Coloured analytical tables : showing the behaviour of the more common metals and acids to the ordinary reagents, with special reference to the colour of the various oxides, salts, precipitates, flames, borax-beads, and blowpipe reactions a class-book for students in hospitals, colleges and schools / by H. Wilson Hake.

  • Hake, H. Wilson (Henry Wilson), 1857-1930
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Coloured analytical tables : showing the behaviour of the more common metals and acids to the ordinary reagents, with special reference to the colour of the various oxides, salts, precipitates, flames, borax-beads, and blowpipe reactions a class-book for students in hospitals, colleges and schools / by H. Wilson Hake. Source: Wellcome Collection.

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    PAKT II.—Detection of some simple Acid-Eadicles, Oxides, and some Organic Substances. The following tests must be made in the order here laid down, and a fresh portion taken for each test. If the substance is insoluble, test for the various acids in the same order, using the special tests mentioned where practicable. Ignite a portion of the solid substance (if a solution evaporate a few drops to obtain the solid). Salts of inorganic acids do not blacken on ignition (A, B, C). Salts of organic acids blacken on ignition {except oxalates and cyanides) and leave a residue {except ammonium, salts); free organic acids and purely organic substances blacken on ignition and finally burn away entirely (Dj E). To the solution add, A. Barium chloride (BaCl2) *, a precipitate indicates :— 1. Sulphates.—S04; white precipitate (BaS04), insoluble in hydrochloric acid, even on boiling. N.B.—Insoluble sulphates. BaS04 and PbS04 are insoluble, and may be detected by conversion into their corresponding sulphides (BaS and PbS) by beating with sodium carbonate (NaC03) on charcoal. (See Sulphides.) The metals may be detected by their blowpipe reactions. 2. Carbonates.—C03; white precipitate (BaC03), soluble in hydrochloric acid and acetic acid with effervescence, due to evolution of carbonic anhy- dride (C0o), which gas turns lime-water milky. N.B.—Insoluble carbonates. All the carbonates, except K._,CO;J, Na2C03, and Am2C03, are insoluble in water; they are dissolved by acids, with effervescence (see above). 3. Phosphates.—P04; white precipitate [BaIIP04 or Ba3(PO,)2], soluble in hydrochloric acid and in acotic acid. N.B.—A solution of a phosphate also yields, when added to a solution of ammonium molybdato strongly acidified with nitric acid, a yellow preci- pitate of ammonic molybdo-phosphate on heating; or if to a solution of a phosphate be added a clear mixture of magnesium sulphate, ammonium chloride and ammonia, a white precipitate (AmMgP04) results. Insoluble phosphates. All the phosphates, except those of the alkalies, are insoluble in water but easily soluble in an acid. The phosphates of Ba, Sr, Ca, and Mg are, when dissolved in an acid, precipitated white by ammonia in the ammonium sulphide group. In the case of the first three, the flames may be used to detect the metals, or the acid solution may be made neutral with ammonia, and then acid with acetic acid, ferric chloride added, and the solu- tion boiled, whereupon ferric phosphate (FeP04) is precipitated; this may be separated by filtration; the metals, remaining in solution as chlorides, may be tested for in the ordinary way, and the phosphoric acid may be detected in the original acid solution by means of the molybdate test. 4. Oxalates.—C204 ; white precipitate (BaC204), soluble in hydrochloric acid, insoluble in acetic acid. N.B.—Oxalates and free oxalic acid do not always blacken on heating. A solution of an oxalate or free oxnlic acid, or a solid or insoluble oxalate, evolves carbonic anhydride (C02) with pure dioxide of manganese (MnO,) and dilute sulphuric acid, indicated by a brisk effervescence; the gas evolved turns lime-water milky. Solid oxalates and free oxalic acid yield with strong sulphuric acid on heating a mixture of carbonic oxide (CO), which may be ignited at the top of the test-tube and burns with a blue flame, and carbonic anhydride (CO,), which turns lime-water milky. Insoluble oxalates. Most of the oxalates are insoluble in water except those of the alkalies; the rest are soluble in mineral acids. The oxalates of Ba, Sr, Ca, and Mg are insoluble in water and are precipitated white from an acid solution by ammonia in the ammonium-sulphide group. The first three metals may be detected by their flames and the Mg by the blowpipe test; the dioxide of manganese test will detect the oxalic acid; or dissolve the ammonia precipitate in dilute hydrochloric acid and add acetate of soda in excess, a white precipitate indicates oxalic acid. * Or if Ag, Pb, or Ilg' are present add barium nitrate [Ba(N03)2].