Water of crystallization - wikipedia Water of crystallization In chemistry, water of crystallization or water of hydration or crystallization water is water that occurs inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. In some contexts, water of crystallization is the total weight of water in a substance at a given temperature and is mostly present in a definite ( stoichiometric ) ratio. Classically, `` water of crystallization '' refers to water that is found in the crystalline framework of a metal complex or a salt, which is not directly bonded to the metal cation. Upon crystallization from water or moist solvents, many compounds incorporate water molecules in their crystalline frameworks. Water of crystallization can generally be removed by heating a sample but the crystalline properties are often lost. For example, in the case of sodium chloride, the dihydrate is unstable at room temperature. Coordination sphere of Na in the metastable dihydrate of sodium chloride ( red = oxygen, violet = Na, green = Cl, H atoms omitted ). Compared to inorganic salts, proteins crystallize with large amounts of water in the crystal lattice. A water content of 50 % is not uncommon for proteins. Contents 1 Nomenclature 2 Position in the crystal structure 3 Analysis 4 Other solvents of crystallization 5 Table of crystallization water in some inorganic halides 6 Hydrates of transition metal sulfates 7 Gallery 8 See also 9 References Nomenclature In molecular formulas water of crystallization can be denoted in different ways : `` hydrated compound ⋅ nH O '' or `` hydrated compound × nH O '' This notation is used when the compound only contains lattice water or when the crystal structure is undetermined. For example Calcium chloride : CaCl 2H O `` hydrated compound ( H O ) '' A hydrate with coordinated water. For example Zinc chloride : ZnCl ( H O ) Both notations can be combined as for example in copper ( II ) sulfate : ( Cu ( H O ) ) SO H O Position in the crystal structure Some hydrogen - bonding contacts in FeSO 7H O. This metal aquo complex crystallizes with water of hydration, which interacts with the sulfate and with the ( Fe ( H O ) ) centers. A salt with associated water of crystallization is known as a hydrate. The structure of hydrates can be quite elaborate, because of the existence of hydrogen bonds that define polymeric structures. Historically, the structures of many hydrates were unknown, and the dot in the formula of a hydrate was employed to specify the composition without indicating how the water is bound. Examples : CuSO 5H O - copper ( II ) sulfate pentahydrate CoCl 6H O - cobalt ( II ) chloride hexahydrate SnCl 2H O - tin ( II ) ( or stannous ) chloride dihydrate For many salts, the exact bonding of the water is unimportant because the water molecules are labilized upon dissolution. For example, an aqueous solution prepared from CuSO 5H O and anhydrous CuSO behave identically. Therefore, knowledge of the degree of hydration is important only for determining the equivalent weight : one mole of CuSO 5H O weighs more than one mole of CuSO. In some cases, the degree of hydration can be critical to the resulting chemical properties. For example, anhydrous RhCl is not soluble in water and is relatively useless in organometallic chemistry whereas RhCl 3H O is versatile. Similarly, hydrated AlCl is a poor Lewis acid and thus inactive as a catalyst for Friedel - Crafts reactions. Samples of AlCl must therefore be protected from atmospheric moisture to preclude the formation of hydrates. Structure of the polymeric ( Ca ( H O ) ) center in crystalline calcium chloride hexahydrate. Three water ligands are terminal, three bridge. Two aspects of metal aquo complexes are illustrated : the high coordination number typical for Ca and the role of water as a bridging ligand. Crystals of hydrated copper ( II ) sulfate consist of ( Cu ( H O ) ) centers linked to SO ions. Copper is surrounded by six oxygen atoms, provided by two different sulfate groups and four molecules of water. A fifth water resides elsewhere in the framework but does not bind directly to copper. The cobalt chloride mentioned above occurs as ( Co ( H O ) ) and Cl. In tin chloride, each Sn ( II ) center is pyramidal ( mean O / Cl - Sn - O / Cl angle is 83 ° ) being bound to two chloride ions and one water. The second water in the formula unit is hydrogen - bonded to the chloride and to the coordinated water molecule. Water of crystallization is stabilized by electrostatic attractions, consequently hydrates are common for salts that contain + 2 and + 3 cations as well as − 2 anions. In some cases, the majority of the weight of a compound arises from water. Glauber 's salt, Na SO ( H O ), is a white crystalline solid with greater than 50 % water by weight. Consider the case of nickel ( II ) chloride hexahydrate. This species has the formula NiCl ( H O ). Crystallographic analysis reveals that the solid consists of ( trans - NiCl ( H O ) ) subunits that are hydrogen bonded to each other as well as two additional molecules of H O. Thus 1 / 3 of the water molecules in the crystal are not directly bonded to Ni, and these might be termed `` water of crystallization ''. Analysis The water content of most compounds can be determined with a knowledge of its formula. An unknown sample can be determined through thermogravimetric analysis ( TGA ) where the sample is heated strongly, and the accurate weight of a sample is plotted against the temperature. The amount of water driven off is then divided by the molar mass of water to obtain the number of molecules of water bound to the salt. Other solvents of crystallization Water is particularly common solvent to be found in crystals because it is small and polar. But all solvents can be found in some host crystals. Water is noteworthy because it is reactive, whereas other solvents such as benzene are considered to be chemically innocuous. Occasionally more than one solvent is found in a crystal, and often the stoichiometry is variable, reflected in the crystallographic concept of `` partial occupancy. '' It is common and conventional for a chemist to `` dry '' a sample with a combination of vacuum and heat `` to constant weight. '' For other solvents of crystallization, analysis is conveniently accomplished by dissolving the sample in a deuterated solvent and analyzing the sample for solvent signals by NMR spectroscopy. Single crystal X-ray crystallography is often able to detect the presence of these solvents of crystallization as well. Other methods may be currently available. Table of crystallization water in some inorganic halides In the table below are indicated the number of molecules of water per metal in various salts. Formula of hydrated metal halides Coordination sphere of the metal Equivalents of water of crystallization that are not bound to M Remarks CaCl ( H O ) ( Ca ( μ - H O ) ( H O ) ) none Case of water as a bridging ligand VCl ( H O ) trans - ( VCl ( H O ) ) two VBr ( H O ) trans - ( VBr ( H O ) ) two bromides and chlorides are usually similar VI ( H O ) ( V ( H O ) ) none iodide competes poorly with water CrCl ( H O ) trans - ( CrCl ( H O ) ) two dark green isomer, aka `` Bjerrums 's salt '' CrCl ( H O ) ( CrCl ( H O ) ) one blue - green isomer CrCl ( H O ) trans - ( CrCl ( H O ) ) none square planar / tetragonal distortion CrCl ( H O ) ( Cr ( H O ) ) none AlCl ( H O ) ( Al ( H O ) ) none isostructural with the Cr ( III ) compound MnCl ( H O ) trans - ( MnCl ( H O ) ) two MnCl ( H O ) cis - ( MnCl ( H O ) ) none cis molecular, the unstable trans isomer has also been detected MnBr ( H O ) cis - ( MnBr ( H O ) ) none cis, molecular MnCl ( H O ) trans - ( MnCl ( H O ) ) none polymeric with bridging chloride MnBr ( H O ) trans - ( MnBr ( H O ) ) none polymeric with bridging bromide FeCl ( H O ) trans - ( FeCl ( H O ) ) two FeCl ( H O ) trans - ( FeCl ( H O ) ) none molecular FeBr ( H O ) trans - ( FeBr ( H O ) ) none molecular FeCl ( H O ) trans - ( FeCl ( H O ) ) none polymeric with bridging chloride FeCl ( H O ) trans - ( FeCl ( H O ) ) two only hydrate of ferric chloride, isostructural with Cr analogue CoCl ( H O ) trans - ( CoCl ( H O ) ) two CoBr ( H O ) trans - ( CoBr ( H O ) ) two CoI ( H O ) ( Co ( H O ) ) none iodide competes poorly with water CoBr ( H O ) trans - ( CoBr ( H O ) ) none molecular CoCl ( H O ) cis - ( CoCl ( H O ) ) none note : cis molecular CoCl ( H O ) trans - ( CoCl ( H O ) ) none polymeric with bridging chloride CoBr ( H O ) trans - ( CoBr ( H O ) ) none polymeric with bridging bromide NiCl ( H O ) trans - ( NiCl ( H O ) ) two NiCl ( H O ) cis - ( NiCl ( H O ) ) none note : cis molecular NiBr ( H O ) trans - ( NiBr ( H O ) ) two NiI ( H O ) ( Ni ( H O ) ) none iodide competes poorly with water NiCl ( H O ) trans - ( NiCl ( H O ) ) none polymeric with bridging chloride CuCl ( H O ) ( CuCl ( H O ) ) none tetragonally distorted two long Cu - Cl distances CuBr ( H O ) ( CuBr ( H O ) ) two tetragonally distorted two long Cu - Br distances Hydrates of transition metal sulfates Transition metal sulfates form mono -, tetra -, and pentahydrates, each of which crystallizes in only one form. The water in these salts typically is coordinated, together with sulfate to the metal center. The sulfates of these same metals also crystallize as both tetragonal and monoclinic hexahydrates, wherein all water is coordinated and the sulfate is a counterion. The heptahydrates, which are often the most common salts, crystallize as monoclinic and the less common orthorhombic forms. In the heptahydrates, one water is in the lattice and the other six are coordinated to the ferrous center. Cr ( SO ) 18H O Formula of hydrated metal sulfate Coordination sphere of the metal Equivalents of water of crystallization that are not bound to M Remarks Cr ( SO ) ( H O ) ( Cr ( H O ) ) six one of several chromium ( III ) sulfates MnSO ( H O ) unknown unknown one of several manganese ( II ) sulfates FeSO ( H O ) ( Fe ( H O ) ) one Common motif for divalent metal sulfates CoSO ( H O ) ( Co ( H O ) ) one Common motif for divalent metal sulfates NiSO ( H O ) ( Ni ( H O ) ) one Common motif for divalent metal sulfates NiSO ( H O ) ( Ni ( H O ) ) none one of several nickel sulfate hydrates CuSO ( H O ) ( Cu ( H O ) ( SO ) ) one sulfate is bridging ligand CdSO ( H O ) Cd ( H O ) SO none bridging water ligand Gallery Hydrated copper ( II ) sulfate is bright blue. Anhydrous copper ( II ) sulfate is white. See also Hydrate Mineral hydration References Jump up ^ Greenwood, Norman N. ; Earnshaw, Alan ( 1997 ). Chemistry of the Elements ( 2nd ed. ). Butterworth - Heinemann. ISBN 0 - 08 - 037941 - 9. Jump up ^ Klewe, B. ; Pedersen, B. ( 1974 ). `` The crystal structure of sodium chloride dihydrate ''. Acta Crystallogr. B30 : 2363 -- 2371. doi : 10.1107 / S0567740874007138. Jump up ^ Yonghui Wang et al. `` Novel Hydrogen - Bonded Three - Dimensional Networks Encapsulating One - Dimensional Covalent Chains :... '' Inorg. Chem., 2002, 41 ( 24 ), pp. 6351 -- 6357. doi : 10.1021 / ic025915o Jump up ^ Carmen R. Maldonadoa, Miguel Quirós and J.M. Salas : `` Formation of 2D water morphologies in the lattice of the salt... '' Inorganic Chemistry Communications Volume 13, Issue 3, March 2010, p. 399 -- 403 ; doi : 10.1016 / j. inoche. 2009.12. 033 Jump up ^ Moeller, Therald ( Jan 1, 1980 ). Chemistry : With Inorganic qualitative Analysis. Academic Press Inc ( London ) Ltd. p. 909. ISBN 0 - 12 - 503350 - 8. Retrieved 15 June 2014. Jump up ^ K. Waizumi, H. Masuda, H. Ohtaki, `` X-ray structural studies of FeBr 4H O, CoBr 4H O, NiCl 4H O, and CuBr 4H O. cis / trans Selectivity in transition metal ( I1 ) dihalide Tetrahydrate '' Inorganica Chimica Acta, 1992 volume 192, pages 173 -- 181. Jump up ^ B. Morosin `` An X-ray diffraction study on nickel ( II ) chloride dihydrate '' Acta Crystallogr. 1967. volume 23, pp. 630 - 634. doi : 10.1107 / S0365110X67003305 Jump up ^ Agron, P.A. ; Busing, W.R. `` Calcium and strontium dichloride hexahydrates by neutron diffraction '' Acta Crystallographica Section C 1986, volume 42, pp. 141 - p1. Jump up ^ violet isomer. isostructural with aluminium compound. Andress, K.R. ; Carpenter, C. `` Kristallhydrate. II. Die Struktur von Chromchlorid - und Aluminiumchloridhexahydrat '' Zeitschrift für Kristallographie, Kristallgeometrie, Kristallphysik, Kristallchemie 1934, volume 87, p446 - p463. Jump up ^ Zalkin, Allan ; Forrester, J.D. ; Templeton, David H. ( 1964 ). `` Crystal structure of manganese dichloride tetrahydrate ''. Inorganic Chemistry. 3 : 529 -- 33. doi : 10.1021 / ic50014a017. ^ Jump up to : `` Structure Cristalline et Expansion Thermique de L'Iodure de Nickel Hexahydrate '' ( Crystal structure and thermal expansion of nickel ( II ) iodide hexahydrate ) Louër, Michele ; Grandjean, Daniel ; Weigel, Dominique Journal of Solid State Chemistry ( 1973 ), 7 ( 2 ), 222 - 8. doi : 10.1016 / 0022 - 4596 ( 73 ) 90157 - 6 Jump up ^ Baur, W.H. `` On the crystal chemistry of salt hydrates. III. The determination of the crystal structure of FeSO ( H O ) ( melanterite ) '' Acta Crystallographica 1964, volume 17, p1167 - p1174. doi : 10.1107 / S0365110X64003000 Jump up ^ Stadnicka, K. ; Glazer, A.M. ; Koralewski, M. `` Structure, absolute configuration and optical activity of alpha - nickel sulfate hexahydrate '' Acta Crystallographica, Section B : Structural Science ( 1987 ) 43, p319 - p325. Jump up ^ V.P. Ting, P.F. Henry, M. Schmidtmann, C.C. Wilson, M.T. Weller `` In situ neutron powder diffraction and structure determination in controlled humidities '' Chem. Commun., 2009, 7527 - 7529. doi : 10.1039 / B918702B Jump up ^ Theppitak, Chatphorn ; Chainok, Kittipong `` Crystal structure of CdSO ( H O ) : A Redetermination '' Acta Crystallographica, Section E. Structure Reports Online 2015, volume 71, pi8 - pi9. doi : 10.1107 / S2056989015016904 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Water_of_crystallization&oldid=829182031 '' Categories : Crystallography Hydrates Talk Contents About Wikipedia Català Dansk Deutsch Eesti Español Esperanto فارسی Français हिन्दी Hrvatski Bahasa Indonesia Nederlands 日本 語 Norsk Oʻzbekcha / ўзбекча Plattdüütsch Polski Português Română Suomi Svenska Українська Tiếng Việt 中文 16 more Edit links This page was last edited on 7 March 2018, at 03 : 29. About Wikipedia

Question: one of most common solvent used for crystallization is
Answer: Water