Who Wrote The Law Of Definite Proportions?

Who Wrote The Law Of Definite Proportions
Joseph Proust The Law of Constant Composition, discovered by Joseph Proust, is also known as the Law of Definite Proportions.

What is the law of definite proportions used for?

Summary –

The law of definite proportions states that a given chemical compound always contains the same elements in the exact same proportions by mass.

How did Joseph Proust prove the law of definite proportions?

Proust’s Law – His second achievement derived from a controversy with C.L. Berthollet on the law of definite proportions, which is sometimes also known as Proust’s Law, Proust studied copper carbonate, the two tin oxides, and the two iron sulfides to prove this law.

  1. He did this by making artificial copper carbonate and comparing it to natural copper carbonate,
  2. With this he showed that each had the same proportion of weights between the three elements involved,
  3. Between the two types of the other compounds, Proust showed that no intermediate compounds exist between them.

Proust published this paper in 1794, and his famous opponent Berthollet did not believe that substances always combine in constant and definite proportions. Moreover, Bethollet claimed that that the products of a reaction depend on the ratio of reactants.

  • Proust’s law was not accepted until 1812, when the Swedish chemist Jöns Jacob Berzelius gave him credit for it.
  • Although Proust was correct in his observations, the reason why reagents behave in the way he described did not become clear until English chemist John Dalton formulated his atomic theory in 1803,

According to Dalton, a fixed number of atoms of one substance always combined with a fixed number of atoms of another substance in forming a compound. Dalton realized that substances must combine in the same proportions by weight as the weight proportions of their atoms,

  • Other chemists had already observed that pure substances do combine in fixed proportions.
  • They called that finding the law of definite (or constant) proportions.
  • Dalton’s theory explained the law.
  • Proust also performed a series of researches to characterize different types of sugars, present in vegetable products.

After the death of his wife in 1817, Proust moved to Angers, where in 1820 he took over the pharmacy of his brother Joachim. In 1819 he became a chevalier of the Legion of Honor, and in 1820 he was granted a pension by Louis XVIII, On July 5, 1826 he died in Angers, France,

Joseph Proust at Encyclopedia Britannica Joseph Proust at Encyclopedia.com Modern Chemistry started with Lavosier Jöns Jacob Berzelius – One of the Founders of Modern Chemistry John Dalton and the Atomic Theory August Kekulé and the Carbon Ring Structure A Life of Discoveries – The Great Michael Faraday Joseph Proust at Wikidata GCSE Chemistry – History of the Model of the Atom #7, Cognito @ youtube Chisholm, Hugh, ed. (1911). “Proust, Joseph Louis”, Encyclopædia Britannica, Vol.22 (11th ed.). Cambridge University Press. Timeline of French Chemists via DBpedia and Wikidata

When was the law of definite proportions discovered?

Law of Definite Proportions (Jeremias Benjamin Richter) Evidence for the existence of atoms was the law of definite proportions proposed by Jeremias Benjamin Richter in 1792. Richter found that the ratio by weight of the compounds consumed in a chemical reaction was always the same.

What is the law of definite proportions and atomic theory?

How did Dalton Atomic Theory explain the law of definite proportions? Answer Verified

Hint: The Dalton Atomic theory was explained by the law of definite proportion which says that the compound formed by combining the atoms contains exactly the same proportion of element by mass. Complete step by step answer: Dalton gave the modern atomic theory and gave six postulates. Note:

The postulates involved in Daltons’ atomic theory are given below.(1) All matter contains indivisible particles called atoms.(2) Atoms belonging to the same element are similar in shape and mass but differ from the atoms of the other element.(3) Atoms cannot be created nor be destroyed.(4) Atoms of the same element combine more than one ratio to form two or more compounds.(5) Atoms of the different elements combine with each other in a simple whole number ratio.(6) The atom is the smallest unit taking part in chemical reaction.The law of definite proportion states that chemical compounds contain exactly the same proportion of element by mass.In other words the law of definite proportion states that elements are always combined in the same proportion by mass.Example: all the compounds containing carbon monoxide contain 42.88 % carbon and 57.12% oxygen by mass.The Dalton atomic theory explains the law of definite proportions.

Dalton proposed that the smallest particle of carbon monoxide is a molecule which contains one oxygen atom and one carbon atom.When oxygen atom contains mass about 1.33 times the carbon atom, carbon monoxide will have the above composition.In chemistry, the law of definite proportion, sometimes called Proust’s law, or law of constant composition states that a given chemical compound always contains its component elements in fixed ratio and does not depend on its source and method of preparation.

: How did Dalton Atomic Theory explain the law of definite proportions?

Did Marcel Proust believe in God?

Background – Proust was born on 10 July 1871 at the home of his great-uncle in the Paris Borough of Auteuil (the south-western sector of the then-rustic 16th arrondissement ), two months after the Treaty of Frankfurt formally ended the Franco-Prussian War,

  • His birth took place at the very beginning of the Third Republic, during the violence that surrounded the suppression of the Paris Commune, and his childhood corresponded with the consolidation of the Republic.
  • Much of In Search of Lost Time concerns the vast changes, most particularly the decline of the aristocracy and the rise of the middle classes, that occurred in France during the fin de siècle,

Proust’s father, Adrien Proust, was a prominent French pathologist and epidemiologist, studying cholera in Europe and Asia. He wrote numerous articles and books on medicine and hygiene. Proust’s mother, Jeanne Clémence (Weil), was the daughter of a wealthy Jewish family from Alsace,

Literate and well-read, she demonstrated a well-developed sense of humour in her letters, and her command of the English language was sufficient to help with her son’s translations of John Ruskin, Proust was raised in his father’s Catholic faith, He was baptized (on 5 August 1871, at the church of Saint-Louis d’Antin ) and later confirmed as a Catholic, but he never formally practised that faith.

He later became an atheist and was something of a mystic, By the age of nine, Proust had had his first serious asthma attack, and thereafter he was considered a sickly child. Proust spent long holidays in the village of Illiers, This village, combined with recollections of his great-uncle’s house in Auteuil, became the model for the fictional town of Combray, where some of the most important scenes of In Search of Lost Time take place.

Illiers was renamed Illiers-Combray in 1971 on the occasion of the Proust centenary celebrations.) In 1882, at the age of eleven, Proust became a pupil at the Lycée Condorcet ; however, his education was disrupted by his illness. Despite this, he excelled in literature, receiving an award in his final year.

Thanks to his classmates, he was able to gain access to some of the salons of the upper bourgeoisie, providing him with copious material for In Search of Lost Time, In spite of his poor health, Proust served a year (1889–90) in the French army, stationed at Coligny Barracks in Orléans, an experience that provided a lengthy episode in The Guermantes’ Way, part three of his novel. As a young man, Proust was a dilettante and a social climber whose aspirations as a writer were hampered by his lack of self-discipline.

His reputation from this period, as a snob and an amateur, contributed to his later troubles with getting Swann’s Way, the first part of his large-scale novel, published in 1913. At this time, he attended the salons of Mme Straus, widow of Georges Bizet and mother of Proust’s childhood friend Jacques Bizet, of Madeleine Lemaire and of Mme Arman de Caillavet, one of the models for Madame Verdurin, and mother of his friend Gaston Arman de Caillavet, with whose fiancée (Jeanne Pouquet) he was in love.

It is through Mme Arman de Caillavet, he made the acquaintance of Anatole France, her lover. Proust had a close relationship with his mother. To appease his father, who insisted that he pursue a career, Proust obtained a volunteer position at Bibliothèque Mazarine in the summer of 1896.

After exerting considerable effort, he obtained a sick leave that extended for several years until he was considered to have resigned. He never worked at his job, and he did not move from his parents’ apartment until after both were dead. His life and family circle changed markedly between 1900 and 1905.

In February 1903, Proust’s brother, Robert Proust, married and left the family home. His father died in November of the same year. Finally, and most crushingly, Proust’s beloved mother died in September 1905. She left him a considerable inheritance. His health throughout this period continued to deteriorate.

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What was Proust famous for?

Marcel Proust Page views 56984 Marcel Proust was an early 20th-century French writer responsible for what is officially the longest novel in the world: À la recherche du temps perdu – which has 1,267,069 words in it; double those in War and Peace,

What is Proust theory?

In chemistry, the law of definite proportions, sometimes called Proust’s law, or law of constant composition states that a given chemical compound always contains its component elements in fixed ratio (by mass) and does not depend on its source and method of preparation.

Who is the founder of ProPortion?

Overview. Thomas Schuurmans is the Owner and Founder of ProPortion, a Fellow at the Royal Society for the encouragement of Arts, manufactures, and Commerce, and a Member of the Directors club at Presidents Institute.

Who invented the ProPortion?

Definition of phi – Phi can be defined by taking a stick and breaking it into two portions. If the ratio between these two portions is the same as the ratio between the overall stick and the larger segment, the portions are said to be in the golden ratio.

  1. This was first described by the Greek mathematician Euclid, though he called it “the division in extreme and mean ratio,” according to mathematician George Markowsky of the University of Maine.
  2. You can also think of phi as a number that can be squared by adding one to that number itself, according to an explainer from mathematician Ron Knott at the University of Surrey in the U.K.

So, phi can be expressed this way: phi^2 = phi + 1 This representation can be rearranged into a quadratic equation with two solutions, (1 + √5)/2 and (1 – √5)/2. The first solution yields the positive irrational number 1.6180339887 (the dots mean the numbers continue forever) and this is generally what’s known as phi.

  1. The negative solution is -0.6180339887.
  2. Notice how the numbers after the decimal point are the same) and is sometimes known as little phi.
  3. One final and rather elegant way to represent phi is as follows: 5 ^ 0.5 * 0.5 + 0.5 This is five raised to the one-half power, times one-half, plus one-half.
  4. Related: The 11 Most Beautiful Mathematical Equations Phi is closely associated with the Fibonacci sequence, in which every subsequent number in the sequence is found by adding together the two preceding numbers.

This sequence goes 0, 1, 1, 2, 3, 5, 8, 13, 21, 34 and so on. It is also associated with many misconceptions. By taking the ratio of successive Fibonacci numbers, you can get closer and closer to phi. Interestingly, if you extend the Fibonacci sequence backward — that is, before the zero and into negative numbers — the ratio of those numbers will get you closer and closer to the negative solution, little phi −0.6180339887

What was John Dalton’s atomic theory?

The first part of his theory states that all matter is made of atoms, which are indivisible. The second part of the theory says all atoms of a given element are identical in mass and properties. The third part says compounds are combinations of two or more different types of atoms.

What did JJ Thomson discover?

J oseph John Thomson was born in Cheetham Hill, a suburb of Manchester on December 18, 1856. He enrolled at Owens College, Manchester, in 1870, and in 1876 entered Trinity College, Cambridge as a minor scholar. He became a Fellow of Trinity College in 1880, when he was Second Wrangler and Second Smith’s Prizeman, and he remained a member of the College for the rest of his life, becoming Lecturer in 1883 and Master in 1918.

  • He was Cavendish Professor of Experimental Physics at Cambridge, where he succeeded Lord Rayleigh, from 1884 to 1918 and Honorary Professor of Physics, Cambridge and Royal Institution, London.
  • Thomson’s early interest in atomic structure was reflected in his Treatise on the Motion of Vortex Rings which won him the Adams Prize in 1884.

His Application of Dynamics to Physics and Chemistry appeared in 1886, and in 1892 he had his Notes on Recent Researches in Electricity and Magnetism published. This latter work covered results obtained subsequent to the appearance of James Clerk Maxwell’s famous “Treatise” and it is often referred to as “the third volume of Maxwell”.

  1. Thomson co-operated with Professor J.H.
  2. Poynting in a four-volume textbook of physics, Properties of Matter and in 1895 he produced Elements of the Mathematical Theory of Electricity and Magnetism, the 5th edition of which appeared in 1921.
  3. In 1896, Thomson visited America to give a course of four lectures, which summarised his current researches, at Princeton.

These lectures were subsequently published as The Discharge of Electricity through Gases (1898). On his return from America, he achieved the most brilliant work of his life – an original study of cathode rays culminating in the discovery of the electron, which was announced during the course of his evening lecture to the Royal Institution on Friday, April 30, 1897.

His book, Conduction of Electricity through Gases, published in 1903 was described by Lord Rayleigh as a review of “Thomson’s great days at the Cavendish Laboratory”. A later edition, written in collaboration with his son, George, appeared in two volumes (1928 and 1933). Thomson returned to America in 1904 to deliver six lectures on electricity and matter at Yale University.

They contained some important suggestions as to the structure of the atom. He discovered a method for separating different kinds of atoms and molecules by the use of positive rays, an idea developed by Aston, Dempster and others towards the discovery of many isotopes.

In addition to those just mentioned, he wrote the books, The Structure of Light (1907), The Corpuscular Theory of Matter (1907), Rays of Positive Electricity (1913), The Electron in Chemistry (1923) and his autobiography, Recollections and Reflections (1936), among many other publications. Thomson, a recipient of the Order of Merit, was knighted in 1908.

He was elected Fellow of the Royal Society in 1884 and was President during 1916-1920; he received the Royal and Hughes Medals in 1894 and 1902, and the Copley Medal in 1914. He was awarded the Hodgkins Medal (Smithsonian Institute, Washington) in 1902; the Franklin Medal and Scott Medal (Philadelphia), 1923; the Mascart Medal (Paris), 1927; the Dalton Medal (Manchester), 1931; and the Faraday Medal (Institute of Civil Engineers) in 1938.

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He was President of the British Association in 1909 (and of Section A in 1896 and 1931) and he held honorary doctorate degrees from the Universities of Oxford, Dublin, London, Victoria, Columbia, Cambridge, Durham, Birmingham, Göttingen, Leeds, Oslo, Sorbonne, Edinburgh, Reading, Princeton, Glasgow, Johns Hopkins, Aberdeen, Athens, Cracow and Philadelphia.

In 1890, he married Rose Elisabeth, daughter of Sir George E. Paget, K.C.B. They had one son, now Sir George Paget Thomson, Emeritus Professor of Physics at London University, who was awarded the Nobel Prize for Physics in 1937, and one daughter. This autobiography/biography was written at the time of the award and first published in the book series Les Prix Nobel,

How did John Dalton discover the law of multiple proportions?

By far Dalton’s most influential work in chemistry was his atomic theory, Attempts to trace precisely how Dalton developed this theory have proved futile; even Dalton’s own recollections on the subject are incomplete. He based his theory of partial pressures on the idea that only like atoms in a mixture of gases repel one another, whereas unlike atoms appear to react indifferently toward each other.

  • This conceptualization explained why each gas in a mixture behaved independently.
  • Although this view was later shown to be erroneous, it served a useful purpose in allowing him to abolish the idea, held by many previous atomists from the Greek philosopher Democritus to the 18th-century mathematician and astronomer Ruggero Giuseppe Boscovich, that atoms of all kinds of matter are alike.

Dalton claimed that atoms of different elements vary in size and mass, and indeed this claim is the cardinal feature of his atomic theory. His argument that each element had its own kind of atom was counterintuitive to those who believed that having so many different fundamental particles would destroy the simplicity of nature, but Dalton dismissed their objections as fanciful.

  • Instead, he focused upon determining the relative masses of each different kind of atom, a process that could be accomplished, he claimed, only by considering the number of atoms of each element present in different chemical compounds,
  • Although Dalton had taught chemistry for several years, he had not yet performed actual research in this field.

In a memoir read to the Manchester Literary and Philosophical Society on October 21, 1803, he claimed: “An inquiry into the relative weights of the ultimate particles of bodies is a subject, as far as I know, entirely new; I have lately been prosecuting this inquiry with remarkable success.” He described his method of measuring the masses of various elements, including hydrogen, oxygen, carbon, and nitrogen, according to the way they combined with fixed masses of each other.

  1. If such measurements were to be meaningful, the elements had to combine in fixed proportions.
  2. Dalton took the fixed proportions for granted, disregarding the contemporary controversy between French chemists Joseph-Louis Proust and Claude-Louis Berthollet over that very proposition.
  3. Dalton’s measurements, crude as they were, allowed him to formulate the Law of Multiple Proportions : When two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in a ratio of small whole numbers.

Thus, taking the elements as A and B, various combinations between them naturally occur according to the mass ratios A : B = x : y or x :2 y or 2 x :y, and so on. Different compounds were formed by combining atomic building blocks of different masses.

  • As the Swedish chemist Jöns Jacob Berzelius wrote to Dalton: “The law of multiple proportions is a mystery without the atomic theory.” And Dalton provided the basis for this theory.
  • The problem remained, however, that a knowledge of ratios was insufficient to determine the actual number of elemental atoms in each compound.

For example, methane was found to contain twice as much hydrogen as ethylene, Following Dalton’s rule of “greatest simplicity,” namely, that A B is the most likely combination for which he found a meretricious justification in the geometry of close-packed spheres, he assigned methane a combination of one carbon and two hydrogen atoms and ethylene a combination of one carbon and one hydrogen atom.

This, we now know, is incorrect, for the methane molecule is chemically symbolized as C H 4 and the ethylene molecule as C 2 H 4, Nevertheless, Dalton’s atomic theory triumphed over its weaknesses because his foundational argument was correct. However, overcoming the defects of Dalton’s theory was a gradual process, finalized in 1858 only after the Italian chemist Stanislao Cannizzaro pointed out the utility of Amadeo Avogadro’s hypothesis in determining molecular masses.

Since then, chemists have shown the theory of Daltonian atomism to be a key factor underlying further advances in their field. Organic chemistry in particular progressed rapidly once Dalton’s theory gained acceptance. Dalton’s atomic theory earned him the sobriquet “father of chemistry.”

What is the law of definite composition simple definition?

Law of definite composition in American English noun.1. Chemistry. the statement that in a pure compound the elements are always combined in fixed proportions by weight.

What does Proust say about love?

‘ Love is space and time measured by the heart.’ ‘In love, happiness is an abnormal state.’ ‘Happiness is beneficial for the body but it is grief that develops the powers of the mind.’

Who proposed the law of definite proportions?

Home Science Chemistry Alternate titles: Proust’s law, law of constant composition law of definite proportions, statement that every chemical compound contains fixed and constant proportions (by mass) of its constituent elements, Although many experimenters had long assumed the truth of the principle in general, the French chemist Joseph-Louis Proust first accumulated conclusive evidence for it in a series of researches on the composition of many substances, especially the oxides of iron (1797).

Another French chemist, Claude Berthollet, who held for indefinite proportions, contested Proust’s findings, but the Scottish chemist Thomas Thomson confirmed some of them and wrote in his article “Chemistry” in the Supplement to the Encyclopædia Britannica (1801) that Proust had definitely proved “metals are not capable of indefinite degrees of oxidation.” The principle was then concretely formulated by the English chemist John Dalton in his chemical atomic theory (1808).

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Erik Gregersen,

What is the law of definite proportions in chemistry?

Home Science Chemistry Alternate titles: Proust’s law, law of constant composition law of definite proportions, statement that every chemical compound contains fixed and constant proportions (by mass) of its constituent elements, Although many experimenters had long assumed the truth of the principle in general, the French chemist Joseph-Louis Proust first accumulated conclusive evidence for it in a series of researches on the composition of many substances, especially the oxides of iron (1797).

Another French chemist, Claude Berthollet, who held for indefinite proportions, contested Proust’s findings, but the Scottish chemist Thomas Thomson confirmed some of them and wrote in his article “Chemistry” in the Supplement to the Encyclopædia Britannica (1801) that Proust had definitely proved “metals are not capable of indefinite degrees of oxidation.” The principle was then concretely formulated by the English chemist John Dalton in his chemical atomic theory (1808).

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The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Erik Gregersen,

What is Proust’s law of definite proportion?

In chemistry, the law of definite proportions, sometimes called Proust’s law, or law of constant composition states that a given chemical compound always contains its component elements in fixed ratio (by mass) and does not depend on its source and method of preparation.

When was the law of constant proportion given?

History – The law of constant proportion was given by Joseph Proust in 1797. This observation was first made by the English theologian and chemist Joseph Priestley, and Antoine Lavoisier, a French nobleman and chemist centered on the process of combustion.

  • I shall conclude by deducing from these experiments the principle I have established at the commencement of this memoir, viz.
  • That iron like many other metals is subject to the law of nature which presides at every true combination, that is to say, that it unites with two constant proportions of oxygen.

In this respect it does not differ from tin, mercury, and lead, and, in a word, almost every known combustible. The law of definite proportions might seem obvious to the modern chemist, inherent in the very definition of a chemical compound. At the end of the 18th century, however, when the concept of a chemical compound had not yet been fully developed, the law was novel.

  1. In fact, when first proposed, it was a controversial statement and was opposed by other chemists, most notably Proust’s fellow Frenchman Claude Louis Berthollet, who argued that the elements could combine in any proportion.
  2. The existence of this debate demonstrates that, at the time, the distinction between pure chemical compounds and mixtures had not yet been fully developed.

The law of definite proportions contributed to, and was placed on a firm theoretical basis by, the atomic theory that John Dalton promoted beginning in 1803, which explained matter as consisting of discrete atoms, that there was one type of atom for each element, and that the compounds were made of combinations of different types of atoms in fixed proportions.

A related early idea was Prout’s hypothesis, formulated by English chemist William Prout, who proposed that the hydrogen atom was the fundamental atomic unit. From this hypothesis was derived the whole number rule, which was the rule of thumb that atomic masses were whole number multiples of the mass of hydrogen.

This was later rejected in the 1820s and 30s following more refined measurements of atomic mass, notably by Jöns Jacob Berzelius, which revealed in particular that the atomic mass of chlorine was 35.45, which was incompatible with the hypothesis. Since the 1920s this discrepancy has been explained by the presence of isotopes; the atomic mass of any isotope is very close to satisfying the whole number rule, with the mass defect caused by differing binding energies being significantly smaller.

When was law of definite proportions first discovered?

History – The law of constant proportion was given by Joseph Proust in 1797. This observation was first made by the English theologian and chemist Joseph Priestley, and Antoine Lavoisier, a French nobleman and chemist centered on the process of combustion.

I shall conclude by deducing from these experiments the principle I have established at the commencement of this memoir, viz. that iron like many other metals is subject to the law of nature which presides at every true combination, that is to say, that it unites with two constant proportions of oxygen.

In this respect it does not differ from tin, mercury, and lead, and, in a word, almost every known combustible. The law of definite proportions might seem obvious to the modern chemist, inherent in the very definition of a chemical compound. At the end of the 18th century, however, when the concept of a chemical compound had not yet been fully developed, the law was novel.

In fact, when first proposed, it was a controversial statement and was opposed by other chemists, most notably Proust’s fellow Frenchman Claude Louis Berthollet, who argued that the elements could combine in any proportion. The existence of this debate demonstrates that, at the time, the distinction between pure chemical compounds and mixtures had not yet been fully developed.

The law of definite proportions contributed to, and was placed on a firm theoretical basis by, the atomic theory that John Dalton promoted beginning in 1803, which explained matter as consisting of discrete atoms, that there was one type of atom for each element, and that the compounds were made of combinations of different types of atoms in fixed proportions.

A related early idea was Prout’s hypothesis, formulated by English chemist William Prout, who proposed that the hydrogen atom was the fundamental atomic unit. From this hypothesis was derived the whole number rule, which was the rule of thumb that atomic masses were whole number multiples of the mass of hydrogen.

This was later rejected in the 1820s and 30s following more refined measurements of atomic mass, notably by Jöns Jacob Berzelius, which revealed in particular that the atomic mass of chlorine was 35.45, which was incompatible with the hypothesis. Since the 1920s this discrepancy has been explained by the presence of isotopes; the atomic mass of any isotope is very close to satisfying the whole number rule, with the mass defect caused by differing binding energies being significantly smaller.

What is Proust’s law of definite proportion?

In chemistry, the law of definite proportions, sometimes called Proust’s law, or law of constant composition states that a given chemical compound always contains its component elements in fixed ratio (by mass) and does not depend on its source and method of preparation.

What is the law of constant composition?

Law of Definition Proportions Example – The law of definite proportions says water will always contain 1/9 hydrogen and 8/9 oxygen by mass. The sodium and chlorine in table salt combine according to the rule in NaCl. The atomic weight of sodium is about 23 and that of chlorine is about 35, so from the law one may conclude dissociating 58 grams of NaCl would produce about 23 g of sodium and 35 g of chlorine.

What are the exceptions to the law of definite proportion?

Exceptions to the Law of Definite Proportions – Although the law of definite proportions is useful in chemistry, there are exceptions to the rule. Some compounds are non-stoichiometric in nature, meaning their elemental composition varies from one sample to another.

  • For example, wustite is a type of iron oxide with an elemental composition varying between 0.83 and 0.95 iron atoms for each oxygen atom (23%–25% oxygen by mass).
  • The ideal formula for iron oxide is FeO, but the crystal structure is such that there are variations.
  • The formula for wustite is written Fe 0.95 O.

Also, the isotopic composition of an element sample varies according to its source. This means the mass of a pure stoichiometric compound will be slightly different depending on its origin. Polymers also vary in element composition by mass, although they are not considered true chemical compounds in the strictest chemical sense.