Reactions before the Blowpipe.—­Metallic tin melts easily.  It is covered in the flame of oxidation into a yellowish-white oxide, which is carried off sometimes by the stream of air which propels the flame.  In the reduction flame, and upon charcoal, melting tin retains its metallic lustre, while a thin sublimate is produced upon the charcoal.  This sublimate is light-yellow while hot, and gives a strong light in the flame of oxidation, and turns white while cooling.  This sublimate is found near to the metal, and cannot be volatilized in the oxidation flame.  In the flame of reduction it is reduced to metallic tin.  Sometimes this incrustation is so imperceptible that it can scarcely be distinguished from the ashes of the charcoal.  If such be the case, moisten it with a solution of cobalt, and expose it to the flame of oxidation, when the sublimate will exhibit, after cooling, a bluish-green color.

Protoxide of tin takes fire in the flame of oxidation, and burns with flame and some white vapor into tin acid, or stannic acid.  In a strong and continued reduction flame, it may be reduced to metal, when the same sublimate above mentioned is visible.  The sesquioxide of tin behaves as the above.

Stannic acid, heated in the flame of oxidation, does not melt and is not volatilized, but produces a strong light, and appears yellowish while hot, but changing as it cools to a dirty-yellow white color.  In a strong and continued flame of reduction, it may be reduced likewise to the metallic state, with the production of the same sublimate as the above.

Borax dissolves tin compounds in the flame of oxidation, and upon platinum wire, very tardily, and in small quantity, to a transparent colorless bead, which remains clear after cooling, and also when heated intermittingly.  But if a saturated bead, after being completely cool, is exposed again to the flame of oxidation, at a low red heat, the bead while cooling is opaque, loses its globular form, and exhibits an indistinct crystallization.  This is the case too in the flame of reduction, but if the bead is highly saturated, a part of the oxide is reduced.

Microcosmic Salt dissolves the oxides in the flame of reduction very tardily in a small quantity to a transparent colorless bead, which remains clear while cooling.  If to this bead sesquioxide of iron is added in proper proportion, the sesquioxide loses its property of coloring the bead, but of course an excess of the iron salt will communicate to the bead its own characteristic color.  In the flame of reduction no further alteration is visible.

Tin-oxides combine with carbonate of soda, in the flame of oxidation upon platinum wire, with intumescence to a bulky and confused mass, which is insoluble in more soda.  Upon charcoal, in the reduction flame, it is easily reduced to a metallic globule.  Certain compounds of tin-oxides, particularly if they contain tantalum, are by fusion with carbonate of soda reduced with difficulty; but by the addition of some borax, the reduction to the metallic state is easily effected.