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Simplified Chemistry

activated carbon

A powdered, granular, or pelleted form of amorphous car­bon characterized by very large surface area per unit volume because of an enormous number of fine pores. Activated carbon is capable of collecting gases, liquids, or dis­solved substances on the surface of its pores. Adsorption on activated carbon is selective, favoring …

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Acid Halid

One of a large group of organic substances possessing the halocar­bonyl group, in which X stands for fluorine, chlorine, bromine, or iodine. The terms acyl and aroyl halides refer to aliphatic or aromatic derivatives, respectively. The great inherent reactivity of acid halides precludes their free existence in nature; all are …

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Acetylene

An organic compound with the formula C2H2 or HC≡CH. The first member of the alkynes, acetylene is a gas with a narrow liquid range; the triple point is -81 °C (-114°F). The heat of formation (ΔHf) is +227 kilojoules/mole, and acetylene is the most endothermic compound per carbon of any …

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Acid base indicators

A substance that reveals, through characteristic color changes, the degree of acidity or basicity of solutions. Indicators are weak organic acids or bases which exist in more than one structural form (tautomers) of which at least one form is colored. Intense color is desirable so that very little indicator is …

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aceton

A chemical compound, CH3COCH3. A colorless liquid with an ethereal odor, it is the first member of the homologous series of aliphatic ketones. Its physical properties include boiling point 56.2°C (133.2°F). melting point -94.8°C (-138.6°F). and specific gravity 0.791. Acetone is used as a solvent for cellulose ethers, cellulose acetate, …

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Acetal

A geminal diether (R1 = H). Ketals, considered a subclass of acetals, are also geminal diethers (R1 = C, aliphatic or aromatic). Acetals are (1) independent structural units or a part of certain biological and commercial polymers, (2) blocking or protect­ing groups for complex molecules undergoing selective synthetic transformations, and …

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Acid and base

Two interrelated classes of chemical compounds, the precise definitions of which have varied considerably with the development of chemistry. Some of these controversies are still unresolved. Acids initially were defined only by their common properties as substances which had a sour taste, dissolved many metals, and reacted with alkalies (or …

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Accelerator mass spectrometry

The use of a combination of mass spectrometers and an accelerator to measure the natural abundances of very rare radioactive isotopes. These abundances are frequently lower than parts per trillion. The most important applications of accelerator mass spectrometry are in archeological and geophysical studies, as, for example, in radiocarbon dating …

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