Chemistry, a branch of physical science, is the study of the composition, properties and behavior of matter. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds. Chemistry is also concerned with the interactions between atoms (or groups of atoms) and various forms of energy (e.g. photochemical reactions, changes in phases of matter, separation of mixtures, properties of polymers, etc.).
17th century 
- It is the study of the Chemists to liberate that unsensual truth from its fetters in things of sense, for through it the heavenly powers are persued with subtle understanding....Knowledge is the sure and undoubted resolution by experiment of all opinions concerning the truth....Experiment is manifest demonstration of the truth, and resolution the putting away of doubt. We cannot be resolved of any doubt save by experiment, and therefore is no better way to make it than on ourselves. Let us therefore verify what we have said above concerning the truth, beginning with ourselves. We have said that piety consists in knowledge of ourselves, and hence it is said that we make philosophical knowledge begin from this also. But no man can know himself unless he know what and not who he is, on whom he depends and whose he is (for by the law of truth no one belongs to himself, and to what end he was made. With this knowledge piety begins, which is concerned with two things, namely, with the Creator and the creature that is made like unto him. For it is impossible for the creature to know himself of himself, unless he first know his Creator....No one can better know the Creator, than the workman is known by his work.
- Gerhard Dorn 1659 c. Theatrum Chemicum Volume 1 phil. med.
18th century 
- We must trust to nothing but facts: These are presented to us by Nature, and cannot deceive. We ought, in every instance, to submit our reasoning to the test of experiment, and never to search for truth but by the natural road of experiment and observation.
- Antoine Lavoisier (1790) Elements of Chemistry, pp. xiii-xxxvii
19th century 
- God does not justify man on the ground of human learning; attainments in chemistry, anatomy, geology, botany, astronomy, or skill in sculpture and painting, — these do not prepare a man to die.
- Albert Barnes (1895) Dictionary of Burning Words of Brilliant Writers. p. 114.
- Men are not allowed to think freely about chemistry and biology: why should they be allowed to think freely about political philosophy?
- Auguste Comte (1798 – 1857) as quoted in A Dictionary of Scientific Quotations (1991) by Alan Lindsay Mackay
- One of the most striking characteristics of this new modification of oxygen is its peculiar odor, and hence Schönbein calls it ozone, from a Greek verb signifying to smell. It frequently happens that a great discovery supplies the wanting links between a number of obscure facts, and thus adds quite as much to our knowledge by its indirect bearings as by the positive additions it makes to the general stock. So it has been with the discovery of ozone. Every one who has used an electrical machine must have noticed the peculiar smell which follows the electrical discharge. This was formerly supposed to be the odor of the electrical fluid itself; but as soon as ozone was discovered, the odor was recognized at once as belonging to this new agent, and it was soon ascertained that electricity is one of the most efficient means of modifying the oxygen of the air.
- Josiah Parsons Cooke (1880). Religion and Chemistry. Charles Scribner’s Sons, New York. p. 116.
- If a possible — nay, reasonable — variation in only one of the forces conditioning the human race, that of gravitation, could so modify our outward form, appearance, and proportions as to make us to all intents and purposes a different race of beings; if mere differences of size can cause some of the most simple facts in chemistry and physics to take so widely different a guise; if beings microscopically small and prodigiously large would simply as such be subject to the hallucinations I have pointed out, and to others I might enlarge upon, is it not possible that we, in turn, though occupying, as it seems to us, the golden mean, may also by the mere virtue of our size and weight fall into misinterpretations of phenomena from which we should escape were we or the globe we inhabit either larger or smaller, heavier or lighter? May not our boasted knowledge be simply conditioned by accidental environments, and thus be liable to a large element of subjectivity hitherto unsuspected and scarcely possible to eliminate?
- William Crookes (1897) Address to the Society for Psychical Research
- Reader! Imagine a school-boy who has outgrown his clothes. Imagine the repairs made on the vestments where the enlarged frame had burst the narrow limits of its inclosure. Imagine the additions made where the projecting limbs had fairly and far emerged beyond the confines of the garment. Imagine the boy still growing, and the clothes, mended all over, now more than ever in want of mending — such is chemistry, and such its nomenclature.
- John Joseph Griffin (1834) Chemical Recreations (7th Edition, 1834) "The Romance of Chemistry" p.189
- We can no more have exact religious thinking without theology, than exact mensuration and astronomy without mathematics, or exact iron-making without chemistry,
- John Hall (Presbyterian pastor) (1895) Dictionary of Burning Words of Brilliant Writers p.580.
- It is a mistake to confound Alchemy with Chemistry. Modern Chemistry is a science which deals merely with the external forms in which the element of matter is manifesting itself. It never produces anything new. We may mix and compound and decompose two or more chemical bodies an unlimited number of times, and cause them to appear under various different forms, but at the end we will have no augmentation of substance, nor anything more than the combinations of the substances that have been employed at the beginning. Alchemy does not mix or compound anything, it causes that which already exists in a latent state to become active and grow. Alchemy is, therefore, more comparable to botany or agriculture than to Chemistry; and, in fact, the growth of a plant, a tree, or an animal is an alchemical process going on in the alchemical laboratory of nature, and performed by the great Alchemist, the power of God acting in nature.
- Franz Hartmann. (1890) In the Pronaos of the Temple of Wisdom, containing the History of the True and the False Rosicrucians. p.129
- The most powerful influence exercised by the Arabs on general natural physics was that directed to the advances of chemistry; a science for which this race created a new era.(...) Besides making laudatory mention of that which we owe to the natural science of the Arabs in both the terrestrial and celestial spheres, we must likewise allude to their contributions in separate paths of intellectual development to the general mass of mathematical science.
- Alexander von Humboldt, Cosmos, H.G. Bohn, 1860, v2, p.589,595
- Chemistry, in its application to animals and vegetables. Endeavours jointly with physiology to enlighten us respecting the mysterious processes and sources of organic life.
- Justus von Liebig (1854) Familiar Letters on Chemistry (London, 1854)
- I wish to establish some sort of system not guided by chance but by some sort of definite and exact principle.
- Dmitri Mendeleev Declared in his treatise “An Outline of the System of the Elements” it was read to the Russian Chemical Society.
- In the four quarters of the globe, who reads an American book? Or goes to an American play? or looks at an American picture or statue? What does the world yet owe to American physicians or surgeons? What new substances have their chemists discovered? Or what old ones have they advanced? What new constellations have been discovered by the telescopes of Americans? Who drinks out of American glasses? Or eats from American plates? Or wears American coats or gowns? or sleeps in American blankets? Finally, under which of the old tyrannical governments of Europe is every sixth man a slave, whom his fellow-creatures may buy and sell and torture?
- Sydney Smith (1820) Referring to the lack of established culture and the established institution of slavery in the United States, in "Review of Seybert’s Annals of the United States", published in The Edinburgh Review (1820).
- "Cellular pathology is not an end if one cannot see any alteration in the cell. Chemistry brings the clarification of living processes nearer than does anatomy. Each anatomical change must have been preceded by a chemical one."
- Rudolf Virchow (1821–1902) cited in: Coper, H., Herken, H., 1963. Dtsch. Med. Wochenschr. 88,2025– 2036.
20th century 
- Space is big. Really big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.
- The nature of the chemical bond is the problem at the heart of all chemistry.
- Bryce Crawford in New Chemistry (1957) by the editors of Scientific American, p. 65
- We must not forget that when radium was discovered no one knew that it would prove useful in hospitals. The work was one of pure science. And this is a proof that scientific work must not be considered from the point of view of the direct usefulness of it. It must be done for itself, for the beauty of science, and then there is always the chance that a scientific discovery may become like the radium a benefit for humanity.
- Marie Curie (1921) Lecture at Vassar College, Poughkeepsie, New York (14 May 1921)
- Within a certain kind of environment, an activity may be checked so that the only meaning which accrues is of its direct and tangible isolated outcome. One may cook, or hammer, or walk, and the resulting consequences may not take the mind any farther than the consequences of cooking, hammering, and walking in the literal — or physical — sense. But nevertheless the consequences of the act remain far-reaching. To walk involves a displacement and reaction of the resisting earth, whose thrill is felt wherever there is matter. It involves the structure of the limbs and the nervous system; the principles of mechanics. To cook is to utilize heat and moisture to change the chemical relations of food materials; it has a bearing upon the assimilation of food and the growth of the body. The utmost that the most learned men of science know in physics, chemistry, physiology is not enough to make all these consequences and connections perceptible. The task of education, once more, is to see to it that such activities are performed in such ways and under such conditions as render these conditions as perceptible as possible.
- The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much too complicated to be soluble. It therefore becomes desirable that approximate practical methods of applying quantum mechanics should be developed, which can lead to an explanation of the main features of complex atomic systems without too much computation.
- Modern warfare, we discovered, was to a far greater extent than ever before a conflict of chemists and manufacturers. Manpower, it is true, was indispensable, and generalship will always, whatever the conditions, have a vital part to play. But troops, however brave and well led, were powerless under modern conditions unless equipped with adequate and up-to-date artillery (with masses of explosive shell), machine-guns, aircraft and other supplies. Against enemy machine-gun posts and wire entanglements the most gallant and best-led men could only throw away their precious lives in successive waves of heroic martyrdom. Their costly sacrifice could avail nothing for the winning of victory.
- David Lloyd George (1938) War Memoirs
- The alchemical tradition assumes that every physical art or science is a body of knowledge which exists only because it is ensouled by invisible powers and processes. Physical chemistry, as it is practiced in the modern world, is concerned principally with pharmaceutical or industrial research projects. It is confined within the boundaries of an all-pervading materialism, which binds labor to the advancement of physical objectives.
- Manly Palmer Hall (1988) Meditation Symbols in Eastern & Western Mysticism
- Somehow, the practice of astronomy, physics, chemistry or biology normally fails to evoke the controversies over fundamentals that today seem endemic among, say, psychologists or sociologists. Attempting to discover the source of that difference led me to recognize the role in scientific research of what I have since called “paradigms.” These I take to be universally recognized scientific achievements that for a time provide model problems and solutions for a community of practitioners.
- Thomas Samuel Kuhn (1962) The Structure of Scientific Revolutions. p.48
- For me chemistry represented an indefinite cloud of future potentialities which enveloped my life to come in black volutes torn by fiery flashes, like those which had hidden Mount Sinai. Like Moses, from that cloud I expected my law, the principle of order in me, around me, and in the world. I was fed up with books, which I still continued to gulp down with indiscreet voracity, and searched for a key to the highest truths; there must be a key, and I was certain that, owing to some monstrous conspiracy to my detriment and the world's, I would not get in school. In school they loaded with me with tons of notions that I diligently digested, but which did not warm the blood in my veins. I would watch the buds swell in spring, the mica glint in the granite, my own hands, and I would say to myself: "I will understand this, too, I will understand everything, but not the way they want me to. I will find a shortcut, I will make a lock-pick, I will push open the doors."
It was enervating, nauseating, to listen to lectures on the problem of being and knowing, when everything around us was a mystery pressing to be revealed: the old wood of the benches, the sun's sphere beyond the windowpanes and the roofs, the vain flight of the pappus down in the June air. Would all the philosophers and all the armies of the world be able to construct this little fly? No, nor even understand it: this was a shame and an abomination, another road must be found.
- Primo Levi (1975) The Periodic Table "Hydrogen"
- There is a narrowness of action, though not of intent, which characterizes university departments, and scientific publications and scientists in general: if it is too popular, it is somehow vulgar and wrong. You can't really speak to those people across the street. I live next to the chemists at MIT, but I never see them. I hardly know who they are, yet between physics and chemistry it is hard to know who should study what molecule. I myself am guilty. We form communities not based on the problems of science, but on quite other things. This is part of the general split between the intelligent member of the public and the scientist who speaks in narrow focus. But the great theoretical problems which I believe the world expects will somehow be solved by science, problems close to deep philosophical issues are the very problems that find the least expertise, the least degree of organization, the least institutional support in the scientific institutions of America or indeed of the world.
- Philip Morrison on specialization in (1995) Nothing is Too Wonderful to be True
- We may, I believe, anticipate that the chemist of the future who is interested in the structure of proteins, nucleic acids, polysaccharides, and other complex substances with high molecular weight will come to rely upon a new structural chemistry, involving precise geometrical relationships among the atoms in the molecules and the rigorous application of the new structural principles, and that great progress will be made, through this technique, in the attack, by chemical methods, on the problems of biology and medicine.
- Linus Pauling, Nobel Lecture (11 December 1954)
- Just think of the differences today. A young person gets interested in chemistry and is given a chemical set. But it doesn't contain potassium cyanide. It doesn't even contain copper sulfate or anything else interesting because all the interesting chemicals are considered dangerous substances. Therefore, these budding young chemists don't get a chance to do anything engrossing with their chemistry sets. As I look back, I think it is pretty remarkable that Mr. Ziegler, this friend of the family, would have so easily turned over one-third of an ounce of potassium cyanide to me, an eleven-year-old boy.
- Linus Pauling In His Own Words (1995) by Barbara Marinacci, p. 29
- The Second Law of Thermodynamics states that all energy systems run down like a clock and never rewind themselves. But life not only 'runs up,' converting low energy sea-water, sunlight and air into high-energy chemicals, it keeps multiplying itself into more and better clocks that keep 'running up' faster and faster. Why, for example, should a group of simple, stable compounds of carbon, hydrogen, oxygen and nitrogen struggle for billions of years to organize themselves into a professor of chemistry? What's the motive? If we leave a chemistry professor out on a rock in the sun long enough the forces of nature will convert him into simple compounds of carbon, oxygen, hydrogen and nitrogen, calcium, phosphorus, and small amounts of other minerals. It's a one-way reaction. No matter what kind of chemistry professor we use and no matter what process we use we can't turn these compounds back into a chemistry professor. Chemistry professors are unstable mixtures of predominantly unstable compounds which, in the exclusive presence of the sun's heat, decay irreversibly into simpler organic and inorganic compounds. That's a scientific fact. The question is: Then why does nature reverse this process? What on earth causes the inorganic compounds to go the other way? It isn't the sun's energy. We just saw what the sun's energy did. It has to be something else. What is it?
- Robert M. Pirsig (1991) Lila
- It has never been in my power to study anything, — mathematics, ethics, metaphysics, gravitation, thermodynamics, optics, chemistry, comparative anatomy, astronomy, psychology, phonetics, economics, the history of science, whist, men and women, wine, metrology, except as a study of semeiotic.
- The recognition of certain basic impossibilities has laid the foundations of some major principles of physics and chemistry; similarly, recognition of the impossibility of understanding living things in terms of physics and chemistry, far from setting limits to our understanding of life, will guide it in the right direction. And even if the demonstration of this impossibility should prove of no great advantage in the pursuit of discovery, such a demonstration would help to draw a truer image of life and man than that given us by the present basic concepts of biology.
- Michael Polanyi (1968) Life's irreducible structure
- I must confess it was very unexpected and I am very startled at my metamorphosis into a chemist.
- Chemistry has been termed by the physicist as the messy part of physics, but that is no reason why the physicists should be permitted to make a mess of chemistry when they invade it.
- Frederick Soddy as quoted in American journal of physics, Volume 14. American Association of Physics Teachers, American Institute of Physics. 1946. p. 248.
- Professor Meitner stated that nuclear fission could be attributed to chemistry. I have to make a slight correction. Chemistry merely isolated the individual substances, but did not precisely identify them. It took Professor Hahn's method to do this. This was his achievement.
- Fritz Strassmann in an interview with the German television, ARD, March 8, 1959.
- I have described at some length the application of Positive Rays to chemical analysis; one of the main reasons for writing this book was the hope that it might induce others, and especially chemists, to try this method of analysis. I feel sure that there are many problems in chemistry, which could be solved with far greater ease by this than any other method. The method is surprisingly sensitive — more so than even that of spectrum analysis, requires an infinitesimal amount of material, and does not require this to be specially purified; the technique is not difficult if appliances for producing high vacua are available.
- J. J. Thomson (1913) Rays of Positive Electricity
- I recognize nothing that is not material. In physics, chemistry and biology I see only mechanics. The Universe is nothing but an infinite and complex mechanism. Its complexity is so great that it borders on randomness, giving the illusion of free will.
- Konstantin Eduardovich Tsiolkovsky (1931) Monism of the Universe
- The philosophy of Bergson, which is a spiritualist restoration, essentially mystical, medieval, Quixotesque, has been called a demi-mondaine philosophy. Leave out the demi; call it mondaine, mundane. Mundane — yes, a philosophy for the world and not for philosophers, just as chemistry ought to be not for chemists alone. The world desires illusion (mundus vult decipi) — either the illusion antecedent to reason, which is poetry, or the illusion subsequent to reason, which is religion. And Machiavelli has said that whosoever wishes to delude will always find someone willing to be deluded. Blessed are they who are easily befooled!
- Miguel de Unamuno (1913) The Tragic Sense of Life
- Like literature, philosophy is not distinguished from other subjects by a specific approach to a subject-matter independent of it. Chemistry deals with chemicals, biology with life and astronomy with very large, very distant objects. Philosophy can boast no such definite subject-matter.
- David Wood (philosopher) (1990) Philosophy At The Limit. p. 69
New millennium 
- "My first heresy says that all the fuss about global warming is grossly exaggerated. Here I am opposing the holy brotherhood of climate model experts and the crowd of deluded citizens who believe the numbers predicted by the computer models. Of course, they say, I have no degree in meteorology and I am therefore not qualified to speak. But I have studied the climate models and I know what they can do. The models solve the equations of fluid dynamics, and they do a very good job of describing the fluid motions of the atmosphere and the oceans. They do a very poor job of describing the clouds, the dust, the chemistry and the biology of fields and farms and forests. They do not begin to describe the real world that we live in. The real world is muddy and messy and full of things that we do not yet understand. It is much easier for a scientist to sit in an air-conditioned building and run computer models, than to put on winter clothes and measure what is really happening outside in the swamps and the clouds. That is why the climate model experts end up believing their own models."
- You don't need something more to get something more. That's what emergence means. Life can emerge from physics and chemistry plus a lot of accidents. The human mind can arise from neurobiology and a lot of accidents, the way the chemical bond arises from physics and certain accidents. Doesn't diminish the importance of these subjects to know they follow from more fundamental things plus accidents.
- "We are honored for research which is today referred to as the "Two Neutrino Experiment". How does one make this research comprehensible to ordinary people? In fact "The Two Neutrinos" sounds like an Italian dance team. How can we have our colleagues in chemistry, medicine, and especially in literature share with us, not the cleverness of our research, but the beauty of the intellectual edifice, of which our experiment is but one brick? This is a dilemma and an anguish for all scientists because the public understanding of science is no longer a luxury of cultural engagement, but it is an essential requirement for survival in our increasingly technological age: In this context, I believe this Nobel Ceremony with its awesome tradition and pomp has as one of its most important benefits; the public attention it draws to science and its practitioners."
- Leon M. Lederman Lederman's speech at the Nobel Banquet, December 10, 1988. (url accessed on October 20, 2008)
- This new quantum mechanics promised to explain all of chemistry. And though I felt an exuberance at this, I felt a certain threat, too. “Chemistry,” wrote Crookes, “will be established upon an entirely new basis…. We shall be set free from the need for experiment, knowing a priori what the result of each and every experiment must be.” I was not sure I liked the sound of this. Did this mean that chemists of the future (if they existed) would never actually need to handle a chemical; might never see the colors of vanadium salts, never smell a hydrogen selenide, never admire the form of a crystal; might live in a colorless, scentless, mathematical world? This, for me, seemed and awful prospect, for I, at least, needed to smell and touch and feel, to place myself, my senses, in the middle of the perceptual world.
- Oliver Sacks (2001) Uncle Tungsten pp. 312–313
- Dead is when the chemists take over the subject.
- ...when I started doing chemistry, I did it the way I fished – for the excitement, the discovery, the adventure, for going after the most elusive catch imaginable in uncharted seas.
- K. Barry Sharpless, Nobel lecture, 2001
- Chemists usually write about their chemical careers in terms of the different areas and the discrete projects in those areas on which they have worked. Essentially all my chemical investigations, however, are in only one area, and I tend to view my research not with respect to projects, but with respect to where I’ve been driven by two passions which I acquired in graduate school: I am passionate about the Periodic Table (and selenium, titanium and osmium are absolutely thrilling), and I am passionate about catalysis. What the ocean was to the child, the Periodic Table is to the chemist; new catalytic reactivity is, of course, my personal coelacanth.
- K. Barry Sharpless, Nobel lecture, 2001
- The most essential example of the theory of self-organisation in chemistry is the theory of non-linear, non-equilibrium thermodynamics of chemical reactions presented by Prigogine and his co-workers.
- Rein Vihalemm (2001) "Chemistry as an Interesting Subject for the Philosophy of Science". p.195
- Whether two molecules are (dis)similar is in the eye of the beholder. Scientists look to fool the receptor - but you really want to fool the patent office.
- S. Stanley Young (2008), assistant director of bioinformatics, National Institute of Statistical Sciences. Appearing in: Lipp, Elizabeth (2008-08-01). "Novel Approaches to Lead Optimization". Genetic Engineering & Biotechnology News (Mary Ann Liebert): pp. 20, 22. Retrieved on 2008-09-28.