motion in the Parts of the Liquors? And does not this Motion argue, that the Parts of the two Liquors in mixing coalesce with Violence, and by consequence rush towards one another with an accelerated Motion?"

"Have not the small Particles of Bodies certain Powers, Virtues, or Forces, by which they act at a distance, not only upon the Rays of Light for reflecting, refracting, and inflecting them, but also upon one another for producing a great Part of the Phænomena of Nature? For it's well known that Bodies act one upon another by the Attractions of Gravity, Magnetism, and Electricity; and these Instances shew the Tenor and Course of Nature, and make it not improbable but that there may be more attractive Powers than these. For Nature is very consonant and conformable to her self. How these Attractions may be perform'd, I do not here consider. What I call Attraction may be perform'd by impulse, or by some other means unknown to me. I use that Word here to signify only in general any Force by which Bodies tend towards one another, whatsoever be the Cause. For we must learn from the Phenomena of Nature what Bodies attract one another, and what are the Laws and Properties of the Attraction, before we enquire the Cause by which the Attraction is perform'd. The Attractions of Gravity, Magnetism, and Electricity, reach to very sensible distances, and so have been observed by vulgar Eyes, and there may be others which reach to so small distances as hitherto escape Observation; and perhaps electrical Attraction may reach to such small distances, even without being excited by Friction."

"The absence of effects due to the earth's motion relative to the ether can be explained on the electromagnetic theory if it is supposed that this theory covers all phenomena. This appears to be a strong argument in favor of the purely electrical nature of matter. It will be convenient now to mention the chief electrical theories of atomic structure which have been proposed. According to Sir J. J. Thomson, atoms consist of solid spheres of positive electricity inside which negative electrons move about freely. ...The electrons will distribute themselves uniformly throughout the sphere so as to neutralize it as completely as possible and can vibrate about their positions of equilibrium. According to Sir J. Larmor, atoms consist of a number of positive and negative electrons describing orbits about each other. ...On this view an atom is a sort of small gaseous nebula without any sort of solid foundation. A third theory recently adopted by Rutherford regards the atom as containing a nucleus of positive electricity with negative electrons outside it; probably describing orbits around it. On this view the atom is a sort of minute solar system. The positive nucleus... provides a definite foundation fixing the identity of the atom. The same may be said of the sphere in Sir J. J. Thomson's theory. ... The most important property of atoms is their extraordinary stability... Negative electrons can be knocked out of atoms by the impact of rapidly moving particles such as the cathode rays and α rays, yet the atoms retain their identity and after regaining negative electrons are unaffected. Facts like these appear to be decisive against Sir J. Larmor's theory. ... These [monatomic] gases ...give spectra containing many lines so that it is certain that their atoms contain electrons which can vibrate. It is necessary to suppose that collisions between these atoms do not set their electrons in vibration, which seems to require the electrons to be protected in some way. This seems to be strongly in favor of Sir J. J. Thomson's theory and against the other two theories, for if the electrons were describing orbits outside it is hard to see how they could escape violent disturbance during a collision. ... Sir J. Larmor's theory and Rutherford's planetary theory are difficult to reconcile with the idea that atoms become firmly fixed together in compounds and rigid solids. On such theories we should expect to have nothing but gases and liquids and only very simple compounds. ... The scattering of α rays led Rutherford to adopt the idea of a positive nucleus, since some α rays are turned through a larger angle than can be explained by the electric forces due to a charge equal to that on one electron. It may be, however, that other forces besides ordinary electric force act on α rays when moving through matter. The α rays are helium atoms which have a radius about 10-8 cm., so that they probably only get through by displacing the atoms of the matter. If we suppose the positive sphere of one atom can not penetrate into that of another then the scattering of a rays by matter can probably be explained on Sir J. J. Thomson's theory."

"The physical doctrine of the atom has got into a state which is strongly suggestive of the epicycles of astronomy before Copernicus."

"The question whether our elementary atoms are in their nature indivisible, or whether they are built up of smaller particles, is one upon which I, as a chemist, have no hold whatever, and I may say that in chemistry the question is not raised by any evidence whatever."

"From Dalton in 1803 to Maxwell in 1866 the atomic picture of matter had progressively taken on shape and detail: by Maxwell's time it... lay at the heart of the classical system. ...all matter was composed of ponderable atoms and, with the 'death' of caloric, the division between corporeals and incorporeals became absolutely sharp. The known incorporeal agencies—radiant heat, light, magnetisim and electricity—had to be dealt with in terms of other concepts."

"Between Bernoulli and Maxwell... Euler, d'Alembert, Lagrange and Hamilton expounded Newton's dynamics] in more and more general forms, until at last all [mechanical] processes... were seen as conforming to... the Principle of the Conservation of Energy, and the Principle of Least Action. This mathematical drive... continued, overflowing beyond... mechanics... [and into] processes involving nonmechanical factors: heat, electricity, vitality, and chemical change... The most comprehensive exposition was given in 1847 by Hermann von Helmholtz... In 1848, J. P. Joule [demonstrated that]... whether he produced heat by the passage of an electric current, or by mechanical effort, the conversion took place at fixed, measurable rates. ...[I]t was natural to look again for an explanation ...Perhaps the production of heat by friction merely transferred mechanical energy from a visible level to an invisible one... the increased motion of the molecules... Clausius and Maxwell turned this view... into a fully-developed branch of mathematics (...from 1857 to 1866.) ...[H]eat theory had been united into the general theory of 'matter in motion'... the random agitation of vast numbers of invisibly-small particles."

"The final step... came in the late 1850s. Up to that time [evidence supporting] the atomic theory had been entirely... chemical... Within... physics, however, the theory had made little progress beyond the brilliant guesswork of Newton's Optics. As a result of Clausius' and Maxwell's new theory of heat and gases, physics at last caught up with chemistry. ...This theory was not entirely new. In outline its mathematical foundations had been worked out [as early as the 1730s] by Daniel Bernoulli... [who] demonstrated that random agitation of the atoms of air would explain Boyle's Law just as well as Newton's theory of repulsive forces; but although ... extended this explanation into a dynamical theory of heat it remained a minority view... overshadowed by Boerhaave's and Lavoisier's [heat as a] material theory. Around 1800... a few... were positively sceptical about caloric... Benjamin Thompson... observed that friction would generate unlimited quantities of heat... though... the material theory retained the allegiance of leading scientists for another half-century."