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35-672: Sodium nitrate is a white deliquescent solid very soluble in water . It is a readily available source of the nitrate anion (NO 3 ), which is useful in several reactions carried out on industrial scales for the production of fertilizers , pyrotechnics , smoke bombs and other explosives , glass and pottery enamels , food preservatives (esp. meats), and solid rocket propellant . It has been mined extensively for these purposes. The first shipment of saltpeter to Europe arrived in England from Peru in 1820 or 1825, right after that country's independence from Spain, but did not find any buyers and

70-406: A phase-change material for thermal energy recovery, owing to its relatively high melting enthalpy of 178 J/g. Examples of the applications of sodium nitrate used for thermal energy storage include solar thermal power technologies and direct steam generating parabolic troughs . Sodium nitrate is used in a steel coating process in which it forms a surface of magnetite layer. Studies have shown

105-444: A bi-layered parallel fiber hygroscopic cell physiology to control the awn's movement for dispersal and self-burial of seeds. Alignment of cellulose fibrils in the awn's controlling cell wall determines direction of movement. If fiber alignments are tilted, non-parallel venation, a helix develops and awn movement becomes twisting (coiling) instead of bending; e.g. coiling occurs in awns of Erodium , and Hesperostipa . Hygroscopicity

140-503: A crunchy, crisp cookie (British English: biscuit) versus a soft, chewy cake. Sugars such as honey , brown sugar , and molasses are examples of sweeteners used to create moister and chewier cakes. Several hygroscopic approaches to harvest atmospheric moisture have been demonstrated and require further development to assess their potentials as a viable water source. Hygroscopic glues are candidates for commercial development. The most common cause of synthetic glue failure at high humidity

175-586: A higher risk of colorectal cancer . Substantial evidence in recent decades, facilitated by an increased understanding of pathological processes and science, exists in support of the theory that processed meat increases the risk of colon cancer and that this is due to the nitrate content. A small amount of the nitrate added to meat as a preservative breaks down into nitrite, in addition to any nitrite that may also be added. The nitrite then reacts with protein-rich foods (such as meat) to produce carcinogenic NOCs ( nitroso compounds). NOCs can be formed either when meat

210-531: A link between increased levels of nitrates and increased deaths from certain diseases including Alzheimer's disease , diabetes mellitus , stomach cancer , and Parkinson's disease : possibly through the damaging effect of nitrosamines on DNA; however, little has been done to control for other possible causes in the epidemiological results. Nitrosamines, formed in cured meats containing sodium nitrate and nitrite, have been linked to gastric cancer and esophageal cancer . Sodium nitrate and nitrite are associated with

245-412: A stress that curls the cover toward the laminated side. This is similar to the function of a thermostat's bimetallic strip . Inexpensive dial-type hygrometers make use of this principle using a coiled strip. Deliquescence is the process by which a substance absorbs moisture from the atmosphere until it dissolves in the absorbed water and forms a solution. Deliquescence occurs when the vapour pressure of

280-599: A strong affinity for water and tendency to absorb moisture from the atmosphere if exposed to it. Unlike hygroscopy, however, deliquescence involves absorbing sufficient water to form an aqueous solution . Most deliquescent materials are salts , including calcium chloride , magnesium chloride , zinc chloride , ferric chloride , carnallite , potassium carbonate , potassium phosphate , ferric ammonium citrate , ammonium nitrate , potassium hydroxide , and sodium hydroxide . Owing to their very high affinity for water, these substances are often used as desiccants , which

315-468: A viewing or imaging mode. It did begin that way, with the word hygroscope referring in the 1790s to measuring devices for humidity level. These hygroscopes used materials, such as certain animal hairs, that appreciably changed shape and size when they became damp. Such materials were then said to be hygroscopic because they were suitable for making a hygroscope. Eventually, the word hygroscope ceased to be used for any such instrument in modern usage , but

350-495: A water-soluble form of nitrogen. Its use, which is mainly outside of high-income countries, is attractive since it does not alter the pH of the soil. Another major use is as a complement to ammonium nitrate in explosives. Molten sodium nitrate and its solutions with potassium nitrate have good thermal stability (up to 600 °C) and high heat capacities. These properties are suitable for thermally annealing metals and for storing thermal energy in solar applications. Sodium nitrate

385-590: A wide variety of other substances. If a compound dissolves in water, then it is considered to be hydrophilic . Zinc chloride and calcium chloride , as well as potassium hydroxide and sodium hydroxide (and many different salts ), are so hygroscopic that they readily dissolve in the water they absorb: this property is called deliquescence . Not only is sulfuric acid hygroscopic in concentrated form but its solutions are hygroscopic down to concentrations of 10% v/v or below. A hygroscopic material will tend to become damp and cakey when exposed to moist air (such as

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420-405: Is a common mechanism of seed dispersal as the movement of dead tissues respond to hygrometric variation, e.g. spore release from the fertile margins of Onoclea sensibilis . Movement occurs when plant tissue matures, dies and desiccates, cell walls drying, shrinking; and also when humidity re-hydrates plant tissue, cell walls enlarging, expanding. The direction of the resulting force depends upon

455-461: Is a general term used to describe a material's ability to absorb moisture from the environment. There is no standard quantitative definition of hygroscopicity, so generally the qualification of hygroscopic and non-hygroscopic is determined on a case-by-case basis. For example, pharmaceuticals that pick up more than 5% by mass, between 40 and 90% relative humidity at 25 °C, are described as hygroscopic, while materials that pick up less than 1%, under

490-464: Is also a food additive used as a preservative and color fixative in cured meats and poultry; it is listed under its INS number 251 or E number E251. It is approved for use in the EU, US and Australia and New Zealand. Sodium nitrate should not be confused with sodium nitrite , which is also a common food additive and preservative used, for example, in deli meats. Sodium nitrate has also been investigated as

525-470: Is also an application for concentrated sulfuric and phosphoric acids . Some deliquescent compounds are used in the chemical industry to remove water produced by chemical reactions (see drying tube ). Hygroscopy appears in both plant and animal kingdoms, the latter benefiting via hydration and nutrition. Some amphibian species secrete a hygroscopic mucus that harvests moisture from the air. Orb web building spiders produce hygroscopic secretions that preserve

560-401: Is also synthesized industrially by neutralizing nitric acid with sodium carbonate or sodium bicarbonate : or also by neutralizing it with sodium hydroxide (however, this reaction is very exothermic): or by mixing stoichiometric amounts of ammonium nitrate and sodium hydroxide , sodium bicarbonate or sodium carbonate : Most sodium nitrate is used in fertilizers, where it supplies

595-433: Is cured or in the body as meat is digested. However, several things complicate the otherwise straightforward understanding that "nitrates in food raise the risk of cancer". Processed meats have no fiber, vitamins, or phytochemical antioxidants, are high in sodium, may contain high fat, and are often fried or cooked at a temperature sufficient to degrade protein into nitrosamines. Nitrates are key intermediates and effectors in

630-571: The 1940s, this conversion process resulted in a dramatic decline in demand for sodium nitrate procured from natural sources. Chile still has the largest reserves of caliche , with active mines in such locations as Valdivia , María Elena and Pampa Blanca, and there it used to be called white gold . Sodium nitrate, potassium nitrate , sodium sulfate and iodine are all obtained by the processing of caliche. The former Chilean saltpeter mining communities of Humberstone and Santa Laura were declared UNESCO World Heritage sites in 2005. Sodium nitrate

665-419: The architecture of the tissue and is capable of producing bending, twisting or coiling movements. Typical of hygroscopic movement are plant tissues with "closely packed long (columnar) parallel thick-walled cells (that) respond by expanding longitudinally when exposed to humidity and shrinking when dried (Reyssat et al., 2009)". Cell orientation, pattern structure (annular, planar, bi-layered or tri-layered) and

700-419: The coefficient of hygroscopic contraction (CHC)—the difference between the two terms being a difference in sign convention. Differences in hygroscopy can be observed in plastic-laminated paperback book covers—often, in a suddenly moist environment, the book cover will curl away from the rest of the book. The unlaminated side of the cover absorbs more moisture than the laminated side and increases in area, causing

735-557: The effects of the opposite-surface's cell orientation control the hygroscopic reaction. Moisture responsive seed encapsulations rely on valves opening when exposed to wetting or drying; discontinuous tissue structures provide such predetermined breaking points (sutures), often implemented via reduced cell wall thickness or seams within bi- or tri-layered structures. Graded distributions varying in density and/or cell orientation focus hygroscopic movement, frequently observed as biological actuators (a hinge function); e.g. pinecones ( Pinus spp. ),

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770-495: The express purpose of maintaining moisture content , hygroscopic materials are known as humectants . Materials and compounds exhibit different hygroscopic properties, and this difference can lead to detrimental effects, such as stress concentration in composite materials . The volume of a particular material or compound is affected by ambient moisture and may be considered its coefficient of hygroscopic expansion (CHE) (also referred to as CME, or coefficient of moisture expansion) or

805-487: The hot-dry desert atmosphere. El Niño/La Niña extreme aridity/torrential rain cycles favor nitrates accumulation through both aridity and water solution/remobilization/transportation onto slopes and into basins; capillary solution movement forms layers of nitrates; pure nitrate forms rare veins. For more than a century, the world supply of the compound was mined almost exclusively from the Atacama desert in northern Chile until, at

840-432: The ice plant ( Aizoaceae spp. ) and the wheat awn ( Triticum spp. ), described below. Two angiospermae families have similar methods of dispersal, though method of implementation varies within family: Geraniaceae family examples are the common stork's-bill ( Erodium cicutarium ) and geraniums ( Pelargonium sp. ); Poaceae family, Needle-and-Thread ( Hesperostipa comata ) and wheat ( Triticum spp. ). All rely upon

875-405: The physical side, a physico-chemical process. Berthelot's principle of reversibility, briefly- that water dried from plant tissue could be restored hygroscopically, was published in "Recherches sur la desiccation des plantes et des tissues végétaux; conditions d'équilibre et de réversibilité," ( Annales de Chimie et de Physique , April 1903). Léo Errera viewed hygroscopicity from perspectives of

910-553: The physicist and the chemist. His memoir "Sur l'Hygroscopicité comme cause de l'action physiologique à distance" ( Recueil de l'lnstitut Botanique Léo Errera, Université de Bruxelles , tome vi., 1906) provided a hygroscopy definition that remains valid to this day. Hygroscopy is "exhibited in the most comprehensive sense, as displayed Hygroscopic substances include cellulose fibers (such as cotton and paper), sugar , caramel , honey , glycerol , ethanol , wood , methanol , sulfuric acid , many fertilizer chemicals, many salts and

945-535: The primary vasculature signaling which is necessary for all mammals to survive. Deliquescent Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment , which is usually at normal or room temperature. If water molecules become suspended among the substance's molecules, adsorbing substances can become physically changed, e.g. changing in volume, boiling point , viscosity or some other physical characteristic or property of

980-569: The salt inside salt shakers during humid weather). Because of their affinity for atmospheric moisture , desirable hygroscopic materials might require storage in sealed containers. Some hygroscopic materials, e.g., sea salt and sulfates, occur naturally in the atmosphere and serve as cloud seeds , cloud condensation nuclei (CCNs). Being hygroscopic, their microscopic particles provide an attractive surface for moisture vapour to condense and form droplets. Modern-day human cloud seeding efforts began in 1946. When added to foods or other materials for

1015-1151: The same conditions are regarded as non-hygroscopic. The amount of moisture held by hygroscopic materials is usually proportional to the relative humidity. Tables containing this information can be found in many engineering handbooks and is also available from suppliers of various materials and chemicals. Hygroscopy also plays an important role in the engineering of plastic materials. Some plastics, e. g. nylon , are hygroscopic while others are not. Many engineering polymers are hygroscopic, including nylon , ABS , polycarbonate , cellulose , carboxymethyl cellulose , and poly(methyl methacrylate) (PMMA, plexiglas , perspex ). Other polymers, such as polyethylene and polystyrene , do not normally absorb much moisture, but are able to carry significant moisture on their surface when exposed to liquid water. Type-6 nylon (a polyamide ) can absorb up to 9.5% of its weight in moisture. The use of different substances' hygroscopic properties in baking are often used to achieve differences in moisture content and, hence, crispiness. Different varieties of sugars are used in different quantities to produce

1050-414: The solution that is formed is less than the partial pressure of water vapour in the air. While some similar forces are at work here, it is different from capillary attraction , a process where glass or other solid substances attract water, but are not changed in the process (e.g., water molecules do not become suspended between the glass molecules). Deliquescence, like hygroscopy, is also characterized by

1085-738: The stickiness and adhesion force of their webs. One aquatic reptile species is able to travel beyond aquatic limitations, onto land, due to its hygroscopic integument . Plants benefit from hygroscopy via hydration and reproduction – demonstrated by convergent evolution examples. Hygroscopic movement (hygrometrically activated movement) is integral in fertilization, seed/spore release, dispersal and germination. The phrase "hygroscopic movement" originated in 1904's " Vorlesungen Über Pflanzenphysiologie ", translated in 1907 as "Lectures on Plant Physiology" ( Ludwig Jost and R.J. Harvey Gibson , Oxford, 1907). When movement becomes larger scale, affected plant tissues are colloquially termed hygromorphs. Hygromorphy

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1120-836: The substance. For example, a finely dispersed hygroscopic powder, such as a salt, may become clumpy over time due to collection of moisture from the surrounding environment. Deliquescent materials are sufficiently hygroscopic that they dissolve in the water they absorb, forming an aqueous solution . Hygroscopy is essential for many plant and animal species' attainment of hydration, nutrition, reproduction and/or seed dispersal . Biological evolution created hygroscopic solutions for water harvesting, filament tensile strength, bonding and passive motion – natural solutions being considered in future biomimetics . The word hygroscopy ( / h aɪ ˈ ɡ r ɒ s k ə p i / ) uses combining forms of hygro- (for moisture or humidity) and -scopy . Unlike any other -scopy word, it no longer refers to

1155-408: The turn of the 20th century, German chemists Fritz Haber and Carl Bosch developed a process for producing ammonia from the atmosphere on an industrial scale (see Haber process ). With the onset of World War I , Germany began converting ammonia from this process into a synthetic Chilean saltpeter , which was as practical as the natural compound in production of gunpowder and other munitions. By

1190-674: The word hygroscopic (tending to retain moisture) lived on, and thus also hygroscopy (the ability to do so). Nowadays an instrument for measuring humidity is called a hygrometer ( hygro- + -meter ). Early hygroscopy literature began circa 1880. Studies by Victor Jodin ( Annales Agronomiques , October 1897) focused on the biological properties of hygroscopicity. He noted pea seeds, both living and dead (without germinative capacity), responded similarly to atmospheric humidity, their weight increasing or decreasing in relation to hygrometric variation. Marcellin Berthelot viewed hygroscopicity from

1225-961: Was dumped at sea in order to avoid customs toll. With time, however, the mining of South American saltpeter became a profitable business (in 1859, England alone consumed 47,000 metric tons). Chile fought the War of the Pacific (1879–1884) against the allies Peru and Bolivia and took over their richest deposits of saltpeter. In 1919, Ralph Walter Graystone Wyckoff determined its crystal structure using X-ray crystallography . The largest accumulations of naturally occurring sodium nitrate are found in Chile and Peru , where nitrate salts are bound within mineral deposits called caliche ore. Nitrates accumulate on land through marine-fog precipitation and sea-spray oxidation/desiccation followed by gravitational settling of airborne NaNO 3 , KNO 3 , NaCl, Na 2 SO 4 , and I, in

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