Qualitative analysis / by William Briggs and R.W. Stewart.

  • William Briggs
Date:
1913
Catalogue details

Licence: Public Domain Mark

Credit: Qualitative analysis / by William Briggs and R.W. Stewart. Source: Wellcome Collection.

    141/180 (page 125)
    boil off H2S from the filtrate, and test for phosphate accord¬ ing to Test 3, page 71. Chlorate and Chloride. Divide the solution into two parts; test one part for chloride with silver nitrate (Test 1, page 59). Evaporate the other part to dryness on a water-bath and warm the residue gently with concentrated hydrochloric acid; if euchlorine (a yellow gas with characteristic odour) is given off, chlorate is indicated. Chloride, Bromide, and Iodide. (a) First remove the iodide.—Add a solution of copper sulphate and ferrous sulphate, till the hydriodic acid is completely precipitated as white cuprous iodide, Cu3I2. 2 CuS04 + 2 FeS04 + 2 KI = CuJ, + Fe2(S04)3 + k2so4. 2 CuS04 + S02 + 2 H20 + 2 KI = Cu2I2+ 2 KHS04 + H2S04 • Filter; confirm iodine in the precipitate by heating with concentrated H2S04. Violet vapours of iodine are evolved. (b) Eemove copper from the filtrate by adding excess of KOH, boiling and filtering : evaporate to dryness, mix the residue intimately with an equal amount of powdered potassium bichromate, and introduce into a small dry retort. Pour over it enough concentrated H2S04 to just cover it, and heat gently. Brown fumes, consisting of a mixture of Cr09Cl2 and bromine, distil over, and condense to a brown liquid which may be collected in a tube slipped over the neck of the retort. 4 KC1 + K„Cr207 + 3 H9S04 = 3 KoS04 + 3 PlO + 2 Cr02Cl2. 6 KBr + K2Cr207 + 7 H9S0, = 0,(80,), +'4 k2S04 + 7 H20 + 3 Br2 Add water to the distillate. The bromine dissolves as such,