Crystals modification

Karfunkel H R, B Rohde, F J J Leusen, R J Gdanitz, emd G Rihs 1993. Continuous Similarity Measure Between Nonoverlapping X-ray Powder Diagrams of Different Crystal Modifications. Journal oj Computational Chemistry 14 1125-1135. 

Ruthenium is a hard, white metal and has four crystal modifications. It does not tarnish at room temperatures, but oxidizes explosively. It is attacked by halogens, hydroxides, etc. Ruthenium can be plated by electrodeposition or by thermal decomposition methods. The metal is one of the most effective hardeners for platinum and palladium, and is alloyed with these metals to make electrical contacts for severe wear resistance. A ruthenium-molybdenum alloy is said to be... 

Samarium has a bright silver luster and is reasonably stable in air. Three crystal modifications of the metal exist, with transformations at 734 and 922oC. The metal ignites in air at about ISOoC. The sulfide has excellent high-temperature stability and good thermoelectric efficiencies up to llOOoC. 

Terbium is reasonably stable in air. It is a silver-gray metal, and is malleable, ductile, and soft enough to be cut with a knife. Two crystal modifications exist, with a transformation temperature of 1289oC. Twenty one isotopes with atomic masses ranging from 145 to 165 are recognized. The oxide is a chocolate or dark maroon color. 

A cmcial development for zinc phosphate coatings came in 1943 when it was found that more uniform and finer crystals would develop if the surface was first treated with a titanium-containing solution of disodium phosphate (6). This method of crystal modification is a prime reason for the excellent paint (qv) adhesion seen on painted metal articles. 

The cmde copper phthalocyanine must be treated to obtain a satisfactory pigment in regard to the crystal modification and optimal particle size... 

Some references cover direct preparation of the different crystal modifications of phthalocyanines in pigment form from both the nitrile—urea and phthahc anhydride—urea process (79—85). Metal-free phthalocyanine can be manufactured by reaction of o-phthalodinitrile with sodium amylate and alcoholysis of the resulting disodium phthalocyanine (1). The phthahc anhydride—urea process can also be used (86,87). Other sodium compounds or an electrochemical process have been described (88). Production of the different crystal modifications has also been discussed (88—93). 

Ammonium chloride [12125-02-9] NH Q, ammonium bromide [12124-97-9] NH Br, and ammonium iodide [12027-06-4] NH I, are crystalline, ionic compounds of formula wts 53.49, 97.94, and 144.94, respectively. Their densities d systematically foUow the increase in formula weight 1.53, 2.40, and 2.52. AH three exist in two crystal modifications (10) the chloride, bromide, and iodide have the CsQ stmcture below temperatures of 184.5, 137.8, and — 17.6°C, respectively each reversibly transforms to the NaQ. stmcture at higher temperatures. 

Forms of Boric Acid. Orthoboric acid, B(OH)3, formula wt, 61.83, crystaUi2es from aqueous solutions as white, waxy plates that are triclinic ia nature sp gi 4, 1.5172. Its normal melting poiat is 170.9°C, however, when heated slowly it loses water to form metaboric acid, HBO2, formula wt, 43.82, which may exist ia one of three crystal modifications. Orthorhombic HBO2-III or a-form d = 1.784 g/mL, mp = 176° C) forms first around 130°C and gradually changes to monoclinic HBO2-II or P-form (d = 2.045 g/mL, mp = 200.9° C). Water-vapor pressures associated with these decompositions foUow. To convert kPa to mm Hg, multiply by 7.5. 

Laser based mass spectrometric methods, such as laser ionization (LIMS) and laser ablation in combination with inductively coupled plasma mass spectrometry (LA-ICP-MS) are powerful analytical techniques for survey analysis of solid substances. To realize the analytical performances methods for the direct trace analysis of synthetic and natural crystals modification of a traditional analytical technique was necessary and suitable standard reference materials (SRM) were required. Recent developments allowed extending the range of analytical applications of LIMS and LA-ICP-MS will be presented and discussed. For example ... 

Calcium carbonate crystal distortion or crystal modification,... 

Crystal growth retardation, function of all-organics 443 Crystal modification, function of all-organics 443... 

Hardegger, E. etal. Helv. Chim. Acta (HCACAV) 40, 1819 (1957). new crystal modifications ... 

The fact that in HPLC only UV-active components are registered, whereas in titration all basic functional groups are detected constitutes a difference in specificity (quality) and sensitivity (quantity) of these two methods relative to a given impurity. See Fig. 4.17 (left). [Solvent A (water) behaves differently from the other four as can be seen from Fig. 4.17 (right). The material was known to exist in a crystal modification that theoretically contains 3.2% water, and moderate drying will most likely drive off only the excess Indeed, the best-dried batches are all close to the theoretical point (circle, arrow in Figs. 4.16-17), and not near zero. This is only partly reflected in Table 4.15, column A for this reason tabular and graphic information has to be combined. Solvent B, which is an alcohol, behaves more like water... 

Figure 4. The effects of W loading on BET surface area and crystal modification of the zirconia support (1073 K calcination).

W e know of many examples of the effect of impurities of crystallization. In many cases impurities will completely inhibit (2-4) nucleus formation. Reading the literature on this subject impresses one with the frequent occurrence of hydrocolloids as crystal modifiers, particularly where sugar or water is the material being crystallized. The use of gelatin, locust bean gum, or sodium alginate in ice cream is just one example of many practical applications of hydrocolloids in crystal modification. 

Fluoran compounds have an optically active spiro-carbon atom. Consequently, some fluoran compounds, especially those having an alkylamino group of four or more carbon atoms at 3 -position, have been found to exhibit crystal modifications as determined by X-ray diffraction. Each crystal modification reveals different physical properties such as melting point, solubility, and affinity with acidic compounds, resulting in different characteristics regarding use for carbonless copying papers, thermosensitive recording papers, and the like. 

Table 1 shows a few examples of fluoran compounds having crystal modifications. 

The structures of typical examples have been mentioned already, such as the substantive DAST-type product 11.60, the distyryldiphenyl 11.15 and the vic-triazole 11.17. Certain FBAs, including these three compounds, can exist in relatively purer, near-colourless 13-crystal modifications or in less pure yellowish crystalline forms. They are most easily prepared in the yellower form but incorporation of this material into a detergent formulation leads to unacceptable discoloration of the powder. Today, these products are supplied in a near-colourless form that may be prepared, for example, by heating an aqueous alkaline suspension of the yellowish material together with a co-solvent. 

Wachtershauser provides a detailed discussion of whether particular crystal modifications of pyrite could have led to homochirality in the biomolecules produced, but his theory appears to be extremely speculative. 

Identification of Peaks from Crystallographic Data. Crystallography is not an issue of X-ray scattering. However, even in materials science crystallographic data are frequently consulted11. Based on such data the crystallizing species (component of a blend, block of a block copolymer, one of the crystal modifications possible) can... 

The listing of patents published by the United States Patent Office was searched for polymorph and solvatomorph patents using the keywords polymorph(s), polymorphic, solvate(s), hydrate(s), crystal form(s), and crystal modification, and the following patents issued during 2005 were returned using these keywords. 

US patent 6,740,669, Crystal modification of l-(2,6-difluorobenzyl)-lH-l,2,3-triazole-4-carboxamide and its use as antiepileptic [109]. The invention relates to the novel modification A or A of the compound l-(2,6-difluorobenzyl)-lH-l,2,3-triazole-4-carboxamide, and its use and pharmaceutical preparations comprising this crystal modification. 

US patent 6,740,753, Olanzapine crystal modification [110]. This invention concerns a novel crystal form of olanzapine, processes for its preparation, and its pharmaceutical use. 

US patent 6,833,379, Crystal modification of torasemide [119], This invention relates to the characterization of a new crystal modification III of torasemide, to a process for its preparation by the use of controlled acidifying of alkaline solutions of torasemide with inorganic or organic acids with or without addition of a crystal seed, to its use as a raw material for the preparation of the crystal modification I of torasemide and of pharmaceutically acceptable salts of torasemide, as well as to pharmaceutical forms containing this new torasemide crystal modification. 

Superconducting only in thin films or under high pressure in a crystal modification not normally stable. Critical temperatures for those elements from [32, Chapter 12]. 

Solid state characterization studies of the previously mentioned polymorphic systems [26-34] all utilize IR as a means to differentiate the various crystal modifications. In some cases, the observation of variations in IR absorption intensities has led to conclusions regarding intramolecular hydrogen bonding [26]. For other systems, fairly complete IR spectral band assignment has allowed for determination of structure for the polymorphic system. In one study [29], DSC-IR was used to identify the polymorphs and determine simultaneously the correlation between thermal events and structural changes. 

P. York, and D. J. W. Grant, Crystal Modifications and Powder Compaction, Proceedings of the Pharmaceutical Technology Conference 86, Cherry Hill, New... 

---