Dominique Georges Pire, 1910-1969

Drawing of Pauling and Pire, ca. 1965

“There is perhaps no surer road to peace than the one that starts from little islands and oases of genuine kindness, islands and oases constantly growing in number and being continually joined together until eventually they ring the world.”

-Dominique Georges Pire, Nobel acceptance speech, 1958.

Tomorrow marks the centenary anniversary of the birth of the Dominican friar and peace activist, Georges Charles Clement Ghislain Pire, born on February 10, 1910 in Dinant Belgium.

At the age of four, Pire was forced to flee with his family from advancing German troops during the First World War. The family spent four years in France before returning to their home, which had been destroyed during the conflict. Years later he studied classics and philosophy at the Collège de Bellevue in Dinant, and took the name Henri Dominique after entering the Dominican monastery of La Sarte in Huy, Belgium. He attended the Dominican university of Rome, Collegio Angelico, and in 1936 was granted a doctorate in theology. After receiving his doctorate, he studied philosophy and sociology at Louvain University for a year before returning to the monastery at Huy to teach.

During and after World War II, Pire provided aid services and camps for children. The camps were essentially missions that fed thousands of Belgian and French children during a time of great conflict. He also worked for a resistance intelligence service throughout the course of the war, where he assisted an underground network that returned downed flyers to Allied forces. For his work during the war, he was awarded the National Recognition Medal, the War Medal, the Military Cross with Palms and the Resistance Medal with Crossed Swords.

It was not until he reached the age of thirty-nine, however, that Pire began his most widely remembered work with European refugees. Pire began by establishing a sponsorship program, in which private individuals would send letters and packages to refugees that were still living in various camps. Soon thereafter, he began helping many refugees to leave their camps, initially by setting up four complexes in Belgium where individuals could live and receive care for the rest of their lives. All of the homes were supported by voluntary work and donations, a common theme of Pire’s biography.

He later expanded his efforts, establishing seven European Villages for refugees at locations in Austria, Belgium and Germany. As part of this effort, he founded an organization to oversee the villages, called Aid to Displaced Persons, which became an international organization in 1957.

A defining component of Dominique Pire’s programs was their targeting of specific types of refugees. His efforts largely benefitted the elderly, the weak and individuals who could or would not easily be reintroduced to society. Pire sought to help people who had little hope of rebuilding a life for themselves and their families without some kind of intimate personal intervention. It was mainly for this particular work that Pire was awarded the Nobel Peace Prize in 1958.

Dominique Pire, ca. 1958.

(Image courtesy of the Nobel Foundation)

Pire used the attention garnered by the Nobel Prize to expand his work. He founded the University of Peace at Huy in 1960, the stated primary purpose of which was to serve as “a University where the participants are instructed in the surest path to peace.” He also founded a new global organization, The Heart Open to the World, which sought to enhance international fraternity.

One of the final projects initiated by Pire was a series of programs that he called Islands of Peace. Pire’s idea was to establish inter-village collaborative partnerships in parts of Pakistan that would seek to improve food production, education services and medical care. The project structure involved the use of outside technical experts to start the programs, with control of the programs eventually being turned over to the local inhabitants.

Though Linus Pauling and Dominique Pire were separated by occupation and their own particular institutions, they both had a vested interest in peace. A substantial portion of the correspondence between Pauling and Pire is a series of letters discussing their contributions to the world peace movement. As one reads the letters, an interesting discourse plays out, stern but polite, in which the two men debate the value of their own individual methods.

After a number of years, another letter from Pire requested Pauling’s help in raising funds for a peace exhibition. Pire also sent Pauling transcripts of three of his lectures; Pauling in turn sent Pire a petition meant to engage the President of the United States.

The petition sent by Pauling to Pire is the most notable of interactions between the two men. It was titled an Appeal by Recipients of the Nobel Peace Prize, and called for an end to the war in Vietnam. The petition does not apportion blame to any of the particular combatants in the war, but is rather a plea to universally end violence and restore guidelines set forth by the Geneva Agreement. It was signed by a number of influential men with an interest in peace, including Father Pire, Linus Pauling and Martin Luther King, Jr.

Choosing to retire after nearly thirty-two years of service, Domique Pire spent the remainder of his days teaching and living at the monastery in Huy. While receiving care at Louvain Roman Catholic Hospital, he died on January 30, 1969, from complications following surgery.

Jacques Monod (1910-1976)

(Image courtesy of the Pasteur Foundation)

As of February 2010, one-hundred years have passed since the birth of renowned molecular biologist, Jacques Lucien Monod.

Monod was born in Paris on February 9, 1910. At the age of seven, he and his family moved to Cannes, France where he eventually attended college. After receiving his baccalauréat in 1928, Monod moved back to Paris to study general chemistry and biology, as well as zoology and geology. He received his Ph.D. from the Sorbonne in late 1940, and continued his research in occupied France throughout World War II.  During the German occupation, Monod joined an armed communist-led resistance group, the Francs-Tireurs et Partisans. He served as an executive officer and was mostly responsible for organization and information.

Of his early life, historian and author Horace Freeland Judson writes

The Monods were one of the noted clans of the professional class of France, far-flung, close-knit, sober, devout, ambitious – and Protestants, exiles for a century. Coming from that family, his father was a painter. His mother was American. Monod was a product of the French academic system; he was dissatisfied with it from the time he first came to the Sorbonne in 1928 to the days of riot and near revolution in Paris in May of 1968, when he publicly crossed the barricades to be on the students’ side.

Later in his career, Monod authored and co-authored well over one-hundred scientific articles before becoming director of the Institut Pasteur in 1971.

Certain of the scientific concepts developed by Monod are now central to modern biology. Among these, Monod is perhaps most widely recognized for his work with enzyme theory and synthesis, largely undertaken in collaboration with François Jacob. The operon model that the tandem developed, which addresses the regulation of gene expression, was hailed by Institut Pasteur researcher Agnes Ullman as a “forerunner of the biotechnological revolution.” Monod is also known for conceptualizing the theory of allostery, an extremely important development for the study of bacterial regulatory mechanisms.

Aside from his impressive assemblage of academic articles, Monod is remembered for a book he wrote titled Chance and Necessity. The book describes, in layman’s terms, the chief findings of molecular biology up to the time of its publication in 1970. The volume also attempts to show that certain consequences for belief systems and ethical behavior follow from the biological framework advanced in the book. The text was very popular, but among his fellow scientists and scholars, proved also to be very controversial.

In 1965 Monod was awarded the Nobel Prize in Medicine, to be shared with two other men from the Institut Pasteur, François Jacob and André Lwoff. The researchers were recognized for “their discoveries concerning genetic control of enzyme and virus synthesis.”  Not long thereafter, Monod was elected as chair of the Collège de France, an honorary institution unique to France.

(Image courtesy of the Nobel Foundation)

Though the two men led vastly different lives, many similarities can be found between Linus Pauling and Jacques Monod. Both men initiated extensive work in the field of biology and biochemistry. Both were awarded a Nobel Prize and appeared often in numerous professional journals and books of their own authoring. The two men also maintained a notable appreciation for the outdoors, were very successful in their fields and were outspoken participants in a number of controversies in and outside of their disciplines.

Monod visited the California Institute of Technology in 1936, nearly five years after Linus Pauling had been made a full professor of Chemistry. Monod had received a Rockefeller fellowship to study genetics at Caltech, around the time when Pauling was shifting more of his attention towards the field of biology. Though they were in close proximity over the summer of Monod’s visit, the two initiated very little in the form of written contact.

Later on, Monod and Pauling did correspond, though not as much as one might expect considering their statures within the scientific community. Monod first contacted Pauling to share a letter that he wrote to the editor of the Bulletin of the Atomic Scientists, protesting the trial and execution of Ethel and Julius Rosenberg for their alleged conspiracy with the former Soviet Union (a matter of great concern to Pauling as well). A second letter came on November 8, 1954 to congratulate Pauling for his Nobel Chemistry Prize. The last recorded exchange between the two was an inquiry by Monod concerning a graduate student’s application that had listed Pauling as a reference.

Upon closer inspection however, it appears that the two may have known each other better than their sparse correspondence suggests. While congratulating him for his Nobel Prize in Chemistry, Monod suggested that Pauling stop by his home in France for dinner during his acceptance trip to Europe. Likewise, a calling card for Mr. & Mme. Jacques Monod can be found among receipts from Pauling’s visit to Paris in 1957. By 1959 the two were on a first name basis, and Monod’s name and work can be found referenced a number of times in Pauling’s speeches and manuscripts.

If the two shared nothing else, it was a persona or way of doing things. Horace Judson, who knew both men and their works very well, wrote of Monod

His style was as quintessentially French as Linus Pauling’s was American. He was a multiple outsider.

In early 1976, after serving as director of the Institut Pasteur for nearly five years, Monod was diagnosed with leukemia. He carried on as director of the Institut throughout a series of burdensome treatments, but passed away on May 31 from related complications. Reportedly, his last words were Je cherche à comprendre – “I am trying to understand.”

A Book Lost to History

The kitchen at the Paulings' original Deer Flat Ranch cabin, 1958.

During the Second World War, when the children were growing up, I think three of the children were still at home or – I don’t know, perhaps the youngest one was still at home – [Ava Helen Pauling] worked for a couple of years as a chemist on a war job making rubber out of plants that would grow in the Mojave.

She was interested in chemistry and knew a lot of chemistry but it was more an intellectual interest.  She was planning to write a cookbook on the science of cooking, because she knew what happened when things were cooked.  She knew what baking powder is and why you use it.  She used to make her own baking powder, instead of just buying baking powder.  Well, she never got that done.  She was a very good cook, but she never wrote the book on the science of cooking.

… It probably wouldn’t have had much of a sale, because the contents might well have been above the heads of most cooks.

-Linus Pauling, 1990.

Linus and Ava Helen in their kitchen at the new Deer Flat Ranch home, 1977.

The Crystal Structure of Enargite

Enargite model, front view.

Enargite, Cu₃AsS₄ (copper = dark silver, arsenic = light silver, sulfer = yellow)

A crystal system classified as orthorhombic pyramidal, with a construction consisting of arsenic or copper atoms surrounded by four sulfur atoms in a tetrahedron.  Each sulfur atom is similarly surrounded by a tetrahedron of one arsenic atom and three copper atoms.

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As we mentioned in this post, in the early 1930s Linus Pauling began turning his attention from silicate crystals to sulfide minerals. The work on silicates was approaching completion, and Pauling hoped to form a similar understanding of sulfide structures.

He began his work with sulfides by studying the first crystal structure that had ever been determined in the United States. The mineral was chalcopyrite, and Pauling discovered that an initial analysis of the mineral’s structure was incorrect, and that the correct structure was twice as large and featured a different atomic distribution than was initially reported. Pauling continued to work with sulfide minerals and other crystals during this time, publishing structural analyses of sulvanite, zunyite and binnite. He was also busy working on the nature of chemical bonds, quantum mechanics, and the theoretical study of covalent crystals and bonds.

Pauling began studying enargite in March 1931, but was forced to temporarily halt his examination both because of difficulties with the photographs used for structural analysis, as well as the pressures of more pressing priorities. He eventually finished his analysis, and published the findings with Sidney Weinbaum in 1934.

Enargite is a somewhat rare mineral, composed of copper, arsenic and sulfide. It is used as a minor ore of copper and as a mineral specimen. It has a very uncommon symmetry, belonging to the hemimorphic class of crystals – hemi meaning “half” and morph meaning “shape.” This name references the tendency of these crystals to generally have different shaped tops compared to their bottoms.

Enargite model, top view.

Pauling and Weinbaum used data from Laue and oscillation photographs of crystals taken in the Philippine Islands to investigate enargite’s structure, and found that it very closely resembled that of wurtzite, a zinc sulfide. The duo determined that the structure of enargite consists of arsenic and copper atoms which are each surrounded by four sulfur atoms, each sulfur atom being similarly surrounded by a tetrahedron of one arsenic atom and three copper atoms.

In their study, Pauling and Weinbaum verified the mainstream theorized structure of enargite, but found some slight discrepancies in the assumed arrangement. They discovered, for example, that the crystal was incorrectly classified, being orthorhombic pyramidal instead of orthorhombic bipyramidal, as was initially believed.

Sidney Weinbaum, June 1950.

Despite his success with enargite, Pauling found the pace of his sulfide work to be slow, and sought help from the Geological Society of America in the form of a grant proposal during the spring of 1934. Pauling requested a total of $4800;  $1200 for a new apparatus and $3600 to provide three years wages for a postdoctoral fellow. The new position would designate a point person to carry out the “extensive and laborious graphical and numerical calculations” needed to determine the structure of more complex crystals and minerals. During the three years covered in the proposal, Pauling planned to determine the structures of pyragyrite, proustite, pentlandite, covellite, chalcocite, and the minerals of the niccolite group.

Unfortunately for Pauling, Waldemar Lindgren, chairman of the Projects Committee of the Geological Society of America, refused the request. He reasoning for rejection rested primarily upon the feeling that more money would need to be spent on the apparatus initially, in order for a supplemental grant to be provided.

Pauling's notes on enargite, ca. 1930s.

Pauling defended the relevancy of his first proposal, but altered his request so that it only included funding for the three year postdoctoral fellow’s salary. After receiving no reply from Lindgren, Pauling once again repeated his request. He never received a response, and was deeply hurt as a result, later revealing that the incident had contributed to leading him away from crystal-structure determinations in favor of the field of biology.

Though Pauling went on to determine several more crystal structures, the incident was a turning point in his career. From this point on, his relationship with crystal structure work moved from a general systematic determination of mineral group structures, to an occasional examination of substances that piqued his curiosity.

Several pages of notes on enargite by Pauling and Weinbaum are available in Pauling’s Research Notebook 8.  For more on Pauling’s structural chemistry work, see the website Linus Pauling and the Nature of the Chemical Bond: A Documentary History.

The Crystal Structure of Sulvanite

Sulvanite model, side view.

Sulvanite, Cu₃VS₄ (copper = light grey, vanadium = dark grey, sulfur = yellow)

A cubic crystal system with perfect cleavage.  Each vanadium atom is surrounded by four sulfur atoms at the corners of a regular tetrahedron.  Each sulfur atom is surrounded by three copper atoms at three corners of a nearly regular tetrahedron, and a vanadium atom – in the negative position – at the fourth corner of this tetrahedron.

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Sulvanite is a rare copper sulfide generally found in hydrothermal copper deposits containing vanadium as a primary sulfide. Its structure was conclusively determined by Linus Pauling and Ralph Hultgren in 1933, but was first examined by J. Orcel and then by W. F. de Jong in 1928. De Jong, using a mineral sample from Burra in Australia, prepared powder X-ray photographs for his determination. Pauling and Hultgren noticed potential discrepancies in de Jong’s final analysis of the crystal structure and decided to examine the mineral themselves using Laue and oscillation photographs.

Previously, Pauling had utilized Laue and spectral photography for crystal determinations. Laue photography involves the analysis of patterns collected by passing X-rays through a crystal to determine the positions of atoms in the unit cell. Spectral photography incorporates the use of two crystals – one whose structure is known for reference, and the other (unknown) crystal whose structure is being determined. The two crystals are rotated in front of an X-ray beam in a manner such that the reflections from the interaction fall onto a photographic plate. The distances between like planes and the type of repeating unit can then be determined.

Laue photographs taken by Linus Pauling, October 1922.

For their examination of sulvanite, Pauling and Hultgren decided to use oscillation photography, of which Pauling had become aware while on a trip to Europe in 1930. During his stay in Ludwigshafen, the scientist Hermann Mark shared with Pauling this method of electron diffraction, and showed him the apparatus that was used to carry out the technique. Upon his return to Pasadena, Pauling had a new graduate student, Lawrence Brockway, construct the electron-diffraction apparatus that was eventually used to help determine the crystal structure of sulvanite.

Herman Mark.

(Image courtesy of the S. N. Bose Project)

Oscillation photography is a type of X-ray diffraction. It is similar in a way to spectral photography, but instead of using a reference crystal, a single crystal is made and oscillated through a small angle on an axis perpendicular to a beam of monochromatic X-rays or particles.

The discovery of a new sulvanite cache in Utah provided the opportunity for Pauling and Hultgren to carry out their examination. A sample was lent to them and they used it to conduct an extensive evaluation of sulvanite’s atomic arrangement. The two initially hypothesized that the structure would be a superstructure of sphalerite. Instead, they found that each copper atom of sulvanite is surrounded by four sulfur atoms at the corners of a nearly regular tetrahedron, and that four atoms of sulfur form a regular tetrahedron around each atom of vanadium.

Pauling and Hultgren were also very interested to find that each sulfur atom in sulvanite is surrounded by three copper atoms which form three corners of a regular tetrahedron.  The fourth corner however, is not formed by copper but by a single vanadium atom found in the negative position – that is, the vanadium atom rests in a “pocket” created by the three sulfur atoms. This particular relationship was unusual in comparison to similar sulfur-containing covalent crystal structures that had been determined with certainty at that time, and the new discovery was a pleasant surprise for both of the researchers.

In the mid-1960s, Pauling briefly revisited the structure of sulvanite in his Research Notebooks 24 and 25.  Much more on Pauling’s breakthroughs as a structural chemist is available on Linus Pauling and the Nature of the Chemical Bond:  A Documentary History.

Roger Kornberg is the 2010 Pauling Legacy Award Winner

Dr. Roger Kornberg

Dr. Roger Kornberg, winner of the 2006 Nobel Prize in Chemistry, will speak in Portland, Oregon on Tuesday, April 20th. His lecture, entitled “The Molecular Basis of Eukaryotic Transcription,” will be held at the Oregon Historical Society’s Miller Pavillion at 8:00 PM. The event is free and open to the public. Seats may be reserved ahead of time by calling the Oregon State University Libraries Special Collections at 541-737-2075, or via email at special[dot]collections[at]oregonstate[dot]edu

Kornberg is visiting Oregon to receive the Linus Pauling Legacy Award, presented by the Oregon State University Libraries. This award is granted once every two years for oustanding achievement in any of Linus Pauling’s areas of research. Past recipients of the award include Daisaku Ikeda, founder of Soka Gakkai International; Nobel laureate physicist Sir Joseph Rotblat; Harvard University biologist Matthew Meselson; Caltech chemist John D. Roberts; and Nobel laureate biophysicist Roderick MacKinnon.

A Stanford University biochemist, Roger Kornberg was awarded the 2006 Nobel Prize in Chemistry for his fundamental studies of the molecular basis of eukaryotic transcription – the process by which DNA is copied. Kornberg’s 1974 discovery of the nucleosome – the basic protein-complex packaging of chromosomal DNA in the nucleus of eukaryotic cells – marked the beginning of his work on DNA. Coupled with his most recent discovery of “The Mediator” protein complex, Kornberg’s impressive program of research has added substantially to the understanding of the mechanisms and regulation of eukaryotic transcription.

Dr. Kornberg received his B.A. in Chemistry from Harvard University and his Ph.D. in Chemical Physics from Stanford University. He completed a postdoctoral fellowship at the Laboratory of Molecular Biology in Cambridge, England before joining the Stanford faculty. He has since co-founded Stanford’s Department of Structural Biology, the first of its kind in the United States. In 1993 he was elected to membership of the National Academy of Sciences.

In addition to the 2006 Nobel Prize in Chemistry, Kornberg is the recipient of numerous scientific awards, including the 2006 Louisa Gross Horwitz Prize, the 2002 Léopold Mayer Prize – the highest award in biomedical sciences granted by the French Academy of Science – and the 2001 Welch prize, among the most prestigious awards available to U.S. chemists.

For more information on Roger Kornberg’s lecture, please see the event website and for more on Kornberg’s work, check out his laboratory website.  As with MacKinnon’s lecture in 2008, fully-transcribed video of Kornberg’s talk will be made available in the weeks following its delivery.

Pauling’s Eulogy for Martin Luther King, Jr.

As we wrote at this time last year, Linus Pauling and Martin Luther King, Jr. had occasion to come into sporadic contact as they pursued their own avenues toward a more peaceful and just world.  The two exchanged a few letters and supported similar causes, including a 1965 appeal to stop the war in Vietnam.  The eldest Pauling child, Linus Jr., even lent his medical expertise to Freedom Marchers walking from Selma to Montgomery, Alabama in March 1965.

Today we honor Dr. King’s memory by publishing, for the first time, a short manuscript that Pauling wrote and delivered on April 9, 1968, five days after King’s assassination.

Having arrived in Amherst, Massachusetts the day before to deliver a series of lectures for the University of Massachusetts’ Distinguished Visitors Program, Pauling likely had little time to collect his thoughts for what, one presumes, was a hastily arranged memorial to King’s life and legacy.

The resulting manuscript then, is unvarnished Pauling and much is revealed in its three pages.  Though Linus and Ava Helen – moving into their late-sixties and weary from the many battles fought over their twenty-plus years of peace work – were reducing their personae as activists, it is clear that their thinking was continuing to evolve well-beyond signature issues like weapons proliferation and radioactive fallout.  And so it is that we find Linus Pauling sharpening the radical edge of his rhetoric and sharing King’s concern with economic issues, as he remembers a man whom he greatly admired.

Page 1.

Dr. Martin Luther King was opposed to violence, to suppression, to the exploitation of man by man.  He devoted his life to justice and morality, to achieving true brotherhood of all men, to abolishing the evils of unrestrained selfishness and hate.

It is not enough for us to mourn him and to show our respect for him.

It is our duty to work to achieve the goals that he pointed out.

Military might, police might, the power of the assassin are being

Page 2.

used by our country to protect an evil economic and social system, based on inequality and injustice.

40 million Americans are miserably poor, with income less than one-fifth the average for their affluent fellow citizens.  This group, the miserably poor, includes half of our black people, but only one-sixth of our white people.

The world as a whole is worse.  2/3 of the people of the world live on 10% of the world’s income, $100 per year per person.

Page 3.

In South America, Southeast Asia, Greece, as well as at home, we have been using our great wealth and power to oppose progress, to oppose reform.

Now, let us pledge ourselves to follow the path of righteousness, the path shown to us by Dr. King.

The Crystal Structure of Chalcopyrite

Chalcopyrite model, top view.

Chalcopyrite, CuFeS₂ (copper = dark silver, iron = orange, sulfur = yellow)

A tetragonal crystal system constructed from sulfur atoms surrounded by two copper atoms and two iron atoms each at the corners of a nearly regular tetrahedron. Each metal atom is surrounded by four sulfur atoms.

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In the early 1930s, Pauling was finishing his work with silicate structure determinations, and began to analyze the crystal structures of sulfide minerals. Pauling opened his study of sulfides with a reinvestigation of chalcopyrite, the structure of which had already been published by C. Lalor Burdick and James H. Ellis in 1917.

C. Lalor Burdick received his M.S. degree from the Massachusetts Institute of Technology in 1914 and his Ph.D. from the University of Basel in 1915. He learned how to use an X-ray ionization spectrometer in the Braggs’ London laboratory, and built one at MIT before moving to Pasadena in 1916. James H. Ellis, a research professor of physical chemistry at Caltech, worked with Burdick and his new spectrometer to carry out the initial chalcopyrite investigation.

Chalcopyrite model, side view.

Chalcopyrite, or copper iron sulfide, looks very similar to and is easily confused with Pyrite (iron sulfide). Chalcopyrite is also just one of the many minerals to have been labeled “fool’s gold,” because of its shiny bright golden color. (In comparison, real gold is more malleable and is buttery yellow in color.) The major use for chalcopyrite is as an ore for copper, though the yield of copper from chalcopyrite compared to that of other copper-yielding ores is relatively low.

Pauling and Brockway’s primary reason for studying chalcopyrite was their mutual interest in inter-atomic distances. The duo was also very critical of the initial investigation of the substance – both the method and the results – by Burdick and Ellis. After an examination of their own oscillation and Laue photographs, Pauling and Brockway concluded that the structure of chalcopyrite is twice as large as was theorized by the Burdick and Ellis examination, and that the distribution of copper and iron atoms is completely different than what was initially reported.

Lawrence Brockway, 1937.

Pauling first began working with Brockway in 1930, when he instructed the new graduate student to construct an electron-diffraction apparatus. Pauling had learned about the electron-diffraction technique from Herman Mark in Ludwigshafen during his trip to Europe in the spring and summer of the same year. Pauling was extremely interested in the possibilities of the technique, and acquired permission from Mark to build and operate the device in Pasadena. After helping Pauling build the electron-diffraction apparatus and publish the analysis of the crystal structure of chalcopyrite, Brockway later went on to set up his own laboratory in Michigan.

Pauling references his and Brockway’s work on chalcopyrite in his Research Notebook 8.  Those interested in the larger story of Pauling’s achievements in structural chemistry are referred to the website Linus Pauling and the Nature of the Chemical Bond: A Documentary History.

The Crystal Structure of Brookite

Brookite model, side view.

Brookite, TiO₂ (titanium = grey, oxygen = red).  An orthorhombic unit constructed by an octahedron of oxygen ions arranged about a single titanium ion. Each octahedron shares three edges with adjoining octahedra.

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After returning from a trip to Europe in 1927, Linus Pauling was appointed to the position of Assistant Professor of Theoretical Chemistry at Caltech, and reinitiated his study of crystal structures in Pasadena. During this time, Pauling was focusing his attention on the crystal structures of silicate minerals. He and other scientists were utilizing X-ray analysis for crystal structure determinations, but the limitations of the technique were becoming more and more apparent as it was applied to increasingly complex crystal structures.

To overcome these difficulties, Pauling formulated a new theory which helped him to determine the structure of brookite, topaz and a number of other complex ionic crystals. The theory, and the work that resulted from it, comprised an important step in the development of his most cited and most used crystal structure work.

Pauling’s new development was called coordination theory, and served as a method for predicting the possible structures of ionic compounds. Pauling contrasted the new theory with another method used previously by crystallographers for similar crystal structure determinations. The previous method involved testing and eliminating all but one of the possible arrangements in order to determine the atomic arrangement of particular crystals. Pauling noted that this method was both very certain in its results, and extremely labor intensive, making it difficult to apply to more complex compounds.

Brookite model, top view.

Pauling’s new method utilized sets of rules to both dismiss unlikely potential chemical structures and to hypothesize an atomic arrangement that would likely match the crystal structure of the compound being examined. Pauling and his associates would then compare the hypothesized arrangement to experimental observations. The new theory closely resembled an earlier technique formulated by William Lawrence Bragg, which applied a method called close-packing. (In this letter, Pauling discusses his crystal structure work with Bragg, including his research on the structure of brookite.)

Pauling first used his extended version of the technique to successfully determine the structure of brookite.  Brookite, or titanium oxide, is a minor ore of titanium and a polymorph with two other minerals. It shares a number of similarities with the minerals rutile and anatase, having the same chemistry but a different structure.  The variety of similar structures largely results from exposure of the basic chemical components to different temperature variations. As such, when exposed to higher temperatures, brookite reverts to the chemical structure of rutile.

J. Holmes Sturdivant, 1948

In their examination of brookite, Pauling and J. Holmes Sturdivant used spectral photographs to determine the dimensions of the possible unit cells, and Laue photographs to determine the smallest possible unit and space group symmetry criteria. Using Pauling’s new coordination theory, they predicted two possible structures for brookite. One of these hypothesized structures turned out to have a space-group symmetry and unit cell matching the spectral and Laue photograph observations. From there, Pauling and Sturdivant were able to determine that the basic unit of arrangement in brookite was that of an octahedron of oxygen ions around a titanium ion.

Following his examination of brookite, Pauling later used coordination theory to determine the structure of topaz. After these successful examinations, he was compelled to develop a set of principles which governed the structures of complex ionic crystals. The principles were described in a set of compiled documents known as the Sommerfeld festschrift papers, and would later be known as “Pauling’s Rules”. Pauling used his examinations of brookite and topaz, as well as the principles developed in their determinations, to write a paper that detailed this work. “The Principles Determining the Structure of Complex Ionic Crystals,” [J. Am. Chem. Soc. 51 (April 1929): 1010-1026.] published in 1929, became the most cited and most used of all of Pauling’s crystal structure papers.

Excerpt from "The principles determining the structure of complex ionic crystals."

For more on Pauling’s achievements in structural chemistry, see Linus Pauling and the Nature of the Chemical Bond:  A Documentary History.

The Crystal Structures of Corundum and Hematite

Corundum model, side view.

Corundum, Al₂O₃ (aluminum = silver; oxygen = red). A hexagonal (rhombohedral) crystal system constructed of aluminum atoms that are each surrounded by six oxygen atoms. The oxygen atoms are not bonded at the corners of a regular octahedron.

Hematite model, side view.

Hematite, Fe₂O₃ (iron = orange; oxygen = red). A hexagonal (rhombohedral) crystal system constructed of iron atoms surrounded by six oxygen atoms not at the corners of a regular octahedron.

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In 1925 Linus Pauling and Sterling Hendricks published a paper detailing the crystal structures of corundum and hematite. It was the fifth crystal structure analysis that Pauling had undertaken. During the early years of his research, Pauling had a tendency to correct the work of others, and the determination of hematite and corundum’s crystal structures was not an exception.

In 1917 the British father and son duo of William Henry and William Lawrence Bragg had studied the structure of ruby using X-rays. Citing this data, they hypothesized in 1924 that each aluminum atom in ruby is equidistant from six oxygen atoms, and that each oxygen atom is equidistant from four aluminum atoms. The Bragg’s used this hypothesis in their later work on theories of birefringence (the refraction of a ray of light into two slightly different and unequal rays) and to explain the intensity of X-ray reflections, in terms of temperature variation, from the faces of ruby crystals.

Hendricks and Pauling were not certain of the Bragg’s methods, and wrote in their analysis of corundum, “an exact knowledge of the arrangement of the constituent atoms in ruby would make the arguments of these papers much more convincing.” (J. Am. Chem. Soc., 47 (1925), p. 781)

Corundum is a gemstone whose varieties include ruby and sapphire. It is an aluminum oxide, and the second hardest mineral known to science after diamond. This property is generally attributed to the strong and short bonds which pull oxygen and aluminum atoms close together, making the crystal unusually hard and very dense.

Corundum model, top view.

Hematite comes in many varieties, each having their own unique name and composition. Hematite is an iron oxide, and very important as an ore of iron. It is also used as a pigment and is collected as a mineral specimen. It is blood red in powdered form, but can be gray, black, red or brown in its solid form. It is also used in jewelry, either as a set stone, or as a piece itself.

Pauling and Hendricks used Laue and spectral photographs, as well as the theory of space groups, to analyze the crystal structures of hematite and corundum. They found that, contrary to the Braggs’ hypothesis, the spacing of atoms in corundum’s atomic structure was not equidistant. Though they confirmed the Braggs’ ratio of oxygen to aluminum atoms, they found that instead of forming the corners of a regular octahedron around aluminum atoms, three of the six oxygen atoms were closer to the aluminum atom than were the other three. Similarly they found that instead of forming the corners of a regular tetrahedron around oxygen atoms, two of the aluminum atoms surrounding each oxygen atom were closer than the other two.

Sir William Lawrence Bragg

Pauling and Hendricks disproved the Braggs’ hypothesis of a constant aluminum-oxygen distance, and found that the Braggs’ value for the distance between aluminum and oxygen was also incorrect. The publication of the Pauling-Hendricks findings and the professional implications of their critique were not missed by the Braggs. Pauling was later told that Lawrence Bragg resented his “intrusion” into the fields of crystallography and mineralogy, and that he considered Pauling to be a competitor. Consequently, many of Pauling’s initial publications, often critiques of the work that others had done, led to the start of what would become a long lasting rivalry between himself and the Braggs.

Pauling later claimed that his view of their relationship was very different, both at the beginning of his academic career and the end of it.   According to Pauling, the work that was initiated to correct the Braggs’ early hypotheses was done in order to strengthen the validity of their subsequent claims. In regards to the influence of atomic arrangements on birefringence, this work was successful.

Pauling had perceived the early relationship between himself and W. L. Bragg as that of professor and student, respecting the work that the Braggs had done, and acknowledging that it had enabled him to study crystallography and chemical bonds upon his entrance to Caltech. In reference to the rivalry perceived by the Braggs, Pauling wrote “I did not think of my own scientific work as being competitive; I found it engrossingly interesting for its own sake.” Overall it seems that Pauling and the Braggs were not merely separated by an ocean, but also by an unfortunate misunderstanding of motives.

Pauling research notebook entries on the structures of corundum and hematite.

More on Pauling and Hendricks’ determination of the structures of corundum and hematite can be found in Pauling’s Research Notebook 4.   The larger story of Pauling’s structural chemistry work, including his relationship with the Braggs, is told in Linus Pauling and the Nature of the Chemical Bond: A Documentary History.