tar

tar and pitch

tar and pitch, viscous, dark-brown to black substances obtained by the destructive distillation of coal, wood, petroleum, peat, and certain other organic materials. The heating or partial burning of wood to make charcoal yields tar as a byproduct and is an ancient method for the production of both tar and pitch. Coal tar is a residue in the manufacture of coal gas and coke. By the application of heat, tar is separated into several materials, one of which is pitch. The terms tar and pitch are loosely applied to the many varieties of the two substances, sometimes interchangeably. For example, asphalt, which is naturally occurring pitch, is called mineral tar and mineral pitch. Tar is more or less fluid, depending upon its origin and the temperature to which it is exposed. Pitch tends to be more solid. When ships were made of wood, tar had numerous uses, and an available supply of tar was an important factor in maritime growth. Tar made vessels watertight and protected their ropes from deterioration. All but small quantities of the tar now produced is fractionally distilled to yield naphtha, creosote, carbolic oil, and other equally important crude products. Among the substances produced by refining the various crude materials are benzene, toluene, cresol, and phenol. Tar from pine wood is used in making soap and medicinal preparations. Pitch is used in the manufacture of roofing paper, in varnishes, as a lubricant, and as a binder for coal dust in the making of briquettes used as fuel. Coal-tar derivatives are used in the manufacture of dyes, cosmetics, and synthetic flavoring extracts.

The Columbia Electronic Encyclopedia™ Copyright © 2022, Columbia University Press. Licensed from Columbia University Press. All rights reserved.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Tar

 

a black viscous substance obtained after distilling the fuel and oil fractions from petroleum. The yield of tar from various petroleums is 15–30 percent based on the petroleum. The main components of tar are oil not distilled during the fractionation of petroleum, petroleum resins, solid asphaltic substances (asphaltenes. carbenes, and carboids), and substances of an acidic nature (asphaltogenic acids and their anhydrides). Tar has a density of 0.95–1.0g/cm³ and a viscosity of 18°-45° of conventional viscosity at 100° C.

Tar containing a considerable amount of oil fractions is called semitar; its viscosity is 18°-25° of conventional viscosity and its flash point, 140° C. Tar is also the name for concentrated residues of petroleum oil (petroleum tar) that undergo multistage refining processes to obtain high-quality motor oils. The residues obtained after the sulfuric acid refining of petroleum products are called acid tars.

Tar is used to prepare petroleum bitumens and in road construction. Semitar is used to lubricate coarse mechanisms. Oil tars are used as plasticizers in the rubber industry and in construction. Cracking and destructive hydrogenation can be used to convert very viscous tars into gasoline, diesel fuel, and other substances.

REFERENCES

Nametkin, S. S. Khimiia nefti [3rd ed.]. Moscow. 1955.
Nefteprodukty: Svoislva, kacheslvo, primennie. Spravochnik. Moscow, 1966.

---

Tar

 

a liquid product of the dry distillation of solid fuels, such as coal and lignite, shales, wood, and peat. The consistency of tar varies from a readily mobile liquid to a mass that flows with difficulty; it is usually dark brown, but it can be almost black. Tar is a complex mixture of organic compounds; its composition depends on the initial material and the method of treatment. The low-temperature (500°-600°C) dry distillation of coal or peat—that is, semicoking—yields so-called primary tar. The coking of coal yields coal tar. The tar formed by heat treating wood is called wood tar.

---

Tar

 

(1) A plucked stringed instrument used in the Caucasus. The tar has an overall length of approximately 900–1,000 mm. It has three pairs of melody strings (or three pairs and one single string) and two pairs of drone strings.

(2) In Arab countries, a small tambourine.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

tar

[tär]

(materials)

A viscous material composed of complex, high-molecular-weight compounds derived from the distillation of petroleum or the destructive distillation of wood or coal.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

coal-tar pitch, tar

A dark brown to black hydrocarbon obtained by the distillation of coke-oven tar; softening point near 150°F (65°C); used in built-up roofing as a waterproofing agent.

McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

tar

1. any of various dark viscid substances obtained by the destructive distillation of organic matter such as coal, wood, or peat

2. another name for coal tar

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

tar

(file format)

("Tape ARchive", following ar) Unix's general purpose archive utility and the file format it uses. Tar was originally intended for use with magnetic tape but, though it has several command line options related to tape, it is now used more often for packaging files together on other media, e.g. for distribution via the Internet.

The resulting archive, a "tar file" (humourously, "tarball") is often compressed, using gzip or some other form of compression (see tar and feather).

There is a GNU version of tar called gnutar with several improvements over the standard versions.

Filename extension: .tar

MIME type: unregistered, but commonly application/x-tar

Unix manual page: tar(1).

Compare shar, zip.

This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

tar

(Tape ARchive) A Unix utility that is used to archive files by combining several files into one. It is often used in conjunction with the "compress" or "gzip" commands to compress the data. The name came from the days when magnetic tape was the predominant storage medium rather than disk. Tar archives are often called "tarballs." See archive formats.

Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.