Qualitative chemical analysis and laboratory practice / by T.E. Thorpe and M.M. Pattison Muir.

  • Thomas Edward Thorpe
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: Qualitative chemical analysis and laboratory practice / by T.E. Thorpe and M.M. Pattison Muir. Source: Wellcome Collection.

    176/273 (page 154)
    V. Acetic Acid (HC2H3O2).—A solution of sodium acetate in water is used. (a) Ferric chloride in neutral solutions produces a deep blood-red colour. This solution, on addition of hydro- chloric acid, turns yellow', and may be thus distinguished from ferric thiocyanate. On boiling the red solution, all the iron is precipitated as a basic acetate, the liquid be- coming colourless, provided the iron be not in excess. (li) Dry acetates, heated with arsenious oxide, yield the very foully-smelling poisonous cacodyl oxide [As(CH3).2]20. {c) With silver nitrate a white precipitate of silver acetate (AgC2H302) is formed in cone, solutions. (4) 'J’reatcd with cone, sulphuric acid and alcohol, the characteristic fruity smell of ethyl acetate (C2H5.C2H3O2) is perceived. VI. hoRMic Acid (HCHO2).—Sodium formate dissolved in water is used. {a) With ferric chloride the formates behave like the acetates. {b) Heated with silver nitrate, a precipitate of metallic silver is produced. Silver formate is first produced this is then reduced to metallic silver (2AgCH02 = 2Ag + CO2 + MCHO2). {c) Mercuric chloride on gently warming produces a white precipitate of mercurous chloride. VII. Ferrocyanic Acid —H^FeCaNc —and Ferro- CYANiDES.—A solution of potassium ferrocyanide is used. {a) Silver nitrate precipitates white silver ferroc}'anide (■^S4^^^C6N6), insoluble in nitric acid and in ammonia, but soluble in potassium cyanide. {h) Ferric chloride jDroduces a dark greenish-blue pre- cipitate of ferric ferrocyanide, Fe4(FeC6N6)3 (Prussian blue), insoluble in dilute acids, but decomposed by caustic potash or soda, w'ith separation of ferric hydrate and formation of an alkaline ferrocyanide.