Qualitative chemical analysis / by C. Remigius Fresenius.

Date:
1869
Catalogue details

Licence: Public Domain Mark

Credit: Qualitative chemical analysis / by C. Remigius Fresenius. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    of manganese, held in the flame, then dipped into powdered nitrate of potassium and heated again in the blowpipe flame, a green bead will be obtained, which becomes bluish on cooling. This reaction depends upon the formation of manganate of sodium (Na^MnOJ. It enables us to detect the smallest traces of manganese. WET REACTIONS. 3. Sulphide of ammonium throws down hydrated sulphide of manganese (MnS) in the form of a light flesh-colored precipi- tate. If the solution is very dilute, the color of the precipitate may appear yellowish white. The precipitate acquires a dark brown color in the air. It is insoluble in sulphide of ammo- nium and in alkalies; but readily soluble in hydrochloric, nitric, and acetic acids. The separation of the precipitate is mate- rially promoted by chloride of ammonium. From very dilute solutions the precipitate separates only after standing some time in a warm place. Solutions containing much free am- monia should be nearly neutralized with hydrochloric acid before precipitation with sulphide of ammonium. If ammonia and sulphide of ammonium are present in considerable excess, the flesh-colored hydrated precipitate often changes in the cold to the green anhydrous sulphide—this alteration occurs rapidly on boiling. Chloride of ammonium interferes with the conversion. 4. Potash^ produces a whitish precipitate of manganous hydrate (MnH^Og), which upon exposure to the air soon acquires a brown color from absorption of oxygen. 5. Ammonia^ produces the same precipitate. The precipi- tation is prevented by the presence of chloride of ammonium. 6. Ferrocyanide of potassium throws down manganous ferrocyanide (MugCygFe). It is reddish-white and soluble in hydrochloric acid. 7. Femcyanide of potassium precipitates manganous ferri- cyanide [Mn3(Cygre)2] as a brown body, insoluble in hydro- chloric acid and ammonia. * Non-volatile organic acids may prevent the precipitation by alkalies (or alkaline carbonates). Sugar interferes with the precipitation by alka- lies, but it does not interfere with the precipitation by alkaline carbonates.
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