(3) on charcoal.  Fuses to a bead, which fumes strongly and
                         incrusts the charcoal with SbO^{3}, and
                         sometimes ZnO, which cannot be volatilized. 
                         Emits a strong smell of arsenic.

  (4) in forceps. —­

  (5) in borax.  The residue obtained on charcoal thoroughly
                         roasted gives a copper reaction, and when the
                         latter has been removed by reduction upon
                         charcoal, an iron reaction.

  (6) in mic. salt.  As in the preceding.

  (7) with carb. soda.  With this flux and a little borax yields a bead
                         of metallic copper; on silver, the alkaline mass
                         gives a sulphur reaction.

  (8) Special reactions.  If the copper bead obtained by fusing upon
                         carbonate of soda be cupelled with assay lead, a
                         silver bead will be obtained.  Or if dissolved in
                         nitric acid and a drop or two of HCl added, a
                         white precipitate of AgCl will be formed, which
                         may be collected and reduced with carbonate of
                         soda upon charcoal.

* * * * *

Mineral.  Tennatite

Formula. ([,Cu=][,Fe=])^{4}[,,,As].

Behavior

  (1) in glass-bulb.  Decrepitates occasionally and gives a red
                         sublimate of [,,,As].

  (2) in open tube.  Evolves [..S] and [...As], which condense and
                         form a white sublimate.

  (3) on charcoal.  Fuses to a magnetic bead giving of arsenical and
                         sulphurous fumes.

  (4) in forceps. —­

  (5) in borax.  As the preceding.

  (6) in mic. salt.  As the preceding.

  (7) with carb. soda.  Yields a copper bead and metallic iron in the
                         form of a dark grey powder.  The fused alkali
                         gives the sulphur reaction.

  (8) Special reactions. —­

* * * * *

Mineral.  Bournonite

Formula. ([,Pb]^{2}[,Cu=])[,,,Sb].

Behavior

  (1) in glass-bulb.  Decrepitates giving off sulfur and, when
                         strongly heated, [,,,Sb] and [...Sb].

(2) in open tube.       Evolves thick white fumes of [...Sb],[.....Sb]
and [.Pb][...Sb].  Also [.S].

  (3) on charcoal.  Fuses readily and incrusts the charcoal with
                         [...Sb] and [.Pb] leaving a dark colored bead.

  (4) in forceps. —­