Microcrystalline, definition

Another aspect of diffraction experiments that is often overlooked is the presence of amorphous materials, the amount of which cannot be easily quantified from a diffraction experiment. As pointed out above, there is no consensus on whether amorphous solids should be considered a form of the substance under investigation. On the one hand, the amorphous component of a given substance is the same chemical as the crystalline material. When melted or dissolved in a solvent the amorphous phase of a molecular material will yield the same molecules as those in crystals, thus falling within McCrone s definition, but will behave as a different solid. On the other hand, an amorphous material may be several different systems. After all, the only difference between a microcrystalline powder and an amorphous powder is the failure to obey the restrictions of Bragg s law. 

The compound [Pt(terpy)(SCH2CH20H)]N03 is a dark red-purple microcrystalline material that is extremely water soluble. The complex is stable in cold aqueous solution for periods up to several weeks. High pH or heating (T >60°) leads to decomposition, however. The electronic absorption spectra of the ter-pyridine thiolato compounds are characteristically definitive in the 300-350 nm region and may be used to determine product purity. Solutions of [Pt(terpy)-(SCH2 CH2 OH)] N03 of less than 15 pM obey Beer s law and exhibit the following absorption maxima and molar extinction coefficients 475 (890), 342 (12,900), 327 (10,700), 311 (10,300), 277 (20,300), and 242 (28,700) nm. 

Paraffin followed by candelilla wax and microcrystalline waxes, and eventually by beeswax, are considered as the most effective moisture barriers derived from edible waxes (Morillon et al. 2002). There is no satisfactory chemical definition for the term wax which is used for a variety of products of mineral, botanical and animal origin that contain various kinds of fatty materials (Table 23.4). The term resins or lacs can also be used for plant or insect secretions that take place along resins ducts, often in response to injury or infection, and result in more acidic substances (Hernandez 1994). However, all waxes tend to contain wax esters as major components, that is, esters of long-chain fatty alcohols with long chain fatty acids. Depending on their source, they may additionally include hydrocarbons, sterol esters, aliphatic aldehydes, primary and secondary alcohols, diols, ketones, triacylglycerols, and so on. 

It would be desirable to know the relative rates of hydrogenation of 1- and 2-hexene. Although we have no definite data relating to this, we did examine the competitive hydrogenation of amorphous catalyst activated at 400°, the relative rate of hydrogenation of 2-hexene was 0.6 that of methylpentene on a microcrystalline catalyst 0.2. This suggests that terminal olefins are hydrogenated more rapidly than nonterminal ones. 

An allotrope of a chemical element is defined as a solid phase (of the pure element) which differs by its crystal structure and therefore by its X-ray diffraction pattern from the other allotropes of that element. This definition can be extended to microcrystalline and amorphous phases which may be characterized either by their diffraction pattern or by suitable molecular spectra. 

TABLE 29 Experimental deactivation rates (see text for definitions), calculated energy transfer efficiencies, Eq. (153), and critical distances for 50% transfer (J ) in microcrystalline samples of [RM(L36)3]" helicates (M = Cr ", Ru") (data from Torelli et al., 2005)... 

Surface unsaturation in microcrystalline carbons, as measured by the fixation of bromine from aqueous solution, is thought to arise from the elimination of acidic C02-complexes, the elimination of two moles of complex generating one ethylenic bond. This is said to be a definite quantity characteristic of a carbon, and it can be enhanced by surface oxidation (treatment with potassium persulphate) followed by evacuation. 

CAS 92045-76-6 EINECS/ELINCS 295-458-3 Synonyms Microcrystalline wax, hydrogenated Paraffin waxes and hydrocarbon waxes, microcrystalline, hydrotreated Definition Microcrystalline wax that has been hydrogenated Uses Viscosity control agent in cosmetics Trade Names Containing Pionier 17106... 

Definition Hydrocarbon derived from petroleum three types paraffin waxes, microcrystalline waxes, and petrolatum waxes Properties Translucent wax, odorless, tasteless very si. sol. in org. soivs. ... 

Petroleum sulfonates, sodium salts Petroleum sulfonic acid, monosodium salt. See Sodium petroleum sulfonate Petroleum thinner. See VM P naphtha Petroleum wax CAS 977051-70-9 UN 1223 (DOT) INS905c Synonyms Microcrystalline wax Petroleum wax, synthetic Refined petroleum wax Classification Petroleum hydrocarbon Definition Hydrocarbon derived from petroleum three types paraffin waxes, microcrystalline waxes, and petrolatum waxes Properties Translucent wax, odorless, tasteless very si. sol. in org. soivs. insol. in water m.p. 48-93 C... 

Properties Gray cryst. mass sol. in water, alcohol, ether m.w. 94.18 dens. 2.32 (0 C) dec. 350 C Toxicoiogy Corrosive to tissues Uses Reagent intermediate Potassium oxidized microcrystalline wax Definition Potassium salt of oxidized microcrystalline wax... 

The word clay has ambivalent definitions (Bergaya, 2000). On the one hand it is used to define any soil particle smaller than 2 pm, but on the other hand it includes a large group of microcrystalline secondary minerals based on hydrous aluminum or magnesium silicates that have sheet-like structures (Manahan, 2000). There are at least two points that make clay minerals so active in natural processes, and became the key for their wide applications (a) The very large surface area that arises from the tiny size of the particles (nano-scale), and... 

Crystallite. The distinction between a crystal and a crystallite is subjective, and there does not appear to be a quantitative definition that differentiates one from the other. A crystallite is generally understood to be a microscopic crystal. It usually exists as one of many similar particles that adhere loosely to one another, being separated by grain boundaries. A crystallite is therefore a primary particle of a poly crystalline (or microcrystalline) solid, which is often referred to as a powder. 

Aggregation is definitively observed, especially at high polymer concentrations and low temperatures. For example, after adding a poor solvent (e.g. methanol) to a solution of P3HT in MTHF ( 1 mg/ml) and successively cooling to — 78°C (dry ice-acetone temperature), microcrystalline material precipitates and can be collected. Powder X-ray scans of these aggregates indicate that this partially crystalline material has the same powder pattern as that of the as-prepared neutral films. 

The catalysis science of supported metal oxide catalysts, especially supported vanadia catalysts, has lagged behind their industrial development. In the 1970s, two models were proposed for the active metal oxide component a three-dimensional microcrystalline phase (e.g., small metal oxide crystallites) or a two-dimensional surface metal oxide overlayer (e.g., surface metal oxide monolayer). In the 1980s, many studies demonstrated that the active metal oxide components were primarily present as two-dimensional surface metal oxide overlayers, below monolayer coverage, and that the surface metal oxide overlayers control the catalytic properties of supported metal oxide catalysts. The synergistic interaction between the surface vanadia overlayer and the underlying oxide support prompted Ceilings to state. . that neither the problem of the structure of suppored vanadium oxide nor that of the special role of TiOa as a support have definitely been solved. Further work on these and related topics is certainly necessary. In more recent years, many fundamental studies have focused on the molecular structural determination of the surface vanadia phase and to a lesser extent the molecular structure-reactivity relationships of supported vanadia catalysts. " ... 

Synonyms Mannitan, Z-9-octadecenoate Definition Monoester of oleic acid and anhydrides derived from mannitol Empirical C24H440g Uses Emulsifier, surfactant in cosmetics Manuf/Distrib. Somerset Cosmetic Co. Variati D-Mannitol, 1,4-anhydro-, 6-dodecanoate. See Mannitan laurate D-Mannitol, dianhydro-, mono-9-octadecenoate, (Z)- D-Mannitol, dianhydro-, monooleate. See Mannide monooleate MAOH. See Methyl amyl alcohol Marble. See Calcium carbonate Mascagnite. See Ammonium sulfate Matting acid. See Sulfuric acid Maxatase. See Protease MC. See Methylcellulose MCC. See Microcrystalline cellulose... 

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