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David Roberts (painter)

David Roberts RA was a Scottish painter. He is known for The Holy Land, Idumea, Arabia and Nubia, a prolific series of detailed lithograph prints of Egypt and the Near East that he produced from sketches he made during long tours of the region; these and his large oil paintings of similar subjects made him a prominent Orientalist painter. He was elected as a Royal Academician in 1841. Apprenticed for seven years to a house painter and decorator named Gavin Beugo, his fellow apprentice being David Ramsay Hay, who became a lifelong friend. During this time he studied art in the evenings. After his apprenticeship was complete, Roberts's first paid job came in the summer of 1815, when he moved to Perth to serve as foreman for the redecoration of Scone Palace. Roberts lived with his parents while looking for work, his next job was to paint scenery for James Bannister's circus on North College Street. This was the beginning of his career as a designer of stage scenery. Bannister liked Roberts's set designs and on 10 April 1816 engaged him at a salary of 25 shillings per week to travel with the circus on a tour of England.

Roberts departed Edinburgh with the circus the same month and travelled to Carlisle, Newcastle and York, returning to Edinburgh in January 1817. During his time with the circus, Roberts was called on to take several minor stage roles as a foil for the clowns' skits. For the first few months of 1817, Roberts worked as the stage designer's assistant at the Pantheon Theatre, Edinburgh, a new joint venture between Bannister and an Italian musician named Corri; however the Pantheon was a financial failure and closed in May 1817. He reluctantly returned to house painting, working on the mansion house of Abercairny, near Perth, designed by Gillespie Graham. Although he was working from 5 a.m. to 7 p.m. he took the opportunity to sketch in the woods around the mansion in the evening. He followed this up with a stint painting imitation wood and marble at a mansion at Condie, near Bridge of Earn, in Perthshire. At the urging of his parents, Roberts returned to Edinburgh in January 1818, where he took employment with John Jackson, a decorative painter.

Working for Jackson during 1818, Roberts decorated Lord Lauderdale's Dunbar House and the library of Craigcrook Castle for Lord Jeffrey, who had leased the property. In 1818, the Pantheon Theatre reopened in Edinburgh. A company from London with their own scene painters was in residence, but after they left, Roberts was able to get work from Corri as a scene painter. While Corri offered Roberts the position on 25 July 1818, he was committed to house-painting work for Jackson and was unable to start at the Pantheon until the winter season; as there was no separate painting room, Roberts had to paint sets directly on the stage, occupied by rehearsals during the day and performances in the evening. Therefore, Roberts began work after the evening production had finished, working through the night. Roberts's work was noticed by Mr. Monro. After the Pantheon closed, Monro moved on to the Theatre Royal, where he arranged for Roberts to be hired as a principal scene-painter. In 1819, Roberts became the scene painter at the Theatre Royal in Edinburgh.

There Roberts met the Scottish actress Margaret McLachlan, said to be the illegitimate daughter of a Highland gypsy girl and a clan chief. They married in 1820, "for pure love". Although the marriage did not last long, it produced Roberts' only daughter, born in 1821. Although he was making a living from scene painting, it was around this time that Roberts began to produce oil paintings seriously. In 1821 he became friends with the artist William Clarkson Stanfield, who joined him to paint scenery at the Theatre Royal, Roberts developed his love of landscape painting. In 1821 the Fine Arts Institution of Edinburgh accepted three of Roberts's paintings – views of Melrose and Dryburgh abbeys – two of which sold. At Stanfield's suggestion, Roberts sent three pictures to the 1822 Exhibition of Works by Living Artists, held in Edinburgh. In 1822 the Coburg Theatre, now the Old Vic in London, offered Roberts a job as a scenic designer and stage painter, he settled in London. After working for a while at the Coburg Theatre, Roberts moved to the Theatre Royal, Drury Lane to create dioramas and panoramas with Stanfield.

A miniature by Roberts from this time shows Margaret as a delicate woman with blonde ringlets, holding the smiling three-year-old Christine. But Roberts' family life was not as idyllic as this picture suggests: Margaret had become an alcoholic, in 1831, Roberts sent her back to Scotland to be cared for by friends. Roberts may have burned some letters from this period in shame at his wife's drinking problem, but he was unusually frank in a letter to a friend, David Ramsay Hay. Roberts and Hay had been an apprentices together, Hay had been seeing a mistress since his own wife had started drinking. "If you do not know our cases are parallel. Yours is not as bad as mine; the state of my nerves is such. But thank God she leaves tomorrow—I hope for ever." In 1824, he exhibited another view of Dryburgh Abbey at the British Institution and sent two works to the first exhibition of the newly formed Society of British Artists. In the autumn of 1824 he visited Normandy, his paintings based on this trip began to lay the foundation of his reputation.

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Catharina Point

Catharina Point Varoli Point, is a rocky point projecting 1.5 km northwards into Drake Passage to form the north extremity of Robert Island in the South Shetland Islands and the northeast side of the entrance to Nevestino Cove. The area was visited by early 19th century sealers operating from nearby Clothier Harbour; the feature is named after the American sealing vessel Catharina under Captain Joseph Henfield that visited the South Shetlands in 1820-21. The point is located at 62°19′41.3″S 59°37′13.9″W, 7.24 km northeast of Fort William, 2.08 km northeast of Hammer Point and 5.27 km west-northwest of Newell Point. L. L. Ivanov. Antarctica: Livingston Island and Greenwich, Robert and Smith Islands. Scale 1:120000 topographic map. Troyan: Manfred Wörner Foundation, 2009. ISBN 978-954-92032-6-4 SCAR Composite Antarctic Gazetteer

Recrystallization (chemistry)

In chemistry, recrystallization is a technique used to purify chemicals. By dissolving both impurities and a compound in an appropriate solvent, either the desired compound or impurities can be removed from the solution, leaving the other behind, it is named for the crystals formed when the compound precipitates out. Alternatively, recrystallization can refer to the natural growth of larger ice crystals at the expense of smaller ones. In chemistry, recrystallization is a procedure for purifying compounds; the most typical situation is that a desired "compound A" is contaminated by a small amount of "impurity B". There are various methods of purification that may be attempted, recrystallization being one of them. There are different recrystallization techniques that can be used such as: Typically, the mixture of "compound A" and "impurity B" is dissolved in the smallest amount of hot solvent to dissolve the mixture, thus making a saturated solution; the solution is allowed to cool. As the solution cools the solubility of compounds in solution drops.

This results in the desired compound dropping from solution. The slower the rate of cooling, the bigger the crystals form. In an ideal situation the solubility product of the impurity, B, is not exceeded at any temperature. In that case the solid crystals will consist of pure A and all the impurity will remain in solution; the solid crystals are collected by filtration and the filtrate is discarded. If the solubility product of the impurity is exceeded, some of the impurity will co-precipitate. However, because of the low concentration of the impurity, its concentration in the precipitated crystals will be less than its concentration in the original solid. Repeated recrystallization will result in an purer crystalline precipitate; the purity is checked after each recrystallization by measuring the melting point, since impurities lower the melting point. NMR spectroscopy can be used to check the level of impurity. Repeated recrystallization results in some loss of material because of the non-zero solubility of compound A.

The crystallization process requires an initiation step, such as the addition of a "seed" crystal. In the laboratory a minuscule fragment of glass, produced by scratching the side of the glass recrystallization vessel, may provide the nucleus on which crystals may grow. Successful recrystallization depends on finding the right solvent; this is a combination of prediction/experience and trial/error. The compounds must be more soluble at the higher temperature than at the lower temperatures. Any insoluble impurity is removed by the technique of hot filtration; this method is the same as the above but. This relies on "impurity B" being soluble in a first solvent. A second solvent is added. Either "compound A" or "impurity B" will be insoluble in this solvent and precipitate, whilst the other of "compound A"/"impurity B" will remain in solution, thus the proportion of first and second solvents is critical. The second solvent is added until one of the compounds begins to crystallize from solution and the solution is cooled.

Heating can be used. The reverse of this method can be used where a mixture of solvent dissolves both A and B. One of the solvents is removed by distillation or by an applied vacuum; this results in a change in the proportions of solvent causing either "compound A" or "impurity B" to precipitate. Hot filtration can be used to separate "compound A" from both "impurity B" and some "insoluble matter C"; this technique uses a single-solvent system as described above. When both "compound A" and "impurity B" are dissolved in the minimum amount of hot solvent, the solution is filtered to remove "insoluble matter C"; this matter may be anything from a third impurity compound to fragments of broken glass. For a successful procedure, one must ensure that the filtration apparatus is hot in order to stop the dissolved compounds crystallizing from solution during filtration, thus forming crystals on the filter paper or funnel. One way to achieve this is to heat a conical flask containing a small amount of clean solvent on a hot plate.

A filter funnel is rested on the mouth, hot solvent vapors keep the stem warm. Jacketed filter funnels may be used; the filter paper is preferably fluted, rather than folded into a quarter. It is simpler to do the filtration and recrystallization as two independent and separate steps; that is dissolve "compound A" and "impurity B" in a suitable solvent at room temperature, remove the solvent and recrystallize using any of the methods listed above. Crystallization requires an initiation step; this can be spontaneous or can be done by adding a small amount of the pure compound to the saturated solution, or can be done by scratching the glass surface to create a seeding surface for crystal growth. It is thought that dust particles can act as simple seeds. Growing crystals for X-ray crystallography can be quite difficult. For X-ray analysis, single perfect crystals are required. A small amount of pure compound is used, crystals are allowed to grow slowly. Several techniques can be used to grow these perfect crystals: Slow evaporation of a single solvent - the compound is dissolved in a suitable solvent and the solvent is allowed to evaporate.

Once the solution is saturated crystals can form. Slow evaporation of a multi-solvent system - the same as above, however as the solvent composition changes due to eva