Substance primary

Absolute method. A synthetic sample containing known amounts of the constituents in question is used. Known amounts of a constituent can be obtained by weighing out pure elements or compounds of known stoichiometric composition. These substances, primary standards, may be available commercially... 

Indications. A red or orange-red colour indicates the presence of a phenolic substance. Primary aryl amines also react. Some basic compounds which contain a phenolic group do not react to this test a combination of this test with the Folin-Ciocalteu Reagent is therefore advised for phenolic compounds. 

The nucleation step is the most critical for the production of different polymorphs and is therefore discussed in some detail below. Nucleation may be primary (which does not require preexisting crystals of the substance that crystallizes) or secondary (in which nucleation is induced by preexisting crystals of the substance). Primary nucleation may be homogeneous, whereby the nuclei of the crystallizing substance arise spontaneously in the medium in which crystallization occurs, or heterogeneous, whereby the nuclei comprise foreign solid matter, such as particulate contaminants (including dust particles or the walls of the container). 

Reduction of tocopherols can be coupled to a number of biological redox substances, primary among which are sulfhydryl compounds and ascorbic acid. The following chain of redox couples could react greatly to increase the antioxygenic capacity of the tocopherols. 

Reacting substances primary and secondary aliphatic amines, amides, nitriles, and pyrrole derivatives for specific hues and fluorescence see p. 

Reacting substances primary nitroparaffins (red color) secondary nitroparaffins (blue-green color) tertiary aliphatic and aromatic nitro-hydrocarbons. 

Other, more complex expressions have been proposed for 1. Muchova and Lednicky [17] took into account the initial nucleation on a heterogeneous substance (primary nucleation) and the growth of the solid (by a mechanism of secondary nucleation see next subsection), in the formation of nuclei of critical size. 

Dimethyl Sulphate Method for hydroxy compounds and for primary and secondary amines, acid amides, etc. The substance is dissolved or suspended in water, a small excess (above the theoretical) of sodium hydroxide added and then the theoretical quantity of dimethyl sulphate, the mixture being finally shaken without external warming. Methylation is usually rapid, the dimethyl sulphate being converted to methyl hydrogen sulphate... 

Benzoyl chloride test (for primary and secondary amines). Place 0-5 ml. (or 0 5 g.) of the compound, 10 ml. of 5 per cent, sodium hydroxide solution and 1 ml. of benzoyl chloride (CAUTION) in a test-tube, stopper the tube and shake until the odour of benzoyl chloride disappears. Examine the properties of the substance formed. 

Benzenesulphonyl chloride test. Proceed as in the benzoyl chloride test, but use 15-20 ml. of 5 per cent, sodium hydroxide solution. Examine the product when the odour of the sulphonyl chloride has disappeared. (If no reaction has occurred, the substance is probably a tertiary amine.) If a precipitate appears in the alkaline solution, dilute with about 10 ml. of water and shake if the precipitate does not dissolve, a secondary amine is indicated. If the solution is clear, acidify it cautioiosly to Congo red with dilute hydrochloric acid a precipitate is indicative of a primary amine. 

Protein tertiary structure is also influenced by the environment In water a globu lar protein usually adopts a shape that places its hydrophobic groups toward the interior with Its polar groups on the surface where they are solvated by water molecules About 65% of the mass of most cells is water and the proteins present m cells are said to be m their native state—the tertiary structure m which they express their biological activ ity When the tertiary structure of a protein is disrupted by adding substances that cause the protein chain to unfold the protein becomes denatured and loses most if not all of Its activity Evidence that supports the view that the tertiary structure is dictated by the primary structure includes experiments m which proteins are denatured and allowed to stand whereupon they are observed to spontaneously readopt their native state confer matron with full recovery of biological activity... 

Nucleic acids are acidic substances present m the nuclei of cells and were known long before anyone suspected they were the primary substances involved m the storage transmission and processing of genetic information There are two kinds of nucleic acids ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) Both are complicated biopolymers based on three structural units a carbohydrate a phosphate ester linkage between carbohydrates and a heterocyclic aromatic compound The heterocyclic aro matic compounds are referred to as purine and pyrimidine bases We 11 begin with them and follow the structural thread... 

The list given below includes the substances that are most used and most useful for the standardization of solutions for precipitation titrations. Primary standard solutions are denoted by the letter (P) in Column 1. 

A big step forward came with the discovery that bombardment of a liquid target surface by abeam of fast atoms caused continuous desorption of ions that were characteristic of the liquid. Where this liquid consisted of a sample substance dissolved in a solvent of low volatility (a matrix), both positive and negative molecular or quasi-molecular ions characteristic of the sample were produced. The process quickly became known by the acronym FAB (fast-atom bombardment) and for its then-fabulous results on substances that had hitherto proved intractable. Later, it was found that a primary incident beam of fast ions could be used instead, and a more generally descriptive term, LSIMS (liquid secondary ion mass spectrometry) has come into use. However, note that purists still regard and refer to both FAB and LSIMS as simply facets of the original SIMS. In practice, any of the acronyms can be used, but FAB and LSIMS are more descriptive when referring to the primary atom or ion beam. 

Because variations in accurate isotope ratio measurements typically concern only a few parts per 1000 by mass and there are no universal absolute ratios, it is necessary to define some standards. For this purpose, samples of standard substances are produced and made available at two major centers IAEA (International Atomic Energy Authority, U.K.) and NIST (National Institute for Standards and Technology, U.S.). Standards from other sources are also available. These primary standards can be used as such, or alternative standards can be employed if the primary ones are not available. However, any alternative standards need to be related accurately to the primary ones (see formulae below). For example, the material PDB (PeeDee belemnite), used particularly as a standard for the ratio of isotopes, is no longer readily available, and a new standard, VPDB,... 

Air pollution can be considered to have three components sources, transport and transformations in the atmosphere, and receptors. The source emits airborne substances that, when released, are transported through the atmosphere. Some of the substances interact with sunlight or chemical species in the atmosphere and are transformed. Pollutants that are emitted directiy to the atmosphere are called primary pollutants pollutants that are formed in the atmosphere as a result of transformations are called secondary pollutants. The reactants that undergo transformation are referred to as precursors. An example of a secondary pollutant is O, and its precursors are NMHC and nitrogen oxides, NO, a combination of nitric oxide [10102-43-9] NO, and NO2. The receptor is the person, animal, plant, material, or ecosystem affected by the emissions. 

Lead Azide. The azides belong to a class of very few useflil explosive compounds that do not contain oxygen. Lead azide is the primary explosive used in military detonators in the United States, and has been intensively studied (see also Lead compounds). However, lead azide is being phased out as an ignition compound in commercial detonators by substances such as diazodinitrophenol (DDNP) or PETN-based mixtures because of health concerns over the lead content in the fumes and the explosion risks and environmental impact of the manufacturing process. 

Jiftertaste. The experience that, under certain conditions, foUows removal of the taste stimulus it may be continuous with the primary experience or may foUow as a different quaUty after a period during which swallowing, saUva, dilution, and other influences may have affected the stimulus substance. 

CGRP has a wide distribution in the nervous system (19) and was the first peptide to be localized to motoneurons (124). It is also found in primary sensory neurons where it is colocalized with substance P (125). CGRP is derived from a precursor stmcturaHy related to the calcitonin precursor. The latter precursor produces two products, calcitonin itself and katacalcin, while the CGRP precursor produces one copy of CGRP (123). Like other peptides, CGRP is cleaved from its precursor by tryptic breakdown between double basic amino acid residues. 

Beilstein File. Beilstein first went on-line on STN International in December 1988 with information on 350,000 compounds, and several months later it was also on Dialog. Beilstein Online now comprises data on five million compounds. The organic substance records contain the critically reviewed and evaluated documents from the beilstein Handbook of Organic Chemist main volume and supplements 1—5, which cover the chemical Hterature from 1779 through 1979. These evaluated data are indicated as Handbook Data in the notes of Hterature references. The Beilstein Eile also contains organic substance records for unreviewed excerpts from the primary Hterature from 1980 to 1991. 

Prior to the 1990s phenyhnercuric acetate was the primary bactericide and fungicide in latex and waterborne paints. Because of the increasing concerns of mercury toxicity and the potential for high consumer and occupational exposures to mercury when present in paints, the U.S. Environmental Protection Agency (EPA) induced U.S. manufacturers of PMA and other mercury compounds to withdraw their registrations for use of these substances as biocides in paints (see AIercury). Mercury compounds are used only for very limited, specific purposes, such as the use of phenyhnercuric mXx.2LX.e[55-68-5] as a bactericide in cosmetic eye preparations (see Cosmetics). 

Tautomerism. Primary and secondary mononitroparaffias are acidic substances which exist ia tautomeric equiUbria with thek nitronic acids. 

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