Special Reactions, 109
A.--METALLIC OXIDES:
First Group.--The Alkalies: Potassa, Soda, Ammonia, and Lithia, 110
Second Group.--The Alkaline Earths: Baryta, Strontia, Lime,
and Magnesia, 115
Third Group.--The Earths: Alumina, Glucina, Yttria, Thorina,
and Zirconia, 121
Fourth Group.--Cerium, Lanthanium, Didymium, Columbium,
Niobium, Pelopium, Titanium, Uranium, Vanadium, Chromium,
Manganese, 124
Fifth Group.--Iron, Cobalt, Nickel, 135
Sixth Group.--Zinc, Cadmium, Antimony, Tellurium, 140
Seventh Group.--Lead, Bismuth, Tin, 149
Eighth Group.--Mercury, Arsenic, 157
Ninth Group.--Copper, Silver, Gold, 161
Tenth Group.--Molybdenum, Osmium, 165
Eleventh Group.--Platinum, Palladium, Iridium, Rhodium,
Ruthenium, 167
Non-Metallic Substances, 168
Tabular Statement of the Reactions of Minerals before
the Blowpipe, 178
Carbon and Organic Minerals, 181
Potassa, 184
Soda, 186
Baryta and Strontia, 190
Lime, 192
Magnesia, 196
Alumina, 200
Silicates, 204
Uranium, 212
Iron, 214
Manganese, 222
Nickel and Cobalt, 226
Zinc, 232
Bismuth, 234
Lead, 238
Copper, 248
Antimony, 256
Arsenic, 260
Mercury, 262
Silver, 264
* * * * *
PREFACE.
It is believed the arrangement of the present work is superior to that
of many of its predecessors, as a vehicle for the facilitation of the
student's progress. While it does not pretend to any other rank than
as an introduction to the larger works, it is hoped that the
arrangement of its matter is such that the beginner may more readily
comprehend the entire subject of Blowpipe Analysis than if he were to
begin his studies by the perusal of the more copious works of
Berzelius and Plattner.
When the student shall have gone through these pages, and repeated the
various reactions described, then he will be fully prepared to enter
upon the study of the larger works. To progress through them will then
be but a comparatively easy task.
The arrangement of this little work has been such as the author and
his friends have considered the best that could be devised for the
purpose of facilitating the progress of the student. Whether we have
succeeded is left for the public to decide. The author is indebted to
several of his friends for valuable contributions and suggestions.
S.
CINCINNATI, _June, 1857_.
* * * * *
THE BLOWPIPE.
* * * * *
Part First.
THE USE OF THE BLOWPIPE.
Perhaps during the last fifty years, no department of chemistry has
been so enriched as that relating to analysis by means of the
Blowpipe.
Through the unwearied exertions of men of science, the use of this
instrument has arrived to such a degree of perfection, that we have a
right to term its use, "Analysis in the _dry_ way," in contradistinction
to analysis "in the _wet_ way." The manipulations are so simple and
expeditious, and the results so clear and characteristic, that the
Blowpipe analysis not only verifies and completes the results of
analysis in the wet way, but it gives in many cases direct evidences
of the presence or absence of many substances, which would not be
otherwise detected, but through a troublesome and tedious process,
involving both prolixity and time; for instance, the detection of
manganese in minerals.
Many substances have to go through Blowpipe manipulations before they
can be submitted to an analysis in the wet way. The apparatus and
reagents employed are compendious and small in number, so that they
can be carried easily while on scientific excursions, a considerable
advantage for mineralogists and metallurgists.
The principal operations with the Blowpipe may be explained briefly as
follows:
(_a._) By _Ignition_ is meant the exposure of a substance to such a
degree of heat, that it glows or emits light, or becomes red-hot. Its
greatest value is in the separation of a volatile substance from one
less volatile, or one which is entirely fixed at the temperature of
the flame. In this case we only take cognizance of the latter or fixed
substance, although in many instances we make use of ignition for the
purpose of changing the conditions of a substance, for example, the
sesquioxide of chromium (Cr^{2}O^{3}) in its insoluble modification;
and as a preliminary examination for the purpose of ascertaining
whether the subject of inquiry be a combination of an organic or
inorganic nature.
The apparatus used for this purpose are crucibles of platinum or
silver, platinum foil, a platinum spoon, platinum wire or tongs,
charcoal, glass tubes, and iron spoons.
(_b._) _Sublimation_ is that process by which we convert a solid
substance into vapor by means of a strong heat. These vapors are
condensed by refrigeration into the solid form. It may be termed a
distillation of a solid substance. Sublimation is of great consequence
in the detection of many substances; for instance, arsenic, antimony,
mercury, etc.
The apparatus used for the purposes of sublimation consist of glass
tubes closed at one end.
(_c._) _Fusion._--Many substances when exposed to a certain degree of
heat lose their solid form, and are converted into a liquid. Those
substances which do not become converted into the liquid state by
heat, are said to be infusible. It is a convenient classification to
arrange substances into those which are fusible with difficulty, and
those which are easily fusible. Very often we resort to fusion for the
purpose of decomposing a substance, or to cause it to enter into
other combinations, by which means it is the more readily detected. If
insoluble substances are fused with others more fusible (reagents) for
the purpose of causing a combination which is soluble in water and
acids, the operation is termed _unclosing_. These substances are
particularly the silicates and the sulphates of the alkaline earths.
The usual reagents resorted to for this purpose are carbonate of soda
(NaO, CO^{2}), carbonate of potash (KO, CO^{2}), or still better, a
mixture of the two in equal parts. In some cases we use the hydrate of
barytes (BaO, HO) and the bisulphate of potash (KO, 2SO^{3}). The
platinum spoon is generally used for this manipulation.
Substances are exposed to fusion for the purpose of getting a new
combination which has such distinctive characteristics that we can
class it under a certain group; or for the purpose of ascertaining at
once what the substance may be. The reagents used for this purpose are
borax (NaO, 2BrO^{3}) and the microcosmic salt (NaO, NH^{4}O, PO^{5},
HO). Charcoal and the platinum wire are used as supports for this kind
of operation.
(_d._) _Oxidation._--The chemical combination of any substance with
oxygen is termed _oxidation_, and the products are termed _oxides_. As
these oxides have qualities differing from those which are
non-oxidized, it therefore frequently becomes necessary to convert
substances into oxides; or, if they are such, of a lower degree, to
convert them into a higher degree of oxidation. These different states
of oxidation frequently present characteristic marks of identity
sufficient to enable us to draw conclusions in relation to the
substance under examination. For instance, the oxidation of manganese,
of arsenic, etc. The conditions necessary for oxidation, are high
temperature and the free admission of air to the substance.
If the oxidation is effected through the addition of a substance
containing oxygen (for instance, the nitrate or chlorate of potash)
and the heating is accompanied by a lively deflagration and crackling
noise, it is termed _detonation_. By this process we frequently
effect the oxidation of a substance, and thus we prove the presence or
the absence of a certain class of substances. For instance, if we
detonate (as it is termed by the German chemists) the sulphide of
antimony, or the sulphide of arsenic with nitrate of potash, we get
the nitrate of antimony, or the nitrate of arsenic. The salts of
nitric or chloric acid are determined by fusing them with the cyanide
of potassium, because the salts of these acids detonate.
(_e._) _Reduction._--If we deprive an oxidized substance of its
oxygen, we term the process _reduction_. This is effected by fusing
the substance under examination with another which possesses a greater
affinity for oxygen. The agents used for reduction are hydrogen,
charcoal, soda, cyanide of potassium, etc. Substances generally, when
in the unoxidized state, have such characteristic qualities, that they
cannot very readily be mistaken for others. For this reason, reduction
is a very excellent expedient for the purpose of discerning and
classifying many substances.
B. UTENSILS.
We shall give here a brief description of the most necessary apparatus
used for analysis in the dry way, and of their use.
_The Blowpipe_ is a small instrument, made generally out of brass,
silver, or German silver, and was principally used in earlier times
for the purpose of soldering small pieces of metals together. It is
generally made in the form of a tube, bent at a right angle, but
without a sharp corner. The largest one is about seven inches long,
and the smallest about two inches. The latter one terminates with a
small point, with a small orifice. The first use of the blowpipe that
we have recorded is that of a Swedish mining officer, who used it in
the year 1738 for chemical purposes, but we have the most meagre
accounts of his operations. In 1758 another Swedish mining officer, by
the name of Cronstedt, published his "Use of the Blowpipe in
Chemistry and Mineralogy," translated into English, in 1770, by Van
Engestroem. Bergman extended its use, and after him Ghan and the
venerable Berzelius (1821). The blowpipe most generally used in
chemical examinations is composed of the following parts: (_Fig._ 1.)
A is a little reservoir made air-tight by grinding the part B into it.
This reservoir serves the purpose of retaining the moisture with which
the air from the mouth is charged. A small conical tube is fitted to
this reservoir. This tube terminates in a fine orifice. As this small
point is liable to get clogged up with soot, etc., it is better that
it should be made of platinum, so that it may be ignited. Two of these
platinum tubes should be supplied, differing in the size of the
orifice, by which a stronger or lighter current of flame may be
projected from it. Metals, such as brass or German silver, are very
liable to become dirty through oxidation, and when placed between the
lips are liable to impart a disagreeable taste. To avoid this, the top
of the tube must be supplied with a mouthpiece of ivory or horn C. The
blowpipe here represented is the one used by Ghan, and approved by
Berzelius. The trumpet mouthpiece was adopted by Plattner; it is
pressed upon the lips while blowing, which is less tiresome than
holding the mouthpiece between the lips, although many prefer the
latter mode.
[Illustration: Fig. 1]
Dr. Black's blowpipe is as good an instrument and cheaper. It
consists of two tubes, soldered at a right angle; the larger one, into
which the air is blown, is of sufficient capacity to serve as a
reservoir.
A chemist can, with a blowpipe and a piece of charcoal, determine many
substances without any reagents, thus enabling him, even when
travelling, to make useful investigations with means which are always
at his disposal. There are pocket blowpipes as portable as a pencil
case, such as Wollaston's and Mitscherlich's; these are objectionable
for continued use as their construction requires the use of a metallic
mouthpiece. Mr. Casamajor, of New York, has made one lately which has
an ivory mouthpiece, and which, when in use, is like Dr. Black's.
[Illustration: Fig. 2]
The length of the blowpipe is generally seven or eight inches, but
this depends very much upon the visual angle of the operators. A
short-sighted person, of course, would require an instrument of less
length than would suit a far-sighted person.
The purpose required of the blowpipe is to introduce a fine current of
air into the flame of a candle or lamp, by which a higher degree of
heat is induced, and consequently combustion is more rapidly
accomplished.
By inspecting the flame of a candle burning under usual circumstances,
we perceive at the bottom of the flame a portion which is of a light
blue color (_a b_), _Fig._ 2, which gradually diminishes in size
as it recedes from the wick, and disappears when it reaches the
perpendicular side of the flame. In the midst of the flame there is a
dark nucleus with a conical form (_c_). This is enveloped by the
illuminating portion of the flame (_d_). At the exterior edge of the
part _d_ we perceive a thin, scarcely visible veil, _a, e, e_, which
is broader near the apex of the flame. The action of the burning
candle may be thus explained. The radiant heat from the flame melts
the tallow or wax, which then passes up into the texture of the wick
by capillary attraction until it reaches the glowing wick, where the
heat decomposes the combustible matter into carbonated hydrogen
(C^{4}H^{4}), and into carbonic oxide (CO).
While these gases are rising in hot condition, the air comes in
contact with them and effects their combustion. The dark portion, _c_,
of the flame is where the carbon and gases have not a sufficiency of
air for their thorough combustion; but gradually they become mixed
with air, although not then sufficient for complete combustion. The
hydrogen is first oxidized or burnt, and then the carbon is attacked
by the air, although particles of carbon are separated, and it is
these, in a state of intense ignition, which produce the illumination.
By bringing any oxidizable substance into this portion of the flame,
it oxidizes very quickly in consequence of the high temperature and
the free access of air. For that reason this part of the flame is
termed the oxidizing flame, while the illuminating portion, by its
tendency to abstract oxygen for the purpose of complete combustion,
easily reduces oxidated substances brought into it, and it is,
therefore, called the flame of reduction. In the oxidizing flame, on
the contrary, all the carbon which exists in the interior of the flame
is oxidized into carbonic acid (CO^{2}) and carbonic oxide (CO), while
the blue color of the cone of the flame is caused by the complete
combustion of the carbonic oxide. These two portions of the flame--the
oxidizing and the reducing--are the principal agents of blowpipe
analysis.
If we introduce a fine current of air into a flame, we notice the
following: The air strikes first the dark nucleus, and forcing the
gases beyond it, mixes with them, by which oxygen is mingled freely
with them. This effects the complete combustion of the gases at a
certain distance from the point of the blowpipe. At this place the
flame has the highest temperature, forming there the point of a blue
cone. The illuminated or reducing portion of the flame is enveloped
outside and inside by a very hot flame, whereby its own temperature is
so much increased that in this reduction-flame many substances will
undergo fusion which would prove perfectly refractory in a common
flame. The exterior scarcely visible part loses its form, is
diminished, and pressed more to a point, by which its heating power is
greatly increased.
_The Blast of Air._--By using the blowpipe for chemical purposes, the
effect intended to be produced is an uninterrupted steady stream of
air for many minutes together, if necessary, without an instant's
cessation. Therefore, the blowing can only be effected with the
muscles of the cheeks, and not by the exertion of the lungs. It is
only by this means that a steady constant stream of air can be kept
up, while the lungs will not be injured by the deprival of air. The
details of the proper manner of using the blowpipe are really more
difficult to describe than to acquire by practice; therefore the pupil
is requested to apply himself at once to its practice, by which he
will soon learn to produce a steady current of air, and to distinguish
the different flames from each other. We would simply say that the
tongue must be applied to the roof of the mouth, so as to interrupt
the communication between the passage of the nostrils and the mouth.
The operator now fills his mouth with air, which is to be passed
through the pipe by compressing the muscles of the cheeks, while he
breathes through the nostrils, and uses the palate as a valve. When
the mouth becomes nearly empty, it is replenished by the lungs in an
instant, while the tongue is momentarily withdrawn from the roof of
the mouth. The stream of air can be continued for a long time, without
the least fatigue or injury to the lungs. The easiest way for the
student to accustom himself to the use of the blowpipe, is first to
learn to fill the mouth with air, and while the lips are kept firmly
closed to breathe freely through the nostrils. Having effected this
much, he may introduce the mouthpiece of the blowpipe between his
lips. By inflating the cheeks, and breathing through the nostrils, he
will soon learn to use the instrument without the least fatigue. The
air is forced through the tube against the flame by the action of the
muscles of the cheeks, while he continues to breathe without
interruption through the nostrils. Having become acquainted with this
process, it only requires some practice to produce a steady jet of
flame. A defect in the nature of the combustible used, as bad oil,
such as fish oil, or oil thickened by long standing or by dirt, dirty
cotton wick, or an untrimmed one, or a dirty wickholder, or a want of
steadiness of the hand that holds the blowpipe, will prevent a steady
jet of flame. But frequently the fault lies in the orifice of the jet,
or too small a hole, or its partial stoppage by dirt, which will
prevent a steady jet of air, and lead to difficulty. With a good
blowpipe the air projects the entire flame, forming a horizontal, blue
cone of flame, which converges to a point at about an inch from the
wick, with a larger, longer, and more luminous flame enveloping it,
and terminating to a point beyond that of the blue flame.
To produce an efficient flame of oxidation, put the point of the
blowpipe into the flame about one third the diameter of the wick, and
about one twelfth of an inch above it. This, however, depends upon
the size of the flame used. Blow strong enough to keep the flame
straight and horizontal, using the largest orifice for the purpose.
Upon examining the flame thus produced, we will observe a long, blue
flame, _a b_, Fig. 3, which letters correspond with the same letters
in Fig. 2. But this flame has changed its form, and contains all the
combustible gases. It forms now a thin, blue cone, which converges to
a point about an inch from the wick. This point of the flame possesses
the highest intensity of temperature, for there the combustion of the
gases is the most complete. In the original flame, the hottest part
forms the external envelope, but here it is compressed more into a
point, forming the cone of the blue flame, and likewise an envelope of
flame surrounding the blue one, extending beyond it from _a_ to _c_,
and presenting a light bluish or brownish color. The external flame
has the highest temperature at _d_, but this decreases from _d_ to
_c_.
[Illustration: Fig. 3]
If there is a very high temperature, the oxidation is not effected so
readily in many cases, unless the substance is removed a little from
the flame; but if the heat be not too high, it is readily oxidized in
the flame, or near its cone. If the current of air is blown too
freely or violently into the flame, more air is forced there than is
sufficient to consume the gases. This superfluous air only acts
detrimentally, by cooling the flame.
In general the operation proceeds best when the substance is kept at a
dull red heat. The blue cone must be kept free from straggling rays of
the yellow or reduction flame. If the analysis be effected on
charcoal, the blast should not be too strong, as a part of the coal
would be converted into carbonic oxide, which would act
antagonistically to the oxidation. The oxidation flame requires a
steady current of air, for the purpose of keeping the blue cone
constantly of the same length. For the purpose of acquiring practice,
the following may be done: Melt a little molybdenic acid with some
borax, upon a platinum wire, about the sixteenth of an inch from the
point of the blue cone. In the pure oxidation flame, a clear yellowish
glass is formed; but as soon as the reduction flame reaches it, or the
point of the blue cone touches it, the color of the bead changes to a
brown, which, finally, after a little longer blowing, becomes quite
dark, and loses its transparency. The cause of this is, that the
molybdenic acid is very easily reduced to a lower degree of oxidation,
or to the oxide of molybdenum. The flame of oxidation will again
convert this oxide into the acid, and this conversion is a good test
of the progress of the student in the use of the blowpipe. In cases
where we have to separate a more oxidizable substance from a less one,
we use with success the blue cone, particularly if we wish to
determine whether a substance has the quality, when submitted to heat
in the blue cone, of coloring the external flame.
A good _reduction_ flame can be obtained by the use of a small orifice
at the point of the blowpipe. In order to produce such a flame, hold
the point of the blowpipe higher above the wick, while the nozzle must
not enter the flame so far as in the production of the oxidation
flame. The point of the blowpipe should only touch the flame, while
the current of air blown into it must be stronger than into the
oxidation flame. If we project a stream, in the manner mentioned, into
the flame, from the smaller side of the wick to the middle, we shall
perceive the flame changed to a long, narrow, luminous cone, _a b_,
Fig. 4, the end _a_ of which is enveloped by the same dimly visible
blueish colored portion of the flame _a, c_, which we perceive in the
original flame, with its point at _c_. The portion close above the
wick, presenting the dull appearance, is occasioned by the rising
gases which have not supplied to them enough oxygen to consume them
entirely. The hydrogen is consumed, while the carbon is separated in a
state of bright ignition, and forms the internal flame.
[Illustration: Fig. 4]
Directly above the wick, the combustion of the gases is least
complete, and forms there likewise, as is the case in the free flame,
a dark blue nucleus _d_.
If the oxide of a metal is brought into the luminous portion of the
flame produced as above, so that the flame envelopes the substance
perfectly, the access of air is prevented. The partially consumed
gases have now a strong affinity for oxygen, under the influence of
the intense heat of that part of the flame. The substance is thus
deprived of a part, or the whole, of its oxygen, and becomes _reduced_
according to the strength of the affinity which the substance itself
has for oxygen. If the reduction of a substance is undertaken on
platinum, by fusion with a flux, and if the oxide is difficult to
reduce, the reduction will be completely effected only in the luminous
part of the flame. But if a substance be reduced on charcoal, the
reduction will take place in the blue part of the flame, as long as
the access of air is cut off; but it is the luminous part of the flame
which really possesses the greatest reducing power.
The following should be observed in order to procure a good reduction
flame:
The wick should not be too long, that it may make a smoke, nor
too short, otherwise the flame will be too small to produce a
heat strong enough for reduction.
The wick must be free from all loose threads, and from
charcoal.
The blast should be continued for a considerable time without
intermission, otherwise reduction cannot be effected.
For the purpose of acquiring practice, the student may fuse the oxide
of manganese with borax, upon a platinum wire, in the oxidation flame,
when a violet-red glass will be obtained; or if too much of the oxide
be used, a glass of a dark color and opaque will be obtained. By
submitting this glass to the reduction flame, it will become colorless
in correspondence to the perfection with which the flame is produced.
Or a piece of tin may be fused upon charcoal, and kept in that state
for a considerable time, while it presents the appearance of a bright
metal on the surface. This will require dexterity in the operator;
for, if the oxidation flame should chance to touch the bright metal
only for a moment, it is coated with an infusible oxide.
COMBUSTION.--Any flame of sufficient size can be used for blowpipe
operations. It may be either the flame of a candle of tallow or wax,
or the flame of a lamp. The flame of a wax candle, or of an oil lamp
is most generally used. Sometimes a lamp is used filled with a
solution of spirits of turpentine in strong alcohol. If a candle is
used, it is well to cut the wick off short, and to bend the wick a
little toward the substance experimented upon. But candles are not the
best for blowpipe operations, as the radiant heat, reflecting from the
substance upon the wax or tallow, will cause it to melt and run down
the side of the candle; while again, candles do not give heat enough.
The lamp is much the most desirable. The subjoined figure, from
Berzelius, is perhaps the best form of lamp. It is made of japanned
tin-plate, about four inches in length, and has the form and
arrangement represented in Fig. 5. K is the lamp, fastened on the
stand, S, by a screw, C, and is movable upwards or downwards, as
represented in the figure. The posterior end of the lamp may be about
one inch square, and at its anterior end, E, about three-quarters of
an inch square. The under side of this box may be round, as seen in
the figure. The oil is poured into the orifice, A, which has a cap
screwed over it. C' is a wickholder for a flat lamp-wick. _a_ is a
socket containing the wick, which, when not in use, is secured from
dirt by the cap. The figures B and _a'_ give the forms of the cap and
socket. The best combustible for this lamp is the refined rape-seed
oil, or pure sweet oil. When this lamp is in use, there must be no
loose threads, or no charcoal on the wick, or these will produce a
smoky flame. The wick, likewise, should not be pulled up too high, as
the same smoky flame would be produced.
[Illustration: Fig. 5]
THE SPIRIT-LAMP.--This is a short, strong glass lamp, with a cap, B,
Fig. 6, fitted to it by grinding, to prevent the evaporation of the
alcohol. The neck _a_ contains a tube C, made of silver, or of tin
plate, and which contains the wick. Brass would not answer so well
for this tube, as the spirits would oxidize it, and thus impart color
to the flame. The wickholder must cover the edge of the neck, but not
fit tight within the tube, otherwise, by its expansion, it will break
the glass. It is not necessary that alcohol, very highly rectified,
should be burnt in this lamp, although if too much diluted with water,
enough heat will not be given out. Alcohol of specific gravity 0.84 to
0.86 is the best.
[Illustration: Fig. 6]
This lamp is generally resorted to by blowpipe analysts, for the
purpose of experiments in glass apparatus, as the oily combustibles
will coat the glass with soot. Some substances, when exposed to the
dark part of the flame, become reduced and, _in statu nascendi_,
evaporated; but by passing through the external part of the flame,
they become oxidized again, and impart a color to the flame. The
spirit flame is the most efficient one for the examination of
substances the nature of which we wish to ascertain through color
imparted to the flame, as that of the spirit-lamp being colorless, is,
consequently, most easily and thoroughly recognized by the slightest
tinge imparted to it.
It is necessary that in operating with such minute quantities of
substances as are used in blowpipe analysis, that they should have
some appropriate support. In order that no false results may ensue, it
is necessary that the supports should be of such a nature that they
will not form a chemical combination with the substance while it is
exposed to fusion or ignition. Appropriate supports for the different
blowpipe experiments are charcoal, platinum instruments, and glass
tubes.
(_a._) _Charcoal._--The value of charcoal as a support may be stated
as follows:
1. The charcoal is infusible, and being a poor conductor of
heat, a substance can be exposed to a higher degree of heat
upon it than upon any other substance.
2. It is very porous, and therefore allows easily fusible
substances (such as alkalies and fluxes) to pass into it,
while other substances less fusible, such as metals, to remain
unabsorbed.
3. It has likewise a great reducing power.
The best kind of charcoal is that of pinewood, linden, willow, or
alderwood, or any other soft wood. Coal from the firwood sparkles too
freely, while that of the hard woods contains too much iron in its
ashes. Smooth pieces, free from bark and knots, should be selected. It
should be thoroughly burnt, and the annual rings or growths should be
as close together as possible.
If the charcoal is in masses, it should be sawed into pieces about six
inches in length by about two inches broad, but so that the
year-growths run perpendicular to the broadest side, as the other
sides, by their unequal structure, burn unevenly.
That the substance under examination may not be carried off by the
blast, small conical concavities should be cut in the broad side of
the charcoal, between the year-growths, with a conical tube of tin
plate about two or three inches long, and one quarter of an inch at
one end, and half an inch at the other. These edges are made sharp
with a file. The widest end of this charcoal borer is used for the
purpose of making cavities for cupellation.
In places where the proper kind of charcoal is difficult to procure,
it is economical to cut common charcoal into pieces about an inch
broad, and the third of an inch thick. In each of these little pieces
small cavities should be cut with the small end of the borer. When
these pieces of charcoal are required for use, they must be fastened
to a narrow slip of tin plate, one end of which is bent into the form
of a hook, under which the plate of charcoal is pushed.
In general, we use the charcoal support where we wish to reduce
metallic oxides, to prevent oxidation, or to test the fusibility of a
substance. There is another point to which we would direct the
student. Those metals which are volatile in the reduction flame,
appear as oxides in the oxidation flame. These oxides make sublimates
upon the charcoal close in the vicinity of the substance, or where it
rested, and by their peculiar color indicate pretty correctly the
species of minerals experimented upon.
(_b._) _Platinum Supports._--The metal platinum is infusible in the
blowpipe flame, and is such a poor conductor of heat that a strip of
it may be held close to that portion of it which is red hot without
the least inconvenience to the fingers. It is necessary that the
student should be cognizant of those substances which would not be
appropriate to experiment upon if placed on platinum. Metals should
not be treated upon platinum apparatus, nor should the easily
reducible oxides, sulphides, nor chlorides, as these substances will
combine with the platinum, and thus render it unfit for further use in
analysis.
(_c._) _Platinum Wire._--As the color of the flame cannot be well
discerned when the substance is supported upon charcoal, in
consequence of the latter furnishing false colors, by its own
reflection, to the substances under examination, we use platinum wire
for that purpose, when we wish to examine those substances which give
indications by the peculiar color which they impart to fluxes. The
wire should be about as thick as No. 16 or 18 wire, or about 0.4
millimetre, and cut into pieces about from two and a half to three
inches in length. The end of each piece is crooked. In order that
these pieces should remain clear of dirt, and ready for use, they
should be kept in a glass of water. To use them, we dip the wetted
hooked end into the powdered flux (borax or microcosmic salt) some of
which will adhere, when we fuse it in the flame of the blowpipe to a
bead. This bead hanging in the hook, must be clear and colorless.
Should there not adhere a sufficient quantity of the flux in the first
trial to form a bead sufficiently large, the hook must be dipped a
second time in the flux and again submitted to the blowpipe flame. To
fix the substance to be examined to the bead, it is necessary, while
the latter is hot, to dip it in the powdered substance. If the hook is
cold, we moisten the powder a little, and then dip the hook into it,
and then expose it to the oxidation flame, by keeping it exposed to a
regular blast until the substance and the flux are fused together, and
no further alteration is produced by the flame.
The platinum wire can be used except where reduction to the metallic
state is required. Every reduction and oxidation experiment, if the
results are to be known by the color of the fluxes, should be effected
upon platinum wire. At the termination of the experiment or
investigation, if it be one, to, clean the wire, place it in water,
which will dissolve the bead.
(_d._) _Platinum Foil._--For the heating or fusing of a substance,
whereby its reduction would be avoided, we use platinum foil as a
support. This foil should be of the thickness of good writing paper,
and from two and a half to three inches long, by about half an inch
broad, and as even and smooth as possible. If it should become injured
by long use, cut the injured end off, and if it should prove too short
to be held with the fingers, a pair of forceps may be used to grasp
it, or it may be placed on a piece of charcoal.
(_e._) _Platinum Spoon._--When we require to fuse substances with the
acid sulphate of potash, or to oxidize them by detonation with nitrate
of potash, whereby we wish to preserve the oxide produced, we
generally use a little spoon of platinum, about from nine to fifteen
millimetres[1] in diameter, and shaped as represented in Fig. 7. The
handle of this spoon is likewise of platinum, and should fit into a
piece of cork, or be held with the forceps.
[1] The French millimetre is about the twenty-fifth part of an
English inch.
[Illustration: Fig. 7.]
(_f._) _Platinum Forceps or Tongs._--We frequently are necessitated to
examine small splinters of metals or minerals directly in the blowpipe
flame. These pieces of metallic substances are held with the forceps
or tongs represented as in Fig. 8, where _ac_ is formed of steel, and
_aa_ are platinum bars inserted between the steel plates. At _bb_ are
knobs which by pressure so separate the platinum bars _aa_, that any
small substance can be inserted between them.
[Illustration: Fig. 8.]
(_g._) _Iron Spoons._--For a preliminary examination iron spoons are
desirable. They may be made of sheet iron, about one-third of an inch
in diameter, and are very useful in many examinations where the use of
platinum would not be desirable.
(_h._) _Glass Tubes._--For the separation and recognition of volatile
substances before the blowpipe flame, we use glass tubes. These should
be about one-eighth of an inch in diameter, and cut into pieces about
five or six inches in length. These tubes should have both ends open.
Tubes are of great value in the examination of volatile substances
which require oxidizing or roasting, and heating with free access of
air. Also to ascertain whether a substance under examination will
sublimate volatile matter of a certain appearance. Such substances are
selenium, sulphur, arsenic, antimony, and tellurium. These substances
condense on a cool part of the tube, and they present characteristic
appearances, or they may be recognized by their peculiar smell. These
tubes must be made of the best kind of glass, white and difficult of
fusion, and entirely free from lead. The substance to be examined must
be put in the tube near one end, and exposed to the flame of the
blowpipe. The end containing the substance must be held lower than the
other end, and must be moved a little over the spirit-lamp before a
draught of air is produced through the tube. It is a good plan to have
a number of these tubes on hand. After having used a tube we cut off
that end of it which contained the substance, with a file, and clean
it from the sublimate, either by heating it over the spirit-lamp, or
with a piece of paper wound around a wire. It sometimes happens that
the substance falls out of the tube before it becomes sufficiently
melted to adhere to the glass. To obviate this, we bend the tube not
far from the end, at an obtuse angle, and place the substance in the
angle, whereby the tube may be lowered as much as necessary. Fig. 9
will give the student a comprehension of the processes described, and
of the manner of bending the tubes.
[Illustration: Fig. 9.]
(_i._) _Glass Tubes closed at one End._--If we wish to expose volatile
substances to heat, with the exclusion of air as much as possible, or
to ascertain the contents of water, or other volatile fluids, or for
the purpose of heating substances which will decrepitate, we use glass
tubes closed at one end. These tubes must be about one-eighth of an
inch wide, and from two to three inches in length. They should be made
of white glass, difficult of fusion, and free from lead. They should
be closed at one end, as figured in the margin, Fig. 10.
[Illustration: Fig. 10.]
When a substance is to be examined for the purpose of ascertaining
whether it contains combustible matter, as sulphur or arsenic, and
where we wish to avoid oxidation, we use these tubes without extending
the closed end, in order that there may be as little air admitted as
possible, as is represented in tube B. But when a substance to be
examined is to be tested for water, or other incombustible volatile
matters, we employ tubes with little bulbs blown at one end, such as
represented at tube A. Here there is room for a circulation of air at
the bottom of the tube, by which the volatile matter rises more
easily. In some cases, it is necessary to draw the closed end out to a
fine point, as in the tubes C and D. Either one or the other of these
tubes is employed, depending upon the nature of the substance used.
The sublimates condense at the upper part of the tube _a_, and can be
there examined and recognized. These tubes, before being used, must be
thoroughly dried and cleaned. In experimenting with them, they should
not be exposed at once to the hottest part of the flame, but should be
submitted to the heat gradually. If the substance is of such a nature
that it will sublime at a low heat, the tube should be held more
horizontal, while a higher heat is attained by bringing the tube to a
more vertical position.
VARIOUS APPARATUS NECESSARY.
_Edulcorator or Washing Bottle._--Take a glass bottle of the capacity
of about twelve ounces, and close the mouth of it very tight with a
cork, through which a short glass tube is fitted airtight. The
external end of this tube is drawn out to a point, with a very fine
orifice. The bottle should be filled about half full of water. By
blowing air into the bottle through the tube, and then turning it
downwards, the compressed air will expel a fine stream of water
through the fine orifice with considerable force. We use this washing
bottle, Fig. 11, for the purpose of rinsing the small particles of
coal from the reduced metals.
[Illustration: Fig. 11.]
_Agate Mortar and Pestle._--This mortar is used for the purpose of
pulverizing hard substances, and for mixing fluxes. As this mortar
will not yield to abrasion, there is no danger of any foreign matter
becoming mixed with the substance pulverized in it. It should be
cleaned after use with pumice stone. Steel mortars are very useful for
the pulverization of hard bodies; but for all those substances which
require great care in their analysis, and which can be obtained in
very minute quantity, the agate mortar alone should be used.
A _hammer_ made of steel is necessary. This should have the edge
square.
A small _anvil_, polished on the surface, is also required. It is
frequently used to test the malleability of metals.
A _knife_, for the purpose of ascertaining the hardness of minerals.
The student should also be provided with several three-edged files,
and likewise with some flat ones.
A _microscope_, an instrument with two lenses, or with such a
combination of lenses, that they may be used double or single, is
frequently necessary for the examination of blowpipe experiments, or
the reaction of the fluxes. Common lenses, howsoever cheap they may
be, are certainly not recommended. A microscope with achromatic lenses
can now be purchased so cheap that there is no longer any necessity of
procuring one with the common lens. Besides, there is no reliability
whatever to be placed in the revelations of the common lens; while on
the contrary, the deceptive appearances which minute objects assume
beneath such lenses are more injurious than otherwise. A small cheap
set of magnifying glasses are all that is required for the purpose of
blowpipe analysis, Fig. 12.
[Illustration: Fig. 12.]
A small _magnet_ should be kept on hand, for the purpose of testing
reduced metals.
_Nippers_, for the purpose of breaking off pieces of minerals for
analysis, without injuring the entire piece, are indispensable, Fig
13.
[Illustration: Fig. 13.]
A pair of _scissors_ is required to trim the wick of the and for the
trimming of the edge of platinum foil.
A small _spatula_ should be kept for the purpose of mixing substances
with fluxes.
THE REAGENTS.
Those substances which possess the property of acting upon other
substances, in such a characteristic manner that they can be
recognized, either by their color, or by their effervescence, or by
the peculiar precipitation produced, are termed _reagents_. The
phenomena thus produced is termed _reaction_. We use those reagents,
or _tests_, for the purpose of ascertaining the presence or the
absence of certain substances, through the peculiar phenomena produced
when brought in contact with them.
The number of reagents employed in blowpipe analysis is not great, and
therefore we shall here give a brief description of their preparation
and use. It is indispensably necessary that they should be chemically
pure, as every admixture of a foreign substance would only produce a
false result. Some of them have a strong affinity for water, or are
deliquescent, and consequently absorb it greedily from the air. These
must be kept in glass bottles, with glass stoppers, fitted air-tight
by grinding.
A. REAGENTS OF GENERAL USE.
1. _Carbonate of Soda._--(NaO, CO^{2}) Wash the bicarbonate of soda
(NaO, 2CO^{2}) upon a filter, with cold water, until the filtrate
ceases to give, after neutralization with diluted nitric acid
(NO^{5}), a precipitate with nitrate of baryta, (BaO, NO^{5}), or
nitrate of silver, (AgO, NO^{5}). That left upon the filter we make
red hot in a platinum, silver, or porcelain dish. One atom of carbonic
acid is expelled, and the residue is carbonate of soda.
A solution of soda must not be changed by the addition of sulphide of
ammonium. And when neutralized with hydrochloric acid, and evaporated
to dryness, and again dissolved in water, there must be no residue
left.
Carbonate of soda is an excellent agent in reduction, in consequence
of its easy fusibility, whereby it causes the close contact of the
oxides with the charcoal support, so that the blowpipe flame can reach
every part of the substance under examination.
For the decomposition and determination of insoluble substances,
particularly the silicates, carbonate of soda is indispensable. But
for the latter purpose, we use with advantage a mixture of ten parts
of soda and thirteen parts of dry carbonate of potash, which mixture
fuses more easily than the carbonate of soda alone.
2. _Hydrate of Baryta_ (BaO, HO).--This salt is used sometimes for the
detection of alkalies in silicates. Mix one part of the substance with
about four parts of the hydrate of baryta, and expose it to the
blowpipe flame. The hydrate of baryta combines with the silicic acid,
and forms the super-basic silicate of baryta, while the oxides become
free. The fused mass must be dissolved in hydrochloric acid, which
converts the oxides into chlorides. Evaporate to dryness, and dissolve
the residue in water. The silicic acid remains insoluble.
The hydrate of baryta is prepared by mixing six parts of finely
powdered heavy-spar (BaO, SO_{3}) with one part of charcoal and one
and a half parts of wheat flour, and exposing this mixture in a
Hessian crucible with a cover to a strong and continuous red heat. The
cooled chocolate-brown mass must be boiled with twenty parts of water,
and, while boiling, there must be added the oxide of copper in
sufficient quantity, or until the liquid will not impart a black color
to a solution of acetate of lead (PbO, [=]A). The liquid must be
filtered while hot, and as it cools the hydrate of baryta appears in
crystals. These crystals must be washed with a little cold water, and
then heated at a low temperature in a porcelain dish until the crystal
water is expelled. The hydrate of baryta melts by a low red heat
without losing its water of hydration.
3. _Bisulphate of Potassa_ (KO, 2SO^{3}).--At a red heat the half of
the sulphuric acid of this salt becomes free, and thus separates and
expels volatile substances, by which we can recognize lithium, boracic
acid, nitric acid, fluoric acid, bromine, iodine, chlorine; or it
decomposes and reveals some other compounds, as, for instance, the
salts of the titanic, tantalic and tungstic acids. The bisulphate of
potash is also used for the purpose of converting a substance into
sulphate, or to free it at once from certain constituents. These
sulphates are dissolved in water, by which we are enabled to effect
the separation of its various constituents.
PREPARATION.--Two parts of coarsely powdered sulphate of potash are
placed in a porcelain crucible, and one part of pure sulphuric acid is
poured over it. Expose this to heat over the spirit-lamp, until the
whole becomes a clear liquid. The cooled mass must be of a pure white
color, and may be got out of the crucible by inverting it. It must be
kept in a fine powder.
4. _Oxalate of Potassa_ (KO, [=]O).--Dissolve bioxalate of potash in
water, and neutralize with carbonate of potash. Evaporate the solution
at a low heat to dryness, stirring constantly towards the close of the
operation. The dry residue is to be kept in the form of a powder.
The oxalate of potash, at a low red heat, eliminates a considerable
quantity of carbonic oxide, which, having a strong affinity for
oxygen, with which it forms carbonic acid, it is therefore a powerful
agent of reduction. It is in many cases preferable to carbonate of
soda.
5. _Cyanide of Potassium_ (Cy, K).--In the dry method of analysis,
this salt is one of the most efficient agents for the reduction of
metallic oxides. It separates not only the metals from their oxygen
compounds, but likewise from their sulphur compounds, while it is
converted through the action of the oxygen into carbonate of potash,
or, in the latter case, combines with the sulphur and forms the
sulphureted cyanide of potassium. This separation is facilitated by
its easy fusibility. But in many cases it melts too freely, and
therefore it is better to mix it, for blowpipe analysis, with an equal
quantity of soda. This mixture has great powers of reduction, and it
is easily absorbed by the charcoal, while the globules of reduced
metal are visible in the greatest purity.
PREPARATION.--Deprive the ferrocyanide of potassium (2KCy + FeCy) of
its water by heating it over the spirit-lamp in a porcelain dish. Mix
eight parts of this anhydrous salt with three parts of dry carbonate
of potash, and fuse the mixture by a low red heat in a Hessian, or
still better, in an iron crucible with a cover, until the mass flows
quiet and clear, and a sample taken up with an iron spatula appears
perfectly white. Pour the clear mass out into a china or porcelain
dish or an iron plate, but with caution that the fine iron particles
which have settled to the bottom, do not mix with it. The white fused
mass must be powdered, and kept from the air. The cyanide of potassium
thus prepared, contains some of the cyanate of potassa, but the
admixture does not deteriorate it for blowpipe use. It must be
perfectly white, free from iron, charcoal, and sulphide of potassium.
The solution of it in water must give a white precipitate with a
solution of lead, and when neutralized with hydrochloric acid, and
evaporated to dryness, it must not give an insoluble residue by
dissolving it again in water.
6. _Nitrate of Potassa, Saltpetre_ (KO, NO^{5}).--Saturate boiling
water with commercial saltpetre, filter while hot in a beaker glass,
which is to be placed in cold water, and stir while the solution is
cooling. The greater part of the saltpetre will crystallize in very
fine crystals. Place these crystals upon a filter, and wash them with
a little cold water, until a solution of nitrate of silver ceases to
exhibit any reaction upon the filtrate. These crystals must be dried
and powdered.
Saltpetre, when heated with substances easy of oxidation, yields its
oxygen quite readily, and is, therefore, a powerful means of
oxidation. In blowpipe analysis, we use it particularly to convert
sulphides (as those of arsenic, antimony, &c.) into oxides and acids.
We furthermore use saltpetre for the purpose of producing a complete
oxidation of small quantities of metallic oxides, which oxidize with
difficulty in the oxidation flame, so that the color of the bead, in
its highest state of oxidation, shall be visible, as for instance,
manganese dissolved in the microcosmic salt.
7. _Biborate of soda, borax_--(NaO + 2BO^{3}).--Commercial borax is
seldom pure enough for a reagent. A solution of borax must not give a
precipitate with carbonate of potassa; or, after the addition of
dilute nitric acid, it must remain clear upon the addition of nitrate
of silver, or nitrate of baryta. Or a small piece of the dry salt,
fused upon a platinum wire, must give a clear and uncolored glass, as
well in the oxidation flame as in the reduction flame. If these tests
indicate a foreign admixture, the borax must be purified by
re-crystallization. These crystals are washed upon a filter, dried,
and heated, to expel the crystal water, or until the mass ceases to
swell up, and it is reduced to powder.
Boracic acid is incombustible, and has a strong affinity for oxides
when fused with them; therefore, it not only directly combines with
oxides, but it expels, by fusion, all other volatile acids from their
salts. Furthermore, boracic acid promotes the oxidation of metals and
sulphur, and induces haloid compounds, in the oxidation flame, to
combine with the rising oxides. Borates thus made, melt generally by
themselves; but admixed with borate of soda, they fuse much more
readily, give a clear bead. Borax acts either as a flux, or through
the formation of double salts.
In borax, we have the action of free boracic acid, as well as borate
of soda, and for that reason it is an excellent reagent for blowpipe
analysis.
All experiments in which borax is employed should be effected upon
platinum wire. The hook of the wire should be heated red hot, and then
dipped into the powdered borax. This should be exposed to the
oxidation flame, when it will be fused to a bead, which adheres to the
hook. This should be then dipped into the powdered substance, which
will adhere to it if it is hot; but if the bead is cool, it must be
previously moistened. Expose this bead to the oxidation flame until it
ceases to change, then allow it to cool, when it should be exposed to
the reduction flame. Look for the following in the oxidation flame:
(1.) Whether the heated substance is fused to a clear bead or
not, and whether the bead remains transparent after cooling. The
beads of some substances, for instance those of the alkaline
earths, are clear while hot; but upon cooling, are milk-white and
enamelled. Some substances give a clear bead when heated and when
cold, but appear enamelled when heated intermittingly or with a
flame which changes often from oxidation to reduction, or with an
unsteady flame produced by too strong a blast. The reason is an
incomplete fusion, while from the basic borate compound a part of
the base is separated. As the boracic acid is capable of
dissolving more in the heat, a bead will be clear while hot,
enamelled when cold, as a part in the latter instance will become
separated.
(2.) Whether the substance dissolves easily or not, and whether
it intumesces from arising gases.
(3.) Whether the bead, when exposed to the oxidation flame,
exhibits any color, and whether the color remains after the bead
shall have cooled, or whether the color fades.
(4.) Whether the bead exhibits any other reaction in the
reduction flame.
The bead should not be overcharged with the substance under
examination, or it will become colored so deeply as not to present any
transparency, or the color light enough to discern its hue.
8. _Microcosmic Salt--Phosphate of Soda and Ammonia_--(NaO, NH^{4}O +
PO^{5}).--Dissolve six parts of phosphate of soda (2NaO, HO, PO^{5}),
and one part of pure chloride of Ammonium (NH^{4}Cl.), in two parts of
boiling water, and allow it to cool. The greatest part of the formed
double salt crystallizes, while the mother-liquid contains chloride of
sodium, and some of the double salt. The crystals must be dissolved in
as little boiling water as possible, and re-crystallized. These
crystals must be dried and powdered.
When this double salt is heated, the water and the ammonia escape,
while the incombustible residue has a composition similar to borax,
viz., a free acid and an easily fusible salt. The effect of it is,
therefore, similar to the borax. The free phosphoric acid expels,
likewise, most other acids from their combinations, and combines with
metallic oxides.
For supports, the platinum wire may be used, but the hook must be
smaller than when borax is used, or the bead will not adhere. As for
all the other experiments with this salt, the microscosmic salt is
used the same as borax.
9. _Nitrate of Cobalt._--(CoO, NO^{5}).--This salt can be prepared by
dissolving pure oxide of cobalt in diluted nitric acid, and
evaporating to dryness with a low heat. The dry residue should be
dissolved in ten parts of water, and filtered. The filtrate is now
ready for use, and should be kept in a bottle with a glass stopper. If
the pure oxide of cobalt cannot be procured, then it may be prepared
by mixing two parts of finely powdered _glance of cobalt_ with four
parts of saltpetre, and one part of dry carbonate of potassa with one
part of water free from carbonate of soda. This mixture should be
added in successive portions into a red-hot Hessian crucible, and the
heat continued until the mass is fused, or at least greatly diminished
in volume. The cooled mass must be triturated with hot water, and then
heated with hydrochloric acid until it is dissolved and forms a dark
green solution, which generally presents a gelatinous appearance,
occasioned by separated silica. The solution is to be evaporated to
dryness, the dry residue moistened with hydrochloric acid, boiled with
water, filtered and neutralized while hot with carbonate of ammonia,
until it ceases to give an acid reaction with test-paper. This must
now be filtered again, and carbonate of potassa added to the filtrate
as long as a precipitate is produced. This precipitate is brought upon
a filter and washed thoroughly, and then dissolved in diluted nitric
acid. This is evaporated to dryness, and one part of it is dissolved
in ten parts of water for use.
The oxide of cobalt combines, with strong heat in the oxidation flame,
with various earths and infusible metallic oxides, and thus produces
peculiarly colored compounds, and is therefore used for their
detection; (alumina, magnesia, oxide of zinc, oxide of tin, etc.) Some
of the powdered substance is heated upon charcoal in the flame of
oxidation, and moistened with a drop of the solution of the nitrate of
cobalt, when the oxidation flame is thrown upon it. Alumina gives a
pure blue color, the oxide of zinc a bright green, magnesia a light
red, and the oxide of tin a bluish-green color; but the latter is only
distinctly visible after cooling.
The dropping bottle, is the most useful apparatus for the purpose of
getting small quantities of fluid. It is composed of a glass tube,
drawn out to a point, with a small orifice. This tube passes through
the cork of the bottle. By pressing in the cork into the neck of the
bottle, the air within will be compressed, and the liquid will rise in
the tube. If now we draw the cork out, with the tube filled with the
fluid, and pressing the finger upon the upper orifice, the fluid can
be forced out in the smallest quantity, even to a fraction of a drop.
10. _Tin._--This metal is used in the form of foil, cut into strips
about half an inch wide. Tin is very susceptible of oxidation, and
therefore deprives oxidized substances of their oxygen very quickly,
when heated in contact with them. It is employed in blowpipe analysis,
for the purpose of producing in glass beads a lower degree of
oxidation, particularly if the substance under examination contains
only a small portion of such oxide. These oxides give a characteristic
color to the bead, and thus are detected. The bead is heated upon
charcoal in the reduction flame, with a small portion of the tin,
whereby some of the tin is melted and mixes with the bead. The bead
should be reduced quickly in the reduction flame, for by continuing
the blast too great a while, the oxide of tin separates the other
oxides in the reduced or metallic state, while we only require that
they shall only be converted into a sub-oxide, in order that its
peculiar color may be recognized in the bead. The addition of too much
tin causes the bead to present an unclean appearance, and prevents
the required reaction.
11. _Silica_ (SiO^{3}).--This acid does not even expel carbonic acid
in the wet way, but in a glowing heat it expels the strongest volatile
acids. In blowpipe analysis, we use it fused with carbonate of soda to
a bead, as a test for sulphuric acid, and in some cases for phosphoric
acid. Also with carbonate of soda and borax, for the purpose of
separating tin from copper.
Finely powdered quartz will answer these purposes. If it cannot be
procured, take well washed white sand and mix it with two parts of
carbonate of soda and two parts of carbonate of potassa. Melt the
materials together, pound up the cooled mass, dissolve in hot water,
filter, add to the filtrate hydrochloric acid, and evaporate to
dryness. Moisten the dry residue with hydrochloric acid, and boil in
water. The silica remains insoluble. It should be washed well, dried,
and heated, and then reduced to powder.
12. TEST-PAPERS.--(_a._) _Blue, Litmus Paper._--Dissolve one part of
litmus in six or eight parts of water, and filter. Divide the filtrate
into two parts. In one of the parts neutralize the free alkali by
stirring it with a glass rod dipped in diluted sulphuric acid, until
the fluid appears slightly red. Then mix the two parts together, and
draw slips of unsized paper, free from alkali, such as fine filtering
paper. Hang these strips on a line to dry, in the shade and free from
floating dust. If the litmus solution is too light, it will not give
sufficient characteristic indications, and if too dark it is not
sensitive enough. The blue color of the paper should be changed to
red, when brought in contact with a solution containing the minutest
trace of free acid; but it should be recollected that the neutral
salts of the heavy metals produce the same change.
(_b._) _Red Litmus Paper._--The preparation of the red litmus paper is
similar to the above, the acid being added until a red color is
obtained. Reddened litmus paper is a very sensitive reagent for free
alkalies, the carbonates of the alkalies, alkaline earths, sulphides
of the alkalies and of the alkaline earths, and alkaline salts with
weak acids, such as boracic acid. These substances restore the
original blue color of the litmus.
(_c._) _Logwood Paper._--Take bruised logwood, boil it in water,
filter, and proceed as above. Logwood paper is a very delicate test
for free alkalies, which impart a violet tint to it. It is sometimes
used to detect hydrofluoric acid, which changes its color to yellow.
All the test-papers are to be cut into narrow strips, and preserved in
closely stopped vials. The especial employment of the test-papers we
shall allude to in another place.
B. ESPECIAL REAGENTS.
13. _Fused Boracic Acid_ (BO^{3}).--The commercial article is
sufficiently pure for blowpipe analysis. It is employed in some cases
to detect phosphoric acid, and also minute traces of copper in lead
compounds.
14. _Fluorspar_ (CaFl^{2}).--This substance should be pounded fine and
strongly heated. Fluorspar is often mixed with boracic acid, which
renders it unfit for analytical purposes. Such an admixture can be
detected if it be mixed with bisulphate of potassa, and exposed upon
platinum wire to the interior or blue flame. It is soon fused, the
boracic acid is reduced and evaporated, and by passing through the
external flame it is reoxidized, and colors the flame green. We use
fluorspar mixed with bisulphate of potassa as a test for lithia and
boracic acid in complicated compounds.
15. _Oxalate of Nickel_ (NiO, [=]O).--It is prepared by dissolving the
pure oxide of nickel in diluted hydrochloric acid. Evaporate to
dryness, dissolve in water, and precipitate with oxalate of ammonia.
The precipitate must be washed with caution upon a filter, and then
dried. It is employed in blowpipe analysis to detect salts of potassa
in the presence of sodium and lithium.
16. _Oxide of Copper_ (CuO).--Pure metallic copper is dissolved in
nitric acid. The solution is evaporated in a porcelain dish to
dryness, and gradually heated over a spirit-lamp, until the blue color
of the salt has disappeared and the mass presents a uniform black
color. The oxide of copper so prepared must be powdered, and preserved
in a vial. It serves to detect, in complicated compounds, minute
traces of chlorine.
17. _Antimoniate of Potassa_ (KO, SbO^{6}).--Mix four parts of the
bruised metal of antimony, with nine parts of saltpetre. Throw this
mixture, in small portions, into a red-hot Hessian crucible, and keep
it at a glowing heat for awhile after all the mixture is added. Boil
the cooled mass with water, and dry the residue. Take two parts of
this, and mix it with one part of dry carbonate of potassa, and expose
this to a red heat for about half an hour. Then wash the mass in cold
water, and boil the residue in water; filter, evaporate the filtrate
to dryness, and then, with a strong heat, render it free of water.
Powder it while it is warm, and preserve it in closed vials. It is
used for the detection of small quantities of charcoal in compound
substances, as it shares its oxygen with the carbonaceous matter, the
antimony becomes separated, and carbonate of potassa is produced,
which restores red litmus paper to blue, and effervesces with acids.
18. _Silver Foil._--A small piece of silver foil is used for the
purpose of detecting sulphur and the sulphides of the metals, which
impart a dark stain to it. If no silver foil is at hand, strips of
filtering paper, impregnated with acetate of lead, will answer in many
cases.
19. _Nitroprusside of Sodium_ (Fe^{2}Cy^{5}, NO^{5}, 2Na).--This is a
very delicate test for sulphur, and was discovered by Dr. Playfair.
This test has lately been examined with considerable ability by Prof.
J.W. Bailey, of West Point. If any sulphate or sulphide is heated by
the blowpipe upon charcoal with the carbonate of soda, and the fused
mass is placed on a watch-glass, with a little water, and a small
piece of the nitroprusside of sodium is added, there will be produced
a splendid purple color. This color, or reaction, will be produced
from any substance containing sulphur, such as the parings of the
nails, hair, albumen, etc. In regard to these latter substances, the
carbonate of soda should be mixed with a little starch, which will
prevent the loss of any of the sulphur by oxidation. Coil a piece of
hair around a platinum wire, moisten it, and dip it into a mixture of
carbonate of soda, to which a little starch has been added, and then
heat it with the blowpipe, when the fused mass will give with the
nitroprusside of sodium the characteristic purple reaction, indicative
of the presence of sulphur. With the proper delicacy of manipulation,
a piece of hair, half an inch in length, will give distinct
indications of sulphur.
_Preparation._--The nitroprussides of sodium and potassium (for either
salt will give the above reactions), are prepared as follows: One atom
(422 grains) of pulverized ferrocyanide of potassium is mixed with
five atoms of commercial nitric acid, diluted with an equal quantity
of water. One-fifth of this quantity (one atom) of the acid is
sufficient to transfer the ferrocyanide into nitroprusside; but the
use of a larger quantity is found to give the best results. The acid
is poured all at once upon the ferrocyanide, the cold produced by the
mixing being sufficient to moderate the action. The mixture first
assumes a milky appearance, but after a little while, the salt
dissolves, forming a coffee-colored solution, and gases are disengaged
in abundance. When the salt is completely dissolved, the solution is
found to contain ferrocyanide (red prussiate) of potassium, mixed with
nitroprusside and nitrate of the same base. It is then immediately
decanted into a large flask, and heated over the water-bath. It
continues to evolve gas, and after awhile, no longer yields a dark
blue precipitate with ferrous salts, but a dark green or slate-colored
precipitate. It is then removed from the fire, and left to
crystallize, whereupon it yields a large quantity of crystals of
nitre, and more or less oxamide. The strongly-colored mother liquid is
then neutralized with carbonate of potash or soda, according to the
salt to be prepared, and the solution is boiled, whereupon it
generally deposits a green or brown precipitate, which must be
separated by filtration. The liquid then contains nothing but
nitroprusside and nitrate of potash or soda. The nitrates being the
least soluble, are first crystallized, and the remaining liquid, on
farther evaporation, yields crystals of the nitroprusside. The sodium
salt crystallizes most easily.--(PLAYFAIR.)
As some substances, particularly in complicated compounds, are not
detected with sufficient nicety in the dry way of analysis, it will
often be necessary to resort to the wet way. It is therefore necessary
to have prepared the reagents required for such testing, as every
person, before he can become an expert blowpipe analyst, must be
acquainted with the characteristic tests as applied in the wet way.
* * * * *
Part II.
INITIATORY ANALYSIS.
Qualitative analysis refers to those examinations which relate simply
to the presence or the absence of certain substances, irrespective of
their quantities. But before we take cognizance of special
examinations, it would facilitate the progress of the student to pass
through a course of Initiatory Exercises. These at once lead into the
special analysis of all those substances susceptible of examination by
the blowpipe. The Initiatory Analysis is best studied by adopting the
following arrangement:
1. EXAMINATIONS WITH THE GLASS BULB.
The glass of which the bulb is made should be entirely free from lead,
otherwise fictitious results will ensue. If the bulb be of flint
glass, then by heating it, there is a slightly iridescent film caused
upon the surface of the glass, which may easily be mistaken for
arsenic. Besides, this kind of glass is easily fusible in the
oxidating flame of the blowpipe, while, in the reducing flame, its
ready decomposition would preclude its use entirely. The tube should
be composed of the potash or hard Bohemian glass, should be perfectly
white, and very thin, or the heat will crack it.
The tube should be perfectly clean, which can be easily attained by
wrapping a clean cotton rag around a small stick, and inserting it in
the tube. Before using the tube, see also that it is perfectly dry.
The quantity of the substance put into the tube for examination should
be small. From one to three grains is quite sufficient, as a general
rule, but circumstances vary the quantity. The sides of the tube
should not catch any of the substance as it is being placed at the
bottom of the tube, or into the bulb. If any of the powder, however,
should adhere, it should be pushed down with a roll of clean paper, or
the clean cotton rag referred to above.
In submitting the tube to the flame, it should be heated at first very
gently, the heat being increased until the glass begins to soften,
when the observations of what is ensuing within it may be made.
If the substance be of an organic nature, a peculiar empyreumatic odor
will be given off. If the substance chars, then it may be inferred
that it is of an organic nature. The matters which are given off and
cause the empyreumatic odor, are a peculiar oil, ammonia, carbonic
acid, acetic acid, water, cyanogen, and frequently other compounds. If
a piece of paper is heated in the bulb, a dark colored oil condenses
upon the sides of the tube, which has a strong empyreumatic odor. A
piece of litmus paper indicates that this oil is acid, as it is
quickly changed to red by contact with it. A black residue is now left
in the tube, and upon examination we will find that it is charcoal.
If, instead of the paper, a piece of animal substance is placed in
the bulb, the reddened litmus paper will be converted into its
original blue color, while charcoal will be left at the bottom of the
tube.
A changing of the substance, however, to a dark color, should not be
accepted as an invariable indication of charcoal, as some inorganic
bodies thus change color, but the dark substance will not be likely to
be mistaken for charcoal. By igniting the suspected substance with
nitrate of potassa, it can quickly be ascertained whether it is
organic or not, for if the latter, the vivid deflagration will
indicate it.
If the substance contains water, it will condense upon the cold
portion of the tube, and may be there examined as to whether it is
acid or alkaline. If the former, the matter under examination is,
perhaps, vegetable; if the latter, it is of an animal nature. The
water may be that fluid absorbed, or it may form a portion of its
constitution,
If the substance contain _sulphur_, the sublimate upon the cold part
of the tube may be recognized by its characteristic appearance,
especially if the substance should be a sulphide of tin, copper,
antimony, or iron. The hyposulphites, and several other sulphides,
also give off sulphur when heated. The volatile metals, mercury and
arsenic, will, however, sublime without undergoing decomposition. As
the sulphide of arsenic may be mistaken, from its color and
appearance, for sulphur, it must be examined especially for the
purpose of determining that point.
_Selenium_ will likewise sublime by heat as does sulphur. This is the
case if selenides are present. Selenium gives off the smell of decayed
horse-radish.
When the persalts are heated they are reduced to protosalts, with the
elimination of a part of their acid. This will be indicated by the
blue litmus paper.
If some of the neutral salts containing a volatile acid be present,
they will become decomposed. For instance, the red nitrous acid water
of the nitrates will indicate the decomposition of the salt,
especially if it be the nitrate of a metallic oxide.
If there is an odor of sulphur, then it is quite probable, if no free
sulphur be present, that a hyposulphite is decomposed.
If an oxalate be present, it is decomposed with the evolution of
carbonic oxide, which may be inflamed at the mouth of the tube; but
there are oxalates that give off carbonic acid gas, which, of course,
will not burn. A cyanide will become decomposed and eliminate nitrogen
gas, while the residue is charred. Some cyanides are, however, not
thus decomposed, as the dry cyanides of the earths and alkalies.
There are several oxides of metals which will sublime, and may be thus
examined in the tube. _Arsenious acid_ sublimes with great ease in
minute octohedral crystals. The oxides of tellurium and antimony will
sublime, the latter in minute glittering needles.
There are several metals which will sublime, and may be examined in
the cold portion of the tube. _Mercury_ condenses upon the tube in
minute globules. These often do not present the metallic appearance
until they are disturbed with a glass rod, when they attract each
other, and adhere as small globules. Place in the tube about a grain
of red precipitate of the drug stores and apply heat, when the oxide
will become decomposed, its oxygen will escape while the vaporized
mercury will condense upon the cold portion of the tube, and may there
be examined with a magnifying glass.
_Arsenic_, when vaporized, may be known by its peculiar alliaceous
odor. Arsenic is vaporized from its metallic state, and likewise from
its alloys. Several compounds which contain arsenic will also sublime,
such as the arsenical cobalt. Place in the bulb a small piece of
arsenical cobalt or "fly-stone," and apply heat. The sulphide of
arsenic will first rise, but soon the arsenic will adhere to the sides
of the tube.
The metals tellurium and cadmium are susceptible of solution, but the
heat required is a high one. This is best done upon charcoal.
The _perchloride of mercury_ sublimes undecomposed in the bulb,
previously undergoing fusion.
The _protochloride of mercury_ likewise sublimes, but it does not
undergo fusion first, as is the case with the corrosive sublimate.
The _ammoniacal salts_ all are susceptible of sublimation, which they
do without leaving a residue. There are, however, several which
contain fixed acids, which latter are left in the bulb. This is
particularly the case with the phosphates and borates. A piece of red
litmus paper will readily detect the escaping ammonia, while its odor
will indicate its presence with great certainty. The halogen compounds
of mercury, we should have mentioned, also sublime, the red iodide
giving a yellow sublimate.
The bulb is also a convenient little instrument for the purpose of
heating those substances which phosphoresce, and likewise those salts
that decrepitate.
Should the above reactions not be readily discerned, it should not be
considered as an indication that the substances are not present, for
they are frequently expelled in such combinations that the above
reactions will not take place. This is often the case with sulphur,
selenium, arsenic, and tellurium. It frequently happens, likewise,
that these substances are in such combinations that heat alone will
not sublime them; or else two or more of them may arise together, and
thus complicate the sublimate, so that the eye cannot readily detect
either substance. Sometimes sulphur and arsenic will coat the tube
with a metal-like appearance, which is deceptive. This coating
presents a metallic lustre at its lower portion, but changing, as it
progresses upward, to a dark brown, light brown, orange or yellow;
this sublimate being due to combinations of arsenic and sulphur, which
compounds are volatilized at a lower temperature than metallic
arsenic.
If certain reagents are mixed with many substances, changes are
effected which would not ensue with heat alone. _Formiate of soda_
possesses the property of readily reducing metallic oxides. When this
salt is heated, it gives off a quantity of carbonic oxide gas. This
gas, when in the presence of a metallic oxide, easily reduces the
metal, by withdrawing its oxygen from it, and being changed into
carbonic oxide. If a little fly-stone is mixed with some formiate of
soda, and heated in the bulb, the arsenic is reduced, volatilized, and
condenses in the cool portion of the tube. By this method, the
smallest portion of a grain of the arsenical compound may be thus
examined with the greatest readiness. If the residue is now washed, by
which the soda is got rid of, the metallic arsenic may be obtained in
small spangles. If the compound examined be the sulphide of antimony,
the one-thousandth part can be readily detected, and hence this method
is admirably adapted to the examination of medicinal antimonial
compounds. The arsenites of silver and copper are reduced by the
formiate of soda to their metals, mixed with metallic arsenic. The
mercurial salts are all reduced with the metal plainly visible as a
bright silvery ring on the cool portion of the tube. The chloride and
nitrate of silver are completely reduced, and may be obtained after
working out the soda, as bright metallic spangles. The salts of
antimony and zinc are thus reduced; also the sulphate of cadmium. The
sublimate of the latter, although in appearance not unlike that of
arsenic, can easily be distinguished by its brighter color. It is, in
fact, the rich yellow of this sublimate which has led artists to adopt
it as one of their most valued pigments.
2. EXAMINATIONS IN THE OPEN TUBE.
The substance to be operated upon should be placed in the tube, about
half an inch from the end, and the flame applied at first very
cautiously, increasing gradually to the required temperature. The
tube, in all these _roasting_ operations, as they are termed, should
be held in an inclined position. The nearer perpendicular the tube is
held, the stronger is the draught of air that passes through it. If
but little heat is required in the open tube operation, the
spirit-lamp is the best method of applying the heat. But if a greater
temperature is required, then recourse must be had to the blowpipe.
Upon the angle of inclination of the tube depends the amount of air
that passes through it, and therefore, the rapidity of the draught
may be easily regulated at the will of the operator. The inclination
of the tube may, as a general rule, be about the angle represented in
Fig. 14.
[Illustration Fig. 14.]
The length of the tube must be about six inches, so that the portion
upon which the substance rested in a previous examination may be cut
off. The portion of the tube left will answer for several similar
operations.
When the substance is under examination, we should devote our
attention to the nature of the sublimates, and to that of the _odors_
of the gases. If sulphur be in the substance experimented upon, the
characteristic odor of sulphurous acid gas will readily indicate the
sulphur. If metallic sulphides, for instance, are experimented upon,
the sulphurous acid gas eliminated will readily reveal their presence.
As it is a property of this gas to bleach, a piece of Brazil-wood test
paper should be held in the mouth of the tube, when its loss of color
will indicate the presence of the sulphurous acid. It often happens,
too, that a slight deposition of sulphur will be observed upon the
cool portion of the tube. This is particularly the case with those
sulphides, which yield sublimates of sulphur when heated in the bulb.
_Selenium_ undergoes but slight oxidation, but it becomes readily
volatilized, and may be observed on the cool portion of the tube. At
the same time the nose, if applied close to the end of the tube, will
detect the characteristic odor of rotten horse-radish. Arsenic also
gives its peculiar alliaceous odor, which is so characteristic that it
can be easily detected. A few of the arsenides produce this odor. The
_sublimates_ should be carefully observed, as they indicate often with
great certainty the presence of certain substances; for instance, that
of arsenic. The sublimate, in this case, presents itself as the
arsenious acid, or the metallic arsenic itself. If it be the former,
it may be discerned by aid of the magnifying glass as beautiful
glittering octohedral crystals. If the latter, the metallic lustre
will reveal it.
But it will be observed that while some of the arsenides are sublimed
at a comparatively low temperature, others require a very high one.
_Antimony_ gives a white sublimate when its salts are roasted, as the
sulphide, or the antimonides themselves, or the oxide of this metal.
This white sublimate is not antimonious acid, but there is mixed with
it the oxide of antimony with which the acid is sublimed. As is the
case with arsenious acid, the antimonious acid may, by dexterous
heating, be driven from one portion of the tube to another.
_Tellurium_, or its acid and oxide, may be got as a sublimate in the
tube. The tellurious acid, unlike the arsenious and antimonious acids,
cannot be driven from one portion of the tube to another, but, on the
contrary, it fuses into small clear globules, visible to the naked eye
sometimes, but quite so with the aid of the magnifying glass.
_Lead_, or its chloride, sublimes like tellurium, and, like that
substance, fuses into globules or drops.
_Bismuth_, or its sulphide, sublimes into an orange or brownish
globules, when it is melted, as directed above, for tellurium. The
color of the bismuth and lead oxides are somewhat similar, although
that of the latter is paler.
If any mineral containing _fluorine_, is fused, first with the
microcosmic salt bead, then put into the tube, and the flame of the
blowpipe be directed _into_ the tube upon the bead, hydrofluoric acid
is disengaged and attacks the inside of the tube. The fluoride of
calcium, or fluorspar, may be used for this experiment.
During the roasting, a brisk current of air should be allowed to pass
through the tube, whereby unoxidized matter may be prevented from
volatilization, and the clogging up of the substance under examination
be prevented.
3. EXAMINATIONS UPON CHARCOAL.
In making examinations upon charcoal, it is quite necessary that the
student should make himself familiar with the different and
characteristic appearances of the deposits upon the charcoal. In this
case I have found the advice given by Dr. Sherer to be the best; that
is, to begin with the examination of the pure materials first, until
the eye becomes familiarized with the appearances of their
incrustations upon charcoal.
The greater part of the metals fuse when submitted to the heat of the
blowpipe, and if exposed to the outer flame, they oxidize. These
metals, termed the noble metals, do not oxidize, but they fuse. The
metals platinum, iridium, rhodium, osmium and palladium do not fuse.
The metal osmium, if exposed to the flame of oxidation, fuses and is
finally dissipated as osmic acid. In the latter flame, the salts of
the noble metals are reduced to the metallic state, and the charcoal
is covered with the bright metal.
We shall give a brief description of the appearance of the principal
elementary bodies upon being fused with charcoal. This plan is that
deemed the most conducive to the progress of the student, by
Berzelius, Plattner, and Sherer. Experience has taught us that this
method is the most efficient that could have been devised as an
initiatory exercise for the student, ere he commences a more concise
and methodical method of analysis. In these reactions upon charcoal,
we shall follow nearly the language of Plattner and Sherer.
SELENIUM is not difficult of fusion, and gives off brown fumes in
either the oxidation or reduction flame. The deposit upon the charcoal
is of a steel-grey color, with a slightly metallic lustre. The deposit
however that fuses outside of this steel-grey one is of a dull violet
color, shading off to a light brown. Under the flame of oxidation this
deposit is easily driven from one portion of the charcoal to another,
while the application of the reducing flame volatilizes it with the
evolution of a beautiful blue light. The characteristic odor of
decayed horse-radish distinguishes the volatilization of this metal.
TELLURIUM.--This metal fuses with the greatest readiness, and is
reduced to vapor under both flames with fumes, and coats the charcoal
with a deposit of tellurous acid. This deposit is white near the
centre, and is of a dark yellow near the edges. It may be driven from
place to place by the flame of oxidation, while that of reduction
volatilizes it with a green flame. If there be a mixture of selenium
present, then the color of the flame is bluish-green.
ARSENIC.--This metal is volatilized without fusing, and covers the
charcoal both in the oxidizing and reducing flames with a deposit of
arsenious acid. This coating is white in the centre, and grey towards
the edges, and is found some distance from the assay. By the most
gentle application of the flame, it is immediately volatilized, and if
touched for a moment with the reducing flame, it disappears, tinging
the flame pale blue. During volatilization a strong garlic odor is
distinctly perceptible, very characteristic of arsenic, and by which
its presence in any compound may be immediately recognized.
ANTIMONY.--This metal fuses readily, and coats the charcoal under both
flames with antimonious acid. This incrustation is of a white color
where thick, but of a bluish tint where it is thin, and is found
nearer to the assay than that of arsenic. When greatly heated by the
flame of oxidation, it is driven from place to place without coloring
the flame, but when volatilized by the flame of reduction, it tinges
the flame blue. As antimonious acid is not so volatile as arsenious
acid, they may thus be easily distinguished from one another.
When metallic antimony is fused upon charcoal, and the metallic bead
raised to a red heat, if the blast be suspended, the fluid bead
remains for some time at this temperature, giving off opaque white
fumes, which are at first deposited on the surrounding charcoal, and
then upon the bead itself, covering it with white, pearly crystals.
The phenomenon is dependent upon the fact, that the heated button of
antimony, in absorbing oxygen from the air, developes sufficient heat
to maintain the metal in a fluid state, until it becomes entirely
covered with crystals of antimonious acid so formed.
BISMUTH.--This metal fuses with ease, and under both flames covers the
charcoal with a coating of oxide, which, while hot, is of an
orange-yellow color, and after cooling, of a lemon-yellow color,
passing, at the edges, into a bluish white. This white coating
consists of the carbonate of bismuth. The sublimate from bismuth is
formed at a less distance from the assay than is the case with
antimony. It may be driven from place to place by the application of
either flame; but in so doing, the oxide is first reduced by the
heated charcoal, and the metallic bismuth so formed is volatilized and
reoxidized. The flame is uncolored.
LEAD.--This metal readily fuses under either flame, and incrusts the
charcoal with oxide at about the same distance from the assay as is
the case with bismuth. The oxide is, while hot, of a dark lemon-yellow
color, but upon cooling, becomes of a sulphur yellow. The carbonate
which is formed upon the charcoal, beyond the oxide, is of a
bluish-white color. If the yellow incrustation of the oxide be heated
with the flame of oxidation, it disappears, undergoing changes similar
to those of bismuth above mentioned. Under the flame of reduction,
it, however, disappears, tinging the flame blue.
CADMIUM.--This metal fuses with ease, and, in the flame of oxidation,
takes fire, and burns with a deep yellow color, giving off brown
fumes, which coat the charcoal, to within a small distance of the
assay, with oxide of cadmium. This coating exhibits its characteristic
reddish-brown color most clearly when cold. Where the coating is very
thin, it passes to an orange color. As oxide of cadmium is easily
reduced, and the metal very volatile, the coating of oxide may be
driven from place to place by the application of either flame, to
neither of which does it impart any color. Around the deposit of
oxide, the charcoal has occasionally a variegated tarnish.
ZINC.--This metal fuses with ease, and takes fire in the flame of
oxidation, burning with a brilliant greenish-white light, and forming
thick white fumes of oxide of zinc, which coat the charcoal round the
assay. This coating is yellow while hot, but when perfectly cooled,
becomes white. If heated with the flame of oxidation, it shines
brilliantly, but is not volatilized, since the heated charcoal is,
under these circumstances, insufficient to effect its reduction. Even
under the reducing flame, it disappears very slowly.
TIN.--This metal fuses readily, and, in the flame of oxidation,
becomes covered with oxide, which, by a strong blast, may be easily
blown off. In the reducing flame, the fused metal assumes a white
surface, and the charcoal becomes covered with oxide. This oxide is of
a pale yellow color while hot, and is quite brilliant when the flame
of oxidation is directed upon it. After cooling, it becomes white. It
is found immediately around the assay, and cannot be volatilized by
the application of either flame.
MOLYBDENUM.--This metal, in powder, is infusible before the blowpipe.
If heated in the outer flame, it becomes gradually oxidized, and
incrusts the charcoal, at a small distance from the assay, with
molybdic acid, which, near the assay, forms transparent crystalline
scales, and is elsewhere deposited as a fine powder. The incrustation,
while hot, is of a yellow color, but becomes white after cooling. It
may be volatilized by heating with either flame, and leaves the
surface of the charcoal, when perfectly cooled, of a dark-red copper
color, with a metallic lustre, due to the oxide of molybdenum, which
has been formed by the reducing action of the charcoal upon the
molybdic acid. In the reducing flame, metallic molybdenum remains
unchanged.
SILVER.--This metal, when fused alone, and kept in this state for some
time, under a strong oxidizing flame, covers the charcoal with a thin
film of dark reddish-brown oxide. If the silver be alloyed with lead,
a yellow incrustation of the oxide of that metal is first formed, and
afterwards, as the silver becomes more pure, a dark red deposit is
formed on the charcoal beyond. If the silver contains a small quantity
of antimony, a white incrustation of antimonious acid is formed, which
becomes red on the surface if the blast be continued. And if lead and
antimony are both present in the silver, after the greater part of
these metals have been volatilized, a beautiful crimson incrustation
is produced upon the charcoal. This result is sometimes obtained in
fusing rich silver ores on charcoal.
SULPHIDES, CHLORIDES, IODIDES, AND BROMIDES.
In blowpipe experiments, it rarely occurs that we have to deal with
pure metals, which, if not absolutely non-volatile, are recognized by
the incrustation they form upon charcoal. Some compound substances,
when heated upon charcoal, form white incrustations, resembling that
formed by antimony, and which, when heated, may, in like manner, be
driven from place to place. Among these are certain sulphides, as
sulphide of potassium, and sulphide of sodium, which are formed by the
action of the reducing flame upon the sulphates of potassa and soda,
and are, when volatilized, reconverted into those sulphates, and as
such deposited on the charcoal. No incrustation is, however, formed,
until the whole of the alkaline sulphate has been absorbed into the
charcoal, and has parted with its oxygen. As sulphide of potassium is
more volatile than sulphide of sodium, an incrustation is formed from
the former sooner than from the latter of these salts, and is
considerably thicker in the former case. If the potash incrustation be
touched with the reducing flame, it disappears with a violet-colored
flame; and if a soda incrustation be treated in like manner, an
orange-yellow flame is produced.
Sulphide of lithium, formed by heating the sulphate in the reducing
flame, is volatilized in similar manner by a strong blast, although
less readily than the sulphide of sodium. It affords a greyish white
film, which disappears with a crimson flame when submitted to the
reducing flame.
Besides the above, the sulphides of bismuth and lead give, when heated
in either flame, two different incrustations, of which the more
volatile is of a white color, and consists in the one case of sulphate
of lead, and in the other of sulphate of bismuth. If either of these
be heated under the reducing flame, it disappears in the former case
with a bluish flame, in the latter unaccompanied by any visible flame.
The incrustation formed nearest to the assay consists of the oxide of
lead or bismuth, and is easily recognized by its color when hot and
after cooling. There are many other metallic sulphides, which, when
heated by the blowpipe flame, cover the charcoal with a white
incrustation, as sulphide of antimony, sulphide of zinc, and sulphide
of tin. In all these cases, however, the incrustation consists of the
metallic oxide alone, and either volatilizes or remains unchanged,
when submitted to the oxidizing flame.
Of the metallic chlorides there are many which, when heated on
charcoal with the blowpipe flame, are volatilized and redeposited as a
white incrustation. Among these are the chlorides of potassium,
sodium, and lithium, which volatilize and cover the charcoal
immediately around the assay with a thin white film, after they have
been fused and absorbed into the charcoal, chloride of potassium forms
the thickest deposit, and chloride of lithium the thinnest, the
latter being moreover of a greyish-white color. The chlorides of
ammonium, mercury, and antimony volatilize without fusing.
The chlorides of zinc, cadmium, lead, bismuth, and tin first fuse and
then cover the charcoal with two different incrustations, one of which
is a white volatile chloride, and the other a less volatile oxide of
the metal.
Some of the incrustations formed by metallic chlorides disappear with
a colored flame when heated with the reducing flame; thus chloride of
potassium affords a violet flame, chloride of sodium an orange one,
chloride of lithium a crimson flame, and chloride of lead a blue one.
The other metals mentioned above volatilize without coloring the
flame.
The chloride of copper fuses and colors the flame of a beautiful blue.
Moreover, if a continuous blast be directed upon the salt, a part of
it is driven off in the form of white fumes which smell strongly of
chlorine, and the charcoal is covered with incrustations of three
different colors. That which is formed nearest to the assay is of a
dark grey color, the next, a dark yellow passing into brown, and the
most distant of a bluish white color. If this incrustation be heated
under the reducing flame, it disappears with a blue flame.
Metallic iodides and bromides behave upon charcoal in a similar manner
to the chlorides. Those principally deserving of mention are the
bromides and iodides of potassium and sodium. These fuse upon
charcoal, are absorbed into its pores, and volatilize in the form of
white fumes, which are deposited upon the charcoal at some distance
from the assay. When the saline films so formed are submitted to the
reducing flame, they disappear, coloring the flame in the same manner
as the corresponding chlorides.
4. EXAMINATIONS IN THE PLATINUM FORCEPS.
Before the student attempts to make an examination in the platinum
forceps or tongs, he should first ascertain whether or not it will
act upon the platinum. If the substance to be examined shall act
chemically upon the platinum, then it should be examined on the
charcoal, and the color of the flame ascertained as rigidly as
possible. The following list of substances produce the color attached
to them.
A. VIOLET.
Potash, and all its compounds, with the exception of the phosphate
and the borate, tinge the color of the flame violet.
B. BLUE.
Chloride of copper, Intense blue.
Lead, Pale clear blue.
Bromide of copper, Bluish green.
Antimony, Bluish green.
Selenium, Blue.
Arsenic, English green.
C. GREEN.
Ammonia, Dark green.
Boracic acid, Dark green.
Copper, Dark green.
Tellurium, Dark green.
Zinc, Light green.
Baryta Apple green.
Phosphoric acid, Pale green.
Molybdic acid, Apple green.
Telluric acid, Light green.
D. YELLOW.
Soda, Intense yellow.
Water, Feeble yellow.
E. RED.
Strontia, Intense crimson.
Lithia, Purplish red.
Potash, Violet red.
Lime, Purplish red.
The student may often be deceived in regard to the colors: for
instance, if a small splinter of almost any mineral be held at the
point of the flame of oxidation, it will impart a very slight yellow
to the flame. This is caused, doubtless, by the water contained in the
mineral. If the piece of platinum wire is used, and it should be wet
with the saliva, as is frequently done by the student, then the small
quantity of soda existing in that fluid will color the flame of a
light yellow hue.
A. THE VIOLET COLOR.
The salts of potash, with the exception of the borate and the
phosphate, color the flame of a rich violet hue. This color is best
discovered in the outer flame of the blowpipe, as is the case with all
the other colors. The flame should be a small one, with a lamp having
a small wick, while the orifice of the blowpipe must be quite small.
These experiments should likewise be made in a dark room, so that the
colors may be discerned with the greatest ease. In investigating with
potash for the discernment of color, it should be borne in mind that
the least quantity of soda will entirely destroy the violet color of
the potash, by the substitution of its own strong yellow color. If
there be not more than the two hundredth part of soda, the violet
reaction of the potash will be destroyed. This is likewise the case
with the presence of lithia, for its peculiar red color will destroy
the violet of the potash. Therefore in making investigations with the
silicates which contain potash, the violet color of the latter can
only be discerned when they are free from soda and lithia.
B. THE BLUE COLOR.
(_a._) _The Chloride of Copper._--Any of the chlorides produce a blue
color in the blowpipe flame, or any salt which contains chlorine will
show the blue tint, as the color in this case is referable to the
chlorine itself. There are, however, some chlorides which, in
consequence of the peculiar reactions of their bases, will not produce
the blue color, although in these cases the blue of the chlorine will
be very likely to blend itself with the color produced by the base.
The chloride of copper communicates an intense blue to the flame, when
fused on the platinum wire. If the heat be continued until the
chlorine is driven off, then the greenish hue of the oxide of copper
will be discerned.
(_b._) _Lead._--Metallic lead communicates to the flame a pale blue
color. The oxide reacts in the same manner. The lead-salts, whose
acids do not interfere with the color, impart also a fine blue to the
flame, either in the platina forceps, or the crooked wire.
(_c._) _Bromide of Copper._--This salt colors the flame of a
bluish-green color, but when the bromine is driven off, then we have
the green of the oxide of copper.
(_d._) _Antimony._--This metal imparts a blue color to the blowpipe
flame, but if the metal is in too small a quantity, then the color is
a brilliant white. If antimony is fused on charcoal, the fused metal
gives a blue color. The white sublimate which surrounds the fused
metal, being subjected to the flame of oxidation, disappears from the
charcoal with a bluish-green color.
(_e._) _Selenium._--If fused in the flame of oxidation, it imparts to
the flame a deep blue color. The incrustation upon charcoal gives to
the flame the same rich color.
(_f._) _Arsenic._--The arseniates and metallic arsenic itself impart
to the blowpipe flame a fine blue color, provided that there is no
other body present which may have a tendency to color the flame with
its characteristic hue. The sublimate of arsenious acid which
surrounds the assay, will give the same blue flame, when dissipated by
the oxidation flame. The platinum forceps will answer for the
exhibition of the color of arsenic, even though the salts be
arseniates, whose bases possess the property of imparting their
peculiar color to the flame, such as the arseniate of lime.
C. THE GREEN COLOR.
(_a._) _Ammonia._--The salts of ammonia, when heated before the
blowpipe, and just upon the point of disappearing, impart to the flame
a feeble though dark green color. This color, however, can only be
discerned in a dark room.
(_b._) _Boracic Acid._--If any one of the borates is mixed with two
parts of a flux composed of one part of pulverized fluorspar, and four
and a half parts of bisulphate of potash, and after being melted, is
put upon the coil of a platinum wire, and held at the point of the
blue flame, soon after fusion takes place a dark green color is
discerned, but it is not of long duration. The above process is that
recommended by Dr. Turner. The green color of the borates may be
readily seen by dipping them, previously moistened with sulphuric
acid, into the upper part of the blue flame, when the color can be
readily discerned. If soda be present, then the rich green of the
boracic acid is marred by the yellow of the soda. Borax, or the
biborate of soda (NaO, 2BO_{3}) may be used for this latter reaction,
but if it be moistened with sulphuric acid, the green of the boracic
acid can then be seen. If the borates, or minerals which contain
boracic acid, are fused on charcoal with carbonate of potash, then
moistened with sulphuric acid and alcohol, then the bright green of
the boracic acid is produced, even if the mineral contains but a
minute portion of the boracic acid.
(_c._) _Copper_. Nearly all the ores of copper and its salts, give a
bright green color to the blowpipe flame. Metallic copper likewise
colors the flame green, being first oxidized. If iodine, chlorine, and
bromine are present, the flame is considerably modified, but the
former at least intensifies the color. Many ores containing copper
also color the flame green, but the internal portion is of a bright
blue color if the compound contains lead, the latter color being due
to the lead. The native sulphide and carbonate of copper should be
moistened with sulphuric acid, while the former should be previously
roasted. If hydrochloric acid is used for moistening the salts, then
the rich green given by that moistened with the sulphuric acid is
changed to a blue, being thus modified by the chlorine of the acid.
Silicates containing copper, if heated in the flame in the platinum
forceps, impart a rich green color to the outer flame. In fact, if any
substance containing copper be submitted to the blowpipe flame, it
will tinge it green, provided there be no other substance present to
impart its own color to the flame, and thus modify or mar that of the
copper.
(_d._) _Tellurium._--If the flame of reduction is directed upon the
oxide of tellurium placed upon charcoal, a green color is imparted to
it. If the telluric acid be placed upon platinum wire in the reduction
flame, the oxidation flame is colored green. Or if the sublimate be
dissipated by the flame of oxidation, it gives a green color. If
selenium be present, the green color is changed to a blue.
(_e._) _Zinc._--The oxide of zinc, when strongly heated, gives a blue
flame. This is especially the case in the reducing flame. The flame is
a small one, however, and not very characteristic, as with certain
preparations of zinc the blue color is changed to a bright white. The
soluble salts of zinc give no blue color.
(_f._) _Baryta._--The soluble salts of baryta, moistened, and then
submitted to the reduction flame, produce a green color. The salt
should be moistened, when the color will be strongly marked in the
outer flame. The insoluble salts do not produce so vivid a color as
the soluble salts, and they are brighter when they have previously
been moistened. The carbonate does not give a strong color, but the
acetate does, so long as it is not allowed to turn to a carbonate. The
chloride, when fused on the platinum wire, in the point of the
reduction flame, imparts a fine green color to the oxidation flame.
This tint changes finally to a faint dirty green color. The sulphate
of baryta colors the flame green when heated at the point of the
reduction flame. But neither the sulphate, carbonate, nor, in fact,
any other salt of baryta, gives such a fine green color as the
chloride. The presence of lime does interfere with the reaction of
baryta, but still does not destroy its color.
(_g._) _Phosphoric Acid._--The phosphates give a green color to the
oxidation flame, especially when they are moistened with sulphuric
acid. This is best shown with the platinum forceps. The green of
phosphoric, or the phosphates, is much less intense than that of the
borates or boracic acid, but yet the reaction is a certain one, and is
susceptible of considerable delicacy, either with the forceps, or
still better upon platinum wire. Sulphuric acid is a great aid to the
development of the color, especially if other salts be present which
would be liable to hide the color of the phosphoric acid. In this
reaction with phosphates, the water should be expelled from them
previous to melting them with sulphuric acid. They should likewise be
pulverized. Should soda be present it will only exhibit its peculiar
color after the phosphoric acid shall have been expelled; therefore,
the green color of the phosphoric acid should be looked for
immediately upon submitting the phosphate to heat.
(_h._) _Molybdic Acid._--If this acid or the oxide of molybdenum be
exposed upon a platinum wire to the point of the reduction flame, a
bright green color is communicated to the flame of oxidation. Take a
small piece of the native sulphide of molybdenum, and expose it in the
platinum tongs to the flame referred to above, when the green color
characteristic of this metal will be exhibited.
(_i._) _Telluric Acid._--If the flame of reduction is directed upon a
small piece of the oxide of tellurium placed upon charcoal, a bright
green color is produced. Or if telluric acid be submitted to the
reduction flame upon the loop of a platinum wire, it communicates to
the outer flame the bright green of tellurium. If the sublimate found
upon the charcoal in the first experiment be submitted to the blowpipe
flame, the green color of tellurium is produced while the sublimate is
volatilized. If selenium be present the green color is changed to a
deep blue one.
D. YELLOW.
The salts of soda all give a bright yellow color when heated in the
platinum loop in the reduction flame. This color is very persistent,
and will destroy the color of almost any other substance. Every
mineral of which soda is a constituent, give this bright orange-yellow
reaction. Even the silicate of soda itself imparts to the flame of
oxidation the characteristic yellow of soda.
E. RED.
(_a._) _Strontia._--Moisten a small piece of the chloride of
strontium, put it in the platinum forceps and submit it to the flame
of reduction, when the outer flame will become colored of an intense
red. If the salt of strontia should be a soluble one, the reaction is
of a deeper color than if an insoluble salt is used, while the color
is of a deeper crimson if the salt is moistened. If the salt be a
soluble one, it should be moistened and dipped into the flame, while
if it be an insoluble salt, it should be kept dry and exposed beyond
the point of the flame. The carbonate of strontia should be moistened
with hydrochloric acid instead of water, by which its color similates
that of the chloride of strontium when moistened with water. In
consequence of the decided red color which strontia communicates to
flame, it is used by pyrotechnists for the purpose of making their
"crimson fire."
(_b._) _Lithia._--The color of the flame of lithia is slightly
inclined to purple. The chloride, when placed in the platinum loop,
gives to the outer flame a bright red color, sometimes with a slight
tinge of purple. Potash does not prevent this reaction, although it
may modify it to violet; but the decided color of soda changes the red
of lithia to an orange color. If much soda be present, the color of
the lithia is lost entirely. The color of the chloride of lithium may
be distinctly produced before the point of the blue flame, and its
durability may be the means of determining it from that of lithium,
as the latter, under the same conditions, is quite evanescent. The
minerals which contain lithia, frequently contain soda, and thus the
latter destroys the color of the former.
(_c._) _Potash._--The salts of potash, if the acid does not interfere,
give a purplish-red color before the blowpipe; but as the color is
more discernibly a purple, we have classed it under that color.
(_d._) _Lime._--The color of the flame of lime does not greatly differ
from that of strontia, with the exception that it is not so decided.
Arragonite and calcareous spar, moistened with hydrochloric acid, and
tried as directed for strontia, produce a red light, not unlike that
of strontia. The chloride of calcium gives a red tinge, but not nearly
so decided as the chloride of strontium. The carbonate of lime will
produce a yellowish flame for a while, until the carbonic acid is
driven off, when the red color of the lime may be discerned.
If the borate or phosphate of lime be used, the green color of the
acids predominates over the red of the lime. Baryta also destroys the
red color of the lime, by mixing its green color with it. There is but
one silicate of lime which colors the flame red, it is the variety
termed tabular spar.
5. EXAMINATIONS IN THE BORAX BEAD.
In order to examine a substance in borax, the loop of the platinum
wire should, after being thoroughly cleaned, and heated to redness, be
quickly dipped into the powdered borax, and then quickly transferred
to the flame of oxidation, and there fused. If the bead is not large
enough to fill the loop of the wire, it must be subjected again to the
same process. By examining the bead, both when hot and cold, by
holding it up against the light, it can be soon ascertained whether it
is free from dirt by the transparency, or the want of it, of the bead.
In order to make the examination of a substance, the bead should be
melted and pressed against it, when enough will adhere to answer the
purpose. This powder should then be fused in the oxidation flame until
it mixes with, and is thoroughly dissolved by the borax bead.
The principal objects to be determined now are: the color of the borax
bead, both when heated and when cooled; also the rapidity with which
the substance dissolves in the bead, and if any gas is eliminated.
If the color of the bead is the object desired, the quantity of the
substance employed must be very small, else the bead will be so deeply
colored, as in some cases to appear almost opaque, as, for instance,
in that of cobalt. Should this be the case, then, while the bead is
still red hot, it should be pressed flat with the forceps; or it may,
while soft, be pulled out to a thin thread, whereby the color can be
distinctly discovered.
Some bodies, when heated in the borax bead, present a clear bead both
while hot and cold; but if the bead be heated with the intermittent
flame, or in the flame of reduction, it becomes opalescent, opaque or
milk-white. The alkaline earths are instances of this kind of
reaction, also glucina oxide of cerium, tantalic and titanic acids,
yttria and zirconia. But if a small portion of silica should be
present, then the bead becomes clear. This is likewise the case with
some silicates, provided there be not too large a quantity present,
that is: over the quantity necessary to saturate the borax, for, in
that case, the bead will be opaque when cool.
If the bead be heated on charcoal, a small tube or cavity must be
scooped out of the charcoal, the bead placed in it, and the flame of
reduction played upon it. When the bead is perfectly fused, it is
taken up between the platinum forceps and pressed flat, so that the
color may be the more readily discerned. This quick cooling also
prevents the protoxides, if there be any present, from passing into a
higher degree of oxidation.
The bead should first be submitted to the oxidation flame, and any
reaction carefully observed. Then the bead should be submitted to the
flame of reduction. It must be observed that the platinum forceps
should not be used when there is danger of a metallic oxide being
reduced, as in this case the metal would alloy with the platinum and
spoil the forceps. In this case charcoal should be used for the
support. If, however, there be oxides present which are not reduced by
the borax, then the platinum loop may be used. Tin is frequently used
for the purpose of enabling the bead to acquire a color for an oxide
in the reducing flame, by its affinity for oxygen. The oxide, thus
being reduced to a lower degree of oxidation, imparts its peculiar
tinge to the bead as it cools.
The arsenides and sulphides, before being examined, should be roasted,
and then heated with the borax bead. The arsenic of the former, it
should be observed, will act on the glass tube in which the
sublimation is proceeding, if the glass should contain lead.
It should be recollected that earths, metallic oxides, and metallic
acids are soluble in borax, except those of the easily reducible
metals, such as platinum or gold, or of mercury, which too readily
vaporize. Also the metallic sulphides, after the sulphur has been
driven off. Also the salts of metals, after their acids are driven off
by heat. Also the nitrates and carbonates, after their acids are
driven off during the fusion. Also the salts of the halogens, such as
the chlorides, iodides, bromides, etc., of the metals. Also the
silicates, but with great tardiness. Also the phosphates and borates
that fuse in the bead without suffering decomposition. The metallic
sulphides are insoluble in borax, and many of the metals in the pure
state.
There are many substances which give clear beads with borax both while
hot and cold, but which, upon being heated with the intermittent
oxidation flame, become enamelled and opaque. The intermittent flame
may be readily attained, not by varying the force of the air from the
mouth, but by raising and depressing the bead before the point of the
steady oxidating flame. The addition of a little nitrate of potash
will often greatly facilitate the production of a color, as it
oxidizes the metal. The hot bead should be pressed upon a small
crystal of the nitrate, when the bead swells, intumesces, and the
color is manifested in the surface of the bead,
6. EXAMINATIONS IN MICROCOSMIC SALT.
Microcosmic salt is a better flux for many metallic oxides than borax,
as the colors are exhibited in it with more strength and character.
Microcosmic salt is the phosphate of soda and ammonia. When it is
ignited it passes into the biphosphate of soda, the ammonia being
driven off. This biphosphate of soda possesses an excess of phosphoric
acid, and thus has the property of dissolving a great number of
substances, in fact almost any one, with the exception of silica. If
the substances treated with this salt consist of sulphides or
arsenides, the bead must be heated on charcoal. But if the substance
experimented upon consists of earthly ingredients or metallic oxides,
the platinum wire is the best. If the latter is used a few additional
turns should be given to the wire in consequence of the greater
fluidity of the bead over that of borax. The microcosmic salt bead
possesses the advantage over that of borax, that the colors of many
substances are better discerned in it, and that it separates the
acids, the more volatile ones being dissipated, while the fixed ones
combine with a portion of the base equally with the phosphoric acid,
or else do not combine at all, but float about in the bead, as is the
case particularly with silicic acid. Many of the silicates give with
borax a clear bead, while they form with microcosmic salt an
opalescent one.
It frequently happens, that if a metallic oxide will not give its
peculiar color in one of the flames, that it will in the other, as the
difference in degree with which the metal is oxidized often determines
the color. If the bead is heated in the reducing flame, it is well
that it should be cooled rapidly to prevent a reoxidation. Reduction
is much facilitated by the employment of metallic tin, whereby the
protoxide or the reduced metal may be obtained in a comparatively
brief time.
The following tables, taken from Plattner and Sherer, will present the
reactions of the metallic oxides, and some of the metallic acids, in
such a clear light, that the student cannot very easily be led astray,
if he gives the least attention to them. It frequently happens that a
tabular statement of reactions will impress facts upon the memory when
long detailed descriptions will fail to do so. It is for this purpose
that we subjoin the following excellent tables.
* * * * *
TABLE I.
A. BORAX.
1. Oxydizing flame.
2. Reducing "
B. MICROCOSMIC SALT.
1. Oxydizing flame.
2. Reducing "
A. BORAX
1. Oxydizing flame
--------------------------------------------------------------------------
Color of Bead.
--+-----------------------------------------------------------------------
| Substances which produce this color
+--------------------------------------+--------------------------------
| in the hot bead. | in the cold bead.
--+--------------------------------------+--------------------------------
Colorless
-----------------------------------------+--------------------------------
| Silica \ | Silica
| Alumina \ | Alumina _
| Oxide of Tin | | Oxide of Tin \
| Telluric Acid | | Telluric Acid \
| Baryta | | Baryta \
| Strontia | | Strontia |
| Lime | | Lime |
| Magnesia | | Magnesia |
| Glucina | In all | Glucina |
| Yttria } proportions. | Yttria |
| Zirconia | | Zirconia |
| Thoria | | Thoria |With
| Oxide of Lanthanum | | Oxide of Lanthanum |intermittent
| | | " " Silver }flame
| Tantalic Acid | | Tantalic Acid |opaque
| Niobic " | | Niobic " |white.
| Pelopic " / | Pelopic " |
| Titanic " _/ | Titanic " |
| _ | |
| Tungstic " \ In small | Tungstic " |
| Molybdic " \ quantity | Molybdic " |
| Oxide of Zinc | only. | Oxide of Zinc /
| " " Cadmium } | " " Cadmium_/
| " " Lead | In large | " " Lead
| " " Bismuth / quantity | " " Bismuth
| " " Antimony / yellow. | " " Antimony
--+-----------+--------------------------+--------------------------------
Yellow, orange-red and reddish-brown.
--+-----------+--------------------------+--------------------------------
| _ |
| Titanic Acid, yellow \ |
| Tungstic Acid, yellow \ |
| Molybdic Acid, dark yellow|when in |
| Oxide of Zinc, pale-yellow|large |
| Oxide of Cadmium, }quantity. |
| pale-yellow |Otherwise |
| Oxide of Lead, yellow |colorless.|
| Oxide of Bismuth, orange / |
| Oxide of Antimony, yellow/ |
| Oxide of Cerium, red | Oxide of Cerium with interm.
| Oxide of Iron, dark red | flame opaque white.
| Oxide of Uranium, red | Oxide of Iron, yellow
| Oxide of Silver | Oxide of Uranium with interm.
| | flame opaque yellow.
| | Oxide of Silver in large
| | proportion, with interm.
| | flame yellow.
| Vanadic Acid, yellow | Vanadic Acid, yellow.
| Oxide of Chromium, dark-red | Oxide of Nickel,
| | reddish-brown.
| | Oxide of Manganese, red to
| | violet.
--+--------------------------------------+--------------------------------
Violet or Amethyst.
--+--------------------------------------+--------------------------------
| Oxide of Nickel |
| " " Manganese | Oxide of Didymium.
| " " Didymium |
--+--------------------------------------+--------------------------------
Blue.
--+--------------------------------------+--------------------------------
| Oxide of Cobalt | Oxide of Cobalt.
| | " Copper, blue to
| | greenish-blue.
--+--------------------------------------+--------------------------------
Green.
--+--------------------------------------+--------------------------------
| Oxide of Copper | Oxide of Chromium, with
| | yellowish tinge.
--+--------------------------------------+--------------------------------
A. BORAX
2. Reducing flame
--+--------------------------------------+--------------------------------
Color of Bead.
--+-----------------------------------------------------------------------
| Substances which produce this color
+--------------------------------------+--------------------------------
| in the hot bead. | in the cold bead.
--+--------------------------------------+--------------------------------
Colorless
--+--------------------------------------+--------------------------------
| Silica | Silica
| Alumina | Alumina
| Oxide of Tin | Oxide of Tin _
| Baryta | Baryta \
| Strontia | Strontia \
| Lime | Lime |
| Magnesia | Magnesia |With
| Glucina | Glucina |intermittent
| Yttria | Yttria }flame
| Zirconia | Zirconia |opaque-white.
| Thoria | Thoria only when |
| | saturated |
| Oxide of Lanthanum | Oxide of Lanthanum |
| " " Cerium | " " Cerium /
| Tantalic Acid | Tantalic Acid _/
| Oxide of Didymium | Oxide of Didymium
| " " Manganese | " " Manganese
| _ | _
| Niobic Acid \ In small | Niobic Acid \ In small
| Pelopic " } proportions. | Pelopic " } proportions.
| _/ | _/
| _ | _
| Oxide of Silver \ | Oxide of Silver \ After
| " " Zinc \ After long | " " Zinc \ long
| " " Cadmium | continued | " " Cadmium | continued
| " " Lead } blowing. | " " Lead } blowing.
| " " Bismuth | Otherwise | " " Bismuth | Otherwise
| " " Antimony| grey. | " " Antimony | grey.
| " " Nickel / | " " Nickel /
| Telluric Acid _/ | Telluric Acid _/
--+--------------------------------------+--------------------------------
Yellow to brown.
--+--------------------------------------+--------------------------------
| Titanic Acid | Titanic Acid.
| Tungstic " | Tungstic "
| Molybdic " | Molybdic "
| Vanadic " |
--+--------------------------------------+--------------------------------
Blue.
--+--------------------------------------+--------------------------------
| Oxide of Cobalt. | Oxide of Cobalt.
| | Titanic Acid with intermittent
| | flame opaque-blue.
--+--------------------------------------+--------------------------------
Green.
--+--------------------------------------+--------------------------------
| Oxide of Iron | Oxide of Iron, bottle-green.
| " " Uranium | Oxide of Uranium, bottle-
| " " Chromium | green.
| | Oxide of Chromium, emerald-
| | green.
| | Vanadic Acid, emerald-green.
--+--------------------------------------+--------------------------------
Opaque-grey. (The opacity generally becomes distinct during cooling.)
--+--------------------------------------+--------------------------------
| _ |
| Oxide of Silver \ | Oxide of Silver._
| " " Zinc \ After | " " Zinc \ After
| " " Cadmium | short | " " Cadmium \short
| " " Lead } blowing. | " " Lead |blowing.
| " " Bismuth | Otherwise | " " Bismuth }Otherwise
| " " Antimony| colorless. | " " Antimony |colorless.
| " " Nickel / | " " Nickel /
| Telluric Acid _/ | Telluric Acid _/
| _ | _
| Niobic Acid \ After long | Niobic Acid\ After long
| Pelopic " | continued blowing | Pelopic " | continued
| } and in | } blowing and
| | considerable | | in considerable
| _/ proportion. | _/ proportion.
| |
--+--------------------------------------+--------------------------------
Opaque red and reddish-brown.
--+--------------------------------------+--------------------------------
| Oxide of Copper | Oxide of Copper.
--+--------------------------------------+--------------------------------
B. MICROCOSMIC SALT.
1. Oxydizing flame.
--+--------------------------------------+--------------------------------
Color of Bead.
--+-----------------------------------------------------------------------
| Substances which produce this color
+--------------------------------------+--------------------------------
| in the hot bead. | in the cold bead.
--+--------------------------------------+--------------------------------
Colorless
--+--------------------------------------+--------------------------------
| _ |
| Silica (only \ | Silica
| slightly soluble)\ |
| Alumina | | Alumina
| Oxide of Tin | | Oxide of Tin _
| Telluric Acid | | Telluric Acid \
| Baryta | | Baryta \
| Strontia | | Strontia |With
| Lime | In all | Lime |intermittent
| Magnesia } proportions. | Magnesia }flame
| Glucina | | Glucina |opaque
| Yttria | | Yttria |white.
| Zirconia | | Zirconia |
| Thoria | | Thoria /
| Oxide of Lanthanum | | Oxide of Lanthanum/
| | | " " Cerium
| Niobic Acid / | Niobic Acid
| Pelopic " _/ | Pelopic "
| Tantalic " | Tantalic "
| Titanic " | Titanic "
| Tungstic " _ | Tungstic "
| Oxide of Zinc \ In small | Oxide of Zinc
| " " Cadmium \ quantity only. | " " Cadmium
| " " Lead } In large | " " Lead
| " " Bismuth | quantity | " " Bismuth
| " " Antimony / yellow. | " " Antimony
| _/ |
--+--------------------------------------+--------------------------------
Yellow, orange, red and brown.
--+--------------------------------------+--------------------------------
| Tantalic Acid _ |
| Titanic " \ |
| Tungstic " | |
| Oxide of Zinc | In large |
| " " Cadmium } quantity. |
| " " Lead | |
| " " Bismuth | |
| " " Antimony _/ |
| " " Silver | Oxide of Silver.
| " " Cerium |
| " " Iron | Oxide of Iron.
| " " Nickel | " " Nickel.
| " " Uranium | " " Uranium,
| | yellowish-green.
| Vanadic Acid | Vanadic Acid.
| Oxide of Chromium |
--+--------------------------------------+--------------------------------
Violet or Amethyst.
--+--------------------------------------+--------------------------------
| Oxide of Manganese | Oxide of Manganese.
| " " Didymium | " " Didymium.
--+--------------------------------------+--------------------------------
Blue.
--+--------------------------------------+--------------------------------
| Oxide of Cobalt | Oxide of Cobalt
| | Oxide of Copper, to
| | greenish-blue.
--+--------------------------------------+--------------------------------
Green.
--+--------------------------------------+--------------------------------
| Molybdic Acid, yellowish-green | Molybdic Acid, yellowish-green.
| Oxide of Copper | Oxide of Uranium,
| | yellowish-green.
| | Oxide of Chromium,
| | emerald-green.
--+--------------------------------------+--------------------------------
B. MICROCOSMIC SALT.
2. Reducing flame.
--+--------------------------------------+--------------------------------
Color of Bead.
--+-----------------------------------------------------------------------
| Substances which produce this color
+--------------------------------------+---------------------------------
| in the hot bead. | in the cold bead.
--+--------------------------------------+--------------------------------
Colorless
--+--------------------------------------+--------------------------------
| Silica (only slightly soluble) | Silica (only slightly soluble).
| Alumina | Alumina.
| Oxide of Tin | Oxide of Tin. _
| Baryta | Baryta \
| Strontia | Strontia \
| Lime | Lime |
| Magnesia | Magnesia |With an
| Glucina | Glucina }intermittent
| Yttria | Yttria |flame
| Zirconia | Zirconia |opaque-
| Thoria | Thoria only when |white.
| | saturated /
| Oxide of Lanthanum | Oxide of Lanthanum/
| " " Cerium | " " Cerium.
| " " Didymium | " " Didymium.
| " " Manganese | " " Manganese.
| Tantalic Acid _ | Tantalic Acid.
| Oxide of Silver \ | Oxide of Silver _
| " " Zinc \ | " " Zinc \ After
| " " Cadmium | After long | " " Cadmium \ long
| " " Lead } continued | " " Lead | continued
| " " Bismuth | blowing. | " " Bismuth } blowing.
| " " Antimony | Otherwise grey. | " " Antimony | Otherwise
| " " Nickel / | " " Nickel / grey.
| Telluric Acid _/ | Telluric Acid _/
--+--------------------------------------+--------------------------------
Yellow, red, and brown.
--+--------------------------------------+--------------------------------
| Oxide of Iron, red | Oxide of Iron.
| Titanic Acid, yellow |
| Pelopic Acid, brown | Pelopic Acid.
| Ferruginous Titanic Acid, blood red | Ferruginous Titanic Acid.
| " Niobic " " | " Niobic "
| " Pelopic " " | " Pelopic "
| " Tungstic " " | " Tungstic "
| Vanadic Acid, brownish |
| Oxide of Chromium, reddish |
--+--------------------------------------+--------------------------------
Violet or Amethyst.
--+--------------------------------------+--------------------------------
| Niobic Acid in large proportion | Niobic Acid in large proportion.
| | Titanic Acid.
--+--------------------------------------+--------------------------------
Blue.
--+--------------------------------------+--------------------------------
| Oxide of Cobalt | Oxide of Cobalt.
| Tungstic Acid | Tungstic Acid.
| Niobic Acid in very large proportion.| Niobic Acid in very large
| | proportion.
--+--------------------------------------+--------------------------------
Green.
--+--------------------------------------+--------------------------------
| Oxide of Uranium | Oxide of Uranium.
| Molybdic Acid | Molybdic Acid.
| | Vanadic "
| | Oxide of Chromium.
--+--------------------------------------+--------------------------------
Opaque-grey. (The opacity generally becomes distinct during cooling.)
--+--------------------------------------+--------------------------------
| Oxide of Silver | Oxide of Silver.
| " " Zinc | " " Zinc.
| " " Cadmium | " " Cadmium.
| " " Lead | " " Lead.
| " " Bismuth | " " Bismuth.
| " " Antimony | " " Antimony.
| " " Nickel | " " Nickel.
| Telluric Acid | Telluric Acid.
--+--------------------------------------+--------------------------------
Opaque-red and reddish brown.
--+--------------------------------------+--------------------------------
| Oxide of Copper | Oxide of Copper.
--+--------------------------------------+--------------------------------
* * * * *
TABLE II.
Metallic Oxides
1. Oxide of Cerium, C^{2}O^{3}.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Dissolves into a red or dark yellow glass (similar to that
produced by iron). During cooling, the color diminishes in the
intensity and becomes finally yellow. If much oxide be dissolved,
an opaque bead may be obtained with an intermittent flame, and a
still larger quantity renders it opaque spontaneously.
in the reducing flame.
The color of the bead becomes paler, so that a bead, which is
yellow in the oxidizing flame, is rendered colorless. With a
large quantity of oxide the bead becomes white and crystalline
on cooling.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
As with borax. During the process of cooling the color entirely
disappears.
in the reducing flame.
Both, when hot and cold, the bead is colorless, by which
character oxide of cerium may be distinguished from oxide of
iron. The glass remains clear even when containing a large
quantity of the oxide.
* * * * *
2. Oxide of Lanthanum, LaO.
Behavior with Borax on Platinum wire
in the oxidizing flame.
Dissolves into a colorless glass, which, when sufficient oxide
is present, may be rendered opaque with an intermittent flame,
and becomes so spontaneously on cooling, when a still larger
amount is dissolved.
in the reducing flame.
As in the oxidizing flame.
Behavior with Mic. Salt on Platinum wire
in the oxidizing flame.
As with borax.
in the reducing flame.