Hydrated crystallines

The chlorides, bromides, nitrates, bromates, and perchlorate salts ate soluble in water and, when the aqueous solutions evaporate, precipitate as hydrated crystalline salts. The acetates, iodates, and iodides ate somewhat less soluble. The sulfates ate sparingly soluble and ate unique in that they have a negative solubitity trend with increasing temperature. The oxides, sulfides, fluorides, carbonates, oxalates, and phosphates ate insoluble in water. The oxalate, which is important in the recovery of lanthanides from solutions, can be calcined directly to the oxide. This procedure is used both in analytical and industrial apptications. 

Some commercially available molecular-sieve products and related materials are shown in Table 6, classified according to the basic 2eohte stmcture types. In most cases, the water content of the commercial product is below 1.5—2.5 wt % certain products, however, are sold as fully hydrated crystalline powders. 

Figure 4. FTIR. spectra a) crystalline, anhydrous lithium tetraborate b) hydrated, crystalline lithium tetraborate c) difference spectrum (55 hour spectrum - 27 hour spectrum) during polymerization in methoxyethanol d) difference spectrum (48 hour spectrum - 24 hour spectrum) during polymerization in THF.

US patent 6,723,728, Polymorphic and other crystalline forms cis-FTC [106], The present invention relates to polymorphic and other crystalline forms of (—)-and ( )-cA-(4-amino-5-fluoro-l-(2-(hydroxymethyl)-l,3-oxathiolan-5-yl)-2(lH)-pyrimidinone, or FTC) [106]. Solid phases of (—)-cz>FTC that were designated as amorphous (—)-FTC, and Forms II and III were found to be distinguishable from Form I by X-ray powder diffraction, thermal analysis properties, and their methods of manufacture. A hydrated crystalline form of ( )-cA-FTC and a dehydrated form of the hydrate, were also disclosed, and can similarly be distinguished from other forms of FTC by X-ray powder diffraction, thermal properties, and their methods of manufacture. These FTC forms can be used in the manufacture of other forms of FTC, or as active ingredients in pharmaceutical compositions. Particularly preferred uses of these forms are in the treatment of HIV or hepatitis B. 

It is the objective of this chapter to discuss the various mechanisms whereby water can interact with solid substances, present methodologies that can be used to obtain the necessary data, and then discuss moisture uptake for nonhydrating and hydrating crystalline solids below and above their critical relative humidities, for amorphous solids and for pharmaceutically processed substances. Finally, transfer of moisture from one substance to another will be discussed. 

The temperature, abbreviated c.m.t., at which a deter-gent/solvent system or a lipid/solvent system passes from a hydrated crystalline state to an isotropic micellar solution. For a number of lipids, the c.m.t. is below the freezing point of the solvent. The Krafft point,, is the c.m.t. at the critical micelle concentration. 

All hydrate structures have repetitive crystal units, as shown in Figure 1.5, composed of asymmetric, spherical-like cages of hydrogen-bonded water molecules. Each cage typically contains at most one guest molecule, held within the cage by dispersion forces. The hydrate crystalline structures and mechanical properties are discussed in Chapter 2. Throughout this book the common name... 

In many simple solids, — for example certain hydrated crystalline salts —, we actually have pairs of protons in definite orientations, and may expect to find a two-fold NMR resonance. This is indeed observed the lines are not narrow and isolated, however, but appear instead as a broadened and partially blended pair of lines, as in Fig. 2 b, the separation of which depends upon the orientation of the crystal in the magnetic field. In such substances, the interactions of the members of each proton pair dominate, but the magnetic interactions between the pairs are not negligible. These many smaller interactions, varying with both r and 6, give rise in effect to... 

FIGURE 1.6 Neutron diffraction pattern of the fully hydrated crystalline phase of n-butylammonium vermiculite measured in reflection geometry X = 4.52 A. 

FIGURE 1.7 Rocking curve on the 001 peak of a fully hydrated crystalline n-butylammonium vermiculite d = 19.4 A. 

A method was presented for recording electron diffraction diagrams of hydrated, crystalline biopolymers, and was applied to mycodextran. 

The water content of p-CD increases with increasing humidity and passes through a plateau region at about 23-3 l /o RH where the water content is about 5-6 water molecules. Another leveling of the plot occurs at humidities of 60-79 /o. Both 12-water and ll-water hydrated crystalline forms have been reported alongwith a dehydrated form. Upon standing for several weeks, the 11-water form will convert to the... 

The sorption of water vapor onto non-hydrating crystalline solids below RHq will depend on the polarity of the surface(s) and will be proportional to surface area. For example, water exhibits little tendency to sorb to non-polar solids like carbon or polytetrafluoroethylene... 

Cromolyn Sodium, USP. Cromolyn stxlium. dlsodium 1.3 - bis (2 -carboxychnimon - 5 - yloxy) -2-hydroxy propane (Intal). is a hygroscopic, white, hydrated crystalline powder that is soluble in water (1 10). It i.s tasteless at first but leaves a very slightly biller aftertaste. The pK of cromolyn is 2.0. It is available as a solution for a nebuliz.cr. an aerosol spray, a nasal solution, an ophthalmic solution, and an oral concentrate. 

Water makes up about 0.023% of the total mass of the earth. About 1.4 X 10 kg of it is distributed above, on, and below the earth s surface. The volume of this vast amount of water is about 1.4 billion km. Most of the earth s water (97.7%) is contained in the oceans, with about 1.9% in the form of ice or snow and most of the remainder (a small fraction of the total) available as freshwater in lakes, rivers, underground sources, and atmospheric water vapor. A small but important fraction is bound to cations in certain minerals, such as clays and hydrated crystalline salts. More than 80% of the surface of the earth is covered with water—as ice and snow near the poles, as relatively pure water in lakes and rivers, and as a salt solution in the oceans. 

Next, consider the free energy relationship between a solvate and a non-solvated form when the activity of the solvent forming the solvate is less than 1 (i.e. solvent composition <100%). The dependence of the relative thermodynamic stability between anhydrous and hydrated crystalline forms on the water activity has been described by Grant and Higuchi (1990). The formation of hydrate crystals from an anhydrous phase is represented as ... 

Water Diffusion in Hydrated Crystalline and Amorphous Sugars... 

In this presentation, two examples of the use of vibrational spectroscopy to probe water-solid interactions in materials of interest to the food and pharmaceutical sciences are described. First, the interaction of water vapor with hydrophilic amorphous polymers has been investigated. Second, water accessibility in hydrated crystalline versus amorphous sugars has been probed using deuterium exchange. In both of these studies, Raman spectroscopy was used as the method of choice. Raman spectroscopy is especially useful of these types of studies as it is possible to control the environment of the sample more easily than with infrared spectroscopy. 

Crystal packing diagram for raffinose pentahydrate. Three of the water molecules are located in a channel (Wl, W2, and W4) and two are located outside of the channel (W3 and W5). For clarity, only the oxygen molecules of the water are shown at 50% of the van der Waals radii. (Source Reproduced from Ahlqvist, M.U.A. and Taylor, L.S. Water diffusion in hydrated crystalline and amorphous sugars monitored using H/D exchange, /. Pharm. Sci., 91, 690-698, 2002. With permission of the copyright owner.)... 

Ahlqvist, M.U.A. and Taylor, L.S. Water diffusion in hydrated crystalline and amorphous sugars monitored using H/D exchange, /. Pharm. Sci., 91, 690, 2002. 

The selenates are formed by oxidation of the selcnites or by fusion of selenium or selenium dioxide with KNOa or Na202. They resemble the sulfates remarkably, in hydration, crystalline form, and solubility. Barium selenate, while highly insoluble in water, is reduced with boiling HC1 solu tion, yielding the soluble H2Se03. This treatment reduces all selenates, and consequently it is of value in the detection of selenium in the higher state of oxidation. 

The base plan unit-cell projection (Figure 2) shows the positions of the water molecules in the unit-cell as deduced from an analysis of the equatorial x-ray diffracted intensities for a fiber diagram recorded at about 50X relative humidity. The water molecules cluster in distinct areas and form a helical column whose symmetry matches that of the xylan chains. In fact, the water of hydration may dictate the symmetry of the xylan chains. The energetically (theoretical) most stable conformation of the xylan chain involves twofold symmetry, whereas in the hydrated crystalline environment, as deduced from x-ray diffraction, the xylan chains possess three-fold symmetry. The water molecules stabilize the three-fold structure by the formation of hydrogen bonds. This structure is an example of columnar hydration which allows a symmetric... 

Dunitz and coworkers reported convincing experimental and theoretical evidence for C - H. . . O hydrogen bonding in the hydrated crystalline form of tricyclic or-... 

There is considerable evidence for the association of Bi3+ ion with nitrate ions in aqueous solution. The nitrate ions appear to be mainly bidentate, and all members of the set Bi(N03) (H20)3 +. .. Bi(N03)4 appear to occur.70 From acid solution various hydrated crystalline salts such as Bi(N03)3 5H20, Bi2(S04)3 and double nitrates of the type M3[Bi(N03)6]2,24H20 can be obtained. Treatment of Bi203 with nitric acid gives bismuthyl salts such as BiO(N03) and Bi202(0H)(N03). Similar bismuthyl salts are precipitated on dilution of strongly acid solutions of various bismuth compounds. Bismuthyl salts are generally insoluble in water. 

The hexaquo ion exists in very strongly acid solutions of ferric salts, in the several ferric alums, MIFe(S04)2- 12H20, and presumably also in the highly hydrated crystalline salts. 

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