_Illustrations._ Examine some oxide of lead, PbO, before the Bp. on Ch., also some oxide of cadmium, CdO. _e._ Decrepitation. _Illustration._ Examine some sodium chloride, NaCl, before the Bp. on Ch. _f._ Deflagration. _Illustrations._ Examine some potassium nitrate, KNO_{3}, before the Bp. on Ch., also some ammonium nitrate, NH_{4}NO_{3}. _g._ Intumescence. _Illustration._ Examine some alum, K_{2}Al_{2}(SO_{4})_{4}, before the Bp. on Ch. _h._ Incandescence. _Illustration._ Examine some oxide of barium, BaO, before the Bp. on Ch. _i._ Formation of a metallic bead--color and malleability. _Illustration._ Examine some silver oxide, AgO, before the Bp. on Ch. ~Examination on Charcoal with Na_{2}CO_{3}.~--Metallic compounds are often difficult to reduce with the blowpipe flame alone, and hence no bead is obtained. In order to facilitate reduction and the obtaining of a metallic bead, the substance in a finely powdered condition is mixed with four parts of sodium carbonate, Na_{2}CO_{3}, and ignited before the Bp. on Ch. The metallic compound is decomposed, the metal being transformed into the carbonate, which in turn, through the agency of the Ch. and the heat of the flame, is reduced to the free metal. Sometimes the reduction is made easier by adding to the substance about its own bulk of potassium cyanide, KCN, which takes up oxygen from the compound and is converted into potassium cyanate, KCNO. The reactions in reducing copper sulphate, CuSO_{4}, with Na_{2}CO_{3} and with KCN before the blowpipe, are here given:-- CuSO_{4} + Na_{2}CO_{3} = CuCO_{3} + Na_{2}SO_{4} } (1) 2CuCO_{3} + C = 3CO_{2} + 2Cu } CuSO_{4} + Na_{2}CO_{3} = CuCO_{3} + Na_{2}SO_{4} } CuCO_{3} = CuO + CO_{2} } (2) CuO + KCN = Cu + KCNO } After obtaining beads, it is well to obtain their coatings, for oftentimes it is only in this way that we can distinguish between the metals. ~Examination in Tube with Na_{2}CO_{3} and Charcoal.~--If the substance in a finely pulverized condition be mixed with twelve parts, Na_{2}CO_{3}, and six parts of charcoal powder and the mixture be placed in an ignition tube and subjected to heat, the acid of the substance combines with the soda and the metal is set free. If this metal is volatile, a sublimate is formed in the upper end of the tube. Mercury deposits in minute globules, which may be seen with the magnifying glass. Arsenic forms a ring, which, when examined with the magnifying glass, is seen to be made up of minute crystals. Ammonia is recognized by its characteristic odor, and also by its turning a slip of moistened red litmus (held over the mouth of the tube) blue. ~Examination on Platinum Wire.~--Many substances possess the property of imparting to the colorless flame of the Bunsen burner characteristic colors.