Efflorescent salts

Efflorescence usually takes place when groundwater penetrates within porous solids, where it leaches (dissolves) soluble salts from the solids. When the water with the leached solids eventually evaporates, the solution migrates toward the surface if the water continues to evaporate, the dissolved salts are redeposited, forming small crystals just below and on the surface of the objects. The forces generated by the crystallization of the efflorescent salts below the surface (in the bulk of the solid), as well as... 

Fig. 1. Effiorescenl acid generating salts present within underground workings of the former Blenkinsopp Colliery (Northumberland, UK). The base of the hammer handle is resting on the contact between the seat-earth and the overlying coal seam. The coal seam is visible in the top third of the photograph, but is entirely obscured down to its contact with the seat-earth by the efflorescent salts, which form a thorough lightly coloured covering on the exposed seam beneath an undulating upper limit which passes a few cm above the hammer head.

Nordstrom, D. K. 1999. Efflorescent salts and their effects on water quality and mine plugging. In Fernandez-Rubio, R. (ed) Mine, Water and Environment. (Proceedings of the International Congress of the International Mine Water... 

C. W. Scheele (1773) noted that a damp mixture of common salt and calcium hydroxide effloresces after some weeks exposure to air, the efflorescent salt is sodium carbonate. It is probable that calcium bicarbonate is formed, which precipitates soluble sodium bicarbonate, and this explains the formation of the efflorescence of soda from salty soils. The observation made by C. W. Scheele... 

An efflorescent salt is one that loses water to the atmosphere. This will occur if the water vapor pressure in equilibrium with the salt is greater than the water vapor pressure in the atmosphere. The mechanism by which CUSO4 5H2O could be efflorescent is that the salt would lose 2 molecules of H2O and simultaneously form 1 formula unit of CUSO4 3H2O for each unit of the original salt that dissociates. Then the above equilibrium equation would apply, since all three components would be present. 

Colorless, very slightly efflorescent salt in the form of small platelike crystals. M.p. 48°C in its water of crystallization. 

Zirconium oxychloride is an important intermediate from which other zirconium chemicals are produced. It readily effloresces, and hydrates with 5—7 H2O are common. The salt caimot be dried to the anhydrous form, and decomposes to hydrogen chloride and zirconium oxide. 

Salpeter-sauresalz. n. salt of nitric acid, nitrate, -schaum, m. wall saltpeter (calcium nitrate efflorescence). 

Salz-ather, m. muriatic ether (old name for ethyl chloride), -ausbluhung,/. efflorescence of salt, -bad, n. salt bath. -base,/, salifiable base (old term), -bedarf, m. salt requirement. -beize, /. (Leather) salt dressing, -bergwerk, n. salt mine, salzbildend, p.a. salt-forming. 

Non-oxidising and weak acids, in contrast to oxidising acids, can penetrate paint films without destroying them they then react with the metal base to form salts with resultant stresses which cause cracks. Magnesium-rich alloys are particularly prone to attack by acids their salts, having considerable volume, in severe cases effloresce through the broken paint films. 

Hydrated salts, as a rule, do not make good standards because of the difficulty of efficient drying. However, those salts which do not effloresce, such as sodium tetraborate Na2B407, 10H2O, and copper sulphate CuS04,5H20, are found by experiment to be satisfactory secondary standards.2... 

Discussion. Sodium thiosulphate (Na2S203,5H20) is readily obtainable in a state of high purity, but there is always some uncertainty as to the exact water content because of the efflorescent nature of the salt and for other reasons. The substance is therefore unsuitable as a primary standard. It is a reducing agent... 

Atmospheric aerosols have a direct impact on earth s radiation balance, fog formation and cloud physics, and visibility degradation as well as human health effect[l]. Both natural and anthropogenic sources contribute to the formation of ambient aerosol, which are composed mostly of sulfates, nitrates and ammoniums in either pure or mixed forms[2]. These inorganic salt aerosols are hygroscopic by nature and exhibit the properties of deliquescence and efflorescence in humid air. That is, relative humidity(RH) history and chemical composition determine whether atmospheric aerosols are liquid or solid. Aerosol physical state affects climate and environmental phenomena such as radiative transfer, visibility, and heterogeneous chemistry. Here we present a mathematical model that considers the relative humidity history and chemical composition dependence of deliquescence and efflorescence for describing the dynamic and transport behavior of ambient aerosols[3]. 

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