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McCrone studies

Dr W.E.Taft of the Purdue Univ Research Foundation. Its crystallography was explored by Dr. W.C.McCrone at Armour Research Foundation and its prepn was studied by Dr. C.R.Morgan ... [Pg.273]

Enantiotropic polymorphs exhibit this transition temperature below their melting temperature (Figure 19.5), which means that the stable modiLcation depends on the temperature of reference This temperature represents the point of equal solubility for the two polymorphs, and one will have greater solubility above this temperature, and one below it. These transitions are often reversible, but may be kinetically limited or outside the temperature range studied. Haleblian and McCrone (1969) have cautioned that an enantiotropic relationship cannot be discounted because of the lack of an observed transition point. The transition can be examined microscopically if the crystal habits differ, or by solubility-temperature curves if the metastable form solubility can be measured before transformation. [Pg.549]

The majority of characterized solvates are stoichiometric, with either water or organic solvents present in a Lxed ratio with the drug molecules. Glibenclamide was isolated as two nonsolvated polymorphs, a pentanol solvate, and a toluene solvate (Suleiman and Najib, 1989). Furosemide could form solvates with dimethylformamide or dioxane (Matsuda and Tatsumi, 1989). Haleblian and McCrone (1969) studied the solid forms of steroids, and found different dissolution rates for two monohydrates of Luprednisolone, a monoethanol and hemiacetone solvate of prednisolone and two monoethanolates and a hemichloroform solvate of hydrocortisone. Other solvents that have been reported to form solvates with drugs include methyl ethyl ketone, propanol, hexane, dimethylsulfoxide, acetonitrile, and pyridine. The potential toxicity concerns eliminate most of these from consideration as practical mechanisms of solubility enhancement for human therapeutics. [Pg.553]

There are many examples of drugs that show slower dissolution rates, lower solubilities, or less absorption in the hydrated form than the anhydrate. Stoltz et al. (1989) studied the dissolution rate of oxyphenbutazone powder in distilled water aftGTThe time to dissolve 50% of the powderwas only 0.75 min for the anhydrate and 22.9 min for the monohydrate. The IDR of the anhydrate was 1.63 times as fast as the monohydrate when compressed discs were used. Haleblian and McCrone (196S reported that the dissolution rate of pellets of Luprednisolone depended on the state of hydration of the drug. Thep-monohydrate dissolved 10% faster than thmonohydrate, but the anhydrate polymorph dissolution rates were 1.6 (form I), 1.4 (form III), or 1.3 times (form II) as fast as the a-monohydrate. [Pg.555]

According to McCrone [46], a polymorph is a solid crystalline phase of a given compound resulting from the possibility of at least two or more different arrangements of the molecules of that compound in the solid state. Polymophs play an important role in a large variety of fields. Lahav and co-workers [47] have carried out very incisive studies on the control of nucleation and crystal polymophism using tailor-made auxiliaries. The importance of polymorphs to an organic solid-state photochemist is obvious. [Pg.437]

The most general use of the microscope for the study of polymorphism is simply for observing the homogeneity or diversity of a crystalline sample. Variations in size, shape or colour may indicate the presence of polymorphism and the need for further examination (see, for instance Fig. 3.2). As noted in Section 2.4.1, differences in crystal habit are not necessarily indicative of polymorphism. Further physical characterization of the individual crystals may involve measurements such as optical constants (Hartshorne and Smart 1960, 1964 Wahlstrom 1969 McCrone et al. 1978) or interfacial angles (Winchell 1943 Porter and Spiller 1951 Terpstra and Codd 1961). [Pg.95]

Kofier, L. and Kofier, A. (1954). Thermo-mikro-methoden zur Kennzeichnung organ-ischer Stoffe und stoffgemiche. (Thermomicromethods for the study of organic compounds and their mixtures). Innsbruck, Wagner. A 1980 translation of this book by Walter C. McCrone is available from McCrone Associates, Inc. [8, 15, 95, 98, 240]... [Pg.358]

McCrone, W. C. (1967). Crystallographic Study ofSC-lOI. Project 883, Chicago, IL. [291]... [Pg.366]

Teetsov, A. S. and McCrone, W. C. (1965). The microscopical study of polymorph stability diagrams. Mtcro.r. Cryst. Front, 15, 13-29. [279t, 280]... [Pg.389]

Polarized light microscopy has long been used in chemical and mlneraloglcal studies, and was raised to a high level of applicability by Walter McCrone and associates, culminating in the extensive Particle Atlas(6), which included Innumerable glasses, organics and polymers. [Pg.398]

Exploratory bench-scale experimental studies were undertaken by Walter C. McCrone Associates, Chicago, 111., primarily to demonstrate (a) that Reaction 1 can produce a gas containing H2S at a concentration... [Pg.219]

Marvin A. Salzenstein directed the experimental studies performed by Walter C. McCrone Associates. He was assisted by Jan Markussen, now of Copenhagen, Denmark. [Pg.235]

The first complete investigation of the a and P polymorphs of lead azide was performed by Miles [42]. Later the crystal structure of Pb(N3)2 was been studied by many other investigators Pfefferkorn [44], Azaroff [45], and Hattori and McCrone [46] for a- and j3-Pb(N3)2 Glen [47], Saha [48], and Choi and Boutin [49] for a-Pb(N3)2 Lamnevik and Soderquist [50, 51] for a, 3,7, and 6 lead azide. The crystal structure of a-Pb(N3)2, as described above, was determined by Choi and Boutin [49] by using three-dimensional neutron-diffraction data, but the crystal structures of the jS, 7, and 6 forms are not yet known. It is found that the P form transforms gradually to the a form in water [45] and also transforms irreversibly to the a form at about 160°C [50]. [Pg.116]

The goal of early stage solid-state analysis is the determination of the tendency of a compound to crystallize into different forms. It may have many forms like sulfathiazole with at least four polymorphs [6] or methylestradiol with one anhydrous form, two hydrated forms and at least two solvated forms [4]. This information guides the course of the future studies. If only one pharmaceutically significant form exists, then the subsequent studies should be straightforward and relatively rapid. If many forms exist, choosing the optimal form for development may require extensive time and study. It is useful to operate on the principle that all organic compounds crystallize in different forms and that the only questions are How many and How important McCrone [7] put the matter this way ... [Pg.297]

Size distribution studies (Shen et al., 1976) indicate that particulates emitted from coal-fired boiler stacks generally have a higher mean diameter than those from oil-fired boilers, but there is a large overlap, especially as particles from different coal combustion techniques also appear to show morphological and size differences due to differing furnace temperatures (McCrone Delly, 1973 Falster Jacobsen, 1982). Particles cannot therefore be classified to fuel-type on size criteria alone. [Pg.338]

Elemental analysis has been performed on particulates from many different combustion sources including car emissions, incinerators and cigarettes, as well as from coal and oil-fired power stations (McCrone Delly, 1973). The results from McCrone Delly and other studies (Shen et al., 1976 Cheng et al., 1976) show that the major elements present in power station emission particulates are, for oil V, Fe, Si, S, and Ca and for coal Fe, Ti, Si, S, K, and Ca. Titanium and vanadium have, therefore, been used in the past as indicative of coal and oil particles, respectively (e.g. Ganor et al., 1988). However, both oil and coal are heterogeneous materials, and vanadium is present in some coals and titanium in some oils. Consequently, these elements do not allow consistent discrimination between fuel... [Pg.338]

L. Kofler and A. Kofler, Thermal Micromethods for the Study of Organic Compounds and Their Mixtures, Wagno" Innsbruck, 1952 translated by McCrone, W. C., McCrone Research Institute Chicago, 1980. [Pg.2334]


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See also in sourсe #XX -- [ Pg.223 ]




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