| 释义 |
specific gravity
specific gravityn. The ratio of the mass of a solid or liquid to the mass of an equal volume of distilled water at 4°C (39°F) or of a gas to an equal volume of air or hydrogen under prescribed conditions of temperature and pressure. Also called relative density.specific gravity n (General Physics) the ratio of the density of a substance to that of water. See relative density specif′ic grav′ity
n. the ratio of the density of any substance to the density of a standard substance, water being the standard for liquids and solids. [1660–70] spe•cif′ic-grav′i•ty, adj. spe·cif·ic gravity (spĭ-sĭf′ĭk)1. An amount equal to the density of a solid or liquid divided by the density of an equal volume of water that is at a temperature of 4°C (39°F).2. An amount equal to the density of a gas divided by the density of an equal volume of air or hydrogen that is at a specified temperature and pressure.Thesaurus| Noun | 1. | specific gravity - the density of a substance relative to the density of waterrelative density - the ratio of the density of something to the density of a standard |
Translationsspecific gravity
specific gravity, ratio of the weight of a given volume of a substance to the weight of an equal volume of some reference substance, or, equivalently, the ratio of the masses of equal volumes of the two substances. Relationship Between Specific Gravity and Density Unlike densitydensity,
ratio of the mass of a substance to its volume, expressed, for example, in units of grams per cubic centimeter or pounds per cubic foot. The density of a pure substance varies little from sample to sample and is often considered a characteristic property of the
..... Click the link for more information. , which has units of mass per volume, specific gravity is a pure number, i.e., it has no associated unit of measure. If the densities of the substance of interest and the reference substance are known in the same units (e.g., both in g/cm3 or lb/ft3), then the specific gravity of the substance is equal to its density divided by that of the reference substance. Similarly, if the specific gravity of a substance is known and the density of the reference substance is known in some particular units, then the density of the substance of interest, in those units, is equal to the product of its specific gravity and the density of the reference substance. The most widely used reference substance for determining the specific gravities of solids and liquids is water. Because the density of water is very nearly 1 g/cm3, the density of any substance in g/cm3 is nearly the same numerically as its specific gravity relative to water. In the English system of units the density of water is about 62.4 lb/ft3, so the near equality between specific gravity and density is not preserved in this system. Specific gravities of gases are often given with dry air as the reference substance. Because the densities of all substances vary with temperature and pressure, the temperature and (particularly for gases) the pressure for both the reference substance and the substance of interest are often included when precise values of specific gravities are given. Methods of Determining Specific Gravity A number of experimental methods for determining the specific gravities of solids, liquids, and gases have been devised. A solid is weighed first in air, then while immersed in water; the difference in the two weights, according to Archimedes' principleArchimedes' principle,
principle that states that a body immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid. The principle applies to both floating and submerged bodies and to all fluids, i.e., liquids and gases.
..... Click the link for more information. , is the weight of the water displaced by the volume of the solid. If the solid is less dense than water, some means must be adopted to fully submerge it, e.g., a system of pulleys or a sinker of known mass and volume. The specific gravity of the solid is the ratio of its weight in air to the difference between its weight in air and its weight immersed in water. Two methods are commonly used for determining the specific gravities of liquids. One method uses the hydrometerhydrometer
, device used to determine directly the specific gravity of a liquid. It usually consists of a thin glass tube closed at both ends, with one end enlarged into a bulb that contains fine lead shot or mercury to cause the instrument to float upright in a liquid.
..... Click the link for more information. , an instrument that gives a specific gravity reading directly. A second method, called the bottle method, uses a "specific-gravity bottle," i.e., a flask made to hold a known volume of liquid at a specified temperature (usually 20°C;). The bottle is weighed, filled with the liquid whose specific gravity is to be found, and weighed again. The difference in weights is divided by the weight of an equal volume of water to give the specific gravity of the liquid. For gases a method essentially the same as the bottle method for liquids is used. Specific gravities of gases are usually converted mathematically to their value at standard temperature and pressure (see STPSTP
or standard temperature and pressure,
standard conditions for measurement of the properties of matter. The standard temperature is the freezing point of pure water, 0°C; or 273.15°K;.
..... Click the link for more information. ). Specific gravity The specific gravity of a material is defined as the ratio of its density to the density of some standard material, such as water at a specified temperature, for example, 60°F (15°C), or (for gases) air at standard conditions of temperature and pressure. Specific gravity is a convenient concept because it is usually easier to measure than density, and its value is the same in all systems of units. See Density specific gravity[spə′sif·ik ′grav·əd·ē] (mechanics) The ratio of the density of a material to the density of some standard material, such as water at a specified temperature, for example, 4°C or 60°F, or (for gases) air at standard conditions of pressure and temperature. Abbreviated sp gr. Also known as relative density. specific gravity1. The ratio of the density of a substance to the density of a reference material (usually water for liquids and air for gases). 2. As applied to a gas piping system, the ratio of the weight of gas of a given volume to the weight of the same volume of air, both measured under the same conditions.specific gravity the ratio of the density of a substance to that of water specific gravity
gravity [grav´ĭ-te] 1. the phenomenon by which two bodies having mass are attracted to each other.2. the gravitational attraction near a large body having mass, particularly near or on the surface of a planet or star.specific gravity see specific gravity.standard gravity (€g) the acceleration due to gravity at mean sea level, 9.80616 meters per second squared.
specific [spĕ-sif´ik] 1. pertaining to a species.2. produced by a single kind of microorganism.3. restricted to a particular structure or function, such as in application or effect.4. a remedy specially indicated for a particular disease.5. in immunology, pertaining to the special affinity of antigen for the corresponding antibody.specific gravity the weight of a substance compared with the weight of an equal amount of some other substance taken as a standard. For liquids the usual standard is water. The specific gravity of water is 1; if a sample of urine shows a specific gravity of 1.025, this means that the urine is 1.025 times heavier than water. (The normal specific gravity of urine is 1.003–1.030.) Specific gravity is measured by means of a hydrometer.spe·cif·ic grav·i·ty (sp. gr.), the weight of any body compared with that of another body of equal volume regarded as the unit; usually the weight of a liquid compared with that of distilled water.specific gravity Lab medicine A measure of the solutes in a fluid; SG is detected in the urine, based on the response of a polymeric acid to surrounding ions. See Dipstick. Cf Nitrites Nephrology The SG reflects the kidney's ability to concentrate urine: if a random urine specimen has an SG > 1. 023, the kidney's ability to concentrate is assumed to be normal ; SG ↑ in SIADH, uncontrolled DM, proteinuria, eclampsia and obstructive uropathy and ↓ in renal tubular damage, chronic renal insufficiency, diabetes insipidus, malignant HTN Occupational safety A physical parameter of a liquid that indicates how heavy it is in relationship to air–≤ 1.0 = lighter than water; ≥ 1.0 = heavier than water, a datum of interest to OSHA, which requires listing of SGs in its Materials Safety Data Sheetsspe·cif·ic grav·i·ty (spĕ-sif'ik grav'i-tē) The weight of any body compared with that of another body of equal volume regarded as the unit; usually the weight of a liquid compared with that of distilled water. spe·cif·ic grav·i·ty (spĕ-sif'ik grav'i-tē) The weight of any body compared with that of another body of equal volume regarded as the unit; usually the weight of a liquid compared with that of distilled water. See SP GR
See SPGspecific gravity
Related to specific gravity: Specific weightWords related to specific gravitynoun the density of a substance relative to the density of waterRelated Words |