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van der Waals bond

Weak forces in crystal structures caused by induced dipoles resulting from
juxtaposition of molecules; e.g., the bonding between electrostatically
neutral layers in the talc structure.

van Dorn sampler

This sediment sampler consists of a Plexiglas cylinder closed at each end
by an ordinary rubber force cup. The two cups are connected by a length of
surgical rubber tubing inside the cylinder, prestressed enough to permit
the force cups to retain the sample in the cylinder. In the armed
position, the two cups are pulled outside the cylinder, where they are
restrained by a releasing mechanism attached to the outside wall. Two
short loops of wire connect the cups to the releasing mechanism. The cups
are released underwater by sending a messenger down the hydrographic wire.
This sampler does not invert, which prevents use of reversing thermometers
in conjunction with sampling. Hunt

Vandyke brown

a. A naturally occurring pigment derived from indefinite mixtures of iron
oxide and organic matter. Obtained from bog earth and peat deposits, or
from ochers containing bituminous matter. CCD, 2
b. Etymol: its use by the 17th-Century Flemish painter Van Dyck.
Syn:ulmin brown

vane

The target of a leveling staff; one of the sights of a compass or
quadrant. Webster 3rd

vane anemometer

a. A small windmill-type instrument used to measure air velocity and to
infer air volume movement. The vane anemometer has been the primary
instrument for airflow measurement since the early 1900's.
Hartman, 2
b. See also:anemometer
c. Consists of several light, flat vanes, usually eight in number, mounted
on radial arms that are attached to a horizontal spindle. This rotor
drives, through a suitable gear train, a counting mechanism that indicates
the revolutions of the rotor. The indicating dial, usually graduated in
feet of air, may be located either concentrically with the rotor, or in a
plane at right angles to the plane of rotation. By observing the number of
revolutions over a timed interval, the velocity of flow is found. The
instrument is available in a number of forms to cover velocities ranging
from 30 to 6,000 ft/min (9.1 to 1,830 m/min). Roberts, 1

vane-axial fan

An airfoil (propeller) or disk fan within a cylinder and equipped with
air-guide vanes either before or after the wheel; includes
driving-mechanism supports for belt drive or direct connection.
Strock, 2

vane shear test

An in-place shear test in which a rod with thin radial vanes at the end is
forced into the soil and the resistance to rotation of the rod is
determined. ASCE

vane shear tester

A device used in soil testing, consisting of flat blades affixed to the
end of a rod. It is forced into the soil, and the torque required to shear
the soil, in situ, is determined as a measure of the shear strength of the
zone tested by rotating the device. Syn:vane tester

vane test

An in-place test to measure the shear strength of fine-grained cohesive
soils and other soft deposits. A rod with four flat radial blades, or
vanes, projecting at 90 degrees intervals is forced into the soil and
rotated; the torque required to rotate the rod is a measure of the
material's shear strength. AGI

vane tester

See:vane shear tester

vanner grease belt

In ore dressing, smelting, and refining, used for separation of valuable
mineral from the gangue (waste minerals) in an ore. DOT

vanoxite

A mineral, V6 O13 .8H2 O(?) ; a mixed-valence oxide;
weakly radioactive; black; in the Colorado Plateau area as a sandstone
cement; also a massive wood replacement associated with carnotite, gypsum,
hewettite, pintadoite, tyuyamunite, and pyrite. See also:kentsmithite

vanthoffite

A monoclinic mineral, Na6 Mg(SO4 )4 ; colorless; at
Wilhelmshall, Stassfurt, Germany.

vanuralite

A monoclinic mineral, Al(UO2 )2 (V2 O8
)(OH).8H2 O ; yellow; at Mounana, Gabon.

vapart mill

A centrifugal grinder for pulverizing ore, coal, and coke. Fay

vapor

a. A substance in the gaseous state as distinguished from the liquid or
solid state. Webster 3rd; Zimmerman
b. Foul air in a mine. CF:gas

vapor barrier

A material intended to prevent the passage of water vapor through a
building wall to prevent condensation within the wall. Strock, 2

vapor density

The relative density of a gas or vapor as compared with some specific
standard (as hydrogen). Abbrev., v d. Webster 3rd; Zimmerman

vaporization

See:evaporation

vapor pressure

The pressure at which a liquid and its vapors are in equilibrium at a
definite temperature. If the vapor pressure reaches the prevailing
atmospheric pressure, the liquid boils. Symbol, p.
Hackh; Handbook of Chemistry and Physics, 2

vapor system

A steam-heating system operating at pressure very near that of the
atmosphere. Strock, 2