Columbia Encyclopedia

Search results

500 results found

Hofmann, August Wilhelm von

(Encyclopedia)Hofmann, August Wilhelm von ouˈgo͝ost vĭlˈhĕlm fən hôfˈmän [key], 1818–92, German organic chemist. He was professor at the Univ. of Berlin from 1865 and was a founder (1868) of the German C...

free energy

(Encyclopedia)free energy or Gibbs free energy, quantity derived from the relationships between heat and work studied in thermodynamics and used as a measure of the relative stability of a physical or chemical syst...

potassium nitrate

(Encyclopedia)potassium nitrate, chemical compound, KNO3, occurring as colorless, prismatic crystals or as a white powder; it is found pure in nature as the mineral saltpeter, or niter. (The name saltpeter is also ...

kaolinite

(Encyclopedia)kaolinite kāˈəlĭnīt [key], clay mineral crystallizing in the monoclinic system and forming the chief constituent of china clay and kaolin. It is a hydrous aluminum silicate commonly formed by the...

hydrogen peroxide

(Encyclopedia)hydrogen peroxide, chemical compound, H2O2, a colorless, syrupy liquid that is a strong oxidizing agent and, in water solution, a weak acid. It is miscible with cold water and is soluble in alcohol an...

synapse

(Encyclopedia)synapse sĭnˈăps [key], junction between various signal-transmitter cells, either between two neurons or between a neuron and a muscle or gland. A nerve impulse reaches the synapse through the axon,...

Ostwald, Wilhelm

(Encyclopedia)Ostwald, Wilhelm vĭlˈhĕlm ôstˈvält [key], 1853–1932, German physical chemist and natural philosopher, b. Riga, Latvia. He was professor of chemistry and director of the chemical laboratory (18...

refining

(Encyclopedia)refining, any of various processes for separating impurities from crude or semifinished materials. It includes the finer processes of metallurgy, the fractional distillation of petroleum into its comm...

ammonium nitrate

(Encyclopedia)ammonium nitrate, chemical compound, NH4NO3, that exists as colorless, rhombohedral crystals at room temperature but changes to monoclinic crystals when heated above 32℃. It is extremely soluble in ...

sulfate

(Encyclopedia)sulfate, chemical compound containing the sulfate (SO4) radical. Sulfates are salts or esters of sulfuric acid, H2SO4, formed by replacing one or both of the hydrogens with a metal (e.g., sodium) or a...