Morphic states

Solid compounds can have four morphic states polymorphic, pseudo-polymorphic (solvates), amorphous, and desolvated solvates. Crystals usually exhibit narrow melting point ranges and defract light under an optical microscope. When a change in the arrangement of... 

Solids may be stirred in a solvent and recovered by filtration, without ever effecting complete dissolution. Reslurrying can be an effective purification, by removing impurities adsorbed to the surface of the crystals. Reslurrying can also change the morphic state of solids (see Chapter 11). 

Methods to distinguish polymorphs are shown in Table 11.3. Byrn [31] suggests that a combination of methods be used to characterize critical solids two for identifying the phase, or morphic state, and two for securing the composition and stoichiometry. 

After formulation, changes in the morphic state of an active ingredient can have a profound effect on the dosage form. The gradual formation of a thermodynamically favored polymorph led to tablet disintegration [23] gradual hydration could also induce transition to another polymorph and create similar difficulties with the dosage form. 

Morphic state It must be clear whether the salt is monomorphic or polymorphic. If it is polymorphic, the relationship between the polymorphic forms (monotropic, enantiotropic), their relative thermodynamic stability (stable or metastable at room temperature) and the temperature range of their physical stability need to be clarified. 

In essence, the test battery should include XRPD to characterize crystallinity of excipients, moisture analysis to confirm crystallinity and hydration state of excipients, bulk density to ensure reproducibility in the blending process, and particle size distribution to ensure consistent mixing and compaction of powder blends. Often three-point PSD limits are needed for excipients. Also, morphic forms of excipients should be clearly specified and controlled as changes may impact powder flow and compactibility of blends. XRPD, DSC, SEM, and FTIR spectroscopy techniques may often be applied to characterize and control polymorphic and hydrate composition critical to the function of the excipients. Additionally, moisture sorption studies, Raman mapping, surface area analysis, particle size analysis, and KF analysis may show whether excipients possess the desired polymorphic state and whether significant amounts of amorphous components are present. Together, these studies will ensure lotto-lot consistency in the physical properties that assure flow, compaction, minimal segregation, and compunction ability of excipients used in low-dose formulations. 

Asymmetric syntheses can even be carried out more easily and more elegantly than by reacting achiral substrates with enantiomerically pure chiral reagents via diastereo-morphic transition states. Instead, one can allow the substrate to react exclusively and via diastereomorphic transition states with an enantiomerically pure species formed in situ from an achiral reagent and an enantiomerically pure chiral additive. The exclusive attack of this species on the substrate implies that the reagent itself reacts sub-... 

Willart, J., Lefebvre, J., Danede, F., Comini, S., Looten, E, and Descamps, M. (2005), Foly-morphic transformation of the G-form of d-sorbitol upon milling Structural and nano-structural analyses, Solid State Communi., 135(8), 519-524. 

In general, minerals in sedimentary and meta-morphic rocks contain ferrous iron (Velde, 1985) which is destined to become iron oxide under conditions of weathering. Oxidation under surface conditions has a tendency to produce iron in the ferric state. Most often the process takes iron out of the silicates and puts it into an oxide phase. In the uppermost layers of mature soils, iron oxide and various silicates, usually non-iron-bearing, are produced. In silicates containing iron, the majority is in the ferric state. The extent of the transformation of iron oxidation state is a rough measure of the maturity of the soil. In the extremely weathered soils one finds only ferric iron and aluminum oxides and hydroxides. These soils are typically red. 

Within each quartet, the morphic relationship between any pair of circles (representing distinct conjunctive states) is marked by an arc or a cross-link (arcs are for mi-to-mi-, mi-to-m2, mi -to-m2, and m2-to-m2 cross-links are for mi-to-my and mi-to-m2). Once the morphic relationships for the arcs are picked, those for the cross-links follow suit. The arcs and crosslinks are drawn very thick, thick, and thin for homomorphic, enantiomorphic, and diastereomorphic relationships, respectively the arcs and cross-links are dashed and dotted for astereomorphic and nonequimorphic relationships, respectively. For a given quartet of circles, every arc or cross-link may reflect any one of the five fundamental morphic relationships (Figure 12.4). 

The PHEMA-based SPE film prepared is flexible, transparent and exhibits a room temperature ionic conductivity of 4.32 x 10 S cm. High ionic conductivity observed for this film [HEMA-NPGMA-1 M LiC104/EC PC (1 1) + 1 wt% H2O] is probably a repercussion of its morphicity. This film can work in the temperature range between -90 and -220°C, which has proved that the PHEMA film is an ideal candidate for the construction of all solid state electrochromic windows. 

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