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A System of Instruction in the Practical Use of the Blowpipe by Anonymous

A >> Anonymous >> A System of Instruction in the Practical Use of the Blowpipe




If alcohol is poured over lime or its compounds and inflamed, a red
color is communicated to the flame. The presence of baryta or soda
prevents this reaction. Lime and its compounds do not dissolve much by
fusion with carbonate of soda. If this fusion is effected on charcoal,
the carbonate of soda is absorbed and the lime remains as a
half-globular infusible mass on the charcoal. This is what
distinguishes lime from baryta and strontia, and is a good method of
separating the former from the latter. Lime and its compounds fuse
with borax in the oxidizing and reducing flames to a clear bead, which
remains clear when cold, but when overcharged with an excess or heated
intermittingly, the bead appears, when cold, crystalline and uneven,
and is not so milk-white as the bead of baryta or strontia, produced
under the same circumstances. The carbonate of lime is dissolved with
a peculiar hissing noise. Microcosmic salt dissolves a large quantity
of lime into a clear bead, which is milky when cold. When the bead has
been overcharged with lime, by a less excess, or by an intermittent
flame, we will perceive in the bead, when cold, fine crystals in the
form of needles. Lime and its compounds form by ignition with nitrate
of cobalt, a black or greyish-black infusible mass.

(_d._) _Magnesia_ (MgO).--Magnesia occurs in nature in several
minerals. It exists in considerable quantity combined with carbonic,
sulphuric, phosphoric, and silicic acids, etc. Magnesia and its
hydrate are white and very voluminous, scarcely soluble in hot or cold
water, and restores moistened red litmus paper to its original blue
color. Magnesia and its hydrate are infusible, the latter losing its
water by ignition. The carbonate of magnesia is infusible, loses its
carbonic acid at a red heat, and shrinks a little. It now exerts upon
red litmus paper an alkaline reaction. The sulphate of magnesia, at a
red heat, loses its water and sulphuric acid, is entirely infusible,
and gives now an alkaline reaction. The artificial Astrachanit (NaO,
SO^{3} + MgO, SO^{3} + 4HO) fuses easily. When fused on charcoal, the
greater part of the sulphate of soda is absorbed, and there remains an
infusible mass.

Magnesia and its compounds do not produce any color in the external
flame, when heated in the point of the blue flame. The most of the
magnesia minerals yield some water when heated in a glass tube closed
at one end.

Magnesia, in the pure state, or as the hydrate, does not fuse with
soda. Some of its compounds are infusible likewise with soda, and
swell up slightly, while others of them melt with soda to a slightly
opaque mass. Some few (such as the borate of magnesia) give a clear
bead with soda, though it becomes slightly turbid by cooling when
saturated with magnesia, and crystallizes in large facets.

Magnesia and its compounds give beads with borax and microcosmic salt
similar to those of lime. By igniting magnesia or its compounds very
strongly in the oxidizing flame, moistening with nitrate of cobalt,
and re-igniting in the oxidation flame, they present, after a
continued blowing, a pale flesh-color, which is more visible when
cold. It is indispensable that the magnesia compounds should be
completely white and free of colored substances, or the color referred
to cannot be discerned. In general the reactions of magnesia before
the blowpipe are not sufficient, and it will be necessary to confirm
its presence or absence by aid of reagents applied in the wet way.


THIRD GROUP.--THE EARTHS, ALUMINA, GLUCINA, YTTRIA, THORINA, AND
ZIRCONIA.

The substances of this group are distinguished from the preceding by
their insolubility in water, in their pure or hydrated state--that
they have no alkaline reaction upon litmus paper, nor form salts with
carbonic acid. The earths are not volatile, and, in the pure state,
are infusible. They cannot be reduced to the metallic state before the
blowpipe. The organic salts are destroyed by ignition, while the
earths are left in the pure state, mixed with charcoal, from the
organic acids. The most of their neutral salts are insoluble in water;
the soluble neutral salts change blue litmus paper to red, and lose
their acids when ignited.

(_a._) _Alumina_ (Al^{2}O^{3}).--This earth is one of our most common
minerals. It occurs free in nature in many minerals, as sapphire,
etc.; or in combination with sulphuric acid, phosphoric acid, and
fluorine, and chiefly silicates. Pure alumina is a white crystalline
powder, or yellowish-white, and amorphous when produced by drying the
hydrate, separated chemically from its salts. Alumina is quite
unalterable in the fire; the hydrate, however, losing its water at a
low red heat. The neutral salts of alumina, with most acids, are
insoluble in water. Those soluble in it have an acid reaction upon
litmus paper, changing the blue into red.

The sulphates of alumina eliminate water when heated in a glass tube
closed at one end. By ignition, sulphurous acid (SO^{2}) is given off,
which can be recognized by its smell, and by its acid reaction upon
blue litmus paper, when a small strip of it moistened is brought
within the orifice of the tube; an infusible residue is left in the
tube.

The greater part of the alumina compounds give off water with heat;
the most of them are also infusible, except a few phosphates and
silicates.

Pure alumina does not fuse with carbonate of soda. The sulphates, when
exposed upon charcoal with soda to the reducing flame, leave a hepatic
residue. The phosphates melt with a little soda, with a hissing noise,
to a semi-transparent mass, but they are infusible with the addition
of soda, and give only a tough mass. This is the case, likewise, with
the silicates of alumina. Fluoride of aluminium melts with carbonate
of soda to a clear bead, spreads by cooling, and appears then
milk-white. Borax dissolves the alumina compounds slowly in the
oxidizing and reducing flames to a clear bead, which is also clear
when cold, or heated intermittingly with a vacillating flame. The bead
is turbid, as well in the heat as the cold, when an excess of alumina
is present. When the alumina compound is added to excess in the
powdered form, the bead appears crystalline upon cooling, and melts
again with great difficulty.

Alumina and its compounds are slowly dissolved in the microcosmic salt
to a bead, clear in both flames, and when hot or cold. When alumina is
added to excess, the undissolved portion appears semi-transparent.
Alumina melts with bisulphate of potash into a mass soluble in water.
When the powdered alumina compounds are strongly ignited in the
oxidizing flame, then moistened with nitrate of cobalt, and re-ignited
in the oxidizing flame, an infusible mass is left, which appears, when
cooled, of an intense blue color. The presence of colored metallic
oxides, in considerable quantity, will alter or suppress this
reaction. The silicates of the alkalies produce, in a very strong
heat, or continued heat, with nitrate of cobalt, a pale blue color.
The blue color produced by alumina is only distinctly visible by
daylight; by candle-light it appears of a dirty violet color.

(_b._) _Glucina._ (G^{2}O^{3}).--Glucina only occurs in a few rare
minerals, in combination with silica and alumina. It is white and
insoluble in the pure state, and its properties generally are similar
to those of alumina. The most of its compounds are infusible, and
yield water by distillation. Carbonate of soda does not dissolve
glucina by ignition. Silicate of glucina melts with carbonate of soda
to a colorless globule. Borax and microcosmic salt dissolve glucina
and its compounds to a colorless bead which, when overcharged with
glucina, or heated with the intermittent flame appears, after cooling,
turbid or milk-white. Glucina yields, by ignition with nitrate of
cobalt, a black, or dark grey infusible mass.

(_c._) _Yttria_ (YO) occurs only in a few rare minerals, and usually
in company with terbium and erbium. Its reactions before the blowpipe
are similar to the preceding, but for its detection in compounds it
will be necessary to resort to analysis in the wet way.

(_d._) _Zirconia_ (Zr^{2}O^{3}).--This substance resembles alumina in
appearance, though it occurs only in a few rare minerals. It is in the
pure state infusible, and at a red heat produces such a splendid and
vivid white light that the eyes can scarcely endure it. Its other
reactions before the blowpipe are analogous to glucina. Microcosmic
salt does not dissolve so much zirconia as glucina, and is more prone
to give a turbid bead. Zirconia yields with nitrate of cobalt, when
ignited, an infusible black mass. To recognize zirconia in compounds
we must resort to fluid analysis.

(_e._) _Thorina_ (ThO).--This is the rarest among the rare minerals.
In the pure state it is white and infusible, and will not melt with
the carbonate of soda. Borax dissolves thorina slowly to a colorless,
transparent bead, which will remain so when heated with the
intermittent flame. If overcharged with the thorina, the bead
presents, on cooling, a milky hue. Microcosmic salt dissolves the
thorina very tardily. By ignition with nitrate of cobalt, thorina is
converted into an infusible black mass,


CLASS II.


FOURTH GROUP. CERIUM, LANTHANIUM, DIDYMIUM, COLUMBIUM, NIOBIUM,
PELOPIUM, TITANIUM, URANIUM, VANADIUM, CHROMIUM, MANGANESE.

The substances of this group cannot be reduced to the metallic state,
neither by heating them _per se_, nor by fusing them with reagents.
They give by fusion with borax or microcosmic salt, colored beads,
while the preceding groups give colorless beads.

(_a._) _Cerium_ (Ce).--This metal occurs in the oxidated state in a
few rare minerals, and is associated with lanthanium and didymium,
combined with fluorine, phosphoric acid, carbonic acid, silica, etc.
When reduced artificially, it forms a grey metallic powder.

(_a._) _Protoxide of Cerium_ (CeO).--It exists in the pure state as
the hydrate, and is of a white color. It soon oxidizes and becomes
yellow, when placed in contact with the air. When heated in the
oxidation flame, it is converted into the sesquioxide, and then is
changed into light brick-red color. In the oxidation flame it is
dissolved by borax into a clear bead, which appears of an orange or
red while hot, but becomes yellow upon cooling. When highly saturated
with the metal, or when heated with a fluctuating flame, the bead
appears enamelled as when cold. In the reduction flame it is dissolved
by borax to a clear yellow bead, which is colorless when cold. If too
much of the metal exists in the bead, it then appears enamelled when
cooled.

Microcosmic salt dissolves it, in the oxidation flame, to a clear
bead, which is colored dark yellow or orange, but loses its color when
cold. In the reduction flame the bead is colorless when either hot or
cold. Even if highly saturated with the metal, the bead remains
colorless when cold. By fusing it with carbonate of soda upon charcoal
in the reduction flame, the soda is absorbed by the charcoal, while
the protoxide of the metal remains as a light grey powder.

(_B._) _Sesquioxide of Cerium_ (Ce^{2}O^{3}).--This oxide, in the pure
state, is a red powder. When heated with hydrochloric acid, it
produces chlorine gas, and is dissolved to a salt of the protoxide. It
is not affected by either the flame of oxidation or of reduction; when
fused with borax or microcosmic salt, it acts like the protoxide. It
does not fuse with soda upon charcoal. In the reduction flame it is
reduced to the protoxide, which remains of a light grey color, while
the soda is absorbed by the charcoal.

(_b._) _Lanthanium_ (La.)--This metal is invariably associated with
cerium. It presents, in its metallic state, a dark grey powder, which
by compression acquires the metallic lustre.

The _oxide of lanthanium_ (LaO) is white, and its salts are colorless.
Heated upon charcoal, it does not change either in the oxidation flame
or that of reduction. With borax, in the flame of oxidation or
reduction, it gives a clear colorless bead. This bead, if saturated,
and when hot, presents a yellow appearance, but is clouded or
enamelled when cold. With microcosmic salt the same appearance is
indicated. It does not fuse with carbonate of soda, but the soda is
absorbed by the charcoal, while the oxide remains of a grey color.

(_c._) _Didymium_ (D).--This metal occurs only in combination with the
preceding ones, and it is therefore, like them, a rare one.

_Oxide of Didymium_ (DO).--This oxide is of a brown color, while its
salts present a reddish-violet or amethyst color. The oxide is
infusible in the oxidation flame, and in that of reduction it loses
its brown color and changes to grey. With borax in the oxidation
flame, it fuses to a clear dark red or violet bead, which retains its
clearness when highly saturated with the oxide, or if heated with a
fluctuating flame.

The reactions with microcosmic salt are the same as with borax.

It does not melt with carbonate of soda upon charcoal, but the oxide
remains with a grey color, while the soda is absorbed by the charcoal.

(_d._) _Columbium,_ (_Tantalum_--Ta).--This rare metal occurs quite
sparingly in the minerals _tantalite_, _yttrotantalite_, etc., as
columbic acid. In the metallic state, it presents the appearance of a
black powder, which, when compressed, exhibits the metallic lustre.
When heated in the air it is oxidized into columbic acid, and is only
soluble in hydrofluoric acid, yielding hydrogen. It is oxidized by
fusion with carbonate of soda or potash.

_Columbic Acid_ (Ta^{2}O^{3}) is a white powder, and is infusible.
When heated in the flame of oxidation or reduction, it appears of a
light yellow while hot, but becomes colorless when cold. With borax,
in the flames of oxidation and reduction, it fuses to a clear bead,
which appears by a certain degree of saturation, of a yellow color so
long as it continues hot, but becomes colorless when cold. If
overcharged, or heated with an intermittent flame, it presents an
enamel white when cool.

It melts with microcosmic salt quite readily in both of the flames, to
a clear bead, which appears, if a considerable quantity of columbic
acid be present, of a yellow color while hot, but colorless when cold,
and does not become clouded if the intermittent flame be applied to
it.

With carbonate of soda it fuses with effervescence to a bead which
spreads over the charcoal. Melted with more soda, it becomes absorbed
by the charcoal.

It yields, moistened with a solution of nitrate of cobalt, and exposed
to the oxidation flame after continued blowing, an infusible mass,
presenting while hot a light grey color, but after being cooled that
of a light red, similar to the color presented by magnesia under the
same circumstances. But if there be some alkali mixed with it, a
fusion at the edges will be manifest, and it will yield by cooling a
bluish-black mass.

(_e._) _Niobium_ (Ni).--This metal occurs as niobic acid in columbite
(tantalite). Niobic acid is in its properties similar to columbic
acid. It is white and infusible. By heating it either in the flames of
reduction or oxidation, it presents as long as it continues hot, a
greenish-yellow color, but becomes white when cool. Borax dissolves it
in the oxidation flame quite readily to a clear bead, which, with a
considerable quantity of niobic acid, is yellow when hot, but
transparent and colorless when cold. A saturated bead is clear when
either hot or cold, but becomes opaque when heated intermittingly.

In the flame of reduction, borax is capable of dissolving more of the
niobic acid, so that a bead overcharged and opaque in the oxidation
flame appears quite clear when heated in the flame of reduction. A
bead overcharged in the flame of reduction, appears by cooling dim and
bluish-grey.

Microcosmic salt dissolves in the flame of oxidation a great quantity
of it to a clear bead, which is yellow while hot, but colorless when
cold.

In the flame of reduction, and in presence of a considerable quantity
of niobic acid, the bead appears while hot of a light dirty blue
color, and when cold, of a violet hue; but by the addition of more
niobic acid, the bead, when hot, is of a dirty dark blue color, and
when cold, of a transparent blue. In the presence of the oxides of
iron, the bead is, while hot, of a brownish-red color, but changing
when cool to a dark yellow.

This acid fuses with an equal quantity of carbonate of soda upon
charcoal, to a bead which spreads very quickly, and is then infusible.
When fused with still more soda, it is absorbed.

When moistened with nitrate of cobalt, and heated in the flame of
oxidation, it yields an infusible mass which appears grey when hot,
and dirty green when cold; but if the heat has been too strong, it is
fused a little at the edges, which present a dark bluish-grey color.

_Pelopium_ (Pe).--This metal occurs as an acid in the mineral
columbite (tantalite), and is very similar to the two preceding
metals.

(_f._) _Pelopic Acid_ (PeO^{3}).--This acid is white, and appears
yellow when heated, but resumes its white color when cold. Borax
dissolves it in the oxidation flame to a clear colorless bead, which
appears, when overcharged and heated intermittingly, enamel-white when
cold. This is likewise the case in the flame of reduction, but when
overcharged the color is light grey, when the bead is cooled.

Microcosmic salt dissolves it in the flame of oxidation, to a clear
yellow bead, which loses its color when cold. In the reduction flame,
when the bead is highly saturated, a violet-brown color is produced.
In presence of the oxides of iron, the reactions are like those of
niobic acid. With carbonate of soda, the reactions are similar to
those of niobic acid. By heating with nitrate of cobalt, it yields a
light grey infusible mass.

(_g._) _Titanium_ (Ti).--This metal occurs occasionally in the slags
of iron works, in the metallic state, as small cubical crystals of a
red color. It is a very hard metal, and very infusible. Titanic acid
occurs in nature crystallized in _anatase_, _arkansite_, _brookite_,
and _rutile_. Titanium is harder than agate, entirely infusible, and
loses only a little of its lustre, which can be regained by fusion
with borax. It does not melt with carbonate of soda, borax, or
microcosmic salt, and is insoluble in every acid except the
hydrofluoric. By ignition with saltpetre it is converted into titanic
acid, which combines with the potassium, forming the titanate of
potassium.

_Titanic Acid_ (TiO^{2}) is white, insoluble, and, when heated, it
appears yellow while hot, but resumes upon cooling its white color.

Borax dissolves it in the oxidation flame to a clear yellow bead,
which when cool is colorless. When overcharged, or heated with the
intermitting flame, it is enamel-white after being cooled. In the
reduction flame, the bead appears yellow, if the acid exists in small
quantity, but if more be added, then it is of an orange, or dark
yellow, or even brown. The saturated bead, when heated intermittingly,
appears when cold of an enamelled blue. By addition of the acid, and
by heating the bead on charcoal in the reduction flame, it becomes
dark yellow while hot, but dark blue, or black and opaque when cold.
This bead appears, when heated intermittingly, of a light blue, and
when cold, enamelled.

Microcosmic salt fuses with it in the oxidation flame to a clear
colorless bead, which appears yellow only in the presence of a
quantity of titanic acid, though by cooling it loses its color. In the
reduction flame this bead exhibits a yellow color when hot, but is red
while cooling, and when cold of a beautiful bluish-violet. If the bead
is overcharged, the color becomes so dark that the bead appears
opaque, though not presenting an enamel appearance. By heating the
bead again in the oxidation flame the color disappears. The addition
of some tin promotes the reduction. If the titanic acid contains oxide
of iron, or if some is added, the bead appears, when cold,
brownish-yellow, or brownish-red.

By fusion with carbonate of soda, titanic acid is dissolved with
effervescence to a clear dark yellow bead, which crystallizes by
cooling, whereby so much heat is eliminated, that the bead, at the
instant of its crystallization, glows with great brightness. A
reduction to a metal cannot, however, be effected. By ignition with a
solution of nitrate of cobalt in the oxidation flame, it yields an
infusible yellowish-green mass.

(_h._) _Uranium_ (U).--This rare metal occurs in the form of protoxide
along with other oxides, in the mineral _pitch-blende_; as peroxide in
_uranite_ and _uran-mica_, associated with phosphoric acid and lime.

In the metallic state it presents the appearance of a dark grey mass,
which is infusible, and remains unchanged when under water, or when
exposed to dry air, but, when heated in the oxidation flame, it
becomes oxidized, with lively sparkling, to a dark green mass,
composed of the protoxide and peroxide.

The _protoxide of uranium_ (UO) is black, uncrystalline, or forms a
brown powder. When exposed to heat it is converted partially into
peroxide, when it has a dark green color.

The _peroxide of uranium_ (U^{2}O^{3}) is of an orange color, while
its hydrate is of a fine yellow color, and in the form of a powder.
The salts are yellow.

By heating it in the oxidation flame, it acquires a dark green color,
and is partly reduced to protoxide. In the reduction flame it presents
a black appearance, and is there completely reduced to protoxide.

Borax dissolves it in the oxidation flame to a clear dark yellow bead,
which is colorless when cold, if the metal is not present in great
quantity. If more of the metal, or peroxide, be added, the bead
changes to orange when hot, and light yellow when cold. When heated
with the intermittent flame, it requires a large quantity of the
peroxide to produce an enamel appearance in the cooled bead.

In the flame of reduction the bead becomes of a dirty green color,
being partly reduced to protoxide, and appears, with a certain degree
of saturation, black, when heated intermittingly, but never enamelled.
The bead appears on charcoal, and with the addition of tin, of a dark
green color.

It fuses with microcosmic salt in the oxidation flame to a clear
yellow bead, which is greenish-yellow when cold. In the reduction
flame it produces a beautiful green bead, which increases when cold.

When fused upon charcoal with the addition of tin, its color is
darker. Carbonate of soda does not dissolve it, although with a very
small portion of soda it gives indications of fusion, but with still
more of the soda it forms a yellow, or light-brown mass, which is
absorbed by the charcoal, but it is not reduced to the metallic state.

(_i._) _Vanadium_ (V).--This very rare mineral is found in small
quantity in iron-ores, in Sweden, and as vanadic acid in a few rare
minerals. The metal presents the appearance of an iron-grey powder,
and sometimes that of a silver-white mass. It is not oxidized either
by air or water, and is infusible.

_Vanadic Acid_ (VO^{3}) fuses upon platinum foil to a deep orange
liquid, which becomes crystalline after cooling. When fused upon
charcoal, one part of it is absorbed, while the rest remains upon the
charcoal and is reduced to protoxide similar in appearance to
graphite.

A small portion of it fuses with borax in the oxidation flame to a
clear colorless bead, which appears, with the addition of more vanadic
acid, of a yellow color, but changes to green when cold.

In the reduction flame the bead is brown while hot, but changes, upon
cooling, to a beautiful sapphire-green. At the moment of
crystallization, and at a degree of heat by which at daylight no
glowing of the heated mass is visible it begins to glow again. The
glow spreads from the periphery to the centre of the mass, and is
caused by the heat liberated by the sudden crystallization of the
mass. It now exhibits an orange color, and is composed of needle
crystals in a compact mass.

Microcosmic salt and vanadic acid fuse in the oxidation flame to a
dark yellow bead which, upon cooling, loses much of its color.

In the reduction flame the bead is brown while hot, but, upon cooling,
acquires a beautiful green color.

Vanadic acid fuses with carbonate of soda upon charcoal, and is
absorbed.

(_k._) _Chromium_ (Cr) occurs in the metallic state only in a very
small quantity in meteoric iron, but is frequently found in union with
oxygen, as oxide in chrome iron ore, and as chromic acid in some lead
ores.

In the metallic state it is of a light grey color, with but little
metallic lustre, very hard, and not very fusible. Acids do not act
upon it, except the hydrofluoric; fused with nitre, it forms chromate
of potassa. It is unaltered in the blowpipe flame.

_Sesquioxide of Chromium_ (Cr^{2}O^{3}).--This oxide forms black
crystals of great hardness, and is sometimes seen as a green powder.
Its hydrate (Cr^{2}O^{3} + 6HO) is of a bluish-grey color. It forms
with acids two classes of isomeric salts, some of which are of a
green color, and the others violet-red or amethyst. The neutral and
soluble salts have an acid reaction upon blue litmus paper, and are
decomposed by ignition.

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