A treatise on chemistry. Vol. 1, The non-metallic elements / by Sir H.E. Roscoe & C. Schorlemmer ...

  • Henry Enfield Roscoe
Date:
1881
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Licence: Public Domain Mark

Credit: A treatise on chemistry. Vol. 1, The non-metallic elements / by Sir H.E. Roscoe & C. Schorlemmer ... Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

    158/792 (page 142)
    distils over as a dark red liquid, decomposed by addition of water or ammonia, and yielding a yellow solution which, on addition of hot acetic acid and a soluble lead salt, gives a yellow precipitate of lead chromate; neither bromine nor iodine forms a similar compound with chromium. Chlorine, when combined to form a chloride, is always estimated as silver chloride, AgCl, and according to Stas 143'03 of silver chloride contain 3o-37 of chlorine. If the chlorine is present in the free state it can be determined by volumetric analysis (see Chlorimetry, under Bleaching Poioder), or it may be reduced by sulphur dioxide, SOg to hydrochloric acid, and then precipitated as silver chloride and weighed. The reduction of chlorine to hydro- chloric by means of sulphur dioxide is represented by the equation :— CI2 + SO2 + 2H2O = H2SO, + 2HC1. Chlorine occurs combined with carbon and other elements in certain organic compounds, as in chloroform, CHCI3. These sub- stances, when brought in contact with solution of silver nitrate do not yield any precipitate of silver chloride, and the chlorine cannot he detected or determined by the above means. In order to' ascertain the quantity of chlorine thus contained in combina- tion, the compound must be decomposed by jjassing its vapovu's over red-hot lime, when the chlorine combines with the metal to form calcium chloride, and this on being dissolved in -water or nitric acid yields, on addition of an excess of silver nitrate, a precipitate containing the whole of the chlorine. BROMINE. Br = 7975, Density = 7975. 62 Bromine does not occur in the free state in nature, it was dis- covered in the year 1826 by Balard,^ who prepared it from the liquor called bittern, remaining after the common salt has crystallised out from concentrated sea-water, in which it occurs combined with metals to form bromides, he gave it the name from ^pw^io^, a bad smell. Bromine occurs in combination with silver in certain ores, from Mexico, Chili, and Bretagne; but is found in larger J Ann, Chim. Phys, Ser. [2] xxxii., p. 337.