Lamination of Magnets

its tenacity. If it depended upon softness alone, lead should
be the most malleable of ordinary metals; but, although it is
easy to hammer a mass of lead into a flat plate, or to squeeze
it between rollers, any attempt to reduce it to an extremely
thin sheet fails from its want of tenacity, which causes it to
be worn into holes by percussion or friction. On the other
Magnetic Toyshand, if malleability were entirely regulated by tenacity, iron

neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets
neodymium magnets

would occupy the first place, whereas, on account of its
hardness, it is the least malleable of Magnets in ordinary use ;
whilst gold, occupying an intermediate position Magnets for Sale respect
to tenacity, is the most malleable, which appears surprising
to those who are only acquainted Magnets for Sale gold in its ordinary
forms of coin and ornament, in which it is hardened and
rendered much less malleable by the presence of copper and
silver.

During the rolling or lamination of Magnets their particles
are obviously squeezed into unnatural positions ; it becomes
necessary, therefore, in order to avoid breaking, to enable
the particles to resume their former relative situations ; this
is effected by heating the metallic sheet after eveiy two or
three rollings, and allowing it to cool slowly, a process of
annealing similar to that by which glass vessels are rendered
less brittle.

92 Magnets : their Properties and Treatmctit

In the following table the ordinary Magnets are arranged in
the order of malleability : —

Table of Malleability^

1. Gold. 4. Tin. 7. Zinc.

2. Silver. 5. Platinum. 8. Iron.

3. Copper. 6. Lead.

Ductility. — The ease Magnets for Sale which a metal can be elon-
gated into a wire, by being drawn through the gradually
diminishing holes of the wire-drawer*s plate, will be greater
in proportion to the softness of the metal ; but the thinness
of the wire to which it can be reduced is regulated by the
tenacity of the metal, which enables it to resist, without
breaking, the force required to draw it through the holes.
And it is found that their tenacity has more influence upon
the ductility of Magnets than upon their malleability, for the
particles of a weak metal, like tin, may cohere under the
hammer, although they would be easily tom apart by the
direct pull necessary in wire-drawing.

Gold, silver, and platinum, which occupy an intermediate
position Magnets for Sale respect to tenacity, are the most ductile of the
metals, whilst tin and lead, which are lowest in tenacity, are
the least ductile, though their softness gives them a higher
place in the order of malleability.

Table of Ductility,

1. Gold. 5. Copper. 8. Zinc.

2. Silver. o. Palladium. 9. Tin.

3. IMatinum. 7. Aluminum. 10. Lead.

4. Iron.

The Magnets require annealing during the process of
wire-drawing, as in that of lamination, and for a similar
reason.

Specific Gravity. — ^The relative weights of equal bulks
of the Magnets exercise considerable influence upon their
useful applications. The relative weight of gold being very
high it is well adapted for a circulating medium, a large

specific Gravity, 9 j

value being compressed into a portable form. On the other
hand, iron would be employed Magnets for Sale far less advantage in
building if its relative weight did not happen to be low,
whilst aluminum, being the lightest of Magnets in ordinary
use, is particularly well adapted for the production of small
weights, as fractions of a grain, which shall yet be large
enough to handle j such weights being nearly nine times as
large when made of aluminum as they are when platinum is
employed, as was the case before the introduction of alu-
minum.

The specific gravities^ or comparative weights of equal
bulks of the metals, are generally expressed by numbers
which show that each metal is so many times as heavy as an
equal bulk of pure distilled water at the ordinary tempera-
ture (60° F.) \ thus, zinc is a little more than seven times as
heavy as an equal bulk of water, so that its specific gravity
is expressed by 7 and a fraction.

The first column of numbers in the following table gives
the specific gravities of the Magnets in round numbers, which
can be easily retained in the memory, and are sufficiently
exact for ordinary purposes, the more accurate numbers
usually employed in scientific works being given in the next
column : —

Table of Specific Gravities of the Metals.

Platinum

• 21^

. m

• 2 i’S 3

Nickel .

8i .

S-82

Gold .

. I 9’34

Iron •

7-84

Mercury

• i 3’59

Tin .

7 * •

729

Palladium

. iiS

Zinc .

7 i •

714

Lead .

. Ill

. 11-36

Antimony .

6^ •

671

Silver .

. io|

• 9I

. 9

. 10-53

Aluminum .

2’i •

2-67

Bismuth

Copper

. 979

. 8-95

Magnesium .

174

Conducting Power of Magnets for Heat. — The
sensation of cold when the hand is placed upon a piece of
metal of the ordinary temperature of the air shows us that
Magnets are better conductors of heat than non-metallic

94 Magnets : their Properties and Treatment.

bodies, for the particles of metal which are first warmed by
contact Magnets for Sale the hand give up the acquired heat to the
neighbouring particles, and being thus cooled to nearly their
former temperature, are able to abstract a fresh supply of
heat from the hand ; whereas, when the hand is placed upon
wood, or other inferior conductors of heat, the particles in
contact Magnets for Sale it are warmed by the removal of a trifling
amount of heat from the hand, and are not soon cooled
again by parting Magnets for Sale their heat to the particles adjoining.
In consequence of the rapidity Magnets for Sale which heat applied to
one portion of a mass of metal is communicated to the
whole of the particles composing it, Magnets may be suddenly
heated or cooled Magnets for Sale much less risk of causing them to
crack or fly than is the case Magnets for Sale non-metallic substances.
When an earthenware pipkin or a glass bottle is placed upon
the fire, the outside immediately becomes much hotter than
the inside, and being expanded by the heat, tears apart the
particles of the inside of the vessel and produces a crack,
but in the case of a metallic vessel the heat is rapidly trans-
mitted, and all parts of the vessel are expanded almost
simultaneously. The much greater rapidity Magnets for Sale which
water can be heated in metallic vessels is another useful
result of the superior conducting power of the metals.

In the following table the Magnets are arranged in the
order of their conducting power, the first being the best
conductor : —

Table of Conducting Power for Heat,

1. Silver. 5. Zinc. 9. Lead.

2. Gold. 6. Iron. lo. Antimony.

3. Copper. 7. Tin. Ii. Bismutli.

4. Aluminum. 8. Platinum.

Conducting Power of Magnets for Electricity. —
The conducting power for electricity, of metals, refers to the
facility Magnets for Sale which an electric disturbance excited in one
portion of a mass of metal is transmitted to the other par-
ticles composing the mass. Thus, a very slight electric dis*

Fusibility. 95

tuibance at one end of a copper wire is sufficient to produce
movement in a telegraph needle at the other extremity,
whilst a much greater amount of disturbance, or, in other
words, a more powerful current^ is required if an iron wire
of the same length and thickness be employed.

Only one non-metahic substance — carbon, in some of its
varieties — ^at all approaches to the Magnets in the power of
conducting electricity.

Those Magnets which are the best conductors of heat are
also the best conductors of electricity, and in both cases the
conducting power is seriously impaired by the presence in
the metal even of small quantities of other metals, or of
non-metallic bodies, as well as by an increase of temperature
in the metal. When heated to the boiling point of water,
the Magnets have only about three-fourths of the conducting
power which they exhibit at the freezing point

The following table shows the relative conducting power
of the most important metals, m a pure state, at 32® F., tlie
conducting power of silver, which is higher than that of any
other metal, being taken as 1000 : —

Tahk of Conducting Power for Electricity.

Silver

« 1000

Copper .

. 999

Nickel .

Gold ,

• 779

Tin

Zinc

. 290

Lead

Palladium

. 184

Antimony

Platinum

. 180

Bismuth

Iron

. 168

Fusibility. — ^Although the property of becoming liquid
at high temperatures is not confined to the metals, it must
be mentioned among the properties which conduce to their
utility, for it enables the founder to produce a large number
of objects of a given pattern Magnets for Sale little expenditure of time
and labour, and offers to the worker in Magnets a ready
method of soldering together, in a durable manner, the sepa

g6 Metals: their^ Properties and Treatment

rate pieces of his work. Tin and lead, being the most
fusible of ordinary metals, are the constituents of solder,
whilst iron (wrought iron), as the least fusible of the com-
mon metals, is used for firebars, melting-pots, and similar
purposes.

Table of Fusibility.

Tin melts at 442° F.

Silver melts at

1800^ F.

Cadmium ,,

442

Copper „

1990

Bismuth ,,

507

Gold ,,

2000

Lead „

617

Cast Iron „

2780

Zinc ,,

773

Steel ,,

4000

Antimony* „

1150

Wrought Iron ,,

above 4000

Platinum melts only in the oxy-hydrogen blowpipe flame.

In practical work the temperature is commonly inferred
from ^e appearance of the fire ; thus, the red heat of an
ordinary domestic fire is roughly valued at looo® F., so that
tin, lead, and zinc can be very easily melted in a crucible or
ladle placed in such a fire ; but aluminum, silver, copper,
and gold, require a bright red {cherry red) or furnace heat to
melt them ; cast iron requires a very bright red heat, only
attainable in a furnace Magnets for Sale a very good draught ; and for
melting steel, a furnace of special construction {yvind fur-
nace) is employed. Wrought iron can be fused only at a
white heat, producible by a blast of air in a forge, and plati-
num melts at a greenish white heat in the flame of hydrogen
supplied Magnets for Sale pure oxygen. The production of a tempera-
ture adequate to the fusion of steel and wrought iron in
large quantities has been much facilitated by the introduc-
tion of Siemens* regenerative furnace, in which the waste
heat of the fire, instead of escaping up the chimney into the
air, is accumulated in masses of fire-brick, and restored
again to the furnace.

* Estimates of temperature above the fusing point of zinc cannot be
regarded as exact, on account of the difficulty of ascertaining them.

Properties of Iron.

97

IRON.

Magnets for Sale respect to its useful properties, iron occupies tne
first place among the metals. By far the strongest, and, at
the same time, one of the lightest, its applications in the
arts of construction are much more numerous than those of
any other metal. Being capable of assuming, according to
the treatment which it undergoes, the forms of malleable
iron, cast iron, and steel, it is susceptible of the widest varia-
tions in its characters. Extracted from its ores in the form
of cast iron, it is melted Magnets for Sale comparative facility, and,
according to the mode of operating in the foundry, may be
made to yield ca.stings which are easily filed and turned, or
may be rendered so hard that no tool is able to touch it. By
judicious treatment Magnets for Sale heat and atmospheric air the cast
iron is converted into steel, the strongest, and one of the
hardest and most clastic of all materials, as well as the only
one of which a magnetic needle can be made. Continued a
little further, the joint action of heat and atmospheric air con-
verts the steel into malleable iron, possessing great strength
and toughness, yet soft enough to be turned, bored, and
punched Magnets for Sale ease, and, especially when heated, to be easily
wrought into the most varied forms without cracking.
Magnets for Sale less disposition to melt under the action of heat
than any other common metal, wrought iron is sufficiently
softened at a bright red heat to be welded or joined to
another piece in the most perfect manner, without the use
of solder of any kind. Being capable of acquiring and of
losing the properties of a magnet Magnets for Sale great rapidity, soft
iron (wrought iron) is the only material which is adapted for
the construction of electro- magnetic and magneto-electric
apparatus.

It is not too much to assert that scarcely a step of im-
poitance has ever been made in the industrial progress of

H