THE METALS.
WHAT METALS ARE—CHARACTERISTICS AND GENERAL PROPERTIES OF
METALS—CLASSIFICATION—SPECIFIC GRAVITY—DESCRIPTIONS.
We have learnt that the elements are divided into metalloids and
metals, but the line of demarcation is very faint. It is very difficult
to define what a metal is, though we can say what it is not. It is
indeed impossible to give any absolute definition of a metal, except as
“an element which does not unite with hydrogen, or with another metal
to form a chemical compound.” This definition has been lately given by
Mr. Spencer, and we may accept it as the nearest affirmative definition
of a metal, though obviously not quite accurate.
A metal is usually supposed to be solid, heavy, opaque, ductile,
malleable, and tenacious; to possess good conducting powers for heat
and electricity, and to exhibit a certain shiny appearance known as
“metallic lustre.” These are all the conditions, but they are by
no means necessary, for very few metals possess them all, and many
non-metallic elements possess several. The “alkali” metals are lighter
than water; mercury is a fluid. The opacity of a mass is only in
relation to its thickness, for Faraday beat out metals into plates so
thin that they became transparent. All metals are not malleable, nor
are they ductile. Tin and lead, for example, have very little ductility
or tenacity, while bismuth and antimony have none at all. Carbon is a
much better conductor of electricity than many metals in which such
power is extremely varied. Lustre, again, though possessed by metals,
is a characteristic of some non-metals. So we see that while we can
easily say what is not a metal, we can scarcely define an actual metal,
nor depend upon unvarying properties to guide us in our determination.
[Illustration: Fig. 396.—Laminater.]
The affinity of metals for oxygen is in an inverse ratio to their
specific gravity, as can be ascertained by experiment, when the
heaviest metal will be the least ready to oxidise. Metals differ in
other respects, and thus classification and division become easier. The
fusibility of metals is of a very wide range, rising from a temperature
below zero to the highest heat obtainable in the blow-pipe, and even
then in the case of osmium there is a difficulty. While there can be no
question that certain elements, iron, copper, gold, silver, etc., are
metals proper, there are many which border upon the line of demarcation
very closely, and as in the case of arsenic even occupy the debatable
land.
SPECIFIC GRAVITY is the relation which the weight of substance bears
to the weight of an equal volume of water, as already pointed out in
PHYSICS. The specific gravities of the metals vary very much, as will
be seen from the table following—water being, as usual, taken as 1:—
Aluminium 2·56
Antimony 6·7
Arsenic 6·
Bismuth 9·7
Cadmium 8·6
Calcium 1·5
Chromium 6·8
Cobalt 8·9
Copper 8·9
Gold 19·3
Indium 7·3
Iridium 21·1
Iron 7·8
Lead 11·3
Lithium ·593
Magnesium 1·74
Manganese 8·
Mercury 13·5
Molybdenum 8·6
Nickel 8·8
Osmium 21·4
Palladium 11·8
Platinum 21·5
Potassium ·865
Rhodium 12·1
Rubidium 1·5
Ruthenium 11·4
Silver 10·5
Sodium ·972
Strontium 2·5
Thallium 11·8
Tin 7·2
Titanium 5·3
Tungsten 17·6
Uranium 18·4
Zinc 7·1
Zircon 4·3
Some metals are therefore lighter and some heavier than water.
The table underneath gives the approximate fusing points of some of the
metals (Centigrade Scale)—
(Ice melts at 0°.)
Platinum[21] about 1500°
Gold ” 1200°
Silver ” 1000°
Cast iron 1000-1200°
Wrought iron ” 1500°
Copper ” 1100°
Antimony ” 432°
Zinc ” 400°
Lead ” 330°
Bismuth ” 265°
Tin ” 235°
Sodium ” 97°
Potassium ” 60°
Mercury ” 40°
There are some metals which, instead of fusing,—that is, passing from
the solid to the liquid state,—go away in vapour. These are volatile
metals. Mercury, potassium, and sodium, can be thus distilled. Some do
not expand with heat, but contract (like ice), antimony and bismuth,
for instance, while air pressure has a considerable effect upon the
fusing point. Some vaporise at once without liquefying; others, such as
iron, become soft before melting.
ALLOYS are combinations of metals which are used for many purposes, and
become harder in union. Amalgams are alloys in which mercury is one
constituent. Some of the most useful alloys are under-stated:—
Name of Alloy. Composition.
Aluminium bronze Copper and aluminium.
Bell metal Copper and tin.
Bronze ” ”
Gun metal ” ”
Brass Copper and zinc.
Dutch metal ” ”
Mosaic gold ” ”
Ormulu ” ”
Tombac ” ”
German silver Copper, nickel, and zinc.
Britannia metal Antimony and tin.
Solder ” ”
Pewter Tin and lead.
Type metal Lead and antimony (also copper at times).
Shot Lead and arsenic.
Gold currency Gold and copper.
Silver currency Silver and copper.
Stereotype metal Lead, antimony, and bismuth.
Metals combine with chlorine, and produce chlorides,
Metals ” ” sulphur ” ” sulphides,
Metals ” ” oxygen ” ” oxides, and so on.
The metals may be classed as follows in divisions:—
Metals of the alkalies as POTASSIUM, SODIUM, LITHIUM, AMMONIUM.
Metals of the alkaline earths as BARIUM, CALCIUM, MAGNESIUM, STRONTIUM.
Metals of the earths as {ALUMINIUM, Cerium, Didymium, Erbium,
{Glucinium, Lanthanum, Terbium,
{Thorium, Yttrium, Zirconium.
Metals proper—
Common Metals as {IRON, MANGANESE, COBALT, NICKEL,
{COPPER, Bismuth, LEAD, TIN, ZINC,
{CHROMIUM, Antimony.
Noble Metals as {MERCURY, SILVER, GOLD, PLATINUM,
{Palladium, Rhodium, Ruthenium,
{Osmium, Iridium.
We cannot attempt an elaborate description of all the metals, but we
will endeavour to give a few particulars concerning the important ones,
leaving many parts for Mineralogy to supplement and enlarge upon. We
shall therefore mention only the most useful of the metals in this
place. We will commence with POTASSIUM.
METALS OF THE ALKALIES.
POTASSIUM has a bright, almost silvery, appearance, and is so greatly
attracted by oxygen that it cannot be kept anywhere if that element be
present—not even in water, for combustion will immediately ensue on
water; and in air it is rapidly tarnished. It burns with a beautiful
violet colour, and a very pretty experiment may easily be performed
by throwing a piece upon a basin of water. The fragment combines with
the oxygen of the water, the hydrogen is evolved, and burns, and the
potassium vapour gives the gas its purple or violet colour. The metal
can be procured by pulverizing carbonate of potassium and charcoal, and
heating them in an iron retort. The vapour condenses into globules in
the receiver, which is surrounded by ice in a wire basket. It must be
collected and kept in naphtha, or it would be oxidised. Potassium was
first obtained by Sir Humphrey Davy in 1807. Potash is the oxide of
potassium, and comes from the “ashes” of wood.
[Illustration: Fig. 397.—Preparation of potassium.]
The compounds of potassium are numerous, and exist in nature, and by
burning plants we can obtain potash (“pearlash”). Nitrate of potassium,
or nitre (saltpetre), (KNO_{3}), is a very important salt. It is found
in the East Indies. It is a constituent of gunpowder, which consists of
seventy-five parts of nitre, fifteen of charcoal, and ten of sulphur.
The hydrated oxide of potassium, or “caustic potash” (obtained from the
carbonate), is much used in soap manufactories. It is called “caustic”
from its property of cauterizing the tissues. Iodide, bromide, and
cyanide of potassium, are used in medicine and photography.
Soap is made by combining soda (for hard soap), or potash (for soft
soap), with oil or tallow. Yellow soap has turpentine, and occasionally
palm oil, added. Oils and fats combine with metallic oxides, and oxide
of lead with olive oil and resin forms the adhesive plaister with which
we are all familiar when the mixture is spread upon linen. Fats boiled
with potash or soda make soaps; the glycerine is sometimes set free
and purified as we have it. Sometimes it is retained for glycerine
soap. Fancy soap is only common soap coloured. White and brown Windsor
are the same soap—in the latter case browned to imitate age! Soap is
quite soluble in spirits, but in ordinary water it is not so greatly
soluble, and produces a lather, owing to the lime in the water being
present in more or less quantity, to make the water more or less “hard.”
[Illustration: Fig. 398.—Machine for cutting soap in bars.]
[Illustration: Fig. 399.—Soap-boiling house.]
SODIUM is not unlike potassium, not only in appearance, but in its
attributes; it can be obtained from the carbonate, as potassium is
obtained from its carbonate. _Soda_ is the oxide of sodium, but the
most common and useful compound of sodium is the chloride, or common
salt, which is found in mines in England, Poland, and elsewhere. Salt
may also be obtained by the evaporation of sea water. Rock salt is
got at Salzburg, and the German salt mines and works produce a large
quantity. The _Carbonate of Soda_ is manufactured from the chloride of
sodium, although it can be procured from the salsoda plants by burning.
The chloride of sodium is converted into sulphate, and then ignited
with carbonate of lime and charcoal. The soluble carbonate is extracted
in warm water, and sold in crystals as soda, or (anhydrous) “soda ash.”
The large quantity of hydrochloric acid produced in the first part
of the process is used in the process of making chloride of lime. A
few years back, soda was got from Hungary and various other countries
where it exists as a natural efflorescence on the shores of some lakes,
also by burning sea-weeds, especially the common bladder wrack (_Fucus
vesiculosus_), the ashes of which were melted into masses, and came
to market in various states of purity. The bi-carbonate of soda is
obtained by passing carbonic acid gas over the carbonate crystals. Soda
does not attract moisture from the air. It is used in washing, in glass
manufactories, in dyeing, soap-making, etc.
_Sulphate of Soda_ is “Glauber’s Salt”; it is also employed in
glass-making. Mixed with sulphuric acid and water, it forms a freezing
mixture. Glass, as we have seen, is made with silicic acid (sand),
soda, potassa, oxide of lead, and lime, and is an artificial silicate
of soda.
LITHIUM is the lightest of metals, and forms the link between alkaline
and the alkaline earth metals. The salts are found in many places in
solution. The chloride when decomposed by electricity yields the metal.
CÆSIUM and RUBIDIUM require no detailed notice from us. They were first
found in the solar spectrum, and resemble potassium.
AMMONIUM is only a conjectural metal. _Ammonia_, of which we have
already treated, is so like a metallic oxide that chemists have come
to the conclusion that its compounds contain a metallic body, which
they have named hypothetically AMMONIUM. It is usually classed amongst
the alkaline metals. The salts of ammonia are important, and have
already been mentioned. Muriate (chloride) of ammonia, or sal-ammoniac,
is analogous to chloride of sodium and chloride of potassium. It is
decomposed by heating it with slaked lime, and then gaseous ammonia is
given off.
[Illustration: Fig. 400.—Mottled soap-frames.]
THE METALS OF THE ALKALINE EARTHS.
BARIUM is the first of the four metals we have to notice in this
group, and will not detain us long, for it is little known in a free
condition. Its most important compound is heavy spar (_sulphate of
baryta_), which, when powdered, is employed as a white paint. The oxide
of barium, BaO, is termed baryta.
_Nitrate of Baryta_ is used for “green fire,” which is made as
follows:—Sulphur, twenty parts; chlorate of potassium, thirty-three
parts; and nitrate of baryta, eighty parts (by weight).
[Illustration: Fig. 401.—Soda furnace.]
* * * * *
CALCIUM forms a considerable quantity of our earth’s crust. It is the
metal of lime, which is the oxide of calcium. In a metallic state it
possesses no great interest, but its combinations are very important to
us. _Lime_ is, of course, familiar to all. It is obtained by evolving
the carbonic acid from carbonate of lime (CaO).
The properties of this lime are its white appearance, and it develops
a considerable amount of heat when mixed with water, combining to make
hydrate of lime, or “slaked lime.” This soon crumbles into powder, and
as a mortar attracts the carbonic acid from the air, by which means it
assumes the carbonate and very solid form, which renders it valuable
for cement and mortar, which, when mixed with sand, hardens. Caustic
lime is used in whitewashing, etc.
_Carbonate of Lime_ (CaCO_{3}) occurs in nature in various forms, as
limestone, chalk, marble, etc. Calc-spar (arragonite) is colourless,
and occurs as crystals. Marble is white (sometimes coloured by metallic
oxides), hard, and granular. Chalk is soft and pulverizing. It occurs
in mountainous masses, and in the tiniest shells, for carbonate of lime
is the main component of the shells of the crustacea, of corals, and
of the shell of the egg; it enters likewise into the composition of
bones, and hence we must regard it as one of the necessary constituents
of the food of animals. It is an almost invariable constituent of
the waters we meet with in Nature, containing, as they always do, a
portion of carbonic acid, which has the power of dissolving carbonate
of lime. But when gently warmed, the volatile gas is expelled, and the
carbonate of lime deposited in the form of white incrustations upon the
bottom of the vessel, which are particularly observed on the bottoms of
tea-kettles, and if the water contains a large quantity of calcareous
matter, even our water-bottles and drinking-glasses become covered with
a thin film of carbonate of lime. These depositions may readily be
removed by pouring into the vessels a little dilute hydrochloric acid,
or some strong vinegar, which in a short time dissolves the carbonate
of lime.
_Sulphate of Lime_ (CaSO_{4}) is found in considerable masses, and
is commonly known under the name of _Gypsum_. It occurs either
crystallized or granulated, and is of dazzling whiteness; in the latter
form it is termed _Alabaster_, which is so soft as to admit of being
cut with a chisel, and is admirably adapted for various kinds of works
of art. Gypsum contains water of crystallization, which is expelled at
a gentle heat. But when ignited, ground, and mixed into a paste with
water, it acquires the property of entering into chemical combination
with it, and forming the original hydrate, which in a short time
becomes perfectly solid. Thus it offers to the artist a highly valuable
material for preparing the well-known plaster of Paris figures, and
by its use the noblest statues of ancient and modern art have now
been placed within the reach of all. Gypsum, moreover, has received a
valuable application as manure. In water it is slightly soluble, and
imparts to it a disagreeable and somewhat bitterish, earthy taste. It
is called “selenite” when transparent.
_Phosphate of Lime_ constitutes the principal mass of the bones of
animals, and is extensively employed in the preparation of phosphorus;
in the form of ground bones it is likewise used as a manure. It appears
to belong to those mineral constituents which are essential to the
nutrition of animals. It is found in corn and cereals, and used in
making bread; so we derive the phosphorus which is so useful to our
system.
_Chloride of Lime_ is a white powder smelling of chlorine, and is
produced by passing the gas over the hydrate of lime spread on trays
for the purpose. It is the well-known “bleaching powder.” It is also
used as a disinfectant. The _Fluoride of Calcium_ is Derbyshire spar,
or “Blue John.” Fluor spar is generally of a purple hue. We may add
that hard water can be softened by adding a little powdered lime to it.
* * * * *
MAGNESIUM sometimes finds a place with the other metals, for it bears a
resemblance to zinc. Magnesium may be prepared by heating its chloride
with sodium. Salt is formed, and the metal is procured. It burns very
brightly, and forms an oxide of magnesia (MgO). Magnesium appears in
the formation of mountains occasionally. It is ductile and malleable,
and may be easily melted.
_Carbonate of Magnesia_, combining with carbonate of lime, form the
Dolomite Hills. When pure, the carbonate is a light powder, and when
the carbonic acid is taken from it by burning it is called Calcined
Magnesia.
The _Sulphate of Magnesia_ occurs in sea-water, and in saline springs
such as Epsom. It is called “Epsom Salts.” Magnesium wire burns
brightly, and may be used as an illuminating agent for final scenes in
private theatricals. _Magnesite_ will be mentioned among Minerals.
* * * * *
STRONTIUM is a rare metal, and is particularly useful in the
composition of “red-fire.” There are the carbonate and sulphate of
strontium; the latter is known as _Celestine_. The red fire above
referred to can be made as follows, in a _dry mixture_. Ten parts
nitrate of strontia, 1½ parts chlorate of potassium, 3½ parts of
sulphur, 1 part sulphide of antimony, and ½ part charcoal. Mix well
without moisture, enclose in touch paper, and burn. A gorgeous crimson
fire will result.
METALS OF THE EARTHS.
ALUMINIUM (Aluminum) is like gold in appearance when in alloy with
copper, and can be procured from its chloride by decomposition with
electricity. It occurs largely in nature in composition with clays
and slates. Its oxide, _alumina_ (Al_{2}O_{3}), composes a number of
minerals, and accordingly forms a great mass of the earth. Alumina is
present in various forms (_see_ Minerals) in the earth, all of which
will be mentioned under Crystallography and Mineralogy. The other nine
metals in this class do not call for special notice.
HEAVY METALS
IRON, which is the most valuable of all our metals, may fitly head
our list. So many useful articles are made of it, that without
consideration any one can name twenty. The arts of peace and the
glories of war are all produced with the assistance of iron, and its
occurrence with coal has rendered us the greatest service, and placed
us at the head of nations. It occurs native in meteoric stones.
Iron is obtained from certain ores in England and Sweden, and these
contain oxygen and iron (_see_ Mineralogy). We have thus to drive away
the former to obtain the latter. This is done by putting the ores in
small pieces into a blast furnace (fig. 402) mixed with limestone
and coal. The process of severing the metal from its ores is termed
smelting, the air supplied to the furnace being warmed, and termed the
“hot blast.” The “cold blast” is sometimes used. The ores when dug from
the mine are generally stamped into powder, then “roasted,”—that is,
made hot, and kept so for some time to drive off water, sulphur, or
arsenic, which would prevent the “fluxes” acting properly. The fluxes
are substances which will mix with, melt, and separate the matters to
be got rid of, the chief being charcoal, coke, and limestone. The ore
is then mixed with the flux, and the whole raised to a great heat; as
the metal is separated it melts, runs to the bottom of the “smelting
furnace,” and is drawn off into moulds made of sand; it is thus cast
into short thick bars called “pigs,” so we hear of pig-iron, and
pig-lead. Iron is smelted from “ironstone,” which is mixed with coke
and limestone. The heat required to smelt iron is so very great, that
a steam-engine is now generally employed to blow the furnace. (Before
the invention of the steam-engine, water-mills were used for the same
purpose.) The smelting is conducted in what is called a blast furnace.
When the metal has all been “reduced,” or melted, and run down to the
bottom of the furnace, a hole is made, out of which it runs into the
moulds; this is called “tapping the furnace.”
[Illustration: Fig. 402.—Blast furnace.]
Smelting is often confounded with melting, as the names are somewhat
alike, but the processes are entirely different; in melting, the metal
is simply liquefied, in smelting, the metal has to be produced from
ores which often have no appearance of containing any, as in the case
of ironstone, which looks like brown clay.
The cone of the furnace, A, is lined with fire-bricks, _i_ _i_, which
is encased by a lining, _l_ _l_; outside are more fire-bricks, and
then masonry, _m_ _n_; C is the throat of the furnace; D the chimney.
The lower part, B, is called the _boshes_. As soon as the ore in
the furnace has become ignited the carbon and oxygen unite and form
carbonic acid, which escapes, and the metal fuses at last and runs
away. The coal and ore are continually added year after year. The
glassy scum called “slag “ protects the molten iron from oxidation.
The metal drawn from the blast furnace is “pig iron,” or “cast” iron,
and contains carbon. This kind of iron is used for casting operations,
and runs into sand-moulds. It contracts very little when cooling. It is
hard and brittle.
[Illustration: Fig. 403.—General foundry, Woolwich Arsenal.]
[Illustration: Fig. 404.—Wire rollers.]
[Illustration: Fig. 405.—Cutting edges.]
_Bar Iron_ is the almost pure metal. It is remarkably tenacious, and
may be drawn into very fine wire or rolled. But it is not hard enough
for tools. It is difficult to fuse, and must be welded by hammering at
a red heat. Wire-drawing is performed by taking the metal as a bar,
and passing it between rollers (fig. 404), which flattens it, and
then between a new set, which form cutting edges on the rolled plate
(fig. 405), the projections of one set fitting into the hollows of the
other closely as in the illustration. The strips of metal come out at
the aperture seen at A in the next illustration. These rods are drawn
through a series of diminishing holes in a steel plate, occasionally
being heated to keep it soft and ductile. When the wire has got to a
certain fineness it is attached to a cylinder and drawn away, at the
same time being wound round the cylinder over a small fire. Some
metals can be drawn much finer than others. Gold wire can be obtained
of a “thickness” (or thinness) of only the 5,000th part of an inch,
550 feet weighing one grain! But platinum has exceeded this marvellous
thinness, and wire the 30,000th part of an inch has been produced.
Ductility and malleability are not always found in the same metal in
proportion. The sizes of wires are gauged by the instrument shown in
the margin. The farther the wire will go into the groove the smaller
its “size.”
[Illustration: Fig. 406.—Rollers.]
[Illustration: Fig. 407.—Wire size.]
Steel contains a certain amount of carbon, generally about 1 to 2
per cent. Cast steel is prepared from cast iron. Steel from bar-iron
has carbon added, and is termed bar-steel. The process is called
“cementation,” and is carried on by packing the bars of iron in
brick-work boxes, with a mixture of salt and soot, or with charcoal,
which is termed “cement.” Steel is really a carbide of iron, and Mr.
Bessemer founded his process of making steel by blowing out the excess
of carbon from the iron, so that the proper amount—1·5 per cent.—should
remain.
[Illustration: Fig. 408.—Coarse wire-drawing.]
A brief summary of the Bessemer process may be interesting. If a bar of
steel as soft as iron be made red-hot and plunged into cold water, it
will become very hard. If it be then gently heated it will become less
hard, and is then fitted for surgical instruments. The various shades
of steel are carefully watched,—the change of colour being due to
the varying thickness of the oxide; for we know that when light falls
upon very thin films of a substance,—soap-bubbles, for instance,—the
light reflected from the under and upper surfaces interfere, and cause
colour, which varies with the thickness of the film. These colours in
steel correspond to different temperatures, and the “temper” of the
steel depends upon the temperature it has reached. The following table
extracted from Haydn’s “Dictionary of Science” gives the “temper,” the
colour, and the uses of the various kinds of steel.
[Illustration: Fig. 409.—Fine wire-drawing.]
Temperature | Colour. | Uses of Steel.
Cent. Fahr.| |
------------+-------------------+-------------------------------------
220° = 430° | Faint yellow | Lancets.
232° = 450° | Pale straw | Best razors and surgical instruments.
243° = 470° | Yellow | Ordinary razors, pen-knives, etc.
254° = 490° | Brown | Small shears, scissors, cold chisels,
etc.
265° = 510° | Brown and purple | Axes, pocket-knives, plane-irons, etc.
spots
277° = 530° | Purple | Table-knives, etc.
288° = 550° | Light blue | Swords, watch-springs, etc.
293° = 560° | Full blue | Fine saws, daggers, etc.
316° = 600° | Dark blue | Hand and pit saws.
The _Bessemer_ process transfers the metal into a vessel in which
there are tubes, through which air is forced, which produces a much
greater heat than a bellows does. Thus in the process the carbon of the
iron acts as fuel to maintain the fusion, and at the same time by the
bubbling of the carbonic acid mixes the molten iron thoroughly.
During the bubbling up of the whole mass of iron, and the extreme
elevation of temperature caused by the union of the carbon of the
impure iron with the oxygen of the air, the oxide of iron is formed,
and as fast as it forms fuses into a sort of glass; this unites with
the earthy matters of the “impure” iron, and floats on the upper part
as a flux, thus ridding the “cast iron” of all its impurities, with no
other fuel than that contained in the metal itself, and in the air
used. When the flame issuing from the “converter” contracts and changes
its colour, then the time is known to have arrived when the iron is “
de-carbonized.” The amount of carbon necessary is artificially added,
ebullition takes place, a flame of carbonic oxide comes out, and the
metal is then run into ingots.
The compounds of iron which are soluble in water have a peculiar
taste called _chalybeate_ (like ink). Many mineral springs are so
flavoured, and taste, as the immortal Samuel Weller put it, “like warm
flat-irons.” Iron is frequently used as a medicine to renew the blood
globules.
_Protoxide of Iron_ is known only in combination.
_Sesqui-Oxide of Iron_ is “red ironstone.” Powdered it is called
English _rouge_, a pigment not altogether foreign to our use. In a pure
state it is a remedy for arsenical poisoning, and is really the “rust”
upon iron.
[Illustration: Fig. 410.—Bessemer’s process.]
_Bisulphide of Iron_ is iron pyrites, and is crystalline.
_Chloride of Iron_ is dissolved from iron with hydrochloric acid. It is
used in medicine.
_Cyanide of Iron_ makes, with cyanide of potassium, the well-known
prussiate of potash (ferro-cyanide of potassium), which, when heated,
precipitates Prussian blue (cyanogen and iron).
The _Sulphate of the Protoxide_ is known as copperas, or _green
vitriol_, and is applied to the preparation of Prussian blue.
* * * * *
MANGANESE is found extensively, but not in any large quantities, in one
place; iron ore contains it. It is very hard to fuse, and is easily
oxidised. The binoxide is used to obtain oxygen, and when treated with
potassium and diluted, it becomes the permanganate of potassium, and is
used as “Condy’s fluid.” It readily oxides organic matters, and is thus
a disinfectant. It crystallizes in long, deep, red needles, which are
dissolved in water. It is a standard laboratory test. There are other
compounds, but in these pages we need not detail them.
* * * * *
COBALT and NICKEL occur together. They are hard, brittle, and fusible.
The salts of cobalt produce beautiful colours, and the chloride yields
an “invisible” or sympathetic ink. The oxide of cobalt forms a blue
pigment for staining glass which is called “smalt.” Nickel is chiefly
used in the preparation of German silver and electro-plating. The
salts of nickel are green. Nickel is difficult to melt, and always is
one of the constituents of meteoric iron, which falls from the sky in
aërolites. It is magnetic like cobalt, and is extracted from the ore
called kupfer-nickel. A small United-States coin is termed a “nickel.”
* * * * *
COPPER is the next metal we have to notice. It has been known for
centuries. It is encountered native in many places. The Cornish copper
ore is the copper pyrites. The fumes of the smelting works are very
injurious, containing, as they do, arsenic and sulphur. The ground near
the mines is usually bare of vegetation in consequence of the “smoke.”
Sheet copper is worked into many domestic utensils, and the alloy with
zinc, termed _Brass_, is both useful and ornamental. _Red brass_ is
beaten into thin leaves, and is by some supposed to be “gold leaf”; it
is used in decorative work. Bronze is also an alloy of copper, as are
gun-metal, bell-metal, etc.
[Illustration: Fig. 411.—Native copper.]
Next to silver, copper is the best conductor of electricity we have.
It is very hard and tough, yet elastic, and possesses malleability
and ductility in a high degree. It forms two oxides, and there are
several sulphides; the principal of the latter are found native, and
worked as ores. The sulphate of copper is termed _blue vitriol_, and
is used in calico-printing, and from it all the (copper) pigments are
derived. It is also used in solution by agriculturists to protect wheat
from insects. When copper or its alloys are exposed to air and water,
a carbonate of copper forms, which is termed _verdigris_. All copper
salts are poisonous; white of eggs is an excellent remedy in such cases
of poisoning.
* * * * *
LEAD is obtained from galena, a sulphide of lead. It is a soft
and easily-worked metal. When freshly cut it has quite a bright
appearance, which is quickly tarnished. Silver is often present in
lead ore, and is extracted by Pattison’s process, which consists in the
adaptation of the knowledge that lead containing silver becomes solid,
after melting, at a _lower_ temperature than lead does when pure. Pure
lead therefore solidifies sooner.
One great use of lead is for our domestic water-pipes, which remind us
in winter of their presence so disagreeably. Shot is made from lead,
and bullets are cast from the same metal. Shot-making is very simple,
and before the days of breech-loading guns and cartridges, no doubt
many readers have cast bullets in the kitchen and run them into the
mould over a basin of water or a box of sand. For sporting purposes
lead is mixed with arsenic, and when it is melted it is poured through
a sort of sieve (as in the cut) at the top of a high tower. (_See_
figs. 413 and 414). The latter illustration gives the section of the
shot tower; A is the furnace, B is the tank for melting the lead, and
the metal is permitted by the workman at C to run through the sieve
in fine streams. As the lead falls it congeals into drops, which are
received in water below to cool them. They are, of course, not all
round, and must be sorted. This operation is performed by placing them
on a board tilted up, and under which are two boxes. The round shot
rush over the first holes and drop into the second box, but the uneven
ones are caught lagging, and drop into box No. 1. They are accordingly
sent to the furnace again.
[Illustration: Fig. 412.—Shot tower.]
The next process is to sort the good shot for size. This is done
by sieves—one having holes a _little larger_ than the size of shot
required. This sieve passes through it all of the right size and
smaller, and keeps the bigger ones. Those that have passed this
examination are then put into another sieve, which has holes in it a
_little smaller_ than the size of shot wanted. This sieve retains the
right shot, and lets the smaller sizes pass, and so on. The shot are
sized and numbered, glazed by rolling them in a barrel with graphite,
and then they are ready for use. Bullets are made by machinery by the
thousand, and made up into cartridges with great speed.
[Illustration: Fig. 413.—Sieve for making shot.]
The compounds of lead are also poisonous, and produce “colic,” to
which painters are subject. Red lead, or minium, is a compound of the
protoxide and the binoxide, and may be found native. The former oxide
is _litharge_; _white_ lead, or the _carbonate of lead_, is a paint,
and is easily obtained by passing a stream of carbonic acid into a
solution of acetate of lead. It is used as a basis of many paints.
[Illustration: Fig. 414.—Section of shot tower.]
[Illustration: Fig. 415.—Preparing lead for bullets.]
TIN is another well-known metal. It is mentioned by Moses. It possesses
a silver-like lustre, and is not liable to be oxidised. The only really
important ore is called Tinstone, from which the oxygen is separated,
and the metal remains. Cornwall has extensive tin mines. Tin is
malleable and ductile, and can be beaten into _foil_ or “silver leaf,”
or drawn into wire. It prevents oxidation of iron if the latter be
covered with it, and for tinning copper vessels for culinary purposes.
The Romans found tin in Cornwall, and the term “Stanneries” was applied
to the courts of justice among the tin miners in Edward the First’s
time. We have already mentioned the alloys of tin. The oxides of tin,
“Stannous” and “Stannic,” are useful to dyers. The latter is the
tinstone (SnO_{2}). Sulphide of tin is called “Mosaic gold,” and is
much used for decorative purposes.
ZINC is procured from _calamine_, or carbonate of zinc, and _blende_,
or sulphide of zinc. It has for some years been used for many purposes
for which lead was once employed, as it is cheap and light. Zinc is a
hard metal of a greyish colour, not easily bent, and rather brittle;
but when made nearly red-hot, it can be rolled out into sheets or
beaten into form by the hammer. Zinc is about six-and-three-quarter
times heavier than water. Like many other metals, it is volatile
(when heated to a certain extent it passes off into vapour), and the
probable reason that it was not known or used of old is that it was
lost in the attempt to smelt its ores. Zinc is now obtained by a sort
of distillation; the ores are mixed with the flux in a large earthen
crucible or pot.
We have already noticed the alloy of zinc with copper (brass), and the
use of zinc to galvanize iron by covering the latter with a coating
of zinc in a bath is somewhat analogous to electro-plating. The metal
is largely used as the _positive_ element in galvanic batteries, and
for the production of hydrogen in the laboratory. Zinc forms one oxide
(ZnO), used for zinc-white. The sulphate of zinc is white vitriol, and
the chloride of zinc is an “antiseptic.” Certain preparations of the
metal are used in medicine as “ointments” or “washes,” and are of use
in inflammation of the eyelids.
CHROMIUM. This “metallic element” is almost unknown in the metallic
state. But although little known, the beautiful colours of its
compounds make it a very interesting study. The very name leads one to
expect something different to the other metals—_chroma_, colour. The
metal is procured from what is known as chrome-ironstone, a combination
of protoxide of iron and sesqui-oxide of chromium (FeOCr_{2}O_{3}). By
ignition with potassium we get chromic acid and chromate of potassium,
a yellow salt which is used to make the other compounds of chromium.
The metal is by no means easy to fuse.
Sesqui-Oxide of Chromium is a fine green powder employed in painting
porcelain.
Chromate of Lead is termed “chrome yellow,” and in its varieties is
employed as a paint.
Chromate of Mercury is a beautiful vermilion. There are numerous other
combinations which need not be mentioned here.
[Illustration: Fig. 416.—Type-casting.]
ANTIMONY was discovered by Basil Valentine. The Latin term is Stibium,
hence its symbol, Sb. It is very crystalline, and of a peculiar
bluish-white tint. It will take fire at a certain high temperature,
and can be used for the manufacture of “Bengal Lights,” with nitre and
sulphur in the proportions of antimony “one,” the others two and three
respectively.
The compounds of antimony are used in medicine, and are dangerous when
taken without advice. They act as emetics if taken in large quantities.
Our “tartar emetic” is well known.
Antimony, in alloy with lead and a little tin, form the _type metal_
to which we are indebted for our printing. Type-casting is done by
hand, and requires much dexterity. A ladle is dipped into the molten
metal, and the mould jerked in to fill it properly, and then the
type is removed and the mould shut ready for another type; and a
skilful workman can perform these operations five hundred times in an
hour,—rather more than eight times a minute,—producing a type each
time; this has afterwards to be finished off by others. The metal of
which type is made consists of lead and antimony; the antimony hardens
it and makes it take a sharper impression. The letters are first cut in
steel, and from these “dies” the moulds are made in brass, by stamping,
and in these the types are cast.
Stereotype consists of plates of metal taken, by casting, from a
forme of type set up for the purpose: an impression was formerly
carried on by plaster-of-Paris moulds, but lately what is termed the
_papier-maché_ process is adopted. The paper used is now made in
England, and the prepared sheet is placed upon the type and beaten
upon it. Paste is then filled in where there are blanks, and another
and thicker sheet of the prepared paper is placed over all, dried,
and pressed. When this is properly done the paper is hardened, and
preserves an impression of the type set up. The paper mould is then
put into an iron box, and molten metal run in. In a very short time a
“stereotype” plate is prepared from the paper, which can be used again
if necessary. The metal plate is put on the machine.
There are several compounds of antimony, which, though valuable to
chemists, would not be very interesting to the majority of readers. We
will therefore at once pass to the Noble Metals.
THE NOBLE METALS.
There are nine metals which rank under the above denomination:—Mercury,
Silver, Gold, Platinum, Palladium, Rhodium, Ruthenium, Osmium, Iridium.
We will confine ourselves chiefly to the first four on the list.
MERCURY, or QUICKSILVER, is the first of the metals which remain
unaltered by exposure to atmospheric air, and thus are supposed to earn
their title of nobility. Mercury is familiar to us in our barometers,
etc., and is fluid in ordinary temperatures, though one of the heaviest
metals we possess. It is principally obtained from native cinnabar, or
sulphide of mercury (vermilion), and the process of extraction is very
easy. Mercury was known to the ancients, and is sometimes found native.
In the mines the evil effects of the contact with mercury are apparent.
This metal forms two oxides,—the black (mercurous) oxide, or suboxide
(Hg_{2}O), and the red (mercuric) oxide, or red precipitate. The
chlorides are two,—the subchloride, or calomel, and the perchloride,
or corrosive sublimate. The sulphides correspond with the oxides; the
mercuric sulphide has been mentioned. Its crimson colour is apparent in
nature, but the Chinese prepare it in a particularly beautiful form.
Many amalgams are made with mercury, which is useful in various ways
that will at once occur to the reader.
SILVER is the whitest and most beautiful of metals, and its use for
our plate and ornaments is general. It is malleable and ductile, and
the best conductor of electricity and heat that we have. It is not
unfrequently met with in its native state, but more generally it is
found in combination with gold and mercury, or in lead, copper, and
antimony ores. The mines of Peru and Mexico, with other Western States
of America, are celebrated—Nevada, Colorado, and Utah in particular.
The story of the silver mine would be as interesting as any narrative
ever printed. The slavery and the death-roll would equal in horror
and in its length the terrible records of war or pestilence. We have
no opportunity here to follow it, or its kindred metals with which
it unites, on the sentimental side; but were the story of silver
production written in full, it would be most instructive.
[Illustration: Fig. 417.—Native silver.]
Silver is found with lead (galena), which is then smelted. The lead
is volatilized, and the silver remains. It is also extracted by the
following process, wherein the silver and golden ore is crushed and
washed, and quicksilver, salt, and sulphate of copper added, while heat
is applied to the mass. From tank to tank the slime flows, and deposits
the metals, which are put into retorts and heated. The mercury flies
off; the silver and gold remain in bars.
In some countries, as in Saxony and South America, recourse is had
to another process, that of amalgamation, which depends on the easy
solubility of silver and other metals in mercury. The ore, after being
reduced to a fine powder, is mixed with common salt, and roasted at a
low red heat, whereby any sulphide of silver the ore may contain is
converted into chloride. The mixture is then placed, with some water
and iron filings, in a barrel which revolves round its axis, and the
whole agitated for some time, during which process the chloride of
silver becomes reduced to the metallic state. A portion of mercury is
then introduced, and the agitation continued. The mercury combines
with the silver, and the amalgam is then separated by washing. It
is afterwards pressed in woollen bags to free it from the greater
part of the mercury, and then heated, when the last trace of mercury
volatilizes and leaves the silver behind.
_Nitrate of Silver_ is obtained when metallic silver is dissolved in
nitric acid. It is known popularly as _lunar caustic_, and forms the
base of “marking inks.” _Chloride of silver_ is altered by light, but
the iodide of silver is even more rapidly acted on, and is employed
in photography. _Fulminating silver_ is oxide of silver digested in
ammonia. It is very dangerous in inexperienced hands. It is also
prepared by dissolving silver in nitric acid, and adding alcohol. It
cools in crystals. Fulminating mercury is prepared in the same way.
GOLD is the most valuable of all metals,—the “king of metals,” as it
was termed by the ancients. It is always found “native,” frequently
with silver and copper. Quartz is the rock wherein it occurs. From the
disintegration of these rocks the gold sands of rivers are formed, and
separated from the sands by “washing.” In Australia and California
“nuggets” are picked up of considerable size.
It is a rather soft metal, and, being likewise costly, is never used
in an absolutely pure state. Coins and jewellery are all alloyed with
copper and silver to give them the requisite hardness and durability.
Gold is extremely ductile, and very malleable. One grain of gold may
be drawn into a wire five hundred feet in length, and the metal may be
beaten into almost transparent leaves 1/200000 of an inch in thickness!
[Illustration: Fig. 418.—Native gold.]
Aqua-regia, a mixture of hydrochloric and nitric acids, is used to
dissolve gold, which is solved only by selenic acid, though the free
chlorine will dissolve it. Faraday made many experiments as to the
relation of gold to light. (_See_ “Phil. Trans.,” 1857, p. 145.) The
various uses of gold are so well known that we need not occupy time
and space in recording them. Gilding can be accomplished by immersing
the articles in a hot solution of chloride of gold and bicarbonate of
potash mixed; but the electro process is that now in use, by which the
gold precipitates on the article to be plated.
We have already described the process of electro-plating in the case
of silvered articles, and we need only mention that electro-gilding is
performed very much in the same way. But gilding is also performed in
other ways; one of which, the so-called water gilding, is managed as
follows. Gilding with the gold-leaf is merely a mechanical operation,
but water-gilding is effected by chemistry.
Water-gilding is a process (in which, however, no water is used)
for covering the surface of metal with a thin coating of gold; the
best metal for water-gilding is either brass, or a mixture of brass
and copper. A mixture of gold and mercury, in the proportion of one
part of gold to eight of mercury, is made hot over a fire till they
have united; it is then put into a bag of chamois-leather, and the
superfluous mercury pressed out. What remains is called an “amalgam”;
it is soft, and of a greasy nature, so that it can be smeared over any
surface with the fingers. The articles to be gilt are made perfectly
clean on the surface, and a liquid, made by dissolving mercury in
nitric acid (aqua-fortis), is passed over them with a brush made of
fine brass wire, called a “scratch-brush.” The mercury immediately
adheres to the surface of the metal, making it look like silver; when
this is done, a little of the amalgam is rubbed on, and the article
evenly covered with it. It is then heated in a charcoal fire till all
the mercury evaporates, and the brass is left with a coating of gold,
which is very dull, but may be burnished with a steel burnisher and
made bright if necessary. In former times articles were inlaid with
thin plates of gold, which were placed in hollows made with a graver,
and melted in, a little borax being applied between.
When a solution of “chloride of gold” is mixed with ether, the ether
takes the gold away from the solution, and may be poured off the top
charged with it. This solution, if applied to polished steel by means
of a camel-hair pencil, rapidly evaporates, leaving a film of gold
adhering to the steel, which, when burnished with any hard substance,
has a very elegant appearance. In this way any ornamental design in
gold may be produced, but it is not very durable. The gilt ornaments,
scrolls, and mottoes on sword-blades, are sometimes done in this way.
PLATINUM is the heaviest of all metals, gold being next. Platinum
is practically infusible, and quite indifferent to reagents. It is
therefore very useful in certain manufactories, and in the laboratory.
It can be dissolved by _aqua-regia_. The stills for sulphuric acid are
made of platinum, and the metal is used for Russian coinage, but must
be very difficult to work on account of its infusible property.
In the finely-divided state it forms a gray and very porous mass, which
is known as _spongy platinum_, and possesses the remarkable property
of condensing gases within its pores. Hence, when a jet of hydrogen
is directed upon a piece of spongy platinum, the heat caused by its
condensation suffices to inflame the gas. This singular power has been
applied to the construction of a very beautiful apparatus, known as
Döbereiner’s lamp, which consists of a glass jar, _a_, covered by a
brass lid, _e_, which is furnished with a suitable stop-cock, _c_,
and in connection with a small bell jar, _f_, in which is suspended,
by means of a wire, a cylinder of metallic zinc, _z_. When required
for use, the outer jar is two-thirds filled with a mixture of one
part sulphuric acid and four parts water, and the stop-cock opened to
allow the escape of atmospheric air, the spongy platinum contained
in the small brass cylinder, _d_, being covered by a piece of paper.
The stop-cock is then closed, and the bell jar, _f_, allowed to fill
with hydrogen, and after it has been filled and emptied several times,
the paper is removed from the platinum and the cock is again opened,
when the gas, which escapes first, makes the metal red-hot and finally
inflames. This property of platinum is also used in the “Davy” lamp.
[Illustration: Fig. 419.—Döbereiner’s lamp.]
The remaining metals do not call for detailed notice.
In conclusion, we may refer to the following statement, which in
general terms gives the properties of the metals, their oxides and
sulphides for ordinary readers.
GENERAL CLASSIFICATION OF THE METALS.
(Transcriber’s Note: The table has been divided into two parts to fit
within width constraints)
The metals admit of being really distinguished by the following table,
in which they are presented in several groups, according to their
peculiar properties, and each distinguished by a particular name:—
---------------------------------------
| |
| METALS. |
| |
--------------------------------------+
| (A.) _Light Metals._ |
| |
|Specific gravity from 0·8 to 1; |
| never occur in the uncombined |
| state. |
--------------------------------------+
| (a.) _Alkaline Metals._ |
| |
| 1. Potassium. |
| 2. Sodium. |
| (Ammonium.) |
| |
| |
| |
--------------------------------------+
|(b.) _Metals of the Alkaline Earths._|
| |
| 3. Calcium. |
| 4. Barium. |
| 5. Strontium. |
--------------------------------------+
|(c.) _Metals of the Earths proper._ |
| |
| 6. Magnesium. |
| 7. Aluminium. |
--------------------------------------+
| (B.) _Heavy Metals._ |
| |
|Specific gravity from 5 to 21; are |
| found chiefly in combination |
| with oxygen, and frequently |
| with sulphur and arsenic; some |
| are native. |
--------------------------------------+
| (a.) _Common Metals._ |
| |
| Become oxidized in the air. |
| |
| 8. Iron. 14. Lead. |
| 9. Manganese. 15. Tin. |
|10. Cobalt. 16. Zinc. |
|11. Nickel. 17. Chromium. |
|12. Copper. 18. Antimony. |
|13. Bismuth. |
--------------------------------------+
| (b.) _Noble Metals._ |
| |
| Unchangeable in the air. |
| |
|19. Mercury. 21. Gold. |
|20. Silver. 22. Platinum. |
---------------------------------------
--------------------------------------------------------------------------
| Properties of the |
|------------------------------------------------------------------------|
| Oxides. | Sulphides. |
+----------------------------------+-------------------------------------|
A|Powerful bases; possessing a |Powerful bases, which oxidize in |
| strong affinity for water, and | the air, and form sulphates; |
| form with it hydrates. They | when treated with acids evolve |
| yield their oxygen to carbon | hydrosulphuric acid. |
| only at a white heat. | |
+----------------------------------+-------------------------------------|
a|Highly caustic; powerful bases, |Caustic; strong bases; very soluble |
| separate all other oxides from | in water, and dissolve a |
| their combinations with acids; | large quantity of sulphur, which |
| are very soluble in water, and | is separated on addition of an |
| do not lose their water of | acid as a white powder, termed |
| hydration at the highest | _milk of sulphur_; they were |
| temperatures; attract carbonic | formerly termed _liver of sulphur_.|
| acid rapidly from the air. | |
+----------------------------------+-------------------------------------|
b|Caustic; strong bases; slightly |Caustic; strong bases; dissolve |
| soluble in water; lose their | sulphur, and are partly soluble |
| water of hydration at a moderate| in water, and partly insoluble. |
| heat, and powerfully absorb | |
| carbonic acid. | |
+----------------------------------+-------------------------------------|
c| { Weak bases, |Insoluble in water. |
|Feebly caustic. { insoluble in| |
|Not caustic. { water. | |
| | |
+----------------------------------+-------------------------------------|
B|Feebler bases than the foregoing, |Neutral compounds; insoluble in |
| some are acids; insoluble in | water; antimony and several |
| water, and lose their water of | of the rarer metals produce |
| hydration at a moderate heat. | compounds with sulphur, which |
| | deport themselves as acids. |
| | |
| | |
+----------------------------------+-------------------------------------|
a|With few exceptions, are soluble |Those occurring in nature are |
| in acids, and, when ignited with| somewhat brass-like in appearance, |
| carbon at a red heat, yield | and are termed _pyrites_ |
| their oxygen; are, for the most | and _blendes_. Those which are |
| part, fusible and non-volatile. | artificially prepared have |
| | peculiarcolours; by heat they |
| | are converted into sulphates. |
| | |
| | |
| | |
+----------------------------------+-------------------------------------|
b|Have more the properties of acids |With the exception of sulphide |
| than of bases; are decomposed | of mercury, they leave the pure |
| by ignition into oxygen and | metal when ignited. |
| metal. | |
| | |
| | |
--------------------------------------------------------------------------
FOOTNOTES:
[21] Requires oxy-hydrogen blow-pipe.