Manual of qualitative analysis / by Robert Galloway.

  • Galloway, Robert.
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: Manual of qualitative analysis / by Robert Galloway. Source: Wellcome Collection.

    199/272 (page 181)
    ples concentrated or dilute hydrochloric acid. W hen, how- ever, hydrobromic acid gas contains any free bromine, which it dissolves in large quantities, the liquid acid has a dark reddish colour. 457. Bromides are decomposed by chlorine, nitric and concentrated sulphuric acids, with the liberation of bromine, which communicates to the liquid a yellowish-red colour. Bromine is soluble in ether, and imparts an orange colour to starch paste. 458. To detect bromine in any compound, add an aqueous solution of chlorine gas; the bromine, being set free, will communicate a yellowish-red tint to the liquid, unless the quantity be very minute; an excess of chlorine should be avoided, since it converts the bromine into the colourless chloride of bromine. If the solution be now agitated with ether, it will remove all the bromine from the liquid, dis- solving it, and forming a yellow-coloured solution. If the ethereal solution, which has been carefully decanted or removed by a pipette, be agitated with potash, the colour will disappear, bromide of potassium and bromate of potash being formed. By evaporating this solution to dryness and igniting the residue, the bromate of potash will be con- verted into bromide of potassium. On heating the bromide along with perowide of manganese and sulphuric acid im a small retort, YELLOWISH-RED vaAPouRS will be evolved unless the quantity be very minute. These vapours, when brought in contract with starch paste, will communicate to it an ORANGE-YELLOW CoLovR, which disappears on expo- sure to the air. : 459. Solid bromides, when distilled with BICHROMATE OF POTASH and CONCENTRATED SULPHURIC ACID, yield pure bromine, which becomes colourless, or nearly so, when treated with excess of ammonia; by this means it is dis-