Johann Wolfgang Döbereiner (December 13, 1780 – March 24, 1849) was a German chemist who is best known for work that foreshadowed the periodic law for the chemical elements.

[edit] Life and work

As a coachman's son, Döbereiner had little opportunity for formal schooling, and so he was apprenticed to an apothecary, reading widely, and attending science lectures. He eventually became a professor at the University of Jena in 1810. In work beginning in 1829,[1] Döbereiner discovered trends in certain properties of selected groups of elements. For example, the average atomic mass of lithium and potassium was close to the atomic mass of sodium. A similar pattern was found with calcium, strontium, and barium, with sulphur, selenium, and tellurium, and also with chlorine, bromine, and iodine. Moreoer, the densities for some of these triads followed a similar pattern. These sets of elements became known as "Dobereiner's Triads".[2][3]

Döbereiner also is known for his discovery of furfural, for his work on the use of platinum as a catalyst, and for a lighter, known as Döbereiner's lamp.

The German writer Goethe was a friend of Döbereiner, attended his lectures weekly, and used his theories of chemical affinities as a basis for his famous 1809 novella Elective Affinities.

World of Scientific Discovery on Johann Wolfgang Döbereiner

The earliest years of Döbereiner's life did not suggest a brilliant future. He was born in Hof, Bavaria, on December 13, 1780, of poor parents. His father was a coachman who could provide Johann with only the most basic education. Although Döbereiner did attend a few lectures in chemistry, botany, mineralogy, philosophy, and languages, he was largely self-taught. Yet, he developed unusual skill in chemical research and caught the eye of Duke Carl August in 1810. Duke Carl appointed Döbereiner to the position of professor extraordinary in chemistry at Jena, a position he held throughout the rest of his academic life. Döbereiner was a man of far-ranging interests and accomplishments. He conducted research on the manufacture of vinegar, the abundance of elements in the Earth's crust, the use of mineral waters for medical purposes, and many other topics in general, pharmaceutical, and analytical chemistry. In 1831 he discovered the chemical compound furfural, obtained from corn cobs, oat and rice hulls, and other cellulose-containing materials. He was one of the first chemists to offer laboratory instruction in chemistry. In the early 1820s, Döbereiner studied the role of platinum metal as a catalyst. Somewhat earlier, Sir Humphry Davy had observed that heated platinum wire greatly increased the rate at which organic compounds oxidize. Döbereiner's contribution was to show that finely divided platinum ("platinum sponge") was even more effective than was solid platinum metal. He even invented a lighter that would generate a flame when gaseous hydrogen came into contact with a spongy platinum catalyst. Most students recognize Döbereiner's name, however, for his contribution to the development of the periodic law. One consequence of Jöns Berzelius ' work on atomic weights was the realization by chemists that the properties of elements might be related to these atomic weights. Around 1817, Döbereiner noticed a pattern among three elements with similar chemical properties, chlorine, bromine, and iodine. Specifically, he noted that the atomic weight of bromine (80.970) was the arithmetic mean of the atomic weights of

chlorine (35.470) and iodine (126.470). The currently accepted atomic weight for bromine was 80.470. Furthermore, the properties of the three elements varied in an orderly manner, from chlorine to bromine to iodine. Döbereiner spoke of this group of elements as a triad. He found two other triads among the known elements. One triad consisted of calcium, strontium, and barium; the other of sulfur, selenium, and tellurium. Other chemists attempted to find other triads among the elements, but, overall, Döbereiner's discovery seemed to be a dead end. Thus, chemists largely ignored the Law of Triads. Not until Dmitri Mendeleev's discovery of the periodic law four decades later did the significance of Döbereiner's discovery finally become apparent. Döbereiner died at Jena on March 24, 1849, twenty years before Mendeleev published his periodic law.

Dmitri Ivanovich Mendeleev (also romanized Mendeleyev or Mendeleef; Russian: Дм трий и́�Ив нович Мендел ева́� е́� listen (help·info)) (8 February [O.S. 27 January] 1834 – 2 February

[O.S. 20 January] 1907), was a Russian chemist and inventor. He is credited as being the creator of the first version of the periodic table of elements. Using the table, he predicted the properties of elements yet to be discovered.

Early Life

Mendeleev was born in the village of Verkhnie Aremzyani, near Tobolsk in Siberia, to Ivan Pavlovich Mendeleev and Maria Dmitrievna Mendeleev (née Kornilieva). His grandfather was Pavel Maximovich Sokolov, a priest of the Russian Orthodox Church from the Tver region.[1] Ivan, along with his brothers and sisters, obtained new family names while attending the theological seminary.[2]

Mendeleev is thought to be the youngest of either 11, 13, 14 or 17 siblings;[3] the exact number differs among sources.[4] His father was a teacher of fine arts, politics and philosophy. Unfortunately for the family's financial well being, his father became blind and lost his teaching position. His mother was forced to work and she restarted her family's abandoned glass factory. At the age of 13, after the passing of his father and the destruction of his mother's factory by fire, Mendeleev attended the Gymnasium in Tobolsk.

In 1849, the now poor Mendeleev family relocated to Saint Petersburg, where he entered the Main Pedagogical Institute in 1850. After graduation, his contraction of tuberculosis caused him to move to the Crimean Peninsula on the northern coast of the Black Sea in 1855. While there he became a science master of the Simferopol gymnasium №1. He returned with fully restored health to Saint Petersburg in 1857.

Later Life

Between 1859 and 1861, he worked on the capillarity of liquids and the workings of the spectroscope in Heidelberg. In late August 1861 he wrote his first book on the spectroscope. On 4 April 1862 he had got engaged to Feozva Nikitichna Leshcheva, and they married on 27 April 1862 at Nikolaev Engineering Institute's church in Saint Petersburg (where he taught).[5] Mendeleev became a professor at the Saint Petersburg Technological Institute and Saint Petersburg State University in 1864 and 1865, respectively. In 1865 he became Doctor of Science for his dissertation "On the Combinations of Water with Alcohol". He achieved tenure in 1867, and by 1871 had transformed Saint Petersburg into an internationally recognized center for chemistry research. In 1876, he became obsessed with Anna Ivanova Popova and began courting her; in 1881 he proposed to her and threatened suicide if she refused. His divorce from Leshcheva was finalized one month after he had married Popova (on 2 April[6]) in early 1882. Even after the divorce, Mendeleev was technically a bigamist; the Russian Orthodox Church required at least seven years before lawful re-marriage. His divorce and the surrounding controversy contributed to his failure to be admitted to the Russian Academy of Sciences (despite his international fame by that time). His daughter from his second marriage, Lyubov, became the wife of the famous Russian poet Alexander Blok. His other children were son Vladimir (a sailor, he took part in the notable Eastern journey of Nicholas   II ) and daughter Olga, from his first marriage to Feozva, and son Ivan and a pair of twins from Anna.

Though Mendeleev was widely honored by scientific organizations all over Europe, including the Copley Medal from the Royal Society of London, he resigned from Saint Petersburg University on 17 August 1890.

In 1893, he was appointed Director of the Bureau of Weights and Measures. It was in this role that he was directed to formulate new state standards for the production of vodka. As a result of his work, in 1894 new standards for vodka were introduced into Russian law and all vodka had to be produced at 40% alcohol by volume.[7]

Mendeleev also investigated the composition of petroleum, and helped to found the first oil refinery in Russia. He recognized the importance of petroleum as a feedstock for petrochemicals. He is credited with a remark that burning petroleum as a fuel "would be akin to firing up a kitchen stove with bank notes."[8]

In 1905, Mendeleev was elected a member of the Royal Swedish Academy of Sciences. The following year the Nobel Committee for Chemistry recommended to the Swedish Academy to award the Nobel Prize in Chemistry for 1906 to Mendeleev for his discovery of the periodic system. The Chemistry Section of the Swedish Academy supported this recommendation. The Academy was then supposed to approve the Committee choice as it has done in almost every case. Unexpectedly, at the full meeting of the Academy, a dissenting member of the Nobel Committee, Peter Klason, proposed the candidacy of Henri Moissan whom he favored. Svante Arrhenius, although not a member of the Nobel Committee for Chemistry, had a great deal of influence in the Academy and also pressed for the rejection of Mendeleev, arguing that the periodic system was too old to acknowledge its discovery in 1906. According to the contemporaries, Arrhenius was motivated by the grudge he held against Mendeleev for his critique of Arrhenius's dissociation theory. After heated arguments, the majority of the Academy voted for Moissan. The attempts to nominate Mendeleev in 1907 were again frustrated by the absolute opposition of Arrhenius.[9]

In 1907, Mendeleev died at the age of 72 in Saint Petersburg from influenza. The crater Mendeleev on the Moon, as well as element number 101, the radioactive mendelevium, are named after him.

Other achievements

Mendeleev made other important contributions to chemistry. The Russian chemist and science historian Lev Chugaev has characterized him as "a chemist of genius, first-class physicist, a fruitful researcher in the fields of hydrodynamics, meteorology, geology, certain branches of chemical technology (explosives, petroleum, and fuels, for example) and other disciplines adjacent to chemistry and physics, a thorough expert of chemical industry and industry in general, and an original thinker in the field of economy." Mendeleev was one of the founders, in 1869, of the Russian Chemical Society. He worked on the theory and practice of protectionist trade and on agriculture.

In an attempt at a chemical conception of the Aether, he put forward a hypothesis that there existed two inert chemical elements of lesser atomic weight than hydrogen. Of these two

proposed elements, he thought the lighter to be an all-penetrating, all-pervasive gas, and the slightly heavier one to be a proposed element, coronium.

Mendeleev devoted much study and made important contributions to the determination of the nature of such indefinite compounds as solutions.

In another department of physical chemistry, he investigated the expansion of liquids with heat, and devised a formula similar to Gay-Lussac's law of the uniformity of the expansion of gases, while in 1861 he anticipated Thomas Andrews' conception of the critical temperature of gases by defining the absolute boiling-point of a substance as the temperature at which cohesion and heat of vaporization become equal to zero and the liquid changes to vapor, irrespective of the pressure and volume.

Mendeleev is given credit for the introduction of the metric system to the Russian Empire.

He invented pyrocollodion, a kind of smokeless powder based on nitrocellulose. This work had been commissioned by the Russian Navy, which however did not adopt its use. In 1892 Mendeleev organized its manufacture.

Mendeleev studied petroleum origin and concluded hydrocarbons are abiogenic and form deep within the earth – see Abiogenic petroleum origin. He wrote: "The capital fact to note is that petroleum was born in the depths of the earth, and it is only there that we must seek its origin." (Dmitri Mendeleev, 1877)

Charles Darwin

Charles Robert Darwin FRS (12 February 1809 – 19 April 1882) was an English naturalist.[I] He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.

He published his theory with compelling evidence for evolution in his 1859 book On the Origin of Species, overcoming scientific rejection of earlier concepts of transmutation of species.[1][2] By the 1870s the scientific community and much of the general public accepted evolution as a fact. However, many favoured competing explanations and it was not until the emergence of the modern evolutionary synthesis from the 1930s to the 1950s that a broad consensus developed that natural selection was the basic mechanism of evolution.[3][4] In modified form, Darwin's scientific discovery is the unifying theory of the life sciences, explaining the diversity of life.[5][6]

Darwin's early interest in nature led him to neglect his medical education at the University of Edinburgh; instead, he helped to investigate marine invertebrates. Studies at the University of Cambridge encouraged his passion for natural science.[7] His five-year voyage on HMS   Beagle established him as an eminent geologist whose observations and theories supported Charles

Lyell's uniformitarian ideas, and publication of his journal of the voyage made him famous as a popular author.[8]

Puzzled by the geographical distribution of wildlife and fossils he collected on the voyage, Darwin began detailed investigations and in 1838 conceived his theory of natural selection.[9] Although he discussed his ideas with several naturalists, he needed time for extensive research and his geological work had priority.[10] He was writing up his theory in 1858 when Alfred Russel Wallace sent him an essay which described the same idea, prompting immediate joint publication of both of their theories.[11] Darwin's work established evolutionary descent with modification as the dominant scientific explanation of diversification in nature.[3] In 1871, he examined human evolution and sexual selection in The Descent of Man, and Selection in Relation to Sex, followed by The Expression of the Emotions in Man and Animals. His research on plants was published in a series of books, and in his final book, he examined earthworms and their effect on soil.[12]

In recognition of Darwin's pre-eminence as a scientist, he was honoured by a major ceremonial funeral in Westminster Abbey, where he was buried close to John Herschel and Isaac Newton.[13] Darwin has been described as one of the most influential figures in human history.[

Childhood and education

Charles Robert Darwin was born in Shrewsbury, Shropshire, England on 12 February 1809 at his family home, the Mount.[16] He was the fifth of six children of wealthy society doctor and financier Robert Darwin, and Susannah Darwin (née Wedgwood). He was the grandson of Erasmus Darwin on his father's side, and of Josiah Wedgwood on his mother's side. Both families were largely Unitarian, though the Wedgwoods were adopting Anglicanism. Robert Darwin, himself quietly a freethinker, had baby Charles baptised in the Anglican Church, but Charles and his siblings attended the Unitarian chapel with their mother. The eight-year-old Charles already had a taste for natural history and collecting when he joined the day school run by its preacher in 1817. That July, his mother died. From September 1818, he joined his older brother Erasmus attending the nearby Anglican Shrewsbury School as a boarder.[17]

Darwin spent the summer of 1825 as an apprentice doctor, helping his father treat the poor of Shropshire, before going to the University of Edinburgh Medical School with his brother Erasmus in October 1825. He found lectures dull and surgery distressing, so neglected his studies. He learned taxidermy from John Edmonstone, a freed black slave who had accompanied Charles Waterton in the South American rainforest, and often sat with this "very pleasant and intelligent man".[18]

In Darwin's second year he joined the Plinian Society, a student natural history group whose debates strayed into radical materialism. He assisted Robert Edmond Grant's investigations of the anatomy and life cycle of marine invertebrates in the Firth of Forth, and on 27 March 1827 presented at the Plinian his own discovery that black spores found in oyster shells were the eggs of a skate leech. One day, Grant praised Lamarck's evolutionary ideas. Darwin was astonished, but had recently read the similar ideas of his grandfather Erasmus and remained indifferent.[19] Darwin was rather bored by Robert Jameson's natural history course which covered geology including the debate between Neptunism and Plutonism. He learned classification of plants, and

assisted with work on the collections of the University Museum, one of the largest museums in Europe at the time.[20]

This neglect of medical studies annoyed his father, who shrewdly sent him to Christ's College, Cambridge, for a Bachelor of Arts degree as the first step towards becoming an Anglican parson. As Darwin was unqualified for the Tripos, he joined the ordinary degree course in January 1828.[21] He preferred riding and shooting to studying. His cousin William Darwin Fox introduced him to the popular craze for beetle collecting which Darwin pursued zealously, getting some of his finds published in Stevens' Illustrations of British entomology. He became a close friend and follower of botany professor John Stevens Henslow and met other leading naturalists who saw scientific work as religious natural theology, becoming known to these dons as "the man who walks with Henslow". When his own exams drew near, Darwin focused on his studies and was delighted by the language and logic of William Paley's Evidences of Christianity.[22] In his final examination in January 1831 Darwin did well, coming tenth out of 178 candidates for the ordinary degree.[23]

Darwin had to stay at Cambridge until June. He studied Paley's Natural Theology which made an argument for divine design in nature, explaining adaptation as God acting through laws of nature.[24] He read John Herschel's new book which described the highest aim of natural philosophy as understanding such laws through inductive reasoning based on observation, and Alexander von Humboldt's Personal Narrative of scientific travels. Inspired with "a burning zeal" to contribute, Darwin planned to visit Tenerife with some classmates after graduation to study natural history in the tropics. In preparation, he joined Adam Sedgwick's geology course, then went with him in the summer for a fortnight to map strata in Wales.[25] After a week with student friends at Barmouth, he returned home to find a letter from Henslow proposing Darwin as a suitable (if unfinished) gentleman naturalist for a self-funded place with captain Robert FitzRoy, more as a companion than a mere collector, on HMS   Beagle which was to leave in four weeks on an expedition to chart the coastline of South America.[26] His father objected to the planned two-year voyage, regarding it as a waste of time, but was persuaded by his brother-in-law, Josiah Wedgwood, to agree to his son's participation.[27]

Inception of Darwin's evolutionary theoryFor more details on this topic, see Inception of Darwin's theory.

While still a young man, Charles Darwin joined the scientific elite

When the Beagle reached Falmouth, Cornwall, on 2 October 1836, Darwin was already a celebrity in scientific circles as in December 1835 Henslow had fostered his former pupil's reputation by giving selected naturalists a pamphlet of Darwin's geological letters.[55] Darwin visited his home in Shrewsbury and saw relatives, then hurried to Cambridge to see Henslow, who advised on finding naturalists available to catalogue the collections and agreed to take on the botanical specimens. Darwin's father organised investments, enabling his son to be a self-funded gentleman scientist, and an excited Darwin went round the London institutions being fêted and seeking experts to describe the collections. Zoologists had a huge backlog of work, and there was a danger of specimens just being left in storage.[56]

Charles Lyell eagerly met Darwin for the first time on 29 October and soon introduced him to the up-and-coming anatomist Richard Owen, who had the facilities of the Royal College of Surgeons to work on the fossil bones collected by Darwin. Owen's surprising results included other gigantic extinct ground sloths as well as the Megatherium, a near complete skeleton of the unknown Scelidotherium and a hippopotamus-sized rodent-like skull named Toxodon resembling a giant capybara. The armour fragments were actually from Glyptodon, a huge armadillo-like creature as Darwin had initially thought.[57][36] These extinct creatures were related to living species in South America.[58]

In mid-December Darwin took lodgings in Cambridge to organise work on his collections and rewrite his Journal.[59] He wrote his first paper, showing that the South American landmass was slowly rising, and with Lyell's enthusiastic backing read it to the Geological Society of London on 4 January 1837. On the same day, he presented his mammal and bird specimens to the Zoological Society. The ornithologist John Gould soon announced that the Galapagos birds that Darwin had thought a mixture of blackbirds, "gros-beaks" and finches, were, in fact, twelve separate species of finches. On 17 February Darwin was elected to the Council of the Geological Society, and Lyell's presidential address presented Owen's findings on Darwin's fossils, stressing geographical continuity of species as supporting his uniformitarian ideas.[60]

Early in March, Darwin moved to London to be near this work, joining Lyell's social circle of scientists and experts such as Charles Babbage,[61] who described God as a programmer of laws. Darwin stayed with his freethinking brother Erasmus, part of this Whig circle and close friend of writer Harriet Martineau who promoted Malthusianism underlying the controversial Whig Poor Law reforms to stop welfare from causing overpopulation and more poverty. As a Unitarian she welcomed the radical implications of transmutation of species, promoted by Grant and younger surgeons influenced by Geoffroy. Transmutation was anathema to Anglicans defending social order,[62] but reputable scientists openly discussed the subject and there was wide interest in John Herschel's letter praising Lyell's approach as a way to find a natural cause of the origin of new species.[52]

Gould met Darwin and told him that the Galápagos mockingbirds from different islands were separate species, not just varieties, and what Darwin had thought was a "wren" was also in the finch group. Darwin had not labelled the finches by island, but from the notes of others on the Beagle, including FitzRoy, he allocated species to islands.[63] The two rheas were also distinct species, and on 14 March Darwin announced how their distribution changed going southwards.[64]

In mid-July 1837 Darwin started his "B" notebook on Transmutation of Species, and on page 36 wrote "I think" above his first evolutionary tree.

By mid-March, Darwin was speculating in his Red Notebook on the possibility that "one species does change into another" to explain the geographical distribution of living species such as the rheas, and extinct ones such as the strange Macrauchenia which resembled a giant guanaco. His thoughts on lifespan, asexual reproduction and sexual reproduction developed in his "B" notebook around mid-July on to variation in offspring "to adapt & alter the race to changing world" explaining the Galápagos tortoises, mockingbirds and rheas. He sketched branching

descent, then a genealogical branching of a single evolutionary tree, in which "It is absurd to talk of one animal being higher than another", discarding Lamarck's independent lineages progressing to higher forms.[65]

Death and legacySee also: Darwin from Insectivorous Plants to Worms

He died at Down House on 19 April 1882. He had expected to be buried in St Mary's churchyard at Downe, but at the request of Darwin's colleagues, after public and parliamentary petitioning, William Spottiswoode (President of the Royal Society) arranged for Darwin to be honoured by a major ceremonial funeral and burial in Westminster Abbey, close to John Herschel and Isaac Newton.[13][141]

Darwin had convinced most scientists that evolution as descent with modification was correct, and he was regarded as a great scientist who had revolutionised ideas. Though few agreed with his view that "natural selection has been the main but not the exclusive means of modification", he was honoured in June 1909 by more than 400 officials and scientists from across the world who met in Cambridge to commemorate his centenary and the fiftieth anniversary of On the Origin of Species.[142] During this period, which has been called "the eclipse of Darwinism", scientists proposed various alternative evolutionary mechanisms which eventually proved untenable. The development of the modern evolutionary synthesis from the 1930s to the 1950s, incorporating natural selection with population genetics and Mendelian genetics, brought broad scientific consensus that natural selection was the basic mechanism of evolution. This synthesis set the frame of reference for modern debates and refinements of the theory