A hygroscopic substance is a substance that absorbs water readily from its surroundings. (The similar sounding but unrelated non-word hydroscopic is sometimes used in error for hygroscopic). Look up absorption in Wiktionary, the free dictionary Absorption may refer to: In physics: absorption (chemistry) - absorption of particles of gas or liquid in liquid or solid material as studied in physical chemistry absorption (optics) - absorption of photons by a material Absorption (acoustics) - absorption of sound waves by a material... A girl in a swimming pool full of water Water (from the Old English word waeter; c. ...

An example of a hygroscopic substance is biodiesel, which absorbs water to about 1200 parts per million (PPM). Other examples are honey, ethanol, methanol, glycerin, concentrated sulfuric acid and concentrated sodium hydroxide. Calcium chloride is so hygroscopic that it eventually dissolves in the water it absorbs. Because of their affinity for atmospheric moisture, hygroscopic materials may need to be stored in sealed containers. Biodiesel sample Biodiesel refers to any diesel-equivalent biofuel usually made of vegetable oils or animal fats. ... Parts per million (ppm) is a measure of concentration that is used where low levels of concentration are significant. ... Honey honey comb A capped frame of honeycomb Honey is a sweet and viscous fluid produced by bees and other insects from the nectar of flowers. ... Ethanol, also known as ethyl alcohol or grain alcohol, is a flammable, colorless chemical compound, one of the alcohols that is most often found in alcoholic beverages. ... Methanol, also known as methyl alcohol or wood alcohol, is a chemical compound with chemical formula CH3OH. It is the simplest alcohol, and is a light, volatile, colourless, flammable, poisonous liquid with a very faint odor. ... Glycerin, also well known as glycerine and glycerol, and less commonly as 1,2,3-propanetriol, 1,2,3-trihydroxypropane, glyceritol, and glycyl alcohol is a colorless, odorless, hygroscopic, and sweet-tasting viscous liquid. ... Sulfuric acid (British English: sulphuric acid), H2SO4, is a strong mineral acid. ... Flash point non flammable Supplementary data page Structure and properties n, εr, etc. ... R-phrases S-phrases , , RTECS number EV9800000, anhydrous EV9810000, dihydrate EV9830000, hexahydrate Supplementary data page Structure & properties n, εr, etc. ... Moisture generally refers to the presence of water in trace amounts. ...

Materials and compounds exhibit different hygroscopic properties, and this difference can lead to detrimental effects, such as stress concentration in composite materials. The amount a particular material or compound is affected by ambient moisture may be considered its Coefficient of Hygroscopic Expansion or Contraction. The difference (Expansion or Contraction) being a difference in sign convention, and a difference in point of view as to whether the difference in moisture leads to contraction or expansion. A common example where difference in this hygroscopic property can be seen is in a paperback book cover. Often in a relatively moist environment the book cover will curl away from the rest of the book. In effect, what has happened is that the unlaminated side of the cover has absorbed more moisture than the laminated side, and has increased in area, causing a stress that curls the cover toward the laminated side. This is similar to how simple bimetal strips are used as torsion springs in thermometers. A bimetal strip consists of two thin layers of metals with different coefficients of thermal expansion bonded together. When the temperature changes, one metal expands more along its length than the other, causing the spring to rotate and create a torque.

History

Nitrocellulose, unlike gunpowder, is not hygroscopic. Smokeless powder facilitated the development of semi-automatic and fully automatic firearms because the hygroscopic residue of gunpowder would jam the mechanisms of such firearms. Hygroscopic components of bullets generally compensate by being readily ignitable by heat or a spark. Nitrocellulose (Cellulose nitrate, guncotton) is a highly flammable compound formed by nitrating cellulose (e. ... Smokeless powder Gunpowder, whether black powder or smokeless powder, is a substance that burns very rapidly, releasing gases that act as a propellant in firearms. ... A firearm is a kinetic energy weapon that fires either a single or multiple projectiles propelled at high velocity by the gases produced by action of the rapid confined burning of a propellant. ... This article is about the projectile, for other uses see bullet (disambiguation). ... Ignition occurs when the heat produced by a reaction becomes sufficient to sustain the reaction, whether it be a fire, an explosion, or nuclear fusion. ...

Building physics

Hygroscopic materials play an important role in buildings; wood is a highly hygroscopic material. Hygroscopic materials have an influence on moisture content in a room. Wood can extract moisture (vapour) from air. The higher the relative humidity, the more vapour wood adsorbs. Many varieties of wood may start to rot if the relative humidity is higher than 80% for long periods. A tree trunk as found at the Veluwe, The Netherlands Wood derives from woody plants, notably trees but also shrubs. ... Moisture content (MC) is a term used in a wide range of scientific and technical areas to express the quantity of water that a material contains. ... Moisture generally refers to the presence of water in trace amounts. ... Vapor (US English) or vapour (British English) is the gaseous state of matter. ... Layers of Atmosphere (NOAA) Earths atmosphere is a layer of gases surrounding the planet Earth and retained by the Earths gravity. ... Relative humidity is the ratio of the current vapor pressure of water in any gas (especially air) to the equilibrium vapor pressure, at which the gas is called saturated at the current temperature, expressed as a percentage. ... This is a list of woods, in particular those commonly used in the timber and lumber trade. ... The aviation term ROT stands for rate one turn. ...

Biology

The seeds of some grasses have hygroscopic extensions which bend with changes in humidity, enabling them to disperse over the ground.

See also

• Deliquescent