Frost resistance of concrete containing brick aggregate Dissertation

Frost resistance of concrete containing brick aggregate - Dissertation Example This amazing ability also allowed him to predict, characterize and exploit the chemical and physical qualities of minerals, metals and other elements found in nature. It is this specific knowledge that makes it possible to develop new applications in the industries such as construction, shipbuilding, manufacturing, food production, etc. Early structures built by early civilizations of Egypt, China, India and other nations are still in existence today, although most of them are in ruins already. Man will always build new structures as habitat and places to work in, sometimes building skyscrapers to maximize the use of limited land. However, a growing realization that Earth's resources are not infinite has lead to the Green Movement in the construction industry these days. A big component of today's modern structures is concrete which makes up more than 60% of the total volume in construction materials. This paper discusses the exciting possibilities of using concrete with brick aggreg ates in them to improve their frost resistance and make them long-lasting. This paper examines the use of brick aggregates instead of the other usual aggregates in cement. Some studies showed brick aggregates concrete to have better qualities (Singh 27). I. Aim of the Project It is the aspiration of every architect and engineer to build structures which can last for long periods of time. The idea is to build for posterity if possible and this can be done with the right types of construction materials. Concrete has always been a favourite material due to its availability, strength and ease of use. The word concrete comes from the Latin concretus which means compact or condensed; this makes concrete desirable as a material of choice. In concrete, builders have found the ideal material to construct grand buildings of all shapes and sizes. Concrete is a composite construction material derived by mixing cement with fly ash, slags, aggregates (made up of gravel, crushed rocks, limestone, granite and a little bit of sand) water and several chemical admixtures. Concrete solidifies into place after mixing it with water in a process known as hydration. The water reacts chemically with the cement to form and bond all its other components together into a hard rock-like material. Concrete is the most widely-used man-made construction material in the world today. A lot of factors determine whether the concrete will stand the test of time. Moreover, engineering structural designs need to take into consideration the actual load weights imposed on the concrete. A concrete structure is exposed to various elements of nature such as wind, rain, earthquakes, fires, moisture and snow, to name just a few. In other words, the durability of a structure is to a large extent determined by its exposure to the elements. An important consideration that allows a concrete mixture to withstand the extreme elements of nature is the design and composition of the aggregates mixture forming the c oncrete. It is in this regard that I am examining how brick aggregates can improve the frost resistance of the concrete. A re-examination of its desired frost-resistant qualities is vital because it will improve concrete structures by making them more durable. It will help in minimising use of scarce construction materials by reducing a need to build new structures to replace old ones. The problem of

International border searches Essay Example for Free

International border searches Essay It is recognized that it is paramount to the U. S. to protect and preserve the integrity of its borders. This involves a constant balancing by the authorities between trade and commerce on one hand and terrorist activities, contraband and illegal immigrants on the other hand. By reason of this, security operations involve border searches and seizures which necessarily have implications on the Fourth Amendment (Vina, 2005). The Fourth Amendment ensures and protects the people from unreasonable searches and seizures and provides, â€Å"â€Å"The right of the people to be secure in their persons, houses, papers, and effects against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized† (U. S. Constitution, Fourth Amendment). The Fourth Amendment is to ensure that the powers of the federal government are not arbitrarily used against its citizens. Legally, â€Å"reasonableness† is required as one to be determined by a judge for the issuance of a search warrant. The judge is said to be independent and impartial as to determine the existence of probable cause so that the police can make the search or arrest [Katz v. U. S. , 347, 357 (1967)]. A violation of the Fourth Amendment will result in the exclusion or suppression of whatever evidence may be gathered pursuant to the exclusionary rule enunciated by the Court in the case of Mapp v. Ohio, 367 U. S. 643 (1961). There are however, exceptions established when reasonableness and warrant requirement are relaxed and therefore â€Å"probable cause is not invariably required either† (Vernonia School Dist. 47J v. Acton, 515 U. S. 646, 653 (1995). This occurs when the interests of the public require more protection than those of private interests. One of these established exceptions to the warrant and probable cause requirement is border search [Camara v. Municipal Court, 387 U. S. 523 (1967)]. Discussion Border search is defined in the case of United States v. Ramsey as â€Å"that searches made at the border, pursuant to the longstanding right of the sovereign to protect itself by stopping and examining persons and property crossing into this country, are reasonable simply by virtue of the fact that they occur at the border, should, by now, require no extended demonstration (431 U. S. 606 (1977)). This does not require a warrant, probable cause or reasonable suspicion (Onecle web site, 2005). The exception of border search is provided for under the United States Code specifically in Chapter 19, subsections 482 and 1582. This exception is premised on the duty of the state to protect its citizens, regulate trade and commerce and enforces immigration laws, thus, authorizing routine stops for searches at the border [U. S. v. Ramsey, 431 U. S. 606 (1977)]. There are two types of border search, namely routine and non-routine (Vina, 2005). In the case of U. S. v. Johnson, the Court explained that routine search include a search without any suspicion and entails very limited invasion of privacy (991 F 2d. 1287, 1291 7th Cir. 1993). This may include a dog sniff of the person, a search and inspection of belongings, luggage and car (Vina, 2005). The non-routine search includes more intrusive methods and is conducted when the authorities have suspicion that there is alimentary canal smuggling. The search may consist of â€Å"destructive searches of inanimate objects, prolonged detentions, strip searches, body cavity searches, and some x-ray examinations† (Vina, 2005). Body cavity searches include searches in cavities such as â€Å"vagina, rectum, or the use of emetics† [Vina, 2005 citing United States v. Ogberaha, 771 F. 2d 655, 657 (2d Cir. 1985) (vagina); United State v. Pino, 729 F. 2d 1357, 1358 (11 th Cir. 1984) (rectum); United States v. Briones, 423 F. 2d 742, 743 (5 th Cir. 1970) (emetics)]. The law requires that ‘reasonable suspicion’ consists in particular and specific facts which a logical person can infer from a wrong doing (U. S. v. Montoya de Hernandez (1985), 473 U. S. 531). There are also instances when border searches are allowed to extend beyond the border, in the following cases, namely: â€Å"(1) the government officials have reasonable certainty or a â€Å"high degree of probability† that a border was crossed; (2) they also have reasonable certainty that no change in the object of the search has occurred between the time of the border crossing and the search; and (3) they have â€Å"reasonable suspicion† that criminal activity was occurring† (U. S. v. Teng Yang (2002), 286 F. 3d. 940). These three requisites must exist and concur to render legal and constitutional, the extended border search by ensuring a â€Å"significant nexus with a border crossing† by the suspect (Vina, 2005). Most often the routine searches give rise to non-routine searches such as for instance where undeclared precious stones are found inside the pocket of the suspect, this resulted into reasonable suspicion thus giving rise to the conduct of non-routine search of strip searches. This yielded an envelope of narcotics (U. S. v. Flores, (1973) 477 F. 2d 608). Conclusion The U. S. government embarked on enhancing border security technologies and operations by reason of the September 11 terrorist attack. Intercepting and aborting terrorist attacks and smuggling of contraband were overstressed. Pieces of legislation are being drafted to harness further training in detection of false or falsified documents, pilot programs are launched for â€Å"surveillance technologies, biometric entry and exit data system and enhanced training of border officials (Vina, 2005). Volunteer programs were also set up to assist in observing and reporting of the movement of illegal aliens such as those launched in Arizona in 2005. This is a â€Å"citizens’ neighborhood watch’ program called the Minuteman Project. References Camara v. Municipal Court, 387 U. S. 523 (1967) Katz v. U. S. , 347, 357 (1967) Mapp v. Ohio, 367 U. S. 643 (1961). Onecle Web site 2005 â€Å" Border searches† Retrieved on October 25, 2007, from http://law. onecle. com/constitution/amendment-04/18-border-searches. html United States Code, Chapter 19, subsections 482 and 1582 U. S. Constitution, Fourth Amendment Vernonia School Dist. 47J v. Acton, 515 U. S. 646, 653 (1995). Vina, S. 2005, Protecting our perimeter:† border searches† under the Fourth amendment CRS Report for Congress. Retrieved on October 25, 2007, from http://www. fas. org/sgp/crs/homesec/RL31826. pdf. United States v. Briones, 423 F. 2d 742, 743 (5 th Cir. 1970) U. S. v. Flores, (1973) 477 F. 2d 608). U. S. v. Johnson, 991 F 2d. 1287, 1291 7th Cir. 1993). U. S. v. Montoya de Hernandez (1985), 473 U. S. 531 United States v. Ogberaha, 771 F. 2d 655, 657 (2d Cir. 1985) (vagina) United States v. Pino, 729 F. 2d 1357, 1358 (11 th Cir. 1984) (rectum); U. S. v. Ramsey, 431 U. S. 606 (1977)]. U. S. v. Teng Yang (2002), 286 F. 3d. 940.

Revealing a Characters True Nature During a Moment of Crisis Essay

In literature, there are many examples of people who are placed in â€Å"fantastic† situations, which served to reveal much about themselves, as Dostoevsky suggests. There are also many instances in which people break down and do something completely uncharacteristic in these same situations, as a result of extreme suffering. One such example, is Gretchen, from Goethe's Faust. She was an ingà ©nue and thus revealed her true character at a crucial point in her life. She was not a murderer, yet she murdered. When all her misdeeds began to drive her mad, she became the most lucid in her discernment of good and evil. â€Å"Her last remarks saved her, as she cried out to God in repentance, she was forgiven. Receiving a spiritual awakening, though out of her mind with grief, she still recognized the devil. She sensed evil in Faust and finally realized that there was no love between them† (RoseDeClementi 3.2). Gretchen's deeds were just as despicable as his, but there was a difference; in her moment of truth, she repented and was redeemed. Faust knew that he was condemned to spend eternity in hell. In this instance, I believe that Dostoevsky was correct because Gretchen was portrayed as a victim of manipulation. Another example in literature of someone who revealed her true character, in crisis, was Antigone, from a story of the same name. â€Å"In the story of Antigone, (who was the daughter of Oedipus), more tragedy awaited her. Taking a stand for what she believed to be an injustice and offense against her god, she buried her dead brother which violated the law, thereby sentencing her to her own death; she was to be placed in a tomb alive and left for dead† (Rose-DeClementi 1.2). Her strong beliefs shaped her character which dictated her ac... ...his into consideration, I behaved responsibly. Even when I began to lose my composure with the hospital workers, who refused to take my friend in right away, my true character was revealed. Generally, crisis situations have a tendency to bring out the worst in me, as with most people. This disputes Dostoevsky's theory, which holds that the true nature of a person will be revealed during moments of crisis. My account, as well as the examples taken from literature, prove that Dostoevsky's theory, although valid, is not indisputable. Works Cited Rose-DeClementi, Theresa. Personal journal 1.1. 4 Sept. 2010. Rose-DeClementi, Theresa. Personal journal 1.2. 10 Sept. 2010. Rose-DeClementi, Theresa. Personal journal 3.2. 20 Oct. 2010. Rose-DeClementi, Theresa. Personal journal 4.1. 25 Oct. 2010. Rose-DeClementi, Theresa. Personal journal 4.2. 6 Nov. 2010.

Salem :: essays research papers

The Salem Witchcraft Trials: A Time of Fear and Confusion   Ã‚  Ã‚  Ã‚  Ã‚     Ã‚  Ã‚  Ã‚  Ã‚  Imagine, just for a minute, living in a time and place where you are not free to practice your own religious or spiritual beliefs and you are forced to live in fear because of persecution by the church and everyone around you. Persecution back in 1692 in Salem Massachusetts was a very real, very serious thing. Those persecuted were hanged, burned, and even pressed against rocks if found guilty of witchcraft. The Salem Witchcraft Trials stands as one of the darkest times in American history of religious tolerance.   Ã‚  Ã‚  Ã‚  Ã‚  The Salem Witchcraft Trails were caused and continued by various events and people. Diseases, natural catastrophes, misfortune, and deaths seemed to be around every corner for the people that lived in Salem. Instead of writing these events off as bad luck people in Salem blamed these horrible things on the Devil. The people of the town believed that the Devil recruits witched and wizards to do his work for him. As soon as something bad happened, the God-fearing people of Salem were quick to blame it on a witch or wizard. Anything a little out of the ordinary like children claiming to see things that someone else could not was blamed on a witch. The people seemed to be always out to find a witch in hopes of stopping their misfortunes. They believed that once the witch was executed all the bad luck they were experiencing would disappear. Since their bad luck never disappeared their witch hunt would not soon be satisfied. The whole tragic trials were apparently started when several young girls were found playing with a ball made of crystal. Only trying to escape their punishment, they claimed to have been forced to do so by a witch. The church tried to seek out and punish the witch or wizard responsible for tormenting the girls and thus started this whole out of control event. The minister of the town, Samuel Parris, not only didn’t help the problem, but added fuel to the fire by telling the town that witches were everywhere and that no one could be trusted. Since people were allowed to testify in court about spirits talking to them, everyone backstabbed each other in order to financially gain another’s property. If you were convicted of being a witch the only way to escape death was to confess.

Arts, Man on Wire, and Bomb the Suburbs

Lilian Sun Maczynska The Literary Imagination 20 August 2012 Arts, Man on Wire, and Bomb the Suburbs Pan to Houston, Texas at night. On an episode of Stephen Fry in America, produced by Andre Singer, standing on a stage in a dimly lit room, surrounded by Houston’s elite, actor and comedian Stephen Fry speaks of the importance of the arts. â€Å"Oscar Wilde quite rightly said, ‘All art is useless’. And that may sound as if that means it’s something not worth supporting. But if you actually think about it, the things that matter in life are useless. Love is useless. Wine is useless. Art is the love and wine of life.It is the extra, without which life is not worth living. † In contrast to Fry, there are people who wish the government would cut funding for the arts. And then there are the artists. People who fight for the right to practice their art, whether they consciously know they’re fighting or not. People who will go to amazing lengths to sh owcase their art, and their dedication and determination is what gets them mentioned year after year after year. People like Philippe Petit, the quirky French high-wire artist who flew from France just to walk on a wire across the Twin Towers, whose life is forever immortalized in the documentary Man on Wire.People like William â€Å"Upski† Wimsatt, one of the most prolific Chicago-born graffiti artists, who inspired a generation of graffiti artists to view graffiti as an art form in his book Bomb the Suburbs!. Using whatever methods they can, illegal or not, they both worked to achieve their dreams and send their message to the world. They managed to pull people out of the blase outlook mentioned in Georg Simmel’s scholarly essay The Metropolis and Mental Life.One of the most prominent situations where an artist’s dream pulled people out of the unconcerned manner in which they carried themselves was the 1974 high-wire walk between the Twin Towers by Philippe Pe tit. High-wire walking is a form of tightrope walking, much like tight-wire walking, which is the simple art of maintaining balance while walking on a tensioned wire. The difference between the two is that high-wire is at a much greater height. The amount of concentration and balance and individual must have to accomplish this is extremely important in the art of tightrope walking. This s a testament to the level of professionalism and dedication that Petit had. Although he gained his notoriety in the US for walking between the twin towers, he was already gaining observations from various other places in the world, such as France, where he walked between the two spires of the Notre Dame Cathedral, and Australia, where he walked between the two sides of the Sydney Harbour Bridge. Petit realized his dream of walking between the Twin Towers when he was sixteen, soon after he had taken up high-wire walking, while in the dentist’s office and seeing an artist’s rendering of the towers as they would look when built.His passion for the art of high wire is best explained by Petit himself in the documentary Man on Wire directed by James Marsh. â€Å"Life should be lived on the edge of life. You have to exercise rebellion: to refuse to tape yourself to rules, to refuse your own success, to refuse to repeat yourself, to see every day, every year, every idea as a true challenge – and then you are going to live your life on a tightrope. † Because of his strong desire to be anything but boring, Petit put everything he had into his art.He practiced with family and friends, letting them help him improve so that one day he would achieve that dream of walking between the Twin Towers. After many years of planning and many hours the previous night setting up, Petit began taking his first steps on the wire. They were all indifferent and did not notice, except the people who were in on ‘the coup’ (his nickname for the act). In 1903, German so ciologist, Georg Simmel speaks of the blase attitude the sights and sounds of the city brought to its inhabitants in his essay The Metropolis and Mental Life. There is perhaps no psychic phenomenon which has been so unconditionally reserved to the metropolis as the blase attitude. The blase attitude results first from the rapidly changing and closely compressed contrasting stimulations of the nerves. † (Simmel par. 5) This is very much the attitude New Yorkers had when Petit started walking across the wire, on the Morning of August 7, 1974. Only after his then girlfriend, Annie Allix, began screaming and pointing to the people around them â€Å"Look! Look! Look, a wire-walker! He’s walking! did people look up and see him, this magnificent artist, walking on the wire, and they were astounded. Said the police officer, Sgt. Charles Daniels, who was sent to apprehend him, † †¦ I observed the tight rope dancer†¦ because you couldn't call him a walker†¦ approximately half-way between the two towers. I personally figured I was watching something that somebody else would never see again in the world. Thought it was once in a lifetime. † By following his dream, no matter the risk (falling to his death, getting arrest d for trespassing), Philippe Petit brought to the world, his own little piece of art, forever immortalized in history, and will always be known as the man who laid in the clouds. Fast forward twenty years, and you’ve wandered into the time period of William â€Å"Upski† Wimsatt. A poor white boy, growing up in the ghetto of Chicago, he was gifted with the art of graffiti. Graffiti is a form of public art, usually spray painted on walls, lamppost, mail boxes, or any other public surfaces, originally used as a form of marking territories between gangs. As time progressed, it became less of a mark of territory, and more of an art form.When graffiti emerged as an art form in the late 1960s in New York City , it was immediately a contentious topic. (Bowen 22) The connotation with gangs and vandalism have fueled the media to paint it in a negative light, and many graffiti artists, or â€Å"writers† as many of them consider themselves, feel that if they spoke up about it, they would be patronized for their art and passion, especially since so many artists came from the ghetto, so instead, they just continued to quietly graffiti on their own, only signing their pieces with their signature, or what is known in the graffiti world as a â€Å"tag†.Above: William â€Å"Upski† Womsott’s tag (left), A piece by Upski entitled â€Å"Upski† (right) A 20-year-old Wimsatt saw the injustice behind this and set out to â€Å"†¦be a pioneering graffiti writer, to be a hip-hop organizer in Chicago, and the be a hip hop journalist. † (Wimsatt 164) in order to revel in the art of graffiti. He writes â€Å"†¦ let’s celebrate the city. Let’s c elebrate the ghetto and the few people who aren’t running away from it. Let’s stop fucking up the city.Let’s stop fucking up the ghetto. Let’s start defending it and making it work for us. † (Wimsatt 11) On the surface of it all, it seems as if Wimsatt only has a strong personal vendetta against suburbs, but he also supports the art of graffiti in a strong way, being an artist himself. With the publication of his book, he inspired a generation of graffiti artists in the 80s and 90s to not hide their art, but to display it proudly and have pride in it and they city in which they live.Although the act of vandalism is illegal (Wimsatt tells of stories where he had to hide and run from the police, or what he perceived to be the police in his paranoia), Wimsatt encourages the act of graffiti in spaces where it can be seen, writing to a fan and fledgling graffiti artist, â€Å"Choose spots that maximize the good impact of the work, while minimizing its b ad side-effects. Maximize public exposure, surprisingness and daring of a piece, while minimizing its insult, and cost to people of the city.The best targets for piecing are usually abandoned buildings, rooftops, and neighborhood permission walls, especially in unexpected places. Questionable targets include all public or private property that gets buffed and raises the cost of living. † (Wimsatt 57) With this, he deliberately proves that he wants to bring recognition and fame to the beauty of the art of graffiti for the art, and not for any destructive reason. Petit and Wimsatt have both brought fame to themselves, and their arts.They both risked getting arrested by the police to be able to showcase this, to inspire a nation, and to motivate a generation. Through diligence, commitment, and persistence, artists every day, not just Philippe Petit and William â€Å"Upski† Wimsatt, contribute to the life force of the arts, as more and more people become aware of the import ance of the arts, and rally to support it. Petit and Though, yes, the arts are not necessary to live, and not every person needs it to be able to sustain a job or anything of the like, however, if one would just imagine the works without art, it is a bleak world.No paintings, no music, no tv, no fashion, no anything that makes this world one worth living in. Like Stephen Fry said, â€Å"Art is the love and wine of life. It is the extra, without which life is not worth living. † 10 Philippe Petit and William â€Å"Upski† Wimsatt unquestionably believe that. Works Cited * Bowen, Tracey E. â€Å"Graffiti Art: A Contemporary Study of Toronto Artists. †Ã‚  Studies in Art Education  41. 1 (1999): 22-23. Print. *   Fry, Stephen. â€Å"Mountains and Plains. †Ã‚  Stephen Fry in America. Dir. John-Paul Davidson and Michael Waldman.BBC. 02 Nov. 2008. Television. * Man on Wire. Dir. James Marsh. Prod. Simon Chinn. By Igor Martinovic, Michael Nyman, J. Ralph, and Jinx Godfrey. Magnolia Pictures, 2008. DVD. * Simmel, Georg. â€Å"Altruists International – 404 Error Page. †Ã‚  Altruists International – 404 Error Page. N. p. , n. d. Web. 23 Aug. 2012. ;http://www. altruists. org/static/files/The%20Metropolis%20and%20Mental%20Life%20(Georg%20Simmel). htm;. * Wimsatt, William Upski. Bomb the Suburbs. New York, NY: Soft Skull, 2000. Print.

How Hitler Came To Power as Chancellor in January of 1933 †History Essay

How Hitler Came To Power as Chancellor in January of 1933 – History Essay Free Online Research Papers How Hitler Came To Power as Chancellor in January of 1933 History Essay The main reasons Hitler became chancellor in January of 1933 were because the Nazi party used a strict regime of sensitive propaganda, the Nazi spokesperson, Hitler basically told the German people what they wanted to hear of how Hitler would end the depression which was sweeping over Germany. The Nazi party also gave the German people a scapegoat for the lost war, the Jews. This would help the German people vent their anger towards someone. They promised to destroy Marxism (which is the earliest type of communism), to abolish the treaty of Versailles which caused the downfall of Germany in the first place. The Treaty of Versailles was ruthlessly cruel and unfair towards the Germans, it took away their dignity and pride in their country it reduced them to practically nothing and still the allied forces wanted more from them. France only agreed to the terms of the treaty if they could bleed Germany dry as well. This would receive great support from the German people, who believe the Weimar republic signed it unfairly and were forced into it by the French. This was one of the weaknesses of the Weimar republic which lost them support. The German people believed the Weimar republic was making a mess of everything to do with reparations and the German people turned towards extremist parties, which offered drastic actions which gave more support. The Nazi party seemed well organised which made them stand out, as there would have been no political parties before this point in time, from the other political parties which were not as well organised and professional as the Nazi’s. The Propaganda which was used for the Nazi party was extremely effective in convincing the German people to vote for them, it showed posters of shadowed people all crowing around a big golden sign which says HITLER in block capitals. This would appeal to the German people as this was the age of the depression, people were homeless, unemployed, and starving. These were the people that were showed in this poster. It shows them that Hitler can change all this and help these main people, if they vote for the Nazi party. The German President of the time, Hindenburg, didn’t want to appoint Hitler a s Chancellor as he didn’t trust Hitler, so Hindenburg reluctantly appoints Von Schleicher as Chancellor. Von Papen picks up that Von Schleicher is struggling to keep a Reichstag majority, so Von Papen secretly agrees to work with Hitler; Von Papen suggests to Hindenburg that Hitler becomes Chancellor and that he, Von Papen, will be in the cabinet. Von Schleicher naturally refuses as he still doesn’t trust Hitler. Von Schleicher eventually accepts defeat in raising support in the Reichstag. Hindenburg is warned that if he places Von Papen as Chancellor then he may trigger a movement against Hindenburg. So Von Papen suggests and persuades Hindenburg that as long as the numbers of Nazi’s in the Reichstag cabinet are limited, even then with Hitler as chancellor the most extreme Nazi policies could be resisted, he also warns that the alternative is a Nazi revolt and a civil war. Hindenburg is pushed into a corner and has no other option than to appoint Hitler as Chan cellor and Von Papen as Vice Chancellor. In my conclusion I believe the propaganda and Hindenburg not having a choice are the 2 main factors in Hitler’s journey to becoming Chancellor. The propaganda gave the German people faith in Hitler and he gave them back their dignity and pride, they recovered everything they lost and now had a strong desire to work harder than before and become stronger than ever. The only way this could all happen is if Hindenburg let Hitler become chancellor, which happened, so then Hitler build up the German people’s confidence and helped them help themselves out of a depression which was crippling the German state. Research Papers on How Hitler Came To Power as Chancellor in January of 1933 - History EssayAppeasement Policy Towards the Outbreak of World War 2Assess the importance of Nationalism 1815-1850 EuropeQuebec and CanadaTwilight of the UAWBook Review on The Autobiography of Malcolm XCapital Punishment19 Century Society: A Deeply Divided EraHip-Hop is ArtArguments for Physician-Assisted Suicide (PAS)Harry Potter and the Deathly Hallows Essay

Year 2 Inorg 2 Moodle Protocol 2014 15 Essay

Year 2 Inorg 2 Moodle Protocol 2014 15 Essay Year 2 Inorg 2 Moodle Protocol 2014 15 Essay Year 2 Inorganic 2 Linkage Isomerism of Some Cobalt Complexes Objectives Upon completion of this experiment you should understand: (1) Techniques of synthesising nitrito-ÃŽ ºO and nitrito-ÃŽ ºN linkage isomers of cobalt(III), understand their structures, and the mechanisms of the reactions by which they form. (2) How to confirm if nitrito-ÃŽ ºO or nitrito-ÃŽ ºN isomers are present using infra-red spectroscopy. Aim This experiment will illustrate linkage isomerism. Introduction A common property of coordination compounds is that they often occur in isomeric forms having the same empirical formula, but with a different arrangement of atoms. Many types of isomerism exist, more so than in organic chemistry e.g. geometrical, optical, ionisation, ligand isomerism etc. (see CH160 lecture notes). Linkage isomers arise because some ligands can bond via one donor atom in one compound, but via a different atom of the same ligand in another compound. Typical examples of linkage isomersism are: NO2– M-NO2 nitrito-ÃŽ ºN (formerly nitro) M-ONO nitrito-ÃŽ ºO (formerly nitrito) CN– M-CN cyanido-ÃŽ ºC (formerly cyano) M-NC cyanido-ÃŽ ºN (formerly isocyano) NCSï€ ­ M-SCN thiocyanato-ÃŽ ºS (thiocyanato) M-NCS thiocyanato-ÃŽ ºN (isothiocyanato) (Note the old names are given for some of these complexes, which may help with background reading.) In this experiment, you will prepare two compounds with identical formula [Co(NH3)5X]Cl2 where X=NO2. One form is red and the other yellow, the difference arises depending on if NO2 is N- or O-bonded to the Co(III); see Equilibrium (1). (1) The equilibrium, above, actually lies well to the right and the only reason the ÃŽ ºO form can be obtained is that it is the first product when the aqua complex [Co(NH3)5OH2]3+, formed as an intermediate, reacts with a nitrite buffer [details are in R.G. Pearson,P.M. Henry, J.G. Bergmann and F. Basolo, J. Am. Chem. Soc., 76, 5920, (1954)]. This reaction is interesting because it is a good example of an intramolecular rearrangement (see R.K Murmann and H. Taube, J. Am. Chem. Soc., 78, 4886, (1954)). It is also possible to reverse this reaction (ÃŽ ºN to ÃŽ ºO) using UV light. In these two isomers the ligand possesses different steric requirements in the two forms, the angle ï  ¡ (see Figure 1 below) being greater than the angle ï  ¢. In the nitrito-ÃŽ ºO isomer, the O–atom bonded to Co also acts as a π– donor ligand, and since the acceptor orbital on Co is already full (t2g6) this is not the thermodynamically favoured bonding mode. In the nititro-ÃŽ ºN isomer, the N–bonded nitro group acts as a Ï€-acceptor ligand, and accepts electron density from the full Co t2g orbital 1 Figure 1: The different steric requirements of nitrito-ÃŽ ºN (left) and nitrito-ÃŽ ºO (right) The rate of isomerisation of the nitrito-ÃŽ ºO to the nitrito-ÃŽ ºN compound can, of course, be determined by UVvisible spectroscopy, since the species are different colours. However in this experiment you will use infra-red spectroscopy to monitor the change. Safety Carry out all experimental work in a fume cupboard; wear safety spectacles and lab coats at all times. Concentrated ammonia (ammonium hydroxide 18.1 M, density = 0.88) Corrosive, vapour intense irritant to eyes and respiratory system, Use in fume cupboard, wear blue nitrile gloves and eye protection. Metal ions Often toxic, wear gloves. Carefully mop up any spillages, and avoid inhaling any metal containing dust powders. The metal salts you will use are all water soluble and small quantities may be dissolved in water for disposal. Sodium nitrite Irritant Concentrated hydrochloric acid (11.65 M HCl) & diluted hydrochloric acid (6 M HCl) Caustic, will burn skin and eyes, irritant vapour. Use in fume cupboard, wear gloves and eye protection, wash away any small spillages with plenty of water. Experimental Protocol Notes You will require a number of ice-cold liquids for these experiments, you will save time if you prepare these solutions first and store on ice. You use three different concentration of