Nitrocellulose is a flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it was known as guncotton. Nitrated cellulose has found uses as a plastic film and in inks and wood coatings. In 1855, the first man-made plastic, was created by Alexander Parkes from cellulose treated with nitric acid and a solvent. In 1868, American inventor John Wesley Hyatt developed a plastic material he named Celluloid, improving on Parkes' invention by plasticizing the nitrocellulose with camphor so it could be processed into finished form and used as a photographic film. Celluloid was used by Kodak, other suppliers, from the late 1880s as a film base in photography, X-ray films, motion-picture films, was known as nitrate film. After numerous fires caused by unstable nitrate films, "safety film" started to be used from the 1930s in the case of X-ray stock and from 1948 for motion-picture film. In 1832 Henri Braconnot discovered that nitric acid, when combined with starch or wood fibers, would produce a lightweight combustible explosive material, which he named xyloïdine.

A few years in 1838, another French chemist, Théophile-Jules Pelouze, treated paper and cardboard in the same way. Jean-Baptiste Dumas obtained a similar material; these substances were unstable and were not practical explosives. However, around 1846 Christian Friedrich Schönbein, a German-Swiss chemist, discovered a more practical solution; as he was working in the kitchen of his home in Basel, he spilled a mixture of nitric acid and sulfuric acid on the kitchen table. He reached for the nearest cloth, a cotton apron, wiped it up, he hung the apron on the stove door to dry, as soon as it was dry, a flash occurred as the apron ignited. His preparation method was the first to be imitated—one part of fine cotton wool to be immersed in 15 parts of an equal blend of sulfuric and nitric acids. After two minutes, the cotton was removed and washed in cold water to set the esterification level and remove all acid residue, it was slowly dried at a temperature below 40 °C. Schönbein collaborated with the Frankfurt professor Rudolf Christian Böttger, who had discovered the process independently in the same year.

By coincidence, a third chemist, the Brunswick professor F. J. Otto had produced guncotton in 1846 and was the first to publish the process, much to the disappointment of Schönbein and Böttger; the process uses nitric acid to convert cellulose into cellulose nitrate and water: 3 HNO3+ C6H10O5 H2SO4→ C6H73O5 + 3 H2OThe sulfuric acid is present as a catalyst to produce the nitronium ion, NO+2. The reaction is first order and proceeds by electrophilic substitution at the C−OH centers of the cellulose. Guncotton is made by treating cotton with concentrated sulfuric acid and 70% nitric acid cooled to 0 °C to produce cellulose trinitrate. While guncotton is dangerous to store, the hazards it presents can be reduced by storing it dampened with various liquids, such as alcohol. For this reason, accounts of guncotton usage dating from the early 20th century refer to "wet guncotton"; the power of guncotton made it suitable for blasting. As a projectile driver, it had around six times the gas generation of an equal volume of black powder and produced less smoke and less heating.

The patent rights for the manufacture of guncotton were obtained by John Hall & Son in 1846, industrial manufacture of the explosive began at a purpose-built factory at Marsh Works in Faversham, Kent, a year later. However, the manufacturing process was not properly understood and few safety measures were put in place. A serious explosion in July of that year killed two dozen workers, resulting in the immediate closure of the plant. Guncotton manufacture ceased for over 15 years. Further research indicated the importance of careful washing of the acidified cotton. Unwashed nitrocellulose may spontaneously ignite and explode at room temperature, as the evaporation of water results in the concentration of unreacted acid; the British chemist Frederick Augustus Abel developed the first safe process for guncotton manufacture, which he patented in 1865. The washing and drying times of the nitrocellulose were both extended to 48 hours and repeated eight times over; the acid mixture was changed to two parts sulfuric acid to one part nitric.

Nitration can be controlled by adjusting reaction temperature. Nitrocellulose is soluble in a mixture of alcohol and ether until nitrogen concentration exceeds 12%. Soluble nitrocellulose, or a solution thereof, is sometimes called collodion. Guncotton containing more than 13% nitrogen was prepared by prolonged exposure to hot, concentrated acids for limited use as a blasting explosive or for warheads of underwater weapons such as naval mines and torpedoes. Safe and sustained production of guncotton began at the Waltham Abbey Royal Gunpowder Mills in the 1860s, the material became the dominant explosive, becoming the standard for military warheads, although it remained too potent to be used as a propellant. More-stable and slower-burning collodion mixtures were prepared using less-concentrated acids at lower temperatures for smokeless powder in firearms; the first practical smokeless powder made from nitrocellulose, for firearms and artillery ammunition, was invented by French

Second Professional Football League (Bulgaria)

The Bulgarian Second Professional Football League known as Second League or Vtora liga, is the second level of the Bulgarian football league system, below First League and above the Third League. Sixteen teams take part in the league, each playing twice against all the other, once home and once away. Most matches are played on Sundays; the league is administered by the Bulgarian Professional Football League. In 2016, the B Group's name was rebranded to Second Professional Football League. A team receives 1 point for a draw. No points are awarded for a loss. First place: Direct promotion to A Group. Second place: Promotion playoff against the 9th place team from A Group. 13th to 16th place: Relegation to V Group. The B group was established in 1950 when the league was divided in two groups - North and South, in each group participating 10 teams; the first champions of the B Republican Football Group are Torpedo. In season 1951 the group is only one - B Republican Football Group with 12 teams; the regulations are - in A Group are going the top team in the final standings from Sofia and the top two teams from the province.

In the next season 1952 the group is formed by 14 teams and from season 1953 the league is divided into five groups - Sofia B Group, North-West B Group, South-West B Group, North-East B Group and South-East B Group. In the next seasons the league had many changes. In 2000 the Bulgarian Football Union changed the name of the division; the league is formed by 18 teams, not like previous seasons - 16 teams. To reduce the teams to 16 again in the next season the last six teams that finish in the final standings in the league were directly relegated. Before the start of season 2001/2002 the league was again renamed; the championship started with 13 teams, because Lokomotiv and Belasitsa united with two teams from A Group - Lokomotiv with PFC Velbazhd Kyustendil and Belasitsa with PFC Hebar Pazardzhik. That meant, that this was the end of professional football in the towns of Kyustendil and Pazardzhik. Returning to the traditions of the B Republican Football Group was the creating of the B Professional Football Group.

16 teams participated in the league, each playing twice against all the other, once home and once away, with no play-offs. Before the start of season 2005/2006 the Bulgarian Football Union decided to divide B Group in two groups - West B Group and East B Group with 14 teams in each group; every team plays 13 matches as 13 matches as away team. The two champions of the groups were directly promoted to A Group and the two teams that finished in second place in their group played a play-off for winning the final third place for promotion in A Group. On May 19, 2008 the two groups were extended to 16 teams. For season 2010/2011 the two groups were reduced again with 12 teams in each, but just before the start of season 2011/2012 the number of teams in the two groups was again reduced - 10 teams in both West B Group and East B Group, with the winners of the groups directly promoting to A Group. The two teams that finished in second place in their group enter in a play-off for winning a place at the final play-off for promotion/relegation with the team that finished 14th in A Group.

Further changes were made before the start of season 2012/2013. The former format of B Group with the two groups was replaced by a single division, formed by fourteen teams; the following table presents the former champions of B Group

Phuket Island light rail transit

The Phuket Island Light Rail Transit project is a planned 58.6 km light rail transit system for Phuket and Phang Nga Provinces in Thailand. The completed project will consist of 23 or 24 stations from Takua Thung District in Phang Nga Province to Phuket City terminating at Chalong. Phase one will connect Phuket International Airport to Chalong; the second phase will extend the line north to Takua Thung District. The line will have both elevated sections; the cost of the project is estimated at 39.4 billion baht. The project is planned to be tendered in late 2019 with construction starting in 2020 for a scheduled 2024 opening of Phase 1; the original plan for mass transit on Phuket Island was first proposed in 2005. However, it was not until 2010 that the Phuket governor proposed a heavy rail metro idea as a requirement for the island to meet increasing tourism and local transport demands. By mid-2014, the project had evolved into a planned light rail line of nearly 60 km in length running from the north of the island to the south.

The Ministry of Transport approved the project in principle in November 2015. Public meetings were held in February 2017 seeking feedback and comments from the public into the project. In April 2017, it was announced that the MRTA had approved the Ministry of Transport's Office of Transport and Traffic Policy and Planning design of the project with a view to seeking cabinet approval in 2018. Cabinet approval was granted on 11 September 2018; the LRT line will run along the north-south axis of Phuket Island. The planned route stretches from Takua Thung in Phang Nga to Chalong in Phuket. Phase one will connect Phuket International Airport with about 40 kilometres. Phase one construction is expected to take three years; the MRTA and the OTP are studying the second phase, from Takua Thung to Phuket Airport. The line is projected to serve up to 70,000 passengers per day, passing by 40 schools and business districts en route. Fares are expected to cost from 15 to 25 baht; some critics have cited officials -- 137 baht.

Contracts for project investment studies were signed by the end of July 2018 and were completed by the end of 2018. They were submitted to the MRTA board for approval by in early 2019, after which they will be reviewed by the Transport Ministry. Bidding for the project should start in 2019. Phuket provincial authorities have been in discussions with both Siemens and Bombardier regarding the project. According to OTP Deputy Director Wilairat Sirisoponsil, the Phuket light rail project design is complete, has been added into the PPP Fast Track. However, detailed design issues have arisen with the Department of Highways opposed to some sections of the project and concerns regarding any impact on road lanes; these design issues should be finalised in June 2019 However, the design changes may increase the overall budget by 2 billion baht according to the MRTA. Chiang Mai light rail transit Khon Kaen Light Rail Transit List of urban rail systems in Thailand