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 called a discovered check. When the moving piece gives check to the opponent's king, the maneuver is often described as a "discovered attack with check". When the discovered attack is itself a check, it is called a "discovered check". If both pieces give check, a double check results. Discovered attacks—especially checks—can win material when the moving piece captures an opposing piece nominally protected by another opposing piece. If the opponent deals with the discovered attack (obligatory if it is a check), the attacking player will have time to return the moving piece out of harm's way. This scenario is often