Prepared Chalk

See calcite calcium carbonate whiting chalk, prepared. 

Prepared calcium carbonate, drop chalk, prepared chalk, whiting, English white, Paris white. Native CaCO, purified by elutriation. 

Synonyms Allied whiting Calcium carbonate (INCI) Calcium carbonate (1 1) Calcium carbonate, precipitated Carbonic acid calcium salt Carbonic acid calcium salt (1 1) Cl 77220 Monocalcium carbonate Pigment white 18 Precipitated calcium carbonate Precipitated chalk Prepared chalk Vienna white White powder Whiting Classification Inorganic salt Empirical CCaOj Formula COj Ca... 

Chalk is a calcium carbonate prepared by precipitation. It is used in many polishing compounds including dentifrices. 

CO2 ( fixed air ), prepared by Joseph Black (aged 24-26), was the first gas other than air to be characterized (i) chalk when heated lost weight and evolved CO2 (genesis of quantitative gravimetric analysis), and (ii) action of acids on carbonates liberates CO2. 

The analysis of a pharmaceutical tablet (6) requires sample preparation that is little more complex as most tablets contain excipients (a solid diluent) that may be starch, chalk, silica gel, cellulose or some other physiologically inert material. This sample preparation procedure depends on the insolubility of the excipient in methanol. As the components of interest are both acidic and neutral, the separation was achieved by exploiting both the ionic interactions between the organic acids and the adsorbed ion exchanger and the dispersive interactions with the remaining exposed reverse phase. 

Finely-divided calcium carbonate obtained from natural sources (chalk, limestone or marble) or as a by-product of another chemical process -precipitated whiting. Strictly speaking, the term whiting should be applied only to material prepared by grinding natural chalk . 

Metal chemical shifts have not found extensive use in relation to structural problems in catalysis. This is partially due to the relatively poor sensitivity of many (but not all) spin 1=1/2 metals. The most interesting exception concerns Pt, which is 33.7% abundant and possesses a relatively large magnetic moment. Platinum chemistry often serves as a model for the catalytically more useful palladium. Additionally, Pt NMR, has been used in connection with the hydrosilyla-tion and hydroformylation reactions. In the former area, Roy and Taylor [82] have prepared the catalysts Pt(SiCl2Me)2(l,5-COD) and [Pt()i-Cl)(SiCl2Me)(q -l,5-COD)]2 and used Pt methods (plus Si and NMR) to characterize these and related compounds. These represent the first stable alkene platinum silyl complexes and their reactions are thought to support the often-cited Chalk-Harrod hydrosilylation mechanism. 

Ammonium carbonate is prepared on a large scale by distilling an intimate mixture of ammonium sulphate with twice its weight of chalk in cylindrical cast-iron vessels, 7 to 10 ft. long and 1J ft. diameter, and fitted with movable leaden covers at each end. Several retorts are heated in one furnace. The vapours from the- retorts are led into stone chambers where the carbonate,is deposited as a crust... 

Mineral Substances.—This class comprises only a few materials, which are used rather as body or coloring matters. Svhnitrctle of bismuth is the. pearl white for the complexion. A less objectionable preparation would be a mixture of native sulphate of baryta and prepared chalk—precipitated carbonate of lime, These latter two, while being as white as the former, are not, like it, discolored by the sulphur fumes in the atmosphere, nor SO particularly injurious to the. skin. ... 

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