Base (chemistry) Base (chemistry) In chemistry, bases are substances that, in aqueous solution, release hydroxide (OH) ions, are slippery to the touch, can taste bitter if an alkali, change the color of indicators (e.g., turn red litmus paper blue), react with acids to form salts, promote certain chemical reactions (base catalysis), accept protons from any proton donor or contain completely or partially displaceable OH ions. Examples of bases are the hydroxides of the alkali metals and the alkaline earth metals (NaOH, Ca(OH), etc., see alkali hydroxide and alkaline earth hydroxide). These particular substances produce hydroxide ions (OH) in aqueous solutions, and are
Alchemy and chemistry in medieval Islam the element's physical properties. Al-Rāzī mentions the following chemical processes: distillation, calcination, solution, evaporation, crystallization, sublimation, filtration, amalgamation, and ceration (a process for making solids pasty or fusible.) Some of these operations (calcination, solution, filtration, crystallization, sublimation and distillation) are also known to have been practiced by pre-Islamic Alexandrian alchemists. In his "Secretum secretorum", Al-Rāzī mentions the following equipment: Alchemy and chemistry in medieval Islam Alchemy and chemistry in Islam refers to the study of both traditional alchemy and early practical chemistry (the early chemical investigation of nature in general) by scholars in the medieval Islamic world. The word "alchemy"