very malleable beads. Dissolve in aqua regia, absorb the yellow solution on filter paper, and moisten with SnCl2, yields purple of Cassius. Platinum.-Reduced on charcoal splinter yields a grey spongy mass, which becomes lustrous when rubbed in the mortar. Observe insolubility in HCl and in HNO3, and solubility in aqua regia, forming a light yellow solution. Iron.-Reduced on charcoal splinter, yields no bead, but minute metallic particles. Crush the end of the splinter in an agate mortar with a little water, and stir gently with a magnetized knife-blade. The finely divided metal will adhere to the knife. Rub this off on filter-paper, dissolve in aqua regia and add K4Fe(CN): observe the blue coloration from formation of Prussian blue. Borax bead: In the oxidizing flame when hot, yellow to brownish red. Nickel.-Reduced on charcoal splinter, yields white lustrous ductile particles, which form a brush on the point of the magnetized knife-blade. Rub these on paper and dissolve in HNO,, and observe the green colour produced. Borax bead: In the oxidizing flame, greyish brown or dirty violet. Upper reducing flame, grey from reduced nickel which often collects to a spongy mass, leaving the bead colourless. Cobalt.-Reduced on charcoal splinter, yields white lustrous ductile particles, which adhere to the magnetized knife-blade. Rub these on paper and moisten with HNO3: observe the red colour, which changes to green on addition of HCl and drying; moisten with water, and observe the disappearance of the colour. Borax bead: In the oxidizing flame, bright blue, unaltered in the lower reducing flame. 60. The following metals are most easily recognized as compounds :-CHROMIUM, MANGANESE, URANIUM. Chromium.-Heated on platinum foil with Na2CO3 and with repeated additions of KNO3, yields a yellow mass soluble in water to a yellow solution. Manganese.-Borax bead amethyst-coloured in the oxidizing flame, colourless bead in the reducing flame. Heated with Na2CO, and KNO„, yields a green bead, soluble in water to a green solution, which turns red on addition of acetic acid. Uranium.-Borax bead yellow, in the oxidizing flame, which becomes green in the reducing flame, especially on addition of SnCl2. The following tests for phosphorus and sulphur compounds are exceedingly delicate : -- Phosphorus.-Ignite the sample, and then powder finely and place in a small test tube about the thickness of a straw, along with a piece of magnesium wire about five millimetres long, which should be covered by the powder. Now heat, and observe the incandescence caused by the formation of magnesium phosphide. Moisten the residue, and observe the highly characteristic smell of phosphuretted hydrogen. Sulphur. Reduced on charcoal splinter with Na,CO, yields Na,S. Break off the charcoal point, place it on a silver coin, and moisten with a drop of water. The silver is at once blackened, owing to the formation of silver sulphide. 61.-PRELIMINARY EXAMINATION OF SINGLE SALTS. Before proceeding to the systematic analysis of single salts or mixtures, it is always advantageous to subject substances to a preliminary examination, in order to ascertain the probable nature of the substance. The tables A and B, which follow, are adapted for the detection of single salts, either soluble or insoluble. TABLE A. PRELIMINARY EXAMINATION OF SINGLE SALTS CONTAINING ONE ACID AND ONE BASE. a. EXAMINATION FOR ACID." Heat the substance in a dry tube, and observe whether (a) Water is given off. If so, test its reaction with litmus paper. Acid reaction indicates Sulphites (105), † Chlorides (111), &c. Alkaline reaction indicates Ammonium Salts (91). (b) A sublimate forms Yellow (or in red globules) indicates Sulphur (60). Ammonium Salts (91). Carbonates (102). (d) The substance alters in colour. To black, indicates Organic matter, to yellow (while hot), indicates Zinc Oxide or Carbonate, to brown, indicates Cadmium Carbonate. Take a fresh portion of the substance, add HCl, and observe whether(e) A gas is evolved with effervescence. Smelling like burning sulphur indicates (Sulphites rotten eggs bitter almonds (105) or Thiosulphates (106). Sulphides (117). Cyanides (114). Peroxides, Chro mates (110), Hypochlorites (115) Carbonates (102). () Try if the substance is soluble in water; if so, add BaCl, solution to a portion of the solution, and observe if a precipitate form. White and insoluble in HCl indicates Sulphates (96). * Certain substances, not acids (e.g. mercury, sulphur, ammonia), are for convenience included here. These numbers refer to the paragraphs where the reactions of the acids and bases are to be found. White and soluble in HCl indicates Phosphates (98), Silicates (103), Oxalates (100), Borates (99), and Fluorides (101). Also Carbonates and Sulphites (see e). If BaCl, has given no precipitate, add AgNO3 to another portion of the solution, and observe if precipitate form. White and insoluble in HNO3 indicates Chlorides (111), or Yellowish-white and insoluble in HNO3 indicates Bromides Yellow and soluble in HNO3 indicates Phosphates (98). (g) If neither water nor HCl has dissolved the substance, try nitric acid; and if this does not dissolve it, try aqua regia; and if this does not dissolve it, examine the substance according to the methods described in Table B, page 58. NOTE.-Use as little acid as possible to dissolve the substance. If nitric acid or aqua regia has been used, evaporate the solution to dryness with HCl before proceeding to examine for the base. 6. EXAMINATION FOR BASE. A solution having been obtained, observe () If HCl produce a precipitate, it indicates Silver (63), Mercurous Salts (64), or Lead (65). (i) If HCl + H2S produce a precipitate, it indicates If black, Mercuric Salts (67), Lead (65), Bismuth (69), or Copper (70). If yellow, Cadmium (71), Arsenic (75), or Stannic Salts (73). If orange, Antimony (74). If brown, Stannous Salts (73). (j) If (NH4) HO + NH4Cl + (NH4)2S produce a precipitate, it indicates If black, Iron (77), Nickel (78), or Cobalt (79). If white, Zinc (80), or Aluminium (81). If flesh-coloured, Manganese (82). If green, Chromium (83). (All Chromium compounds are coloured.) (k) If (NH4) HO + NH4Cl + (NH4)2CO3 produce a precipitate, it indicates (2) If not precipitated by the above reagents, it indicates Magnesium (89), precipitated by Na2HPO4 + (NH4)HO (white). Potassium (90) (tinges flame violet). Sodium (92) ( yellow). Or Ammonium Salts (91) heated with NaHO give smell of NH3. |