Rhenium

From Wikipedia, the free encyclopedia

Rhenium,  ₇₅Re

Rhenium
Pronunciation	/ˈriːniəm/ ​(REE-nee-əm)
Appearance	silvery-grayish
Standard atomic weight Ar, std(Re)	186.207(1)
Rhenium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Tc ↑ Re ↓ Bh tungsten ← rhenium → osmium
Atomic number (Z)	75
Group	group 7
Period	period 6
Block	d-block
Element category	Transition metal
Electron configuration	[Xe] 4f14 5d5 6s2
Electrons per shell	2, 8, 18, 32, 13, 2
Physical properties
Phase at STP	solid
Melting point	3459 K ​(3186 °C, ​5767 °F)
Boiling point	5903 K ​(5630 °C, ​10,170 °F)
Density (near r.t.)	21.02 g/cm3
when liquid (at m.p.)	18.9 g/cm3
Heat of fusion	60.43 kJ/mol
Heat of vaporization	704 kJ/mol
Molar heat capacity	25.48 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 3303 3614 4009 4500 5127 5954
Atomic properties
Oxidation states	−3, −1, 0, +1, +2, +3, +4, +5, +6, +7 (a mildly acidic oxide)
Electronegativity	Pauling scale: 1.9
Ionization energies	1st: 760 kJ/mol 2nd: 1260 kJ/mol 3rd: 2510 kJ/mol
Atomic radius	empirical: 137 pm
Covalent radius	151±7 pm
Spectral lines of rhenium
Other properties
Natural occurrence	primordial
Crystal structure	​hexagonal close-packed (hcp)
Speed of sound thin rod	4700 m/s (at 20 °C)
Thermal expansion	6.2 µm/(m·K)
Thermal conductivity	48.0 W/(m·K)
Electrical resistivity	193 nΩ·m (at 20 °C)
Magnetic ordering	paramagnetic
Magnetic susceptibility	+67.6·10−6 cm3/mol (293 K)
Young's modulus	463 GPa
Shear modulus	178 GPa
Bulk modulus	370 GPa
Poisson ratio	0.30
Mohs hardness	7.0
Vickers hardness	1350–7850 MPa
Brinell hardness	1320–2500 MPa
CAS Number	7440-15-5
History
Naming	after the river Rhine (German: Rhein)
Discovery	Masataka Ogawa (1908)
First isolation	Masataka Ogawa (1919)
Named by	Walter Noddack, Ida Noddack, Otto Berg (1925)
Main isotopes of rhenium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct 185Re 37.4% stable 187Re 62.6% 4.12×1010 y β− 187Os

Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-gray, heavy, third-row transition metal in group 7 of the periodic table. With an estimated average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust. Rhenium has the third-highest melting point and highest boiling point of any stable element at 5903 K. Rhenium resembles manganese and technetium chemically and is mainly obtained as a by-product of the extraction and refinement of molybdenum and copper ores. Rhenium shows in its compounds a wide variety of oxidation states ranging from −1 to +7.

Discovered in 1908, rhenium was the second-last stable element to be discovered. It was named after the river Rhine in Europe.

Nickel-based superalloys of rhenium are used in the combustion chambers, turbine blades, and exhaust nozzles of jet engines. These alloys contain up to 6% rhenium, making jet engine construction the largest single use for the element. The second-most important use is as a catalyst: rhenium is an excellent catalyst for hydrogenation and isomerization, and is used for example in catalytic reforming of naphtha for use in gasoline (rheniforming process). Because of the low availability relative to demand, rhenium is expensive, with price reaching an all-time high in 2008/2009 US$10,600 per kilogram (US$4,800 per pound). Due to increases in rhenium recycling and a drop in demand for rhenium in catalysts, the price of rhenium has dropped to US$2,844 per kilogram (US$1,290 per pound) as of July 2018.

History

Rhenium (Latin: Rhenus meaning: "Rhine") was the second last-discovered of the elements that have a stable isotope (other new elements discovered in nature since then, such as francium, are radioactive). The existence of a yet-undiscovered element at this position in the periodic table had been first predicted by Dmitri Mendeleev. Other calculated information was obtained by Henry Moseley in 1914. In 1908, Japanese chemist Masataka Ogawa announced that he had discovered the 43rd element and named it nipponium (Np) after Japan (Nippon in Japanese). However, recent analysis indicated the presence of rhenium (element 75), not element 43, although this reinterpretation has been questioned by Eric Scerri. The symbol Np was later used for the element neptunium, and the name "nihonium", also named after Japan, along with symbol Nh, was later used for element 113. Element 113 was also discovered by a team of Japanese scientists and was named in respectful homage to Ogawa's work.

Rhenium is generally considered to have been discovered by Walter Noddack, Ida Noddack, and Otto Berg in Germany. In 1925 they reported that they had detected the element in platinum ore and in the mineral columbite. They also found rhenium in gadolinite and molybdenite. In 1928 they were able to extract 1 g of the element by processing 660 kg of molybdenite. It was estimated in 1968 that 75% of the rhenium metal in the United States was used for research and the development of refractory metal alloys. It took several years from that point before the superalloys became widely used.

Characteristics

Rhenium is a silvery-white metal with one of the highest melting points of all elements, exceeded by only tungsten and carbon. It also has one of the highest boiling points of all elements. It is also one of the densest, exceeded only by platinum, iridium and osmium. Rhenium has a hexagonal close-packed crystal structure, with lattice parameters a = 276.1 pm and c = 445.6 pm.

Its usual commercial form is a powder, but this element can be consolidated by pressing and sintering in a vacuum or hydrogen atmosphere. This procedure yields a compact solid having a density above 90% of the density of the metal. When annealed this metal is very ductile and can be bent, coiled, or rolled. Rhenium-molybdenum alloys are superconductive at 10 K; tungsten-rhenium alloys are also superconductive around 4–8 K, depending on the alloy. Rhenium metal superconducts at 1.697±0.006 K.

In bulk form and at room temperature and atmospheric pressure, the element resists alkalis, sulfuric acid, hydrochloric acid, dilute (but not concentrated) nitric acid, and aqua regia.

Isotopes

Rhenium has one stable isotope, rhenium-185, which nevertheless occurs in minority abundance, a situation found only in two other elements (indium and tellurium). Naturally occurring rhenium is only 37.4% ¹⁸⁵Re, and 62.6% ¹⁸⁷Re, which is unstable but has a very long half-life (≈10¹⁰ years). This lifetime can be greatly affected by the charge state of rhenium atom. The beta decay of ¹⁸⁷Re is used for rhenium-osmium dating of ores. The available energy for this beta decay (2.6 keV) is one of the lowest known among all radionuclides. The isotope rhenium-186m is notable as being one of the longest lived metastable isotopes with a half-life of around 200,000 years. There are twenty-five other recognized radioactive isotopes of rhenium.

Compounds

Rhenium compounds are known for all the oxidation states between −3 and +7 except −2. The oxidation states +7, +6, +4, and +2 are the most common. Rhenium is most available commercially as salts of perrhenate, including sodium and ammonium perrhenates. These are white, water-soluble compounds.

Halides and oxyhalides

The most common rhenium chlorides are ReCl₆, ReCl₅, ReCl₄, and ReCl₃. The structures of these compounds often feature extensive Re-Re bonding, which is characteristic of this metal in oxidation states lower than VII. Salts of [Re₂Cl₈]²⁻ feature a quadruple metal-metal bond. Although the highest rhenium chloride features Re(VI), fluorine gives the d⁰ Re(VII) derivative rhenium heptafluoride. Bromides and iodides of rhenium are also well known. 

Like tungsten and molybdenum, with which it shares chemical similarities, rhenium forms a variety of oxyhalides. The oxychlorides are most common, and include ReOCl₄, ReOCl₃.

Oxides and sulfides

Perrhenic acid (H₄Re₂O₉) adopts an unconventional structure.

 

The most common oxide is the volatile colourless Re₂O₇. Rhenium trioxide ReO₃ adopts a perovskite-like structure. Other oxides include Re₂O₅, ReO₂, and Re₂O₃. The sulfides are ReS₂ and Re₂S₇. Perrhenate salts can be converted to tetrathioperrhenate by the action of ammonium hydrosulfide.

Other compounds

Rhenium diboride (ReB₂) is a hard compound having the hardness similar to that of tungsten carbide, silicon carbide, titanium diboride or zirconium diboride.

Organorhenium compounds

Dirhenium decacarbonyl is the most common entry to organorhenium chemistry. Its reduction with sodium amalgam gives Na[Re(CO)₅] with rhenium in the formal oxidation state −1. Dirhenium decacarbonyl can be oxidised with bromine to bromopentacarbonylrhenium(I):

Re₂(CO)₁₀ + Br₂ → 2 Re(CO)₅Br

Reduction of this pentacarbonyl with zinc and acetic acid gives pentacarbonylhydridorhenium:

Re(CO)₅Br + Zn + HOAc → Re(CO)₅H + ZnBr(OAc)

Methylrhenium trioxide ("MTO"), CH₃ReO₃ is a volatile, colourless solid has been used as a catalyst in some laboratory experiments. It can be prepared by many routes, a typical method is the reaction of Re₂O₇ and tetramethyltin:

Re₂O₇ + (CH₃)₄Sn → CH₃ReO₃ + (CH₃)₃SnOReO₃

Analogous alkyl and aryl derivatives are known. MTO catalyses for the oxidations with hydrogen peroxide. Terminal alkynes yield the corresponding acid or ester, internal alkynes yield diketones, and alkenes give epoxides. MTO also catalyses the conversion of aldehydes and diazoalkanes into an alkene.

Nonahydridorhenate

Structure of ReH

 

A distinctive derivative of rhenium is nonahydridorhenate, originally thought to be the rhenide anion, Re⁻, but actually containing the ReH²⁻
₉ anion in which the oxidation state of rhenium is +7.

Occurrence

Molybdenite

Rhenium is one of the rarest elements in Earth's crust with an average concentration of 1 ppb; other sources quote the number of 0.5 ppb making it the 77th most abundant element in Earth's crust. Rhenium is probably not found free in nature (its possible natural occurrence is uncertain), but occurs in amounts up to 0.2% in the mineral molybdenite (which is primarily molybdenum disulfide), the major commercial source, although single molybdenite samples with up to 1.88% have been found. Chile has the world's largest rhenium reserves, part of the copper ore deposits, and was the leading producer as of 2005. It was only recently that the first rhenium mineral was found and described (in 1994), a rhenium sulfide mineral (ReS₂) condensing from a fumarole on Kudriavy volcano, Iturup island, in the Kuril Islands. Kudriavy discharges up to 20–60 kg rhenium per year mostly in the form of rhenium disulfide. Named rheniite, this rare mineral commands high prices among collectors.

Production

Ammonium perrhenate

 

Commercial rhenium is extracted from molybdenum roaster-flue gas obtained from copper-sulfide ores. Some molybdenum ores contain 0.001% to 0.2% rhenium. Rhenium(VII) oxide and perrhenic acid readily dissolve in water; they are leached from flue dusts and gasses and extracted by precipitating with potassium or ammonium chloride as the perrhenate salts, and purified by recrystallization. Total world production is between 40 and 50 tons/year; the main producers are in Chile, the United States, Peru, and Poland. Recycling of used Pt-Re catalyst and special alloys allow the recovery of another 10 tons per year. Prices for the metal rose rapidly in early 2008, from $1000–$2000 per kg in 2003–2006 to over $10,000 in February 2008. The metal form is prepared by reducing ammonium perrhenate with hydrogen at high temperatures:

2 NH₄ReO₄ + 7 H₂ → 2 Re + 8 H₂O + 2 NH₃

Applications

The Pratt & Whitney F-100 engine uses rhenium-containing second-generation superalloys

 

Rhenium is added to high-temperature superalloys that are used to make jet engine parts, using 70% of the worldwide rhenium production. Another major application is in platinum–rhenium catalysts, which are primarily used in making lead-free, high-octane gasoline.

Alloys

The nickel-based superalloys have improved creep strength with the addition of rhenium. The alloys normally contain 3% or 6% of rhenium. Second-generation alloys contain 3%; these alloys were used in the engines for the F-15 and F-16, whereas the newer single-crystal third-generation alloys contain 6% of rhenium; they are used in the F-22 and F-35 engines. Rhenium is also used in the superalloys, such as CMSX-4 (2nd gen) and CMSX-10 (3rd gen) that are used in industrial gas turbine engines like the GE 7FA. Rhenium can cause superalloys to become microstructurally unstable, forming undesirable TCP (topologically close packed) phases. In 4th- and 5th-generation superalloys, ruthenium is used to avoid this effect. Among others the new superalloys are EPM-102 (with 3% Ru) and TMS-162 (with 6% Ru), as well as TMS-138 and TMS-174.

CFM International CFM56 jet engine still with blades made with 3% rhenium

 

For 2006, the consumption is given as 28% for General Electric, 28% Rolls-Royce plc and 12% Pratt & Whitney, all for superalloys, whereas the use for catalysts only accounts for 14% and the remaining applications use 18%. In 2006, 77% of the rhenium consumption in the United States was in alloys. The rising demand for military jet engines and the constant supply made it necessary to develop superalloys with a lower rhenium content. For example, the newer CFM International CFM56 high-pressure turbine (HPT) blades will use Rene N515 with a rhenium content of 1.5% instead of Rene N5 with 3%.

Rhenium improves the properties of tungsten. Tungsten-rhenium alloys are more ductile at low temperature, allowing them to be more easily machined. The high-temperature stability is also improved. The effect increases with the rhenium concentration, and therefore tungsten alloys are produced with up to 27% of Re, which is the solubility limit. Tungsten-rhenium wire was originally created in efforts to develop a wire that was more ductile after recrystallization. This allows the wire to meet specific performance objectives, including superior vibration resistance, improved ductility, and higher resistivity. One application for the tungsten-rhenium alloys is X-ray sources. The high melting point of both elements, together with their high atomic mass, makes them stable against the prolonged electron impact. Rhenium tungsten alloys are also applied as thermocouples to measure temperatures up to 2200 °C.

The high temperature stability, low vapor pressure, good wear resistance and ability to withstand arc corrosion of rhenium are useful in self-cleaning electrical contacts. In particular, the discharge occurring during the switching oxidizes the contacts. However, rhenium oxide Re₂O₇ has poor stability (sublimes at ~360 °C) and therefore is removed during the discharge.

Rhenium has a high melting point and a low vapor pressure similar to tantalum and tungsten. Therefore, rhenium filaments exhibit a higher stability if the filament is operated not in vacuum, but in oxygen-containing atmosphere. Those filaments are widely used in mass spectrometers, in ion gauges and in photoflash lamps in photography.

Catalysts

Rhenium in the form of rhenium-platinum alloy is used as catalyst for catalytic reforming, which is a chemical process to convert petroleum refinery naphthas with low octane ratings into high-octane liquid products. Worldwide, 30% of catalysts used for this process contain rhenium. The olefin metathesis is the other reaction for which rhenium is used as catalyst. Normally Re₂O₇ on alumina is used for this process. Rhenium catalysts are very resistant to chemical poisoning from nitrogen, sulfur and phosphorus, and so are used in certain kinds of hydrogenation reactions.

Other uses

The isotopes ¹⁸⁸Re and ¹⁸⁶Re are radioactive and are used for treatment of liver cancer. They both have similar penetration depth in tissue (5 mm for ¹⁸⁶Re and 11 mm for ¹⁸⁸Re), but ¹⁸⁶Re has advantage of longer lifetime (90 hours vs. 17 hours).

¹⁸⁸Re is also being used experimentally in a novel treatment of pancreatic cancer where it is delivered by means of the bacterium Listeria monocytogenes.

Related by periodic trends, rhenium has a similar chemistry to that of technetium; work done to label rhenium onto target compounds can often be translated to technetium. This is useful for radiopharmacy, where it is difficult to work with technetium – especially the 99m isotope used in medicine – due to its expense and short half-life.

Precautions

Very little is known about the toxicity of rhenium and its compounds because they are used in very small amounts. Soluble salts, such as the rhenium halides or perrhenates, could be hazardous due to elements other than rhenium or due to rhenium itself. Only a few compounds of rhenium have been tested for their acute toxicity; two examples are potassium perrhenate and rhenium trichloride, which were injected as a solution into rats. The perrhenate had an LD₅₀ value of 2800 mg/kg after seven days (this is very low toxicity, similar to that of table salt) and the rhenium trichloride showed LD₅₀ of 280 mg/kg.

A. S. Neill

From Wikipedia, the free encyclopedia

A. S. Neill
Born	Alexander Sutherland Neill 17 October 1883 Forfar, Scotland
Died	23 September 1973 (aged 89) Aldeburgh, Suffolk, England
Occupation	Educator, author
Known for	Founding Summerhill School, advocacy of personal freedom for children, progressive education

Alexander Sutherland Neill (17 October 1883 – 23 September 1973) was a Scottish educator and author known for his school, Summerhill, and its philosophies of freedom from adult coercion and community self-governance. Raised in Scotland, he was a poor student, but became a schoolteacher at several schools across the country before attending the University of Edinburgh in 1908–1912. He took two jobs in journalism before World War I, and taught at Gretna Green Village School during the first year of the war, writing his first book, A Dominie's Log (1915), as a diary of his life as head teacher. He joined the staff of a school in Dresden in 1921, founding Summerhill on his return to England in 1924. Summerhill received widespread renown in the 1920s to 1930s and then in the 1960s to 1970s, due to progressive and counter-culture interest. Neill wrote 20 books in his lifetime, his bestseller being the 1960 Summerhill, a compilation of four previous books on his school, read widely among the free school movement in the 1960s onwards.

Early life and career

Alexander Sutherland Neill was born in Forfar, Scotland, on 17 October 1883 to George and Mary Neill. He was their fourth son; one of the eight surviving children out of 13. He was raised in an austere, Calvinist house with values of fear, guilt, and adult and divine authority, which he later repudiated. As a child, he was obedient, quiet, and uninterested in school. His father was the village dominie (Scottish schoolmaster) of Kingsmuir, near Forfar in eastern Scotland, and his mother had been a teacher before her marriage. The village dominie held a position of prestige, hierarchically beneath that of upper classes, doctors, and clergymen. As typical of Scottish methods at the time, the dominie controlled overcrowded classrooms with his tawse, as corporal punishment. Neill feared his father, though he later claimed his father's imagination as a role model for good teaching. Scholars have interpreted Neill's harsh childhood as the impetus for his later philosophy, though his father was not shown to be harsher to Allie (as Neill was known) than to anyone else. Neill's mother (née Sutherland Sinclair) insisted on high standards for her family, and demanded comportment to set the family apart from the townspeople.

Children usually left the local school for Forfar Academy at the age of 14, and with his father a teacher, Neill was especially expected to do so. Instead of wasting time and money, Neill went to work as a junior clerk in an Edinburgh gas meter factory. His parents took pity on his hatred of the job, homesickness, and its low pay, and so Neill became an apprentice draper in Forfar. He found the work stultifying and came home after a foot inflammation. Neill tried to take an examination that would raise his pay grade, but could not bring himself to study. Now 15, his parents decided to make him his father's assistant "pupil teacher". The children liked Neill, though he received poor marks from a school inspector. He taught a wider range of topics as his self-confidence grew, and he developed an interest in mathematics from the Forfar Academy maths master. After four years, he tried for teacher training college, but came nearly last in his class. He continued as a pupil teacher in Bonnyrigg and Kingskettle, where he found the teachers' instruction militant and loathsome. He stayed in Kingskettle for three years, during which he learned Greek from a local priest, an experience that increased his interest in academicism and sublimated his interest in priesthood into a desire to attend university. After studying with the priest and the Forfar math master, Neill passed his university entrance exam and preliminary teacher's certification.

Neill became an assistant teacher at the Newport Public School in the wealthy Newport-on-Tay, where he learned to dance and appreciate music and theatre. He also fell in love, and Margaret became an obsession of his. He adopted progressive techniques at this school, and abandoned the tawse for other forms of establishing discipline. Neill was friendly and relaxed with his pupils, and described his two years there as "the happiest of [his] life thus far". He finished his university entrance exams and received his full teaching certification.

In 1908, at the age of 25, Neill enrolled in the University of Edinburgh. He began as an agriculture student, at his father's behest for a well-salaried career, but switched to English literature by the end of his first year. Neill was excluded from cultural events due to his lack of funds, but participated in sports, showed interest in the military, and wrote for The Student (the university magazine) and the Glasgow Herald. He became the student paper's editor during his last year, which opened Neill to a world of culture. He also felt more confident to pursue women. In his editorials, Neill criticized the tedium of lectures and the emphasis on tests instead of critical thinking. He began to develop his thoughts about the futility of forced education, and the axiom that all learning came from intrinsic interest. Neill graduated in 1912 and began to edit encyclopedias and similar reference books. He took a new job as art editor of the Piccadilly Magazine, but its operations were halted by the 1914 onset of World War I, in which he served as an officer in the army. He returned to Scotland, working as a head teacher at Gretna Green School during the first year of the war. The diary he wrote for this year was published as a book, A Dominie's Log, in November 1915 by Herbert Jenkins, and received good reviews for its humour and narrative style.

Neill was invited to join a progressive school in Dresden in 1921. The school moved to a monastery near Vienna in 1923, where the townspeople did not receive it well. He moved to England in 1924 and started Summerhill in Lyme Regis, where the name came from the estate.

Summerhill School

Summerhill, 1993

 

The school picked up some notoriety and the average enrolment was 40 pupils. In 1927, it moved to Leiston, where it remained.

Neill credited Summerhill's environment instead of himself for the school's reformatory successes. Neill used to offer psychoanalytic therapy ("private lessons", since he was not a licensed therapist) for children who arrived as delinquents from other institutions, but later found love, affirmation and freedom to be better cures.

The Summerhill classroom was popularly assumed to reflect Neill's anti-authoritarian beliefs, though their classes were traditional in practice. Neill did not show outward interest in classroom pedagogy, and was mainly interested in student happiness. He did not consider lesson quality important, and thus there were no distinctive Summerhillian classroom methods. Leonard Waks wrote that, like Homer Lane, Neill thought all teaching should follow student interest, and that teaching method did not matter much once student interest was apparent. In a review of an algebra lesson taught by Neill as recounted through Herb Snitzer's Living at Summerhill, Richard Bailey described Neill's teaching technique as "simply awful" for his lack of student engagement, inarticulate explanations, and insults directed at students. Bailey criticized Neill's absolution of responsibility for his pupils' academic performance, and his view that charismatic instruction was a form of persuasion that weakened child autonomy. Ronald Swartz referred to Neill's method as Socratic, about which Bailey disagreed.

Neill was not religious. Despite this, he would flippantly remark that Summerhill was the only Christian school in England when its philosophy was compared with that of Christ. Neill saw the doctrine of "original sin" as a means of control and sought a world ruled by love and self-examination. Like Freud, he felt that children who were denied understanding of their sexuality in their youth became adults who were similarly fearful of their own sexuality.

Philosophy

Neill felt that children (and human nature) were innately good, and that children naturally became just and virtuous when allowed to grow without adult imposition of morality. Children did not need to be coaxed or goaded into desirable behaviour, as their natural state was satisfactory and their natural inclinations "in no way immoral". If left alone, children would become self-regulating, reasonable and ethical adults. Together with Homer Lane, Neill supported personal freedoms for children to live as they please without adult interference, and called this position "on the side of the child". Neill's practice can be summarised as providing children with space, time, and empowerment for personal exploration and with freedom from adult fear and coercion.

The aim of life, to Neill, was "to find happiness, which means to find interest." Likewise, the purpose of Neill's education was to be happy and interested in life, and children needed complete freedom to find their interests. Neill considered happiness an innate characteristic that deteriorated if children were denied personal freedom. Such unhappiness led to repressed and psychologically disordered adults. He blamed a "sick and unhappy" society for widespread unhappiness. Neill claimed that society harboured fears of life, children and emotions that were continually bequeathed to the next generation. He felt that children turned to self-hate and internal hostility when denied an outlet for expression in adult systems of emotional regulation and manipulation. Likewise, children taught to withhold their sexuality would see such feelings negatively, which would fuel disdain for self. Neill thought that calls for obedience quenched the natural needs of children. Moreover, their needs could not be fulfilled by adults or a society that simultaneously prolonged their unhappiness, although perhaps a school like Summerhill could help.

Neill... believed that the best thing teachers could do was to leave children alone to develop naturally. Denis Lawton, Education and Social Justice, p. 78

As for "interest", Neill felt it came organically and spontaneously as a prerequisite for learning. Neill considered forced instruction (without pupil interest) a destructive waste of time. Earlier in his career, he wrote that human interest releases emotions that otherwise congests a person. He added that education's role is to facilitate that release, with Summerhill actualizing this concept. Neill never defines "true interest" and does not account for the social influences on child interest. Bailey felt that this omission discredits Neill's position against external influence. Bailey also cited "adaptive preferences" literature, where human interests change based on their surroundings and circumstances, as evidence of how intrinsic interest can be externally influenced. Bailey also dubbed Neill's views on intelligence as "innatist" and fatalist — that children had naturally set capabilities and limitations. Neill saw contemporary interventionist practice as doing harm by emphasising conformity and stifling children's natural drive to do as they please.

Neill did not identify with the progressive educators of his time. They advocated far gentler authority in child-rearing, which Neill considered more insidious than overt authority and altogether unnecessary. All imposed authority, even if meant well, was unjustified. He felt that adults asserted authority for its feelings of power, and that this motive was a type of repression. In Neill's philosophy, the goal was maintenance of happiness through avoidance of repressive habits from society. Despite Neill's common citation as a leader within progressive education, his ideas were considerably more radical, and he was called an extremist by other radicals. Unlike Friedrich Fröbel, Neill did not view children with romantic innocence. He saw their animalistic traits as qualities to be "outgrown with time and freedom". Neill also considered his role in providing emotional support.

Emotional education trumped intellectual needs, in Neill's eyes, and he was associated with anti-intellectualism. In actuality, he had a personal interest in scholarship and used his autobiography near the end of his life to profess the necessity of both emotion and intellect in education, though he often took jabs at what he saw to be education's overemphasis on book-learning. Neill felt that an emotional education freed the intellect to follow what it pleased, and that children required an emotional education to keep up with their own gradual developmental needs. This education usually entailed copious amounts of play and distance from the adult anxieties of work and ambition. Neill was influenced by Sigmund Freud's theories of psychoanalysis, Homer Lane's interpretation of Freud, and later, by the unorthodox sexual theories of Wilhelm Reich. The reverence for Reich appears in the abundant correspondence between them. Neill accepted Reich's claims about cosmic energy and his utopian ideas on human sexuality. In Reich's view, "discharge" of sexual energy leads to happiness, whereas lack of such discharge leads to unhappiness and "rigidity". Although not a trained therapist, Neill gave psychoanalytic private lessons to individual children, designed to unblock impasses in their inner energies. Neill also offered body massage, as suggested by Reich. Neill later found that freedom cured better than this therapy.

Richard Bailey placed Neill alongside William Godwin, Jean-Jacques Rousseau, Voltaire, and Robert Owen in Thomas Sowell's "unconstrained vision" tradition, where human potential is naturally unlimited and human development is dependent on environment and not incentives. Bailey also compared Neill's thoughts on coercion to those of Godwin, who felt that regulation through reward and punishment stunted growth. Neill saw moral instruction as a wedge between natural instinct and conformity and thought children were best off without it. Neill trusted the natural inclinations of children and saw no need to externally and purposefully influence their behaviour. Denis Lawton likened Neill's ideas to Rousseauan "negative education", where children discover for themselves instead of receiving instruction. Neill is commonly associated with Rousseau for their similar thoughts on human nature, although Neill claimed to not have read Rousseau's Emile, or On Education until near the end of his life. John Cleverley and D. C. Phillips declared Neill "the most notable figure in the Rousseauean tradition", and Frank Flanagan credited Neill with actualising what Rousseau envisaged. Marc-Alexandre Prud-homme and Giuliano Reis found the comparison "inappropriate" on the basis of Rousseau's views on gender.

Peter Hobson found Neill's philosophy of education incomplete, oversimplified, without a "coherent theory of knowledge", and too dependent on his experience instead of philosophical position. When presented with Hobson's position, four experts on Neill and Summerhill considered his assertions "irrelevant". Joel Spring likened Neill's views on the family to that of Mary Wollstonecraft, in that the parents would share power equally.

Freedom, not licence

When Neill said children should be free, he did not mean complete freedom, but freedom without licence—that everyone can do as they like unless such action encroaches upon another's freedom. As such, adults could and should protect children from danger, but not trample their self-regulation. Neill emphasised that adult removal from child affairs was distinct from disregard for their security. He felt that children met their own limits naturally. Neill believed in equal rights between parents and children, and that undesirable "disciplined" or "spoiled" homes were created when those rights were imbalanced. He felt it unnecessary to fulfil all of childhood's requests and had great disdain for spoiled children. Summerhill children were naturally restricted by the school's limited teaching expertise and low funds.

Bailey wrote that Neill did not have full faith in self-regulation due to his emphasis on the necessity of making specific environments for children. Robin Barrow argued that Neill's idea of self-regulation was contradictory, when its intent was, more simply, the extent to which children need to abide by external restraints. Bailey added that children cannot know the extent to which dull and unknown subjects can be exciting without guidance. He felt that Neill's belief in children's innate and realistic wisdom did not accommodate human characteristics "such as error, prejudice, and ignorance", ascribed genius-level intelligence to children, and did not consider social aspects in child decision-making.

Self-governance

Self-governance was a central idea to Summerhill, and is perhaps its "most fundamental feature". Summerhill held a weekly general meeting that decided the school's rules and settled school disputes, where every member of the community—staff and student alike—had a single vote. Almost everyone in the school attended the meeting, and children always held the majority. Meetings were managed by an elected Chairperson. At times, the school had over 200 rules.

Summerhill sought to produce individualists conscious of their surrounding social order, and Neill chose the self-governance of Homer Lane's Little Commonwealth for the basis of that lesson. The general meeting replaced teacher authority with communal control, which freed teachers from their roles as disciplinarians and instructed children in the role of democratic participation and the role of rules. Additionally, reports of teacher–student disputes were rare. Neill felt that the community's authority never created resentment in those subject to sanctions. Sven Muller contended that the meeting was more useful than discipline for creating civic-minded citizens. An ex-pupil recalled some of the wild ideas Neill would propose at the meeting, and while the students would vote him down, she later recounted how the exercise was also intended as a lesson for the staff on the power of the meeting and communal authority. Neill considered self-governance "the most valuable asset in education and life" and the general meeting "more important than all the textbooks in the world".

On occasion, Neill exercised unilateral decision-making as the owner of the school, despite his emphasis on the authority figure-less nature of the school. Instances include when he once made a decision after the group's discussion protracted, and when he once asserted himself dictator. Ultimately, the school's freedom was Neill's to structure.

Writings

Neill wrote 20 books in his lifetime. His style was simple and friendly, unlike didactic literature from the era. His topics included the balance of authority and the thoughts–feelings relationship.

Summerhill

The 1960 release of Summerhill catapulted Neill into the public view. Richard Bailey described its result as "an American cult" of Summerhillian schools and their support organizations. The book sold well and made Neill into a figurehead of new interest in education. Bailey added that the unpretentious book's message was easier to impart than Deweyan thought, and that its release inspired Neill's education critic contemporaries as to the viability of their ideas.

Reception and legacy

Critics regard Neill's influence and importance with mixed opinion. Supporters counted Neill amongst the world's most influential educationists. UNESCO listed Neill within its 100 most important educationists worldwide. The Times Educational Supplement listed him in its 12 most important British educationists of the millennium. Herb Kohl declared Neill "one of the greatest democratic educators of the last century" in 2005. Academics and teachers cited Summerhill as the common ancestor for free schools, and Neill was poised to become a public figure during Summerhill's heyday in the 1970s. Its detractors do not classify Summerhill as a school. Max Rafferty called Summerhill "a caricature of education" and felt threatened by the implications of "the spread of Neill's hedonism to the majority of the next generation". Others criticized Neill for his progressive ideals despite agreement on his critique of traditional schools, and bemoaned his "outdated radicalism" and "dangerously enthusiastic following in teaching training institutions".

Richard Bailey wrote that Summerhill received most of its public attention in the 1920s to 1930s and in the 1960s to 1970s, which were milieux of social change (progressivism and the counterculture, respectively). Neill was known in British education circles by the 1920s and was "probably Britain's first educational celebrity" in the 1930s, though he was not driven by his reception. Journal reviews called Neill "the most popular writer on education today" and said of his works, "Nearly all the more alive and up-to-date teachers in Britain have read and argued about his notions". He was known via his books as a figure in the new psychoanalysis. The accessible 1960 Summerhill crowned Neill the leader of a new avant-garde education and he became symbolic of the rebel decade.

Neill is generally associated with democratic schools as a leader in its tradition. H. A. T. Child associated Summerhill with the Bedales School, Alfred the Great, and Child's Dartington Hall School, and David Gribble wrote about schools around the world following Neill's teachings in 1998.^{[citation needed]} Timothy Gray linked the release of Summerhill with the rise of writers Herb Kohl, Jonathan Kozol, Neil Postman, and Ivan Illich. Scholars debate whether Neill fits best in a progressive or more radical tradition.

Few of Neill's acolytes continued his work after his death. His family maintained Summerhill, with Neill's daughter as its headmaster as of 2013. Others influenced by Neill included John Aitkenhead, Michael Duane, and R. F. Mackenzie. Richard Bailey wrote that Maria Montessori and Rudolf Steiner's followers were more evangelical in character, and that Neill deterred would-be devotees. He specifically discouraged American association with his school in both name and likeness. By 1972, Ray Hemmings wrote that Neill's ideas were misinterpreted in the hands of other schools. Hemmings found Neill to have moderate influence on state schools in areas such as teacher–student interactions. Neill's views on sexuality and non-compulsory lessons did not have widespread acceptance. Herb Snitzer said that Neill "influenced thousand of teachers". Both George Dennison and Bailey felt Neill's influence to not be easily measurable, with Dennison adding that non-Summerhill schools continue to adopt Neillian thought.

Neill was awarded three honorary degrees: a master's and two honorary doctorates. One doctorate was from the Newcastle University in 1966. He was reportedly very proud of the awards.