ASTM D4175 Terminology Relating to Petroleum, Petroleum Products, and Lubricants
vapor-liquid ratio, n - of a liquid, the ratio, at a specified temperature and pressure, of the volume of vapor in equilibrium with liquid to the volume of liquid sample charged, at 32°F (0°C).
vapor pressure, n - the pressure exerted by the vapor of a liquid when in equilibrium with the liquid.
vapor temperature reading, n - temperature of saturated vapor measured in the distillation column below the vapor tube, as determined by the prescribed conditions of the test.
corrected vapor temperature reading, n - temperature reading, as described in , corrected for barometric pressure.
variance, n - a measure of the dispersion of a series of accepted results about their average. It is equal to the sum of the squares of the deviation of each result from the average, divided by the number of degrees of freedom.
variance, between-laboratory, n - that component of the overall variance due to the difference in the mean values obtained by different laboratories.
DISCUSSION - When results obtained by more than one laboratory are compared, the scatter is usually wider than when the same number of tests are carried out by a single laboratory, and there is some variation between means obtained by different laboratories. Differences in operator technique, instrumentation, environment, and sample "as received" are among the factors that can affect the between laboratory variance. There is a corresponding definition for between-operator variance.
DISCUSSION - The term "between-laboratory" is often shortened to "laboratory" when used to qualify representative parameters of the dispersion of the population of results, for example, as "laboratory variance".
varnish, n - in internal combustion engines, a hard, dry, generally lustrous deposit that can be removed by solvents but not by wiping with a cloth.
varnish, n - in manual transmissions and final drive axles, a hard, dry, generally lustrous deposit that can be removed by solvents but not by wiping with a cloth.
viable titer, n - the number of living microbes present per unit volume, mass, or area.
DISCUSSION - Viable titer is reported in terms of either colony forming units (CFU) or most probable number (MPN) per millilitre, milligram, or centimetre squared.
viscosity, n - the ratio between the applied shear stress and rate of shear. It is sometimes called the coefficient of dynamic viscosity. This value is thus a measure of the resistance to flow of the liquid. The SI unit of viscosity is the pascal second (Pa.s). The centipoise (cP) is one millipascal second (mPa.s) and is often used.
viscosity - the ratio between the applied shear stress and rate of shear, sometimes called the coefficient of dynamic viscosity. This value is thus a measure of the resistance to flow of the liquid. The SI unit of viscosity is the Pascal second [Pa•s]. A centipoise (cP) is one milliPascal second [mPa•s].
viscosity, n - the ratio between the applied shear stress and the rate of shear. It is sometimes called the coefficient of dynamic viscosity. This coefficient is a measure of the resistance to flow of the liquid. In the SI, the unit of viscosity is the Pascal•second; often the milliPascal•second or its equivalent the centiPoise is found more convenient.
apparent viscosity - the viscosity of a non-Newtonian fluid at a given shear rate or shear stress determined by this test method.
viscosity - the ratio of shear stress to shear rate. Viscosity of a liquid is a measure of the internal friction of the liquid in motion. The unit of dynamic viscosity is the pascal second. For a Newtonian liquid, the viscosity is constant at all shear rates. For a non-Newtonian liquid, viscosity will vary depending on shear rate.
viscosity, apparent - the viscosity determined by this method, expressed in pascal seconds. Its value may vary with the
spindle and rotational speed selected because many hot melts are non-Newtonian.
viscosity index (VI), n - an arbitrary number used to characterize the variation of the kinematic viscosity of a fluid with temperature.
viscosity loss (VL), n - a measure of the decrease in an oil's viscosity.
DISCUSSION - Viscosity Loss is a property measured for a finished oil. Permanent Shear Stability Index (q.v.) is a property calculated for a single component. Some test methods report VL as a relative change, which is dimensionless (for example, Test Methods D2603, D3945, D5275, D621). Some test methods and specifications report VL as an absolute change, which has the same dimensions as the viscosity measurements (for example, Specification D4485 and Test Methods D5119 and D5621).
VL - in viscometry, abbreviation for viscosity loss.
void, n - an unfilled space enclosed within an apparently solid carbon or graphite body.
volatile fuels - relatively wide boiling range volatile distillate.
DISCUSSION - These are identified as Jet B in Specification D1655 or the military grade known as JP-4. Any fuel or mixture having a flash point less than 38°C must be considered volatile.
volume count, n - the product of the area under a peak and a response factor.
volume count, n - the product of a slice area (or an area under a peak) and a volume response factor.
volume response factor, n - a constant of proportionality that relates the area under a chromatogram to liquid volume.
