Impurities light

Amido species of Mn" are known. The binary compound Mn(NH2)2 is obtained75 as an impure light yellow product from KNH2 and Mn(SCN)2 in liquid NH3, but is stable only in the absence of air and water and below room temperature. The compounds M2[Mn(NH2)4] (M = Na, K, Rb, Cs), however, are relatively robust in the absence of water. The yellow crystalline compounds were obtained76 by dissolving Mn in a liquid NH3 solution of the alkali metal. An X-ray analysis of the K+ salt confirms77 the expected tetrahedral [MnN4] anion, with Mn—N = 2.12(4) A. 

The light yellow microcrystalline [PPN][FeBr(CO)3(CN)2] is moderately air sensitive and reacts slowly with air to yield an impure light yellow solid. Complex [PPN][FeBr(CO)3(CN)2] is readily soluble in organic solvents, such as tetrahy-drofuran, acetonitrile, and dichloromethane. Although THF solution of complex [PPN][FeBr(CO)3(CN)2] is moderately air sensitive at room temperature, it should be handled under an inert atmosphere. 

Note that S2 is a large distillation column, with about 50 theoretical stages, operating at high reflux. The separation in S3 is easy, and requires only few stages. Note that S4 and S5 are small units, but of particular importance, because of their function S4 is the only exit of light impurities (Lights), while S5 is the only exit of the heavy impurities (Heavies). 

Petroleum Available in fractions of b.p. 40-60°, 60-80°, 80-100°, 100-120° yy Frequently called light petroleum or petrol ether. Unless specially purified, contains sulphur derivatives, etc.y as impurities. 

Absolute diethyl ether. The chief impurities in commercial ether (sp. gr. 0- 720) are water, ethyl alcohol, and, in samples which have been exposed to the air and light for some time, ethyl peroxide. The presence of peroxides may be detected either by the liberation of iodine (brown colouration or blue colouration with starch solution) when a small sample is shaken with an equal volume of 2 per cent, potassium iodide solution and a few drops of dilute hydrochloric acid, or by carrying out the perchromio acid test of inorganic analysis with potassium dichromate solution acidified with dilute sulphuric acid. The peroxides may be removed by shaking with a concentrated solution of a ferrous salt, say, 6-10 g. of ferrous salt (s 10-20 ml. of the prepared concentrated solution) to 1 litre of ether. The concentrated solution of ferrous salt is prepared either from 60 g. of crystallised ferrous sulphate, 6 ml. of concentrated sulphuric acid and 110 ml. of water or from 100 g. of crystallised ferrous chloride, 42 ml. of concentrated hydiochloric acid and 85 ml. of water. Peroxides may also be removed by shaking with an aqueous solution of sodium sulphite (for the removal with stannous chloride, see Section VI,12). 

In a 1-litre three-necked flask, fitted with a mechanical stirrer, reflux condenser and a thermometer, place 200 g. of iodoform and half of a sodium arsenite solution, prepared from 54-5 g. of A.R. arsenious oxide, 107 g. of A.R. sodium hydroxide and 520 ml. of water. Start the stirrer and heat the flask until the thermometer reads 60-65° maintain the mixture at this temperature during the whole reaction (1). Run in the remainder of the sodium arsenite solution during the course of 15 minutes, and keep the reaction mixture at 60-65° for 1 hour in order to complete the reaction. AUow to cool to about 40-45° (2) and filter with suction from the small amount of solid impurities. Separate the lower layer from the filtrate, dry it with anhydrous calcium chloride, and distil the crude methylene iodide (131 g. this crude product is satisfactory for most purposes) under diminished pressure. Practically all passes over as a light straw-coloured (sometimes brown) liquid at 80°/25 mm. it melts at 6°. Some of the colour may be removed by shaking with silver powder. The small dark residue in the flask solidifies on cooling. 

Optical Properties. Brightness, or visual whiteness of paper, can be defined as the degree to which light is reflected uniformly over the visible spectmm. Since pulp and typical impurities tend to be yellowish, blue dye is sometimes added in addition to appropriate fillers. The percentage reflectance is usually measured in the blue end of the spectmm at or near 457 nm (14). 

Anhydrous FeF is prepared by the action of Hquid or gaseous hydrogen fluoride on anhydrous FeCl (see Iron compounds). FeF is insoluble in alcohol, ether, and ben2ene, and sparingly soluble in anhydrous HF and water. The pH of a saturated solution in water varies between 3.5 and 4.0. Low pH indicates the presence of residual amounts of HF. The light gray color of the material is attributed to iron oxide or free iron impurities in the product. 

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