What Chemical Turns Urine Blue on Exposure to Sunlight After Eating Buckthorn

Orpiment

Orpiment, due to its golden color, was used in ancient times as a pigment and dye, while realgar was a common red pigment for paints and dyes.

From: Handbook of Arsenic Toxicology , 2015

Arsenic

Swaran J.S. Flora , in Handbook of Arsenic Toxicology, 2015

1.3.1 Arsenosulfides

Arsenopyrite (FeAsS), orpiment (As ₂S₃), and realgar (AsS/As₄S₄) are the most common arsenic sulfide minerals, occurring primarily in hydrothermal and magmatic ore deposits. Arsenic is commonly found in sulfide-bearing mineral deposits; especially with gold mineralization. Orpiment, due to its golden color, was used in ancient times as a pigment and dye, while realgar was a common red pigment for paints and dyes. Realgar decomposes in air to a yellow-orange compound para-realgar; consequently, old unrestored paintings have a yellow-orange tinge over a red color. Arsenic can exist in sulfide minerals either as a dominant mineral-forming element or as an impurity. Arsenic release into nature is a slow process as a result of mineral weathering; however, physical forces such as grinding, crushing, and pulverization from mining activities greatly increase the release rate. Arsenosulfides also combine with transition metals such as Co, Ni, and Cu to form a variety of other sulfides and sulfosalts [16].

In arsenic sulfides, elemental arsenic and sulfur are covalently bonded with different arrangements of As-S and As-As units. In arsenopyrite, each Fe atom is octahedrally coordinated by three As and three S atoms through edges and corners. In dimeric form ([As-S)]⁻²) each As or S atom is tetrahedrally coordinated to three Fe atoms and one S-As atom. In the presence of water and oxygen, the arsenic present in arsenopyrite rapidly oxidizes to As⁺², As⁺³, As⁺⁵, and a precipitate in the form of scorodite (FeAsO₄·2H₂O) or amorphous Fe(III) arsenate [17].

In realgar and its polymorphs As-As and S-S, dimers form a discrete molecular cage-like structure in which units are connected by van der Waals forces. Polymorphs of realgar, alacrinite (As₈S₉), and amorphous arsenic sulfide can also occur in hydrothermal deposits, volcanic emissions, intrusive igneous rocks, and hot springs. Realgar exists as high and low temperature polymorphs and at about 240°C α-realgar converts to β-realgar. α-Realgar in exposure to oxygen and sunlight converts to another polymorph, para-realgar.

In orpiment (As₂S₃), molecular units are present in chain form and connected by bridging S atoms and cross-linked by van der Waals attraction forces. Both the minerals realgar and orpiment are stable over a wide range of temperature; however, orpiment possesses a greater stability range due to reduced sulfur fugacity [18].

Oxidation of arsenopyrite is the widespread mechanism for the distribution of arsenic into the environment. Arsenopyrite is formed under high temperature and a reductive environment, such as areas around buried plant roots or other nuclei of decomposing organic matter. Pyrite readily oxidizes in aerobic conditions with the formation of iron oxides and traces of arsenic. Arsenic is also found associated with phosphate minerals; however, the concentrations are less than those of oxide and sulfide minerals. By substituting Si⁴⁺, Al³⁺, Fe³⁺, and Ti⁴⁺ arsenic can also be found associated with many other minerals; however, the concentrations are comparatively less.

Other arsenosulfides of transition metals are also known and the most common are enargite (Cu₃AsS₄), cobaltite (CoAsS), and gersdoeffite (NiAsS). Enargite is orthorhombic thio-arsenate where each arsenic atom is coordinated with four sulfur atoms as (AsS₄)⁻³ [19]. Below 300°C enargite is converted to its polymorph luzonite with tetragonal geometry.

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Arsenic, Antimony, and Bismuth Production

F. Habashi , in Encyclopedia of Materials: Science and Technology, 2001

(a) Arsenic sulfides

Arsenic sulfides occurring in nature are realgar, As₄S₄ ; orpiment, As ₂S₃; arsenopyrite, FeAsS; and enargite, Cu₃AsS₄. Realgar can be distilled without decomposition while orpiment melts at 310 °C and boils at 707 °C without decomposition. Both are insoluble in water and acids, even in concentrated HCl, but dissolve readily in alkaline reagents, especially alkali sulfide solutions, forming thiosalts. For example:

$\begin{array}{c}{\text{As}}_2{\text{S}}_3+3{\text{S}}^{2-}\to 2{[{\text{AsS}}_3]}^{3-}\\ {\text{As}}_2{\text{S}}_3+6{\text{OH}}^{-}\to {[{\text{AsS}}_3]}^{3-}+{[{\text{AsO}}_3]}^{3-}+3{\text{H}}_2\text{O}\end{array}$

Arsenic sulfides are precipitated from an acidified solution containing trivalent arsenic by H₂S:

$2{\text{As}}^{3+}+3{\text{H}}_2\text{S}\to {\text{As}}_2{\text{S}}_3+6{\text{H}}^{+}$

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Six-membered Rings with Three or more Heteroatoms, and their Fused Carbocyclic Derivatives

A. Güven , in Comprehensive Heterocyclic Chemistry III, 2008

9.17.6.12.1 1,3,5,2,4,6-Trithiatriarsinane-2,4,6-trithiol, arsenic(iii) sulfide, and pararealgar

UV absorption spectra have been calculated for 1,3,5,2,4,6-trithiatriarsinane-2,4,6-trithiol 158 and arsenic(iii ) sulfide (orpiment, As ₄S₆) 157 in aqueous solution at CIS and TD B3LYP levels of theory using the 6-311+G(2d,p) basis set <2001MI239>. The bond distances, vibrational frequencies, gas-phase energetics, and proton affinity of 158 have been estimated by means of MO theory <1995MI4591>.

The reaction of arsenic, AsCl₃, and AlCl₃ with sulfur in a closed ampoule led to the pentathiatriarsabicyclo cation 159 in 50% yield ( Scheme 51 ) <2005ZFA2450>.

Scheme 51.

Pararealgar 160 , a polymorph of realgar 161 , crystallizes in the monoclinic space group. The characterization of tetraarsenic(iii) tetrasulfide (pararealgar) 160 by means of Raman spectroscopy was performed by Trentelman and Stodulski <1996ANC1755>. Valence and core-level binding energy shifts of pararealgar 160 have been determined by Bullen et al. using X-ray photoelectron studies <2003MI319>. The crystal structure of pararealgar 160 was investigated by Bonazzi et al. <1995MI400, 1996MI874, 2003MI1463> and Kyono et al. <2005MI1563>. A single crystal of pararealgar was obtained by light exposure of realgar 161 . The realgar 161 is transformed into pararealgar and produces the As₄S₅ molecule if oxygen is present. The additional S-atom contributes to anisotropic expansion. An S-atom in the As₄S₅ molecule is released from one of the equivalent As–S–As linkages in As₄S₅, which becomes the As₄S₄ molecule of pararealgar. After the As₄S₅ molecule is divided into a S-atom (radical) and the As₄S₄ pararealgar molecule, the free S-atom is reattached to another As₄S₄ realgar molecule, and reproduces an As₄S₅ molecule <2003MI1463>. The structure 160 consists of discrete covalently bonded As₄S₄ molecules, which are held together by van der Waals forces.

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Arsenic

R.W. KappJr., in Encyclopedia of Toxicology (Third Edition), 2014

Background

The word arsenic has several derivations including from the Syriac word (al) zarniqa (

), the Persian word zarnikh, (ᖆᖅ ᘆᘐᖂ), and the Greek word arsenikon (Aρσενικóν). It is also related to the similar Greek word arsenikos (Aρσενικóς), meaning 'masculine' or 'potent.' The word was subsequently adopted into Latin as arsenicum and ultimately into French and English as arsenic. Arsenic compounds have been known since the days of Ancient Greece and Rome when arsenic sulfide or orpiment (As ₂S₃) was used by physicians to heal and by murderers to poison. Arsenic compounds were mined by the early Chinese, Greek, and Egyptian civilizations who found it could be produced from its ores easily that made it one of the first recognized as an element by early alchemists. Alchemy existed from about 500 BC to about the end of the sixteenth century. Alchemists were on a quest to turn various metals into precious metals such as gold and searching for ways to have eternal life. While most of alchemy was shrouded in mysticism and magic, a number of early techniques were later found to be useful in modern chemistry. The discovery of arsenic is credited to alchemist Albert the Great (Albertus Magnus 1193–1280), a German Dominican friar who achieved fame for his advocacy in the peaceful coexistence of science and religion. He heated As₂S₃ with soap and formed elemental arsenic. The first directions for the preparation of the metalloid arsenic, however, are found in the writings of Paracelsus (1493–1541), the father of modern toxicology.

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Pharmacological Advances in Natural Product Drug Discovery

David J. Newman , in Advances in Pharmacology, 2020

4.2 Realgar or As₄S₄

This compound has almost as long a history as trisenox in TCM and similarly has efficacy in the treatment of APL (Liu, Lu, Wu, Goyer, & Waalkes, 2008; Lu et al., 2002 ). Three arsenicals, two of which contain sulfides of arsenic and one that contains the trioxide are known in TCM; orpiment (As ₂S₃), realgar (As₄S₄), and arsenolite (contains arsenic trioxide, As₂O₃, discussed earlier). Realgar was frequently included as an ingredient in oral TCM mixtures for its antipyretic, anti-inflammatory, antiulcer, anti-convulsive, and anti-schistosomiasis actions, but the pharmacological basis for such an inclusion has not been be fully justified.

In 2018, Wang et al. published an interesting article (Wang et al., 2018) demonstrating that by treating realgar with acidophilic bacteria, they obtained what they have named "realgar transforming solution or RTS," where the active ingredient is inorganic trivalent arsenic, though they reported a significant number of other inorganic entities related to arsenic in the mixture. By using the K562 WT cell line and its Adriamycin-resistant mutant line, K562/ADR, they demonstrated that RTS strongly induced apoptosis in both cell lines, plus there was induction of autophagy at much lower doses of RTS (measured as As III) than from using realgar or trisenox. Thus, they consider that their RTS is a viable option for treatment. It certainly produces a more soluble form than the regular involved treatment methodologies, but no data is currently available comparing the actual inorganic components in these cases.

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Arsenic

Katherine A. James , ... Jerome O. Nriagu , in International Encyclopedia of Public Health (Second Edition), 2017

Chemical Characteristics

Arsenic (As) is a natural element, ubiquitous in the environment, cycling through water, land, air, and living systems. It is a metalloid, possessing both metallic and nonmetallic properties, and is the third element in Group VA of the periodic table. As the 20th most abundant element in the earth's crust, arsenic has an average soil concentration of 5–13   mg   kg⁻¹. In regions of volcanic activity, the average arsenic content of soils is higher, around 20   mg   kg⁻¹ . Arsenic is concentrated in magnetic sulfides and iron ores, most commonly associated with sulfide and oxide complexes in soil and rock formations. Some of the more prominent arsenic-bearing minerals include orpiment (As ₂S₃), realgar (AsS), arsenopyrite (FeAsS), and scorodite (FeAsO₄·2H₂O) (Bissen and Frimmel, 2003).

In nature, arsenic is found in oxidation states of +V (arsenate), +III (arsenite), 0 (arsenic), and −III (arsine) (Bissen and Frimmel, 2003). In the aqueous environment, the oxyanions consisting of arsenite species (H₃AsO₃, ${{\mathrm{H}}_2\mathrm{As}{\mathrm{O}}_3}^{-}$ , ${\mathrm{HAs}{\mathrm{O}}_3}^{2-}$ , and ${\mathrm{As}{\mathrm{O}}_3}^{3-}$ ) and arsenate species (H₃AsO⁴, ${{\mathrm{H}}_2\mathrm{As}{\mathrm{O}}_4}^{-}$ , ${\mathrm{HAs}{\mathrm{O}}_4}^{2-}$ , and ${\mathrm{As}{\mathrm{O}}_4}^{3-}$ ) predominate. Arsenite species tend to predominate in groundwater under reducing conditions, whereas arsenate species are more frequently found under oxidizing conditions. Exceptions, however, are common in the natural environment, where arsenate and arsenite species are found in both reducing and oxidizing waters. Bacteria, fungi, yeasts, and animals can methylate inorganic arsenic species to form monomethyl arsenic (MMA) and dimethyl arsenic (DMA) (Bissen and Frimmel, 2003).

The mobility of arsenic compounds in soils depends on the pH value, the redox potential, organic matter, clay and sand content, and other elements in the soil (Bissen and Frimmel, 2003). Arsenic in soil has the potential to be transported in wind or in runoff, or can leach into the subsurface soil; however, many arsenic compounds strongly partition to soil or sediment under oxidizing conditions, resulting in limited mobility. Under reducing conditions, as can occur during flooding or in underwater sediment, arsenic absorbed to iron and manganese oxides may be released. Microbes can also play a role in arsenic dissolution from sediment.

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The Netherlands

Yuri Bruinen De Bruin , Jacqueline Van Engelen , in Information Resources in Toxicology (Fourth Edition), 2009

Short History of Toxicology in The Netherlands

The First Developments (1800–1950)

Before World War II, toxicological research in The Netherlands was dispersed over several institutions. The first lecturer in toxicology was the physician A.W.M. van Hasselt (1814–1902), who taught toxicology at the State Military Training Hospital. In 1848 he published a book entitled De noodzakelijkheid van algemeen toezigt op het gebruik van vergiften (The Need to Regulate the Use of Venoms). Although Van Hasselt contributed significantly to the training and practical skills of physicians, he did not succeed in establishing continuity in the practice of toxicology.

The first professor of toxicology at Leiden University was the pharmacist E.A. van der Burg, who was appointed in 1877. His major accomplishment was the application of the emerging discipline of analytical chemistry in the confirmation of criminal poisoning. He established his name in the famous mass murder case of Goeie Mie ('good Mary') of Leiden in 1881–82. She poisoned at least 100 people, 27 of whom died, with the arsenic compound orpiment. This was confirmed by Van der Burg's analysis in exhumed bodies by means of the arsenic mirror method developed by Marsh some years before. Van der Burg and his successors continued to play a central role in forensic toxicology until the 1950 when the Central Laboratory of Forensic Sciences, now the Netherlands Forensic Institute, was founded.

Post 1950

Toxicology as a biomedical discipline emerged in The Netherlands after World War II. This process was invigorated on the one hand by the need to develop antidotes against chemical warfare agents, and on the other by the emergence of the chemical industry in The Netherlands and the need to protect the workforce and general population. The result was a prosperous growth of all aspects of toxicology in the Dutch universities, and industrial and governmental institutions. Among others, four people can be identified who have been instrumental in this development: Ernst M. Cohen (biological toxicology, TNO and Leiden University), Herman van Genderen (biological toxicology, RIVM and University of Utrecht), Ad N.P. van Heijst (clinical toxicology, RIVM and Utrecht University Hospital) and Reinier L. Zielhuis (occupational and environmental toxicology, University of Amsterdam) were pioneers each in his own field. The result was a flourishing toxicology community in The Netherlands, in which all aspects of the discipline were covered, ranging from molecular to public health aspects.

1979: Establishment of the Foundation of the Netherlands Society of Toxicology, Training and Accreditation

Toxicologists soon outnumbered the other professions in the Netherlands Society of Physiology and Pharmacology, necessitating the foundation of the Netherlands Society of Toxicology (NVT: Nederlandse Vereniging voor Toxicologie) in 1979. Within 10 years, the NVT, with a membership of 750, became the 4th largest toxicology society in the world, after the United States, Japanese, and British. In the 1980s, the NVT was the first European society to develop a system of postdoctoral training and accreditation, which formed the model for the European registration as Eurotox Registered Toxicologist.

2007: Current Situation of Toxicology in the Netherlands

At present, toxicology is practiced in a broad sense with the aim to protect man and its environment. Major subfields of toxicology consist of Nutrition Toxicology, Medicinal Toxicology, Occupational Toxicology, Genetic Toxicology, Environmental Toxicology, Teratology and Reproductive Toxicology, Toxicological Pathology, Toxicology and Risk Assessment and In-Vitro Toxicology.

The education and registration of toxicologists remain an important area of the Netherlands Society of Toxicology, which actively encourages the education in toxicology at all universities. After completion of education there are two ways to register as a toxicologist in the Netherlands. The first route – primarily the route followed by PhD – students with additional training with post-doctoral education in toxicology proceeds via the Dutch 'Association for Education to Biomedical Scientific Research' (Dutch abbreviation: SMBWO) and leads to registration as Medical Biological Researcher-Toxicologist. The second route to registration as a toxicologist is operated by the Society itself. A detailed 'Concilicum Toxicologicum (CT)' specifies all requirements to qualify for registration. Every 5 years the registration has to be renewed. A registration committee and an independent committee of appeal have been established.

Recently, a number of toxicology departments at several universities and university medical centres had to stop their activities. This development conflicts with the current increasing (international) need for well-trained toxicologists working for the Dutch Universities and research and policy support and implementation institutions like the RIVM, TNO, Notox and other private and governmental organizations. The Netherlands Society of Toxicology is undertaking major efforts to fulfill these needs and to return toxicology to the flourishing position it held in previous years.

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Molecular Mechanisms of Arsenic Toxicity

Khairul Islam , ... Hua Naranmandura , in Advances in Molecular Toxicology, 2015

4.2 Clinical uses of arsenic

Medicinal products of numerous arsenic compounds have been used for more than 2400 years in ancient Greece and Rome. In Mongolia, China, and India, different arsenic compounds have been employed to treat all kinds of diseases [185,186] . The father of western medicine and the ancient Greek physician Hippocrates administered orpiment (As ₂S₃) and realgar (As₂S₂) for the treatment of ulcer, although these are now considered human carcinogens [186–189]. More recently, arsenic has also been used to treat several diseases and conditions including the respiratory diseases, plague, malaria, trypanosomiasis, syphilis, and cancer [186,187,190,191]. Approximately, 60 different arsenic preparations have been developed and distributed during the lengthy history of this agent and many of these preparations are still in use.

Although arsenic was found to be beneficial in many disease states and side effects or later repercussions of therapy were inconsistent from patient to patient, concerns among medical professionals about toxicities associated with arsenic use, especially long-term use, arose in later years. The IARC and the US EPA has classified arsenic as a known human carcinogen [138,139] based on several epidemiological studies. In spite of the roles of arsenic compounds in toxicity and potential to cause cancer, several arsenic compounds have been recently rediscovered and formulated in order to manage and treat different conditions that may not respond to other agents or stopped responding to them. Arsenic compounds such as Trisenox (arsenic trioxide (As₂O₃)), Darinaparsin (i.e., dimethylarsinous glutathione, DMAIII(GS)), and GSAO (4-(N-(S-glutathionylacetyl) amino)phenylarsonous acid) are in clinical trials of U.S. Food and Drug Administration for the treatment of cancers such as leukemias and lymphomas and solid tumors [91,192,193]. Trisenox finally received approval from the U.S. FDA in 2000 as one of the most effective novel anticancer agent for the treatment of acute promyelocytic leukemia (APL).

A substantial body of evidence has accumulated during recent years suggesting the mechanisms by which the drug produces remissions in patients with APL. APL is characterized by a chimeric gene caused by reciprocal translocation between 15 and 17 chromosomes, t(15;17), moreover, the gene encodes PML-RARα fusion protein. The basic mechanism through which As₂O₃ is considered to be an effective against APL is by induction of cellular differentiation via degradation of the PML-RARα protein. Regarding the molecular mechanism of PML-ARα degradation, it has been suggested that As₂O₃ is able to bind with cysteine residues in zinc fingers located within the RBCC domain of PML-RARα (The PML protein contains three cysteine-rich zinc-binding domains, a RING-finger, two B-boxes (B1 and B2) and a predicted α-helical Coiled-Coil domain, which together form the RBCC) or PML causing PML oligomerization and degradation [194].

On the other hand, As₂O₃ has been shown to inhibit the growth and/or induces APL cell death at higher doses [195], but the high doses are at risk of causing side effects [196–202]. However, retinoic acid-induced differentiation and arsenite-induced differentiation along with apoptosis has been suggested as the probable mechanism of actions exerted on APL patients [197]. For As₂O₃, the mitochondrial membrane potential (Δψm) has been suggested to be one of the targets. Opening of mitochondrial permeability transition pore for the release of pro-apoptotic proteins, and cytochrome c has been proposed to occur as a result of As₂O₃-induced loss of Δψm, which leads to caspase activation [196]. Similarly, voltage-dependent anion channel has been suggested to be another As₂O₃ target that may release cytochrome c and cause apoptosis [202].

In previous studies, the induction of apoptosis and/or differentiation have been suggested depending upon the concentrations of arsenic used [195]; however, some of the investigations attributed the type of cell line that were used for different effects of arsenic [196,200]. As₂O₃ has successfully targeted PML-RARα and treated APL. Moreover, in different in vitro investigations, it has also been shown to target malignant lymphocytic cells without inducing differentiation and causing growth inhibition and cell expiration. Thus, As₂O₃ has been suggested for future treatment of lymphoproliferative disorders [203,204]. Similarly, break point cluster (BCR) and abelson (ABL), the tyrosine kinases which are recognized to cause aberrant transformations become activated in different leukemias [205] and As₂O₃-induced death in BCR–ABL expressing lymphoblast [206,207]. The BCR–ABL kinase in myeloma cells have been known to activate numerous downstream signaling pathways which are responsible for increased proliferation and reduced apoptosis [208]. The in vitro investigations have also demonstrated a few of the myeloma cell lines to be sensitive to As₂O₃-induced destruction [209].

The alteration in the (Δψm) and an increase in the activity of caspase have been associated with As₂O₃-induced growth inhibition without affecting Bcl or Bcl-2-associated X proteins [206,210]. Moreover, Mathas et al. suggested that As₂O₃ showed a pharmacological reduction of Hodgkin lymphoma by inhibiting the activity of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-кB). They observed the attenuation of xenotransplanted L540Cy Hodgkin tumors in a mouse model and observed reduction in NF-кB activity after giving 3.75   mg As₂O₃/kg [211]. In another study, [212] an effect of As₂O₃ on lymphoid lineage cells was observed and it was found that As₂O₃ showed no significant effect on cell viability and proliferation (except for NB4 cell).

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Arsenic Toxicology☆

Robert W. Kapp , in Reference Module in Biomedical Sciences, 2018

Background and Introduction

Arsenic is such a critical chemical to the field of toxicology as well as culture and civilizations throughout the centuries that is deserves a thorough understanding of the history, of its discovery and its current standing—the good the bad- and the ugly.

Dioscorides, a Greek physician from the 1st century CE, pharmacist and botanist who wrote a 5 volume Pharmacopeia entitled "De Materia Medica" which was actively used in medicine for almost 1500 years was the first to described arsenic. He described it as a poison in the first century since it possessed ideal properties for menacing and/or lethal activities. These properties included lack of color, odor or taste when mixed in food or drink, effective at very small doses thus making its transport quite simple and its prevalence which made it readily available to all classes of society. First and foremost, arsenic was a handy and almost perfect poison. The word "arsenic" has several derivations including from the Syriac word (al) zarniqa (ܠܐ ܙܐܦܢܝܐ), the Persian word zarnikh, (زرنيخ) and the Greek word arsenikon (Αρσενικόν). It is also related to the similar Greek word arsenikos (Αρσενικός), meaning "masculine" or "potent." The word "arsenic" has subsequently been adopted into Latin as arsenicum and then ultimately into both French and English as arsenic.

Arsenic compounds were mined by the early Chinese, Greek and Egyptian civilizations who found it could be produced from its ores easily which made it one of the first recognized as an element by early alchemists. Alchemy existed from about 500   BCE to about the end of the 16th century. Alchemists were individuals who attempted to turn various metals into precious metals such as gold and were searching for the elixir of immortality—a "potion" that grants the drinker eternal life. Alchemists also were in search of an "alkahest" or universal solvent which could dissolve every other substance and could provide invaluable medicinal qualities. Of course, none of that has come to fruition even yet today; however, while most of alchemy was shrouded in mysticism and magic, some of the early chemical techniques were later found to be useful in modern chemistry. In fact, the alchemist Albert the Great (Albertus Magnus 1193–1280) is credited for the discovery of the element arsenic. Albertus Magnus was a German Dominican Friar and bishop who was also a well-respected scientist, philosopher, astrologer, theologian, spiritual writer, ecumenist, and diplomat of his era. He was a forceful and knowledgeable advocate for the peaceful co-existence of science and religion. His intellect and advocacy were so much-admired that present day scholars such as James A. Weisheipl and Joachim R. Söder have referred to him as perhaps the most prominent German philosopher and theologian of the Middle Ages. The Catholic church also agreed that he was an important figure as he was Beatified in 1622 and Canonized in 1931 some 600   years after his death. Albertus Magnus heated As₂S₃ with soap and formed elemental arsenic which was a standard alchemy procedure. Hence the credible transition from alchemy to science was mediated by Albert Magnus. Paracelsus (1493–1541), the father of modern toxicology, is credited with writing the first directions for the preparation of the metalloid arsenic.

For thousands of years arsenic sulfide or orpiment (As ₂S₃) has been used by physicians to heal. In 1908 Paul Ehrlick and Sahachiro Hata developed the drug organarsenical (Salvaran) which was effective in treating syphilis and African trypanosomiasis (sleeping sickness; however, blindness was a common side effect in this treatment making its common use questionable. Oskar Dressel and Richard Kothe developed another organoarsenic drug (Suramin) which also was very effective without the high degree of secondary effects. Melarsoprol (another organoarsenical) was developed in the 1940s by Sanofi-Aventis and has been used medically to treat late-stage sleeping sickness since 1949.

On the other hand, arsenic has been used for intentional poisonings far longer and frequently than its use as a healing agent. It is believed that Nero used arsenic to kill his stepbrother—Britannicus—in order to secure Nero becoming Emperor of Rome back in the 1st century. In 82   CE, in an attempt to stem what was becoming an epidemic of large-scale poisonings, the Roman dictator and constitutional reformer Lucius Cornelius Sulla issued the Lex Cornelia, which is considered to be the first law written against poisoning. In Italy, during the Middle Ages, the most widely accused of poisoners were the family of Borgias, in particular Pope Alexander VI, and his son, Cesare and his daughter Lucretia—all of whom were skilled at poisoning their many enemies. Other notable deaths which were probably due to arsenic include, George III in 1820, Napoleon in 1821, Simon Bolivar in 1830 and Emperor Guangxu in 1908. It was commonplace for women to poison men during the 1830s and 1840s whose deaths would profit them. The most well-known female poisoner from this era was Madame Marie Lafarge of France who is believed to have poisoned her husband with arsenic in 1840. She was arrested and tried for murder in September in that year. This case became notable, not only because it was one of the first trials to be followed by the public through daily newspaper reports, but also because it was the first successful application of forensic toxicological evidence although it was quite dramatic turnaround of events in the end. The perplexing issue for the prosecution was that although arsenic was available to the killer and was found in the food, none could be found in the body of the victim. A test for arsenic had been developed 3   years earlier by a British chemist—James Marsh. Local chemists had run the test and found it was negative for arsenic in the victim's body which evidently dispelled the idea that Charles Lafarge was poisoned with arsenic. Mathieu Orfila—a well-respected Spanish toxicologist and an acknowledged authority of the Marsh test—was asked by the prosecution to re-examine the negative Marsh test results. Madame Lafarge's defense team was quite confident she was going to be acquitted of the charges and readily provided additional tissue samples for testing to Dr. Orfila. Upon re-examined the samples in the courtroom, Dr. Orfila ultimately proved the tests were positive for arsenic in the body of the victim and the local chemists had not performed the original tests properly… and each of the chemists agreed they had performed the test incorrectly in open court. This caused a huge uproar in court for the defense who immediately called their own expert witness—Francois-Vincent Raspail—a well-known French chemist, lawyer, politician and physician—who was not only one of the founders of the cell theory of biology but a known nemesis of Dr. Orfila at the time. Dr. Raspail quickly agreed to appear to refute Orfila's findings as he had done on several previous occasions, but the court had already reached its decision by the time he arrived to testify. As a result, Marie Lafarge was found guilty and ultimately sentenced to life imprisonment. Whether or not Dr. Raspail's testimony would have overturned the verdict remains a mystery; however, he soon thereafter wrote articles that called for Madam Lafarge's release because of the ineptitude of Dr. Orfila and the testing procedures. While Madam Lafarge's sentence was not overturned, many in the public felt she was wrongfully accused – primarily because of the questioning of the forensic evidence by Dr. Raspail. Further adding to the controversy was Madam Lafarge herself who also wrote several volumes of her Memoirs from prison that were published in 1841. She was cultured and a talented writer who was able to create further doubt in minds of the public about her guilt with her articulate writings. When she became stricken with tuberculosis in 1952, following a plea to Napoleon III from her doctors, she was freed in June 1852 and transported to a spa in Ussat by a great-uncle and his daughter. She died there a few months later, swearing her innocence to the end. Her remains lie beneath a upside down cross in the Ornolac cemetery—yet another mystery—satanic or St. Peter martyrdom? The Madam Lefarge arsenic poisoning case presented one of the most dramatic and celebrated entrances for any scientific discipline—and in this case it was forensic toxicology. Books, plays and movies were written about the case—the most famous being Charles Dickens' fictional character Madame Thérèse Defarge in the novel "A Tale of Two Cities." Madam Defarge is also believed to symbolize the nature of the terror that was commonplace during the French Revolution (1793–94) in which societal radicals engaged in political persecution of enemies of the Revolution—real or imagined. Over16 thousand citizens were executed in France during that period on grounds of sedition to the new republic particularly targeting people with aristocratic heritage.

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Art Works Studied Using IR and Raman Spectroscopy*

Howell G.M. Edwards , in Encyclopedia of Spectroscopy and Spectrometry (Second Edition), 1999

Paintings

The use of IR and Raman spectroscopies for the characterization of paint pigments depends on two critical factors: first, the ability to record good-quality spectra nondestructively from small paint flakes or chips, and second, the provision of a database of mineral, natural, and synthetic pigments on which the basis of a comparison and attribution can be made. Some examples of the success of vibrational spectroscopic methods will now be given to illustrate the potential of these techniques for pigment analysis and the conservation of degraded media.

Several databases now exist for the comparison of unknown pigments with contemporary specimens. A most useful basis for the attribution of specimens is provided by synthetic pigments, for which the dates of first manufacture or use are well established. For example, titanium(IV) oxide (TiO₂) is the most important white pigment in use today; its two major naturally occurring forms are rutile and anatase, which have been in use as paint media since 1923 and 1947, respectively. Their identification by vibrational spectroscopy is unambiguous; hence, if either is found on a disputed Renaissance painting, it could indicate a forgery or at least a recently restored work. It is interesting that the distinction between these two forms of TiO₂ is not achievable with X-ray fluorescence techniques normally used for pigment analysis in art.

A rather different example is provided by the work of Guys, who painted social life in France between 1843 and 1860. Seventy samples taken from 43 of Guys' works revealed a heavy dependence on newly synthesized and experimental pigments at that time, including Prussian blue, Cobalt blue, and French ultramarine, sometimes in admixture and unique to an artist of his time. Restoration, therefore, needs careful attention to unusual combinations of experimental pigments. A similar study emerges from the FT-IR study of Morisot's work, Bois de Boulogne; this also showed the presence of novel combinations of pigments, but ones that were more stable than others that were in use at that time. Analysis of paint flakes from the Virgin and Child , a suspected fifteenth-century work, not only revealed the presence of expected organic binders and varnishes but also suggested that a very heavy reworking had taken place more recently, and that the work could be a forgery. On the 'Jónsbók' Icelandic manuscript, six pigments were identified by Raman microscopy, only bone white being indigenous to Iceland; the others, vermilion, orpiment, realgar, red ochre, and azurite would all have been imported.

The most important naturally occurring and synthetic inorganic pigments used over periods of time and which feature in paintings from medieval to contemporary ages are given in Tables 1–7 along with the year of manufacture or documented use; the tables are constructed according to color or type, viz., blue, black, brown/orange, green, red, white, and yellow. These tables form the basis of dating of paintings and manuscripts by vibrational spectroscopy. The stability of inorganic mineral pigments relative to 'fugative' organic dyes was realized in mediaeval times.

Table 1. Blue inorganic pigments

Pigment	Chemical name	Formula	Date/Source a
Azurite	Basic copper(II) carbonate	2CuCO3·Cu(OH)2	Mineral
Cerulean blue	Cobalt(II) stannate	CoO·nSnO2	1821
Cobalt blue	Cobalt(II)-doped alumina glass	CoO·Al2O3	1775
Egyptian blue	Calcium copper(II) silicate	CaCuSi4O10	Third millennium BC/Mineral
Lazurite (from lapis lazuli)	Sulfur radical anions in a sodium aluminosilicate matrix	Na8[Al6Si6O24]S n	Mineral/1828
Manganese blue	Barium manganate(VII) sulfate	Ba(MnO4)2+BaSO4	1907
Phthalocyanine blue (Winsor blue)	Copper(II) phthalocyanine	Cu(C32H16N6)	1936
Posnjakite	Basic copper(II) sulfate	CuSO4·3Cu(OH)2·H2O	Mineral
Prussian blue	Iron(III) hexacyanoferrate(II)	Fe4[Fe(CN)6]3·14–16H2O	1704
Smalt	Cobalt(II) silicate	CoO·nSiO2(+ K2O+Al2O3)	c.1500
Verdigris	Basic copper(II)	Cu(O2CCH3)2·2Cu(OH)2	Mineral

a

Either the pigment is specified to be a mineral or the date of its manufacture is listed.

Table 2. Black inorganic pigments

Pigment	Chemical name	Formula	Date/Source
Ivory black a	Calcium phosphate+carbon	Ca3(PO4)2+C+MgSO4	Fourth century BC?
Lamp black	Amorphous carbon	C	∼3000 BC
Magnetite	Iron(II, III) oxide	Fe3O4	Mineral
Mineral black	Aluminium silicate+carbon (30%)	Al2O3·nSiO2+C	Mineral
Vine black	Carbon	C	Roman

a

Bone black is similar to ivory black.

Table 3. Brown/orange inorganic pigments

Pigment	Chemical name	Formula	Date/Source
Cadmium orange	Cadmium selenosulfide	Cd(S, Se) or CdS (>5 μm)	Late nineteenth century
Ochre (goethite)	Iron(III) oxide hydrate	Fe2O3·H2O+clay, etc.	Mineral
Sienna (burnt)	Iron(III) oxide	Fe2O3+clay, etc.	Antiquity?

Table 4. Green inorganic pigments

Pigment	Chemical name	Formula	Date/Source
Atacamite	Basic copper(II) chloride	CuCl2·3Cu(OH)2	Mineral
Chromium oxide	Chromium(III) oxide	Cr2O3	Early nineteenth century
Cobalt green	Cobalt(II) zincate	CoO·nZnO	1780
Emerald green	Copper(II) arsenoacetate	Cu(C2H3O2)2·3Cu(AsO2)2	1814
Green earth – a mix of celadonite and glauconite	Hydrous aluminosilicate of magnesium, iron and potassium	Variations on K[(AlIIIFeIII)(FeIIMgII)] (AlSi3·Si4)O10(OH)2	Mineral
Malachite	Basic copper(II) carbonate	CuCO3·Cu(OH)	Mineral
Permanent green deep	Hydrated chromium(III) oxide+barium sulfate	Cr2O3·2H2O+BaSO4	Latter half of nineteenth century
Phthalocyanine green	Copper(II) chlorophthalocyanine	Cu(C32H15ClN8)	1938
Pseudo-malachite	Basic copper(II) phosphate	Cu3(PO4)2·2Cu(OH)2	Mineral
Verdigris (basic)	Basic copper(II) acetate	Cu(C2(C2H3O2)2·2Cu(OH)2	Mineral and synthetic (BC)
Viridian	Hydrated chromium(III) oxide	Cr2O3·2H2O	1838 (?1850)

Table 5. Red inorganic pigments

Pigment	Chemical name	Formula	Date/Source
Cadmium red	Cadmium selenide	CdSe	c.1910
Chrome red	Basic lead(II) chromate	PbCrO4·Pb(OH)2	Early nineteenth century
Litharge	Lead(II) oxide	PbO	Antiquity
Realgar	Arsenic(II) sulfide	As2S2	Mineral
Red lead (minimum)	Lead(II, IV) oxide	Pb3O4	Antiquity
Red ochre	Iron(III) oxide+clay+silica	Fe2O3·H2O+clay+silica	Mineral
Vermilion (cinnabar) a	Mercury(II) sulfide	HgS	Mineral and synthetic (thirteenth century)

a

Limited lightfastness (→black form).

Table 6. White inorganic pigments

Pigment	Chemical name	Formula	Date/Source
Anatase	Titanium(IV) oxide	TiO2	1923
Barytes	Barium sulfate	BaSO4	Mineral
Bone white	Calcium phosphate	Ca3(PO4)2	Antiquity
Chalk (whiting)	Calcium carbonate	CaCO3	Mineral
Gypsum	Calcium sulfate	CaSO4·2H2O	Mineral
Kaolin	Layer aluminosilicate	Al2(OH)4Si2O5	Mineral
Lead white	Lead(II) carbonate (basic)	2PbCO3·Pb(OH)2	Mineral and synthetic (500–1500 BC)
Lithopone	Zinc sulfide and barium sulfate	ZnS+BaSO4	1874
Rutile	Titanium(I) oxide	TiO2	1947
Zinc white	Zinc oxide	ZnO	1834

Table 7. Yellow inorganic pigments

Pigment	Chemical name	Formula	Date/Source
Barium yellow	Barium chromate	BaCrO4	Early nineteenth century
Cadmium yellow	Cadmium sulfide	CdS	Mineral (greenockite)+synthetic c.1845
Chrome yellow	Lead(II) chromate	PbCrO4 or PbCrO4·2PbSO4	1809
Cobalt yellow (aureolin)	Potassium cobaltinitrite	K3[Co(NO2)6]	1861
Lead antimonate yellow	Lead(II) antimonate	Pb2Sb2O7 or Pb3(SbO4)2	Antiquity
Lead tin yellow	Lead(II) stannate	[I] Pb2SnO4	Antiquity?
		[II] PbSn0.76Si0.24O3	Antiquity?
Massicot	Lead(II) oxide	PbO	Antiquity
Ochre	Geothite+clay+silica	Fe2O3·H2O+clay+silica	Mineral (and synthetic)
Orpiment	Arsenic(II) sulfide	As2S3	Mineral
Strontium yellow	Strontium chromate	SrCrO4	Early nineteenth century
Zinc yellow	Zinc chromate	ZnCrO4	Early nineteenth century

The principal dyes used by medieval dyers were indigo from woad for blue, alizarin and purpurin from madder for red, and luteolin from weld or crocetin from saffron for yellow; some had been used long before the Middle Ages and weld was known in the Stone Age. Organic pigments have also been used on manuscripts, notably saffron, weld, indigo, woad, Tyrian purple, madder, and carmine.

Many natural products were extracted from lichens in the past and used to dye textiles. Notable among these were orchil for purple and crottle for brown. Other dye plants can yield greens, browns, and blacks (in the last case, e.g. marble gall from oak Quercus trees with added iron sulfate).

Organic pigments are prone to both fluorescence and photochemical degradation. Moreover, they often scatter only very weakly, perhaps owing to the fact that they may have been made into colorfast lakes with a mordant such as alum; hence they are difficult to identify uniquely on a manuscript owing to the lack of concentration of pigment at the sampling point. The better known organic dyes and pigments are listed in Table 8.

Table 8. Organic pigments and dyes

Colour	Pigment	Formula/Composition	Origin (Date)
Blue	Indigo	Indigotin C16H10N2O2	Plant leaf (BC), synthetic (1878)
Black	Bitumen	Mixture of hydrocarbons	BC
Brown	Sepia	Melanin	Ink of cuttlefish (c.1880)
	Van Dyck brown	Humic acids	Lignite containing manganese (sixteenth century?)
		Allomelanins
Green	Sap green	Organic dye	Buckthorn berry (fourteenth century?), coal-tar dye
Purple	Tyrian purple	6,6′-Dibromoindigotin, C16H8Br2N2O2	Marine mollusc (1400 BC), synthetic (1903)
Red	Carmine	Carminic acid, C22H20O13	Scale insect, cochineal (Aztec)
		Kermesic acid, C16H10O8	Scale insect, kermes (antiquity)
	Madder	Alizarin, C14H8O4	Madder root (3000 BC)
		Purpurin, C14H8O5	Synthetic alizarin (1868)
	Permanent red	Various azo dyes	Synthetic (after 1856)
Yellow	Gamboge	α- and β-Gambogic acids C38H44O8 and C29H36O6	Gum-resin (before 1640)
	Hansa yellow	Various azo dyes	Synthetic (1900)
	Indian yellow	Magnesium salt of euxanthic acid	Cow urine (fifteenth century)
			MgC19H16O11·5H2O
	Quercitron	Quercitrin C21H20O11	Inner bark of Quercus oak
	Saffron	Crocetin C20H24O4	Crocus flower stigma (antiquity)
	Weld	Luteolin C15H10O6	Plant foliage (Stone Age)

The Raman and IR spectra of organic pigments and dyes of relevance to artwork have now been recorded, including those of modern dyes such as methyl blue (a synthetic triarylmethane dye), methyl violet, and perylene reds.

Perhaps the greatest advances in recent years in the field of nondestructive pigment identification in artworks have come from historiated manuscripts that have been studied using Raman microscopy. In situ analyses of the brightly colored initials and borders of the fourteenth-century Icelandic 'Jónsbók', Chinese manuscripts, illuminated Latin texts and early medieval Bibles have demonstrated the power of the technique. From samples that often represented only a 20   μm fragment that had fallen into the bindings of early manuscripts, FT-IR and Raman microscopies have made considerable advances in the knowledge of color hue technology in medieval times; for example, the different blues in a historiated initial could be attributed to a finer particle size and not to a dilution with other materials or colors. Useful information has also been provided about additives and binding media.

On some paintings and manuscripts, an inappropriate blend of adjacent colors or mixtures of pigments and binders was achieved; Raman microscopy has identified two examples of these in cadmium sulfide and copper arsenoacetate (which yields black copper sulfide) and egg tempera with lead white (which yields black lead sulfide). The term 'inappropriate' here refers to the instability of pigments and pigment mixtures resulting in a chemical reaction over periods of time and through aerial or substratal influences.

Where the pigment is colored, the choice of exciting line for Raman spectroscopy is extremely important because absorption of the scattered light by the sample may affect the spectrum. In such cases, the exciting line is chosen to fall outside the contour of the electronic absorption bands of the pigment. Vermilion (HgS) and red ochre (Fe₂O₃) give poor-quality Raman spectra using green excitation but give strong Raman spectra when excited with red radiation. An interesting example of the effects due to absorption of laser radiation is provided by the Raman spectra of red lead (Pb₃O₄) obtained using 514.5 and 632.8   nm excitation (Figure 7). In each case, well-defined Raman spectra are obtained, but only with 632.8   nm excitation is the spectrum that of the genuine material; that obtained with 514.5   nm excitation matches that of massicot (PbO). These observations may be explained because red lead can be converted into massicot by heat. Red lead absorbs 514.5   nm radiation strongly, leading to localized heating that results in conversion of the irradiated particle or particles into massicot. Since 632.8   nm radiation is not absorbed by the red lead, there is minimal local heating with this exciting line and thus no decomposition.

Figure 7. Illustration of the effect of wavelength of laser excitation on the Raman spectra of a pigment, red lead (Pb₃O₄), excited with (a) 514.5 nm and (b) 632.8 nm radiation. The genuine spectrum is (b); the spectrum excited by green radiation in (a) corresponds to massicot (PbO), converted from Pb₃O₄ by localized heating in the laser beam. Reproduced with permission from Bert SP, Clark RJH, and Withnall R (1992) Nondestructive pigment analysis of artefacts by Raman microscopy. Endeavour, New Series 16: 66–73, © 1992 Elsevier Science.

For colored pigments, the absorption of exciting radiation can be used to advantage to produce enhanced Raman scattering through the resonance Raman effect. This is particularly useful for weakly scattering species, and selection of excitation within the contour of an electronic absorption band of a chromophore can produce a spectral intensity several orders of magnitude larger than that obtained in conventional Raman spectra. A classic example of this is provided by the deep blue mineral lapis lazuli, Na₈[Al₆Si₆O₂₄]S _n , where the species S₂ ⁻ and S₃ ⁻ are responsible for the color. The species S₃ ⁻, although present to an extent of <1% in the pigment, gives such an intense Raman spectrum with green–red excitation that no bands due to the host lattice are observed. Other techniques fail to discriminate the presence of S₃ ⁻ in the aluminosilicate lattice.

The Raman spectrum is sensitive to both composition and crystal form, as is demonstrated by titanium(IV) dioxide, the most important white pigment in use today. White pigments normally present considerable problems in pigment identification, comprising sulfates, carbonates, and phosphates, which are easily distinguished in Raman spectroscopy (Figure 8). The symmetric vibration of the anion gives rise to an intense band at ∼1000   cm⁻¹ for sulfates, ∼1050   cm⁻¹ for carbonates, and ∼960   cm⁻¹ for phosphates. The exact wavenumber of these bands are also sensitive to the cation (1050   cm⁻¹ for PbCO₃ and 1085   cm⁻¹ for CaCO₃). This factor becomes extremely important in database construction since artistic vocabulary generally describes the color rather than a precise mineral origin, for example, cadmium yellow, although strictly CdS has also been designated for organic substitutes of similar hue. Old recipes for obtaining pigment colors are often vague and employ unidentifiable materials; the same chemical compound or mixture can even have different names according to geographical locality or historical period. For example, three contemporary samples designated Naples Yellow, assumed to be Pb₂(SbO₄)₂ – a lead antimonate – have been shown by Raman spectroscopy to be a lead antimony oxide, Pb₂Sb₂O₆, another oxide, Pb₂Sb₂O₃, and the third sample mainly Pb₂(CrO₄)₂, but also containing PbCO₃. None of the samples tested actually proved to be Naples Yellow of the assumed formula!

Figure 8. Raman spectra of white pigments; differentiation between (a) lead white (PbCO₃), (b) chalk (CaCO₃), and (c) bone white (Ca₃(PO₄)₂). Reproduced with permission from Best SP, Clark RJH, and Withnall R (1992) Nondestructive pigment analysis of artefacts by Raman microscopy. Endeavour, New Series 16: 66–73, © 1992 Elsevier Science.

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