NMR (Nuclear Magnetic Resonance) spectroscopy is a type of spectroscopy that allows chemists to see the structure of a molecule. Certain atoms' nuclei have certain magnetic properties when placed in a strong magnetic field. Atoms like carbon, hydrogen, and fluorine can be detected in this way.
A chemical sample is prepared by placing a tiny amount of the sample in an NMR tube. It is dissolved in a special solvent like heavy water (see deuterium) or chloroform-d, then the tube is placed into the NMR machine. The machine is a large magnet, like an MRI. Some atoms in the sample will become excited when it is in the magnet, and when the sample is removed, the atoms will go back to a lower energy state. A computer connected to the NMR can detect this change in excitement and it will cause different peaks and bumps to appear on the NMR diagram. A chemist can print this diagram and study the various peaks.
Most NMR machines can only detect excitement from one type of atom. For example, an H NMR can only "see" hydrogen atoms. A C NMR can only see activity from carbon atoms.
An NMR diagram displays an x-axis with units of parts per million, or "shift." Peaks that occur farther to the left in the diagram (these peaks are said to be shifted downfield) represent hydrogen atoms that are closer to electronegative atoms like oxygen or nitrogen, or connected to an aromatic (benzene) ring. Hydrogen atoms that are adjacent to other hydrogen atoms can split peaks as well. If there are n hydrogen atoms "next door" to a single one, that single one's peak will be split into n+1 peaks. For example, if a hydrogen atom is adjacent to three others, that hydrogen atom will be split into 4 smaller peaks, called a quartet. Hydrogen atoms that are part of O-H or N-H bonds won't be split, but they will appear on the diagram as a rounded lump, called a broad peak. By looking at all these factors in a diagram, a chemist can figure out what compounds are in his or her sample, and they can determine if the compound they have made is pure.
Mercury(I) sulfate
Mercury(I) sulfate, also known as mercurous sulfate, is a chemical compound. Its chemical formula is HgSO. It has mercury and sulfate ions in it. The mercury is in its +1 oxidation state.
Mercury(I) sulfate is a whitish-yellow solid. It is not soluble in water. It does dissolve in dilute nitric acid.
It is made by dissolving a large amount of mercury in concentrated sulfuric acid. It can also be made by reacting mercury(I) nitrate with any sulfate or sulfuric acid.
Italian Renaissance art
Italian Renaissance art is a style of painting and sculpture that began in the late 13th century (1200s) with the work of the painter Giotto and a sculptor Nicola Pisano. The Renaissance way of painting and sculpting did not become the usual style until about 100 years later. From 1400 to about 1600 many artists in Italy used and developed the style. Leonardo da Vinci is a very famous example of an artist in this style.
The city of Florence is a birthplace of the Renaissance and in particular, of Renaissance art.
Italian Renaissance painting can be divided into four periods:
The Proto-Renaissance begins with the works of the painter Giotto and includes Taddeo Gaddi, Orcagna and Altichiero and the sculptor Nicola Pisano.
The Early Renaissance was the time of the painters Masaccio, Fra Angelico, Uccello, Piero della Francesca and Verrocchio, and the sculptors Ghiberti and Donatello.
The High Renaissance was the time of Leonardo da Vinci, Raphael and Titian as well as Michelangelo who was famous as a sculptor and as a painter.
The Mannerist period was the time of Andrea del Sarto, Pontormo and Tintoretto and the sculptors Giambologna and Cellini.
Cosimo de' Medici was intelligent, deeply religious, very rich, and wanted to be remembered as a man who did great things for Florence. He was a great patron of the arts and learning. He paid artists to make many beautiful paintings and sculptures. He collected many books, that were given to the Friary of St Mark so that a library could be made and many people could use them. After Cosimo, his sons Piero and Giovanni, and his grandsons Lorenzo and Giuliano continued to be patrons of the arts and of learning. They gathered a group of philosophers, poets and artists together in the "Medici Academy".
Cunard Line
Cunard Line is a shipping company that was founded in 1840 and runs cruise ships all over the world.
Cunard was formed in 1840 by Samuel Cunard after he decided to start a company that would carry mail from England to the United States. England paid for the costs of this service, since the country wanted a more regular service than the sailing ships of the time could do. Cunard started with four steam ships that made crossings of the Atlantic Ocean once a week. The company became known for its record of good safety–while ships of other companies often sank, killing many people, these sorts of things rarely happened to Cunard.
By the early 1900s, though, Cunard was faced with many other ships from several countries also competing with it for passengers going across the Atlantic. This caused the company to build three new ships, larger and faster than the ones before them. They were named RMS "Mauretania", RMS "Lusitania" and RMS "Aquitania". Theses ships made Cunard back into a leading shipping line, even though "Lusitania" was sunk during World War I by a German submarine, killing 1,200 people.
In 1934, another big Cunard ship, the RMS "Queen Mary", began service. She was the largest ship ever built at that time. During World War II, "Queen Mary" and another new ship like her, "Queen Elizabeth", carried many soldiers to support England and the US.
By the 1960s, people preferred to cross the Atlantic by jet airplanes rather than by ships, so Cunard sold most of their ships, or made them cruise ships instead of ocean liners. Cunard still decided to build one new ocean liner, though, RMS "Queen Elizabeth 2". She started service in 1969 and became a very popular ship because she made both cruises and crossings of the Atlantic.
In 1998, Carnival Corporation bought Cunard. Soon after, the company decided to build a new ocean liner that would make both cruises and Atlantic crossings like "Queen Elizabeth 2", but would be bigger. This ship entered service in 2004 and is named RMS "Queen Mary 2".
Cunard operates three ships as of 2010, and has operated many more in the past. The three that are in service are RMS "Queen Mary", MS "Queen Victoria", and MS "Queen Elizabeth".
Emulsifier
An emulsifier is an additive which helps two liquids mix. For example, water and oil separate in a glass, but adding an emulsifier will help the liquids mix together. Some examples of emulsifiers are egg yolks and mustard.
Emulsifiers belong to the surfactants, usually with a grease-loving (lipophilic) and a water-loving (hydrophilic) part, which can nest around boundary layers between aqueous and greasy parts. Grease and water repel each other, making an emulsion without emulsifier easily fall apart. An emulsifier prevents this rejection because it projects the water-loving side towards the water and the fat-loving side towards the fat. The extent to which the hydrophilic or lipophilic character dominates is represented by the HLB value of the surfactant (HLB = Hydrophilic-Lipophilic Balance). A high HLB value (10 to 18) indicates a hydrophilic substance suitable for emulsifying fats or oils in water. Substances with a low HLB (3 to 8) are lipophilic and suitable for water-in-oil emulsions.
Cosmetics
Emulgators are used in cosmetics for example in creams and bath oils. A cream consists largely of an emulsion of fat in water or of water in fat, while a bath oil often contains an emulsifier to partially distribute the oil in the water. Without an emulsifier, the oil would float on the water. Examples of emulsifiers used in cosmetic products are glyceryl monostearate, Polysorbate 20, accasia, tragacanth agar, and pectin.