Acetylene of 180°. Acetylene was discovered in 1836 by Edmund Davy, who identified it as a "new carburet of hydrogen". It was rediscovered in 1860 by French chemist Marcellin Berthelot, who coined the name "acétylène". Berthelot's empirical formula for acetylene (CH), as well as the alternative name "quadricarbure d'hydrogène" ("hydrogen quadricarbide"), were incorrect because chemists at that time used the wrong atomic mass for carbon (6 instead of 12). Berthelot was able to prepare this gas by passing vapours of organic compounds (methanol, ethanol, etc.) through a red-hot tube and collecting the effluent. He also found that acetylene was formed by
Discovered attack 2.hxg6++. The result is a "double discovered check": One check is given by the rook, discovered by the capturing pawn's move; the other by the bishop, discovered by the captured pawn's removal. Such a check is extremely rare in practical play, but is sometimes found in problems. The diagram illustrates a trap in the Advance Variation of the French Defence, based on a discovered attack. If, after 1.e4 e6 2.d4 d5 3.e5 c5 4.c3 Nc6 5.Nf3 Qb6 6.Bd3 cxd4 7.cxd4, Black mistakenly attempts to win White's d4-pawn with 7...Nxd4 8.Nxd4 Qxd4 (diagram), White can play 9.Bb5+, a discovered attack (White's