Columbia Encyclopedia

(Encyclopedia) optical activity, the ability of asymmetric compounds to rotate the orientation of planar polarized light. Such compounds and their mirror images are know as enantiomers, or optical isomers. Although ...

(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...

(Encyclopedia) Overbeck, Johann Friedrich yōˈhän frēˈdrĭkh oˈvərbĕk [key], 1789–1869, German religious painter. Expelled from the Vienna Academy because of his opposition to its classicism, he went to Rom...

(Encyclopedia) palmtop or hand-held personal computer, lightweight, small, battery-powered, general-purpose programmable computer. It typically had a miniaturized full-function, typewriterlike keyboard for input and...

(Encyclopedia) asphalt ăsˈfôlt, –fălt [key], brownish-black substance used commonly in road making, roofing, and waterproofing. Chemically, it is a natural mixture of hydrocarbons. It varies in consistency fro...

(Encyclopedia) mastic, resin obtained from the small mastic tree Pistacia lentiscus (of the sumac family), found chiefly in Mediterranean countries. When the bark of the tree is injured, the resin exudes in drops. I...

(Encyclopedia) Percheron horse pûrˈchərŏnˌ [key], breed of draft horse developed in NW France, originally of Flemish origin, but also containing some Arabian blood (see Arabian horse). For a heavy horse, it has...

(Encyclopedia) phlogiston theory flōjĭsˈtŏn [key], hypothesis regarding combustion. The theory, advanced by J. J. Becher late in the 17th cent. and extended and popularized by G. E. Stahl, postulates that in all...

(Encyclopedia) photoengraving, photomechanical process in the graphic arts, used principally for reproducing illustrations. The subject is photographed, and the image is recorded on a sensitized metal plate, which i...

(Encyclopedia) Moronobu (Hishikawa Moronobu) hēshēkäˈwä mōrōˈnōbo͞o [key], c.1618–c.1694, Japanese painter and color-print designer of the ukiyo-e school. He began his career as an embroiderer. His first...