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Home >> Chemistry Dictionary >> Pauil Exclusion Principle - Perfume Chemistry
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Parylene polymers. A series of polymers derived from di-p-xylyene, (CH2C6H4CH2)2. Used for dielectric coatings in electronic equipment.
PAS. 4 Ammoniosalicylic acid.
Pascal. The SI unit of pressure equal to one newton per square metre.
Paschen Lines. The lines represent transitions to the n=3 level. These lines occur in the infrared region.
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Passive. Describing a solid that has reacted with another substance to yield a protective layer, so that further reaction stops. The solid is said to have been rendered passive.
Pauli exclusion principle. In any atom no two electrons can have all four quantum numbers the same.See exclusion principle.
PB. Lead.
PCB. Polychlorinated biphenyls.
Pd. Palladium.
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P-Block elements. The elements of main groups IIIA, IV-A, V A, VIA, VII A and O. The electrons occupy p-levels.
Pearl. A secretion consisting mainly of calcium carbonate, CaCO3, produced by various molluscs.
Pearl ash. Potassium carbonate, K2CO3, made from wood ashes.
Peat. A naturally-occurring, brown, fibrous mass of partially decayed plant material. The calorific values of peat on a dry basis range from about 16-20 MJ/kg. Used for firing power stations or can be converted to peat charcoal by low temperature carbonization
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Pencil lead. A mixture of graphite with day in various proportions, to give different degrees of hardness.
Penicillin. Refers to an antibiotic which is derived from the mould pencillium notatum, specifically it is known as penicillin Cr and belongs to a class of similar substances called penicillins. They used to treat a variety of infections caused by bacteria.
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Pentose. A carbohydrate with five C atoms. Of the aldopentoses, both stereoisomers of arabinose and the D-forms of xylose and ribose occur naturally; lyxose does not occur naturally. There are four (two pairs of stero-isomers) possible ketopentoses.
Peptidases. Proteolytic enzymes. Some, called endopeptidases attack the internal links of a peptide chain, e.g. trypsin and chymotrypsin, and others called exopeptidases, attack at both ends of the chains.
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Peptide. A compound of two or more amino acids formed by condensation of the – NH2 group of one acid and the carboxyl group of another. The peptide linkage, - NH-CO-, results.
Peptones. Organic substances produced by the hydrolysis of proteins by the action of pepsin in the stomach. They are soluble in water, and are absorbed by the body.
Percussion cap. A device used in fire-arms. If consists of a small copper cylinder containing mercuric fulminate or other violent explosive that will explode on being struck, thus, initiating the explosion of the main charge.
Perfect Gas. (Ideal gas). A theoretical concept of a gas that would obey the gas laws exactly. Such a gas would consists of perfectly elastic molecules, the volume occupied by the actual molecules, and the forces of attraction between them, being zero or negligible.
Perfume chemistry. The broad contents of perfumes are (of plant origin), flower oils, natural extracts from resins, gums, etc., and fixatives (e.g. ambergris, civet) which render the perfume more lasting. Materials used in perfumery are both natural and synthetic.
Peri. A prefix sometimes used to denote the positional relationship between groups occupying the 1,8 positions on the naphthalene ring. As a special case the two groups may be part of a third ring, 1-Naphthylamine-8-sulphonic acid is sometimes referred to as peri acid.
Period. The horizontal rows in the conventional periodic table. There are seven periods.
Periodic acids. A series of unstable acids formed by the addition of water to the hypothetical, I2O7, e.g., HIO4. They are known in the form of their salts, the periodates.
Periodic law. The principle which states that the physical and chemical properties of elements are a periodic function of their proton number. The concept was first used in 1869 by the Russian Chemist Dimitri Mendelew using relative atomic mass rather than proton number.
Periodic table. A table of elements arranged in order of increasing atomic number to show relationship in chemical nature between elements.
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