diatomaceous earth

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diatom (dīˈətŏmˌ, –tōmˌ), unicellular organism of the kingdom Protista, characterized by a silica shell of often intricate and beautiful sculpturing. Most diatoms exist singly, although some join to form colonies. They are usually yellowish or brownish, and are found in fresh- and saltwater, in moist soil, and on the moist surface of plants. They carry chlorophylls a and c and the carotenoid fucoxanthin contained in plastids. They reproduce asexually by cell division. Some 40,000 species (5,600 living species) are either bilaterally or radially symmetrical. For the most part they lack flagella. Although most diatoms are autotrophic, some heterotrophic or symbiotic species can be found in particular habitats. The living matter of each diatom is enclosed in a shell of silica that it secretes. These shells are marked by minute pores or depressions that allow the living organism access to its environment. As the principal constituent of plankton (see marine biology), diatoms are an important food source for fish and other aquatic animals, e.g., the baleen whales.

When aquatic diatoms die they drop to the bottom, and the shells, not being subject to decay, collect in the ooze and eventually form the material known as diatomaceous earth (sometimes called kieselguhr). When it occurs in a more compact form as a soft, chalky, light-weight rock, it is called diatomite. Deposits of diatomaceous material, formed underwater in past geologic time and now exposed above water, are found in all parts of the world. Diatomite is much used as an insulating material against both heat and sound, in making dynamite and other explosives, and for filters, abrasives, and similar products. Most of the earth's limestone has been deposited by diatoms, and much petroleum is of diatom origin.

Diatoms are classified in the phylum (division) Chrysophyta, class Bacillariophyceae.

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diatomaceous earth

[¦dī·ə·tə¦mā·shəs ′ərth]
A yellow, white, or light-gray, siliceous, porous deposit made of the opaline shells of diatoms; used as a filter aid, paint filler, adsorbent, abrasive, and thermal insulator. Also known as kieselguhr; tripolite.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

diatomite, diatomaceous earth, kieselguhr

A white or light gray, chalky, natural siliceous material; obtained by mining deposits of fossil remains of small marine life; used as an extender in paints, as an aggregate in lightweight concrete, as a waterproofing material in portland cement, as a filter for water, and as an abrasive.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
References in periodicals archive ?
Candida rugosa lipase, Celite 545, Sephadex G-25 (medium), chitosan (low molecular weight), glycerol, caprylic acid, and sodium hydroxide (purity > 98%) were purchased from Sigma Aldrich (St.
Ltd., advertisement in Chemistry in Canada promoted CELITE, a trademarked brand name for diatomaceous earth, for the filtration of consumer and industrial goods.
Kanwar, "Properties and stability of celite immobilized lipase of a thermophilic Bacillus sp.
Air benzene sampling was performed using Chromosorb 106[R] stainless steel passive samplers (Celite Corp.) in Milan and Genoa, and Radiello passive samplers (Supelco) in Cagliari.
was dissolved in MeOH, treated with activated charcoal and filtered over celite. The methanolic solution was passed through an ion-exchange resin (Amberlite IRA400 OH) column, evaporated and further purified by preparative chromatography on silica gel (mobile phase: MeOH:water:NH3 (25%), 15:3:1) to obtain compound 3 (Rf 0.3, blue fluorescent band under 365 nm, red after treatment with Dragendorff s reagent) (yield - 140 mg).
Celite (Sigma) was used as a marker; it was included at 20 g/kg in experiment 1 and at 10 g/kg in experiment 2.
Dorf also held top leadership positions at Celite Systems, Nortel Networks, Synch Research, AT&T Network Systems, AT&T Paradyne, Cullinet Software, and IBM.
Hemochron Celite Activated Clotting Time (ACT) (International Technidyne Corporation, Edison, NJ, USA).