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calcium carbonate

(Encyclopedia)calcium carbonate, CaCO3, white chemical compound that is the most common nonsiliceous mineral. It occurs in two crystal forms: calcite, which is hexagonal, and aragonite, which is rhombohedral. Calci...

Wöhler, Friedrich

(Encyclopedia)Wöhler, Friedrich frēˈdrĭkh vöˈlər [key], 1800–1882, German chemist. He studied under the German chemist Leopold Gmelin and J. J. Berzelius, a Swedish chemist, and in 1836 was appointed profe...

eye

(Encyclopedia)CE5 Cross section of human eye eye, organ of vision and light perception. In humans the eye is of the camera type, with an iris diaphragm and variable focusing, or accommodation. Other types of ey...

herbicide

(Encyclopedia)herbicide hrˈbəsīdˌ [key], chemical compound that kills plants or inhibits their normal growth. A herbicide in a particular formulation and application can be described as selective or nonselectiv...

mercuric chloride

(Encyclopedia)mercuric chloride or mercury (II) chloride, chemical compound, HgCl2, a white powder of colorless rhombohedral crystals, somewhat soluble in water. It is also called bichloride of mercury or corrosive...

night blindness

(Encyclopedia)night blindness, inability to see normally in subdued light. It is usually a result of vitamin A deficiency. The rod cells, one of two light-sensitive areas of the retina of the eye, are impaired in t...

Magnus, Heinrich Gustav

(Encyclopedia)Magnus, Heinrich Gustav hīnˈrĭkh go͝osˈtäf mägˈno͝os [key], 1802–70, German chemist, physicist, and educator. In 1831 he became lecturer and in 1834 professor of physics and technology at t...

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 ...

agrimony

(Encyclopedia)agrimony ăgˈrĭmōˌnē [key], any plant of the genus Agrimonia, perennials of the family Rosaceae (rose family) native to north temperate zones, to Brazil, and to Africa. They are found wild in the...

VX

(Encyclopedia)VX vēˈĕks [key], nerve gas several times more toxic than sarin but less volatile. It kills within minutes if inhaled or deposited on the skin; protection from VX would require both protective suits...