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Rubber vulcanization with sulfur - technical implementation

Rubber vulcanization with sulfur - technical implementation


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Do you have problems understanding the learning unit rubber vulcanization with sulfur - technical implementation? Then you may be missing the following basics:

Rubber40 min.

ChemistryMacromolecular ChemistryPolymers

According to DIN 53 501, uncrosslinked but crosslinkable polymers with rubber-elastic properties at room temperature are called rubbers. The learning unit gives an overview of the historical development and briefly introduces the individual types of rubber.

Sulfur vulcanization of rubber - principle40 min.

ChemistryMacromolecular ChemistryPolymer networks

The vulcanization of rubber by sulfur was discovered by chance in 1839. It was only later that the principle was understood and the process improved through a variety of additives. Since the amount of sulfur added and the resulting degree of crosslinking influence the properties of the vulcanizate, this process enables the synthesis of materials with very different properties.


Working hours: part time. The mini learning group is looking for committed, qualified teachers m / f / d for tutoring and exam preparation (MSA) in the subject physics 7th - 10th grade, mostly in individual lessons, occasionally also in small groups (2 - 4 students). Addressed are teachers (also on parental leave or retirement).

Working hours: part time. The mini learning group is looking for committed, qualified teachers m / f / d for tutoring and exam preparation (MSA) in the subject physics 7th - 10th grade, mostly in individual lessons, occasionally also in small groups (2 - 4 students). Addressed are teachers (also on parental leave or retirement).


Rubber vulcanization with sulfur - Technical implementation - Chemistry and physics

Alchemy (also called alchemy) originated in the 1st century AD in Egypt, its center was originally in Alexandria. The first person to describe alchemical working methods in detail was a woman named "Maria", about whose life practically nothing is known. In the writings of Maria, pumps and devices for distillation are described, as well as the implementation of the magnum opus. Zosimos of Panopolis lived in Alexandria in the 4th century and already knew the writings of Mary. One of the most famous Arab alchemists was Jabir ibn Hayyan (also Jabir arabicus), who is said to have lived in the 8th century.

Around 1150 the first Arabic works were translated into Latin, so alchemy found its way into the medieval cultural area of ​​Europe. However, the early alchemical writings were written in Greek. The origin of the Latin term "alchemy" (and the German word "chemistry") is very complex. The Greek word chymeiea means "melting", from which became in Arabic kimiya. In connection with the Arabic article "Al" means al-kimiya as much as "doctrine of metal casting". The meaning is possibly even more original. In & Aumlgyptischen the word means kemet the fertile, black earth of the Nile Delta.

In the thought of alchemy, the chemical-technical aspect, for example metal extraction, was interwoven with spiritual ideas. The ultimate goal of metal transformation was the production of gold with the help of the philosopher's stone. Again and again, bans on practicing alchemy were issued. Often the prohibitions only served to underpin the claim to power that the kings and rulers embodied with their gold possession. Because many of them weren't quite sure whether the transmutation of metals like lead or mercury to gold might not be possible after all. This would have seriously affected the value of gold.

The highest spiritual goal of alchemy consisted in the "release" from matter, in the perfection and purification of the soul. According to a modern interpretation, one could also see the self-discovery processes of humans as such a goal. From the philosophy of Aristotle the term "materia prima" was adopted, an idea that all things consist of a structureless basic principle. Therefore, Aristotle's idea of ​​the four elements fire, earth, water and air was widespread in alchemical thought. In contrast to the philosopher Aristotle, however, the alchemists believed that they could materially prepare the primordial matter in a substance. To conceal the "chemical and divine art" they introduced secret symbols; the preparation methods were often described vaguely and very mystically. The possibility of the transmutation of metals was vehemently advocated by some alchemists, for example at Geber, but others like Albertus Magnus denied this possibility. According to the ideas of alchemy, the human being as "microcosm" is an image and center of meaning of the macrocosm, of the entire creation (cf. Paracelus, there also & gtTreiprinzipienlehre). Alchemists like Johann Rudolph Glauber were rather pure practitioners who were hardly interested in mystical theories. Based on Jabir, however, many of the alchemists in the Middle Ages advocated the Mercurius-Sulfur theory.

Chemical marriage: union (coitus) of the complementary principles Sulfur (Pater Sol) and Mercurius (Mater Luna) the claws in the earth symbolize the Materia prima Figure from: Mylius, Anatomiae auri sive tyrocinium medico-chymicum 1628

The notions of basic principles contained in matter are widespread to this day. Hence one cannot speak of an "end" of alchemy. Robert Boyle (1627-1691) laid the foundation for the term element as we understand it today. "He was the one who convincingly demonstrated that there had to be a lot more elements rather than four elements - water, earth, fire, air - in order to explain the diversity of substances and that an element must be used to denote those uniform substances that one no longer in two different ways can convert other substances. " (Quote from Peter Buck in & gtHistory of the Periodic Table). In addition, Boyle is considered to be the founder of the modern empirical method, which questions a theory and backs it up through numerous, verified variation experiments. But even with Antoine de Lavoisier, who refuted the phlogiston theory, we still find the ideas of the "principes", of the original principles that build up matter. But Lavoisier also introduced a quantitatively measuring science. The specification of the concept of element and atom by modern chemistry and physics removed natural science even further from the original, alchemical ways of thinking.

However, alchemy has always experienced a renaissance, so Johann Wolfgang von Goethe (1749-1832) dealt intensively with alchemy and the psychoanalyst Carl Gustav Jung (1875-1961) recognized archetypal processes in the subconscious in his patients' dream symbols correlate to the process of alchemy becoming self.

Artificially producing gold is an ancient dream of mankind. Attempts to do this were made in ancient times, for example in ancient Egypt. The key substance for this was in alchemy Philosopher's Stone (also stone of the philosophers or Lapis philosophorum). With the Philosopher's Stone one often hoped to find an elixir that would promise eternal life. One imagined a kind of magical powder with which the metal conversion, the Transmutation, succeeded. The process of making the Philosopher's Stone was referred to as the & # 8222 large work & # 8220 (Magnum opus). The initiated alchemist, who mastered the knowledge of the great secrets of alchemy, was considered to be Adept. The adepts lived in secrecy or often traveled around under assumed names. According to tradition, some adepts actually owned the philosopher's stone.

During the work process, the colors that appear played an important role. The success of the great work was believed to be recognized by the appearance of redness (rubedo). Gold and mercury were often used as the starting material. What is remarkable is the fact that even with a gold content of up to 10% the mercury practically does not change its more fluid appearance. Many serious alchemists described gold making in their works. Others made fun of the goldmakers' methods of deception and described their methods. Pope John XXII. (1244-1334) issued a verdict against alchemy, which, however, was rarely followed.

Some & # 8222 alchemists & # 8220 claimed that they could produce gold and went from farm to farm to demonstrate a & # 8222 sample & # 8220 of their alleged art. Many rulers and rulers fell for it and made funds available to the goldmakers, even if the goldmaker could clearly see the need for money. The art of the demonstration consisted in smuggling gold in as inconspicuously as possible. Due to their sophistication, some achieved great fame for a while, such as the Italian gold maker Dominico Emanuele Caetano, who was executed in 1709 on the Prussian fortress of K & uumlstrin on the orders of Frederick I on a gallows covered with tinsel. The pharmacist's assistant and initial gold maker Johann Friedrich B & oumlttger (1682-1719) had more luck. In the same year of Caetano's execution, B & oumlttger presented the invention of European porcelain. However, Ehrenfried Walther von Tschirnhaus, who died in 1708, was also heavily involved in the development of European porcelain.

In 1722 the French chemist & Eacutetienne Geoffroy (1672-1731), who had become famous for his table on the relationship of chemical substances, published a treatise in which he described in detail the deceitful methods of gold makers. He described crucibles with double shutters or wooden rods with a cavity into which gold could be smuggled. According to Geoffroy, a common "trick" of the gold makers was a prepared nail in which one half of gold was soldered to one half of iron. The gold was coated with an iron color, this peeled off during the "transmutation process" and the gold appeared. Geoffroy was able to present nails prepared in this way by fraudulent goldmakers as evidence. The Grand Duke of Toscana even kept such a nail. Geoffroy's evidence seemed so devastating that from the time Geoffroy's publication until today hardly anyone believed in the production of alchemical gold.

Zosimos of Panopolis
lived in Alexandria between 350 and 420 AD

The work of Zosimos mainly contains quotations from older authors. In an exchange of letters with a woman named Thesobeia, Zosimos warns of a fraudulent gold maker. Thesobeia are dedicated to 28 treatises written in letter form. Unfortunately only fragments of it have survived. In one part, Zosimos speaks of the origins of alchemy and reports on the oppressive conditions during gold mining in the mines of the Egyptian kings. He also describes various processing methods for metal extraction and technical equipment and furnaces in which sulfur is sublimed. In addition to the letters of Zosimo, there are also writings with visionary ideas. It is possible that alchemical, secret working methods are described there in encrypted form.

Jabir ibn Hayyan (also called "Geber arabicus")
lived in the 8th century (approx. 725-812)

The work "Corpus Gabirianum" is ascribed to Jabir. This is a summary of the knowledge of that time. However, it is controversial whether this work can be entirely ascribed to Jabir. Parts of it could only have been written later. In any case, it is interesting that the mineral lures are already mentioned therein. It also describes the working method of fractional distillation. The work also refers to the Mercurius-Sulfur principle. Volatility was ascribed to mercury, its existence as a liquid metal embodied the principle of persistence, and sulfur embodied the principle of flammability. This so-called Mercurius-Sulfur theory was taken up by many later alchemists, for example Albertus Magnus. So the alchemists believed that the metals matured in the earth under the influence of these principles. With mercury, Geber spoke of "the matter of metals", Paracelsus added the principle "Sal" (the salt that embodies the human body) in his three-principle doctrine. Jabir was also the first to describe the production of ammonia by distilling hair.

Avicenna (Abdallah ibn Sina)
born before 980 in Afshana (Uzbekistan), died 1037 in Hamadan (Persia)

Avicenna left a huge work behind and has influenced the entire Arab world to this day. He lived as a court official in the residence of the then Shah of Persia. Two writings are of importance to alchemy: The book Qanun (Latin Canon) represents a summary of all medical knowledge since Aristotle. This includes the galenic medicine of Galenus of Pergamon (129-199). The work is divided into five parts. In the first part, Avicenna goes into the epistemological foundations of medicine. In the second part he lists almost 800 active pharmaceutical ingredients. In the third part he describes diseases that affect individual organs or parts of the body. In the fourth part he deals with diseases such as fever and symptoms of poisoning that affect the whole body. The fifth part describes the preparation instructions for medicinal products. The book concludes with a section on body hygiene and a healthy lifestyle.

The rather philosophical book "Kitab ash-Shifa" (Book of Mental Recovery) is a scientific encyclopedia dealing with subjects such as arithmetic, astronomy, ethics, geometry, logic, mathematics, natural philosophy or theology. The philosopher and physician Avicenna was not an alchemist, he even fought against prevailing doctrines of alchemy. So he questioned the authenticity of the gold made by alchemists. Nevertheless, he had a lasting influence on many alchemists, mainly because of his medical work, because practicing alchemy was traditionally almost always associated with the production of remedies.

Lullus, Raimundus
born around 1232 in Palma de Mallorca, died around 1315 in an unknown location

Raimundus Lullus initially lived as a Spanish nobleman at the king's court. Later he turned to religion and became a deeply devout missionary. His publications included numerous works on philosophy, theology, medicine, mathematics, astrology and law. On his travels he wanted to evangelize Muslims, Jews and people of different faiths to the Catholic faith and even advocated the marches on the cross. The philosopher Lullus tried to derive general truths by combining concepts, for example in the book "Logica Nova" (The new truth). According to legend, he is said to have survived the stoning by an angry crowd in North Africa around 1315. On the way back from Tunis to Mallorca he probably died of the consequences.

Pseudo-lullus
After Raimundus Lullus' death, numerous alchemical works were foisted. Therefore, today it is difficult to decide who wrote the lyrics. In this context one speaks of the "pseudo-Lullian" work. This probably includes the book "Testamentum", which was written around 1332. Based on Roger Bacon, the book is divided into a theoretical and a practical part. In the "Theoria", alchemy is described as "scientia experimentalis", an empirical science that describes and researches nature. The highest goal is the production of the Philosopher's Stone and the simultaneous healing of the human body and soul. In the pseudo-Lullian work, numerous alchemical working processes are described, for example the production of ammonium carbonate by heating rotten urine or the production of pure wine spirit (today: ethyl alcohol) by multiple distillation and subsequent purification. The effect of nitric acid on metals and the preparation of parting water ("aqua fortis acuta", 50% nitric acid) and royal water is already described in the pseudo-Lulli writings.

Libavius ​​summarized the chemical knowledge of his time in his main work "Alchemia" (first edition 1597). The first part of the work describes the structure of a multi-storey laboratory. In addition, numerous ovens and other work equipment will be presented. In the second part, Libavius ​​deals with the production of medicines, various substances and tinctures. In his writings, Libavius ​​also described for the first time the production of a substance similar to hydrochloric acid by annealing table salt and clay.

literature
Meitzner, Bettina: The devices of chemical art - The treatise "De Sceuastica Artis" by Andreas Libavius ​​from 1606, Stuttgart 1995

Like Paracelsus, Basilius Valentinus represented the doctrine of three principles. In addition, he was a follower of the microcosm-macrocosm teaching. According to this idea, the human being is a microcosm as an image of the macrocosm or the rest of creation. The origins of astrology, which propagates the influence of the stars on humans, can also be seen in this idea. The working methods described by Basilius Valentinus are of chemical historical importance: Shortly after Libavius ​​he described the production of hydrochloric acid or the conversion of "vitriol" (copper sulphate) with table salt, which resulted in "aqua caustica". In addition, there is the historically first representation of fancy gold (cf. also at & gtGlauber), as well as working methods for cleaning gold and a description of the various vitriols (today: sulfates). In his writings, numerous ways of representing metals from ores are described. Basilius' method for extracting the antimony is considered to be the first working instruction for the preparation of the pure metal.

The book "The Skeptical Chemist" caused a tremendous sensation in the professional world and led to the fact that one paid closer attention to the processes involved in chemical reactions. This laid the experimental basis for later theories such as Lavoisier's oxidation theory.

While Boyle's theories were sometimes interpreted as a revolution in chemistry in the 17th century, he was still associated with traditional alchemy. He kept his own alchemical writings secret or wrote them down in encrypted notes. So he stuck to the conviction that a transmutation of the metals or a conversion of the elements was possible. He firmly believed that he had found a red earth with the abilities of a "philosopher's stone".

literature
Boyle, Robert: The skeptical chemist, Reprint Thun - Frankfurt a.M. 2000

Stahl, Georg Ernst
born on October 21, 1660 in Ansbach, died on May 14, 1734 in Berlin

Stahl studied medicine in Jena from 1679. After receiving his doctorate, he first taught in Jena and in 1687 became the personal physician of Duke Johann Ernst of Saxe-Weimar. In 1694 he was appointed professor of medicine at the University of Halle. From 1715 until the end of his life he was the personal physician of King Friedrich Wilhelm I of Prussia in Berlin.

The strict demarcation of dead matter from the living organism, which is determined by its soul to a goal-oriented behavior, is something new with Stahl, this idea is no longer alchemical. The air, the water and the earth were still three elementary principles for steel. Stahl's phlogiston theory was also still tainted with alchemical ideas (see also & gtLavoisier). According to the phlogiston theory, all combustible substances should contain a "fuel" or a "phlogiston" that escapes during combustion. According to Stahl, this mixes with the air and makes it unsuitable for maintaining further burns ("phlogistic air"). When the process is reversed, the phlogiston is reintroduced. Stahl was the discoverer of the reversibility of such reactions (today one would say: redox reactions), but it was only Lavoisier who was able to interpret the processes correctly with his oxidation theory.


Domschke studied chemistry at the TU Dresden. During the experimental implementation of his diploma thesis on streptopolymethine dyes with Walter König (1954) a bottle with about 100 ml acetyl nitrate exploded, causing him to lose both hands. Nevertheless, he continued to work successfully in experiments until his retirement. He was a research assistant from 1956 and received his doctorate in 1960 with a thesis “About 1-benzyl-2-methyl-5-methoxy-indole derivatives as possible antagonists of serotonin”. He completed his habilitation in 1965 at the TU Dresden with a habilitation thesis on "The effect of enamines on p-benzoquinone (a contribution to the Nenitzescu reaction)". For political reasons he did not become an associate lecturer until 1984. In 1990 he became associate professor and in 1992 professor of organic chemistry at the TU Dresden. After the fall of the Berlin Wall, as Vice Dean for Chemistry and Food Chemistry (1991 to 1994), he was jointly responsible for the restructuring of the chemistry department at the TU Dresden. From 1992 to 1996 he was liaison lecturer at the German National Academic Foundation (from 1994 head liaison lecturer for the TU Dresden).

Domschke is one of the authors of the standard work Organikum (staff up to the 21st edition [1]) and author of the organic-chemical part in textbook 7 of the complex textbook chemistry (4 editions). [2]

Domschke mainly dealt with nitrogen and sulfur-nitrogen heterocycles. During research on thionitroso compounds, he discovered a new class of persistent sulfur-nitrogen radicals, the 1,2,3-dithiazolyls, together with R. Mayer, S. Bleisch, A. Bartl and A. Staško. Another area of ​​work was polycondensed aromatics, which are among others. suitable as organic storage media for lithium cells. He is the inventor and co-inventor of several patents z. B. Perylene pigments. Scientifically, he worked closely with the Institute for Chemical Physics of the Slovak Technical University in Bratislava and the Dresden Central Institute for Materials Research of the former Academy of Sciences of the GDR (later: Institute for Solid State Research, IFW Dresden).


Chemical process science

An important aspect of technical chemistry is the understanding of the material combination of industrial organic and inorganic chemistry. The basic chemicals are initially created from the organic raw materials crude oil, coal and renewable raw materials. A large number of intermediate and end products are produced from this.

Chemical process science continues to examine the processes and reaction procedures of the most important industrial chemical products.

Starting with the raw materials crude oil, natural gas, coal and, in recent years, increasingly renewable raw materials, chemical basic products such as olefins and aromatics are first manufactured.

These are then processed into intermediate products such as alcohols, phenols, aldehydes, ketones, carboxylic acids or amines.

The end products of the chemical industry, such as polymers, detergents, pesticides, pharmaceuticals and dyes, are made from the basic and intermediate products.

The raw materials of industrial inorganic chemistry include air, sulfur, sodium chloride, coke and water, from which the end products such as acids, alkalis, fertilizers, glass, pigments, catalysts and materials can be produced via a few intermediate stages such as ammonia and chlorine.

The task of technical chemistry is to determine the most economical process routes from the possible synthesis routes available, depending on the availability of the raw materials and taking into account the energy consumption.

Chemical processes differ in the type of chemical reaction carried out, for example chlorination, hydrogenation, nitration, oxidation, polymerization or sulfonation. The energy can be supplied in various ways, for example thermally, electrochemically or photochemically.

If both types of reaction management are possible, not only technical conditions but also market-economy aspects can influence the decision as to whether a process is to be carried out continuously or discontinuously as a batch process. Continuous systems are usually suitable for a product that is manufactured in large quantities, while a batch process often allows greater flexibility in product variation, but at the expense of the quantity produced.

Further classification features for chemical processes are the number of stages carried out (single / multi-stage), the heat release (endo / exothermic) and the type of catalysis used (homogeneous / heterogeneous / biocatalytic).


Exams at the Institute for Technical Chemistry

We would like to give you some pointers from our side.

In the Rector's circular dated February 9, 2021, the preferred implementation of online exams instead of face-to-face exams was expressly ordered. The Institute for Technical Chemistry will consistently implement this and offer all exams in the available digital exam formats.

The exams are offered in electronic form via OPAL as a written distance exam (paper-pencil) with digital support.

There is no need for you to worry, and we would like to enable you to take part in the exams in technical chemistry and the associated cross-institute modules as easily as possible. The examination content is primarily based on the teaching content of the individual lessons and revision courses.

We also offer you the opportunity to take part in trial events for the digital exams to take away your worries about the technical challenges. We are aware that some of the exams according to the examination schedule will soon be pending and hope that you will be able to take part in one of the test dates for the respective exams.

The following options are available for the technical chemistry exams on February 18, 2021:

Tuesday 16.02.2021 11:00 a.m. - 12:00 p.m.

Wednesday February 17th, 2021 8:00 a.m. - 9:00 a.m.

The following options are available to you for the technical chemistry exams on February 25th, 2021:

Tuesday 23.02.2021 11:00 a.m. - 12:00 p.m.

Wednesday 24.02.2021 8:00 a.m. - 9:00 a.m.

The following options are available to you for the technical chemistry exams on March 19, 2021:

Wednesday, March 17th, 2021 8:00 a.m. - 9:00 a.m.

Thursday, March 18th, 2021 11:00 a.m. - 12:00 p.m.

Regardless of the test rounds, we ask you to enroll in the appropriate examination modules.

We are always available to answer your questions as far as we can and support a smooth course of study.


Doctoral candidates in chemistry, physics, materials science or a comparable subject

The Federal Institute for Materials Research and Testing (BAM) is a scientific and technical higher federal authority based in Berlin. As a departmental research institution of the Federal Ministry for Economic Affairs and Energy, we research, test and advise on the protection of people, the environment and property. The focus of our activities in materials science, materials technology and chemistry is the technical safety of products and processes.

Become part of our team of committed employees!

  • Research on the topic of "Automated approaches to the development of intuitive rules in solid-state chemistry and physics" or on the topic of "Accelerated material search through chemical heuristics and machine learning"
  • Execution of density functional theory calculations (e.g. with the Vienna Ab Initio Simulation Package) and use of methods from the field of machine learning and automation
  • Chemical and physical interpretation of the results
  • Carrying out collaborative work
  • Regular reporting to the supervisors and presentation of the results at internal and international conferences
  • Successfully completed academic university degree (diploma, master's degree) in chemistry, physics, materials science or a comparable subject
  • Good knowledge of solid state chemistry or physics
  • Good knowledge of quantum chemistry or quantum mechanics
  • First experience in modeling and simulation in the field of chemistry, physics or related subjects and first experience in programming
  • Basic knowledge and practical experience in at least one of the following areas: density functional theory and software packages such as VASP, Python programming, machine learning
  • Very good written and spoken English skills are a prerequisite
  • Good academic writing and presentation skills in front of an audience
  • Good communication and information behavior, goal-oriented and structured way of working, initiative / willingness and ability to work, ability to work in a team and willingness to cooperate as well as willingness to learn
  • Interdisciplinary research at the interface to politics, economy and society
  • Work in national and international networks with universities, research institutions and industrial companies
  • Excellent equipment and infrastructure
  • Flexible working hours, mobile working

Federal Institute for Materials Research and Testing
Unit Z.3 - Personnel
Under the oaks 87
12205 Berlin
www.bam.de

If you have any technical questions about this position, Dr. Janine George on the phone number +49 30 8104-3318 or by email at.

BAM pursues the goal of professional equality between women and men. We therefore particularly welcome applications from women. In addition, BAM supports the integration of severely disabled people and therefore expressly welcomes their applications. With regard to the fulfillment of the application requirements, the application documents are examined individually. Recognized severely disabled people will be given preference if they are equally qualified.

The advertised position requires a high degree of physical aptitude.


Rubber vulcanization with sulfur - Technical implementation - Chemistry and physics

You want your Refresh your school knowledge or Fill in knowledge gaps in math, physics, biology or chemistry? To digital techniques prepare in your studies? Then you have come to the right place with the bridging courses at our university.

The math courses are aimed at those interested all Subjects, especially in natural science or technical courses.

The bridging courses in physics, chemistry and biology are particularly suitable for those interested in these or comparable subjects as a minor.

Digital teaching is increasingly becoming a matter of course. You will receive important information about digital learning in an introductory unit.

The next dates in 2021:

Digital learning: 08/31 at 9 a.m. - 12 p.m.
Mathematics: 01-03.09. and 06-10.09. 9 am-12:30pm
Digital learning: 13.09. at 9 a.m. - 12 p.m.
Chemistry: 13-17 September always N.N. o'clock
Digital learning: 20.09. at 9 a.m. - 12 p.m.
Physics: September 20-24 always N.N. o'clock
Biology: 27-29 September 10 a.m. to 1 p.m.

These courses will be on-line offered and possibly in part in presence. The proportions cannot yet be precisely planned and will be determined in July. The introductions to digital learning finden ausschließlich online statt und dienen insbesondere vorbereitend für die anderen Kurse. Als technische Voraussetzung benötigen Sie eine stabile Internetverbindung, eine Audioausgabe und einen Browser, vorzugsweise Edge oder Chrome. Firefox wird weniger empfohlen.

Die technische Durchführung der Brückenkurse hängt von der Anzahl Teilnehmer*innen ab und wird nach Eingang aller Anmeldungen geplant. Die Information darüber erfolgt rechtzeitig vorher per Mail.


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Vergolden von Münzen

devices
Becherglas 100 ml, großes Becherglas (z.B. 400 ml) dieses dient als Wasserbad
Heizplatte oder Dreifuß und Drahtnetz, Glasstab, Kupfermünzen z.B. 1,2 und 5-Cent-Münzen, Metallzange oder Pinzette, Bunsenbrenner, Stofftuch

Abzug ist nicht notwendig. Schutzbrille und Handschuhe sind selbstverständlich zu tragen.

Execution:
10 ml destilliertes Wasser und 5 Plätzchen Ätznatron (NaOH) in das kleinere Becherglas geben. Eine Spatelspitze Zinkpulver und die Münzen hinzugeben. Das kleine Becherglas ins große Becherglas geben, welches ca. 1 cm mit Wasser gefüllt ist und als Wasserbad dient. Alles auf eine Heizplatte geben (oder Dreifuß mit Drahtnetz) und solange erhitzen bis das Wasser im großen Becherglas siedet.

Hinweis: Natronlauge neigt zu einem Siedeverzug. Auch wenn die Siedetemperatur schon erreicht ist, siedet es zunächst noch nicht. Dann kommt es aber zum plötzlichen Sieden und Herausspritzen der Flüssigkeit. Im Wasserbad kann einem das nie passieren, das Natronlauge erst über 100°C siedet und im Wasserbad nie über 100°C erhitzt wird.

Münzen mit einer Pinzette oder Metallzange aus der Natronlauge nehmen, mit Wasser abwaschen und mit einem Stofftuch polieren. Die polierten Münzen am Rand mit der Pinzette in die Bunsenbrennerflamme kurz (einige Sekunden) in die Flamme halten. Münze umdrehen und wieder kurz in die Flamme halten. Beim Abkühlen sollte die Münze nun wie Gold aussehen, sonst das Erwärmen in der Flamme wiederholen.

Explanations
Zink reagiert mit Kupfer zu Messing. Leider kann man so echtes Gold nicht machen.

Das Zink ist bestrebt mit dem Kupfer einen Mischkristall zu bilden. Da Zink an der Luft sich mit einer Oxidschicht überzieht, geht diese Legierungsbildung nur, wenn die Zinkoberfläche sauber ist. Die Natronlauge löst diese Zinkoxidschicht auf unter Bildung von Natriumzinkat, welches sich nun in der Lösung befindet. Die Zinkatome diffundieren (wandern) in die Cu-Schicht hinein. Beim Polieren wird das überschüssige Zink entfernt und es bleibt eine silbrige Schicht einer Zn-Cu-Verbindung auf der Oberfläche zurück. Es handelt sich dabei um eine spröde, Zn-reiche intermetallische Zn-Cu-Verbindung (ε-Phase). Bei Erwärmen können Zn-Atome schneller in die darunterliegende Cu-Schicht diffundieren, dabei nimmt die Zn-Konzentration an der Oberfläche ab und es entstehen die in Messing übliche α-Phase (Cu-reicher Mischkristall bis 36,8% Zn) oder die β-Phase (ab 50 % Zn). Bei 32,5 bis 36,8% Zn existieren beide Mischkristallphasen.


Domschke studierte Chemie an der TU Dresden. Während der experimentellen Durchführung seiner Diplomarbeit über Streptopolymethinfarbstoffe bei Walter König (1954) explodierte eine Flasche mit etwa 100 ml Acetylnitrat, wodurch er beide Hände verlor. Trotzdem war er bis zu seinem Ruhestand weiterhin erfolgreich experimentell tätig. Er war ab 1956 Forschungsassistent und wurde 1960 mit einer Arbeit „Über 1-Benzyl-2-methyl-5-methoxy-indolderivate als mögliche Antagonisten des Serotonins“ promoviert. Er habilitierte sich 1965 an der TU Dresden mit einer Habilitationsschrift über „Die Einwirkung von Enaminen auf p-Benzochinon (Ein Beitrag zur Nenitzescu-Reaktion)“. Aus politischen Gründen wurde er erst 1984 außerordentlicher Dozent. 1990 wurde er außerordentlicher Professor und 1992 Professor für Organische Chemie an der TU Dresden. Nach der Wende war er als Prodekan für Chemie und Lebensmittelchemie (1991 bis 1994) mitverantwortlich für die Umstrukturierung des Fachbereichs Chemie an der TU Dresden. Von 1992 bis 1996 war er Vertrauensdozent der Studienstiftung des Deutschen Volkes (ab 1994 leitender Vertrauensdozent für die TU Dresden).

Domschke ist einer der Autoren des Standardwerks Organikum (Mitarbeiter bis zur 21. Auflage [1] ) und Autor des organisch-chemischen Teils im Lehrbuch 7 des komplexen Lehrwerks Chemie (4 Auflagen). [2]

Domschke befasste sich vor allem mit Stickstoff- und Schwefel-Stickstoff-Heterocyclen. Bei Untersuchungen zu Thionitrosoverbindungen entdeckte er gemeinsam mit R. Mayer, S. Bleisch, A. Bartl und A. Staško eine neue Klasse persistenter Schwefel-Stickstoff-Radikale, die 1,2,3-Dithiazolyle. Ein weiteres Arbeitsgebiet waren polykondensierte Aromaten, die sich u. a. als organische Speichermedien für Lithiumzellen eignen. Er ist Erfinder und Miterfinder mehrerer Patente z. B. über Perylen-Pigmente. Wissenschaftlich arbeitete er eng zusammen mit dem Institut für Chemische Physik der slowakischen Technischen Hochschule Bratislava und dem Dresdener Zentralinstitut für Werkstofforschung der ehemaligen Akademie der Wissenschaften der DDR (später: Institut für Festkörperforschung, IFW Dresden).


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