for:--

_a._ Whether the substance is volatile or non-volatile.

_Illustrations._ Examine before the Bp. on Ch. some arsenious oxide,
As_{2}O_{3}, also some alumina, Al_{2}O_{3}.

_b._ Whether the substance is fusible or infusible.

_Illustrations._ Examine before the Bp. on Ch. some silver oxide, AgO,
also some zinc oxide, ZnO.

_c._ Whether the substance is alkaline or non-alkaline when placed upon
moistened red litmus.

_Illustrations._ Ignite some calcium carbonate, CaCO_{3}, before the Bp.
on Ch., and place residue on moistened red litmus. In like manner,
examine some magnesium carbonate, MgCO_{3}.

_d._ Color of coating on Ch. caused by combination of metal and oxygen
due to heat of Bp. flame.

_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} +