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A mechanical pencil or clutch pencil is a pencil with a replaceable and mechanically extendable solid pigment core called a "lead" / ˈ l ɛ d /. The lead , often made of graphite , is not bonded to the outer casing, and the user can mechanically extend it as its point is worn away from use.
The only metal having an ionisation energy higher than some nonmetals (sulfur and selenium) is mercury. [citation needed] Mercury and its compounds have a reputation for toxicity but on a scale of 1 to 10, dimethylmercury ((CH 3) 2 Hg) (abbr. DMM), a volatile colourless liquid, has been described as a 15. It is so dangerous that scientists have ...
Lead for mechanical pencils Flexible pencils. Mechanical pencils use mechanical methods to push lead through a hole at the end. These can be divided into two groups: with propelling pencils an internal mechanism is employed to push the lead out from an internal compartment, while clutch pencils merely hold the lead in place (the lead is ...
Oxygen is an insulator in all of its forms. It has a high ionisation energy (1313.9 kJ/mol), moderately high electron affinity (141 kJ/mol), and high electronegativity (3.44). Oxygen is a strong oxidising agent (O 2 + 4e → 2H 2 O = 1.23 V at pH 0). Metal oxides are largely ionic in nature. [7] Sulfur. Sulfur is a bright-yellow moderately ...
That same year Rotring launched its first drawing board, and the "Tikky" mechanical pencil was released in 1979. The "Art Pen", a fountain pen suitable for calligraphy , was launched in 1984. During the decade, Rotring set new subsidiaries in other European countries, while the "600" mechanical pencil was introduced in 1989.
Silver mechanical pencil Catalogue from 1898 Sampson Mordan (c. 1790 – 9 April 1843) was a British silversmith and a co-inventor of the first patented mechanical pencil . During his youth, he was an apprentice of the inventor and locksmith Joseph Bramah , who patented the first elastic ink reservoir for a fountain pen .