The times. [volume] (Washington [D.C.]) 1897-1901, 1898-08-29
Concentration of Heat in a
Small Compass.
THE FOURTH ELECTRIC ERA
A Temperature of Not Far From
Six Thousand Degrees Fahrenheit
Reached by Efcetricity-How the
Temperature Is Measured-The
Amount of Heat Almost UnIimited.
(Fron the Boston Transcript

have been three distinct eras in the prac-
teal applications of electricity The first
was characterized by its use in teIeg-
raphy, the second by its application to
lighting and the third by its employment
in the transmission of power We are
now entering upon a fourth era. in which
electricity may be said to pay back its
debt TO the energy which produces it by
generating heat in the electric furnace
This use of electricity has already revo-
lutionized certain processes in the arts.
The heat of the furnace is generated by
an electric arc such as we see In the
case of the arc lights on our city streets.
This arc is produced by current of elec-
tricity flowing through the intensely heat
ed air between two pieces of carbon. The
furnace consists of box or paralleIOpipsd
of limestone, having a cavity Of similar
shape cut into il. The electric current is
led into the cavity by means of pieces.
terminals or electrodes. as they are tech
nically called. of hard carbon which pass
through holes cut in opposite sides of the
cavity. Then the oxide of the metal which
one desires to fuse Is mixed with carbon
powder and is packed around the carbon
terminals and is reduced by the great
heat developed by the voltaic arc. pro-
duced BY the electric current flowing
through the cavity from one carbon ter
minaI 10 the other. In this way aluminium
is produced. and in similar way car
bide of lime which on being dropped into
the water gives forth the gas acetylene
in great quantity.
For scientific experimentation the cavity
holds a small crucible. which is composed
of mixture of carbon and magnesia- In
this crucible are placed the substances
which are TO be melted. There IS no metal
which has not been fused by this fur
mace. Even platinum and iridium, both
of which remain solid in the hottest fur
mace such as had hitherto been used.
| melt like wax in the electric furnace.
Sometimes carbon tube is fixed in the
latter furnace across the line OF direc-
| ton of the carbon terminals or IN
/ other words, at right angles to them
| and so placed that IL is about one-half
/ an inch below the intense yOItaic arc
| and about the same distance from the
| bottom of the limestone cavity In this
carbon tube are placed the substances
which are 10 be heated. Material can
be introduced into one end of this tube
and after 1t is heated can be drawn of
/ by tipping the tube, without stopping
the current in the furnace.
! in order TO produce diamonds iron is
melted with a large quantity of carbon
| powder. and when the mixture has at
| tanned a high temperature-over 5000 de-
grees Fahrenheit-it is suddenly plunged
| into cold water or bath Of molten lead
| The lead. being a better conductor Of
heat than cold water. more suddenly
/ deprives the mixture Of lis heat. On ex-
| anIiaing the Stag small cOIoriess crys-
! tails of carbon are found which are
| identical in their properties with natur-
| al diamonds.
The electric furnace has the great ad-
vantage over other furnaces in its pow
| er 10 IocaIize the heat N narrow COM
| pass. and the amount of heat We can
| produce in such a furnace is almost
/ unlimited An amount of heat energy
| equivalent 10 200 horse power has been
| produced in an electric furnace cavity
which is not larger than an ordinary
| umbIer of water Sometimes a power
| Jul magnet is used 10 direct the electric
/ arc upon a certain region in the furnace
4 magnet has the property Of attracting
| OF repelling an cleo ric current and the
/ voltaic arc in the furnace is such an
| electrical current With such an ar
/ rangemsnt. namely, voltaic are and a
magnet. We have practically a powerful
| blowpipe. which meIts glass and the
i 1tlcldlS Ike wax ana N3DOE1Z=S even me
| lime walls of the furnace There are
number of electric furnaces at Niagara
/ Falls. which are used 10 reduce the OK
| ides of metals and 70 form such sub
| stances as carbide of lime. from which
| acetylene is generated and eorundum,
| which is used as a grinding agent in the
| arts.
| 1 have said that the temperature OBJ
| tanned by the electric furnace is not far
Il & F-ab IN
| substances which are available for max
ing thermometers are melted by such
| heat the question naturally arises how
| can we measure suth a high temporal
| ture? II must be confessed that we can
| not measure II accurately and can only
form an estimate This estimate can be
| made by electrical means SCppOSe chat
"a measured quantity of electricity is
sent through a thin strip of Platinum or
a filament similar to that IN an Edison
| lamp. The heat given out by the glowing
| platinum or carbon flament depends
| upon tlhe quantity of electricity which
we can force through it. We can meas
ure this quality very accurately and
from it determine the amount of heat
given out by the filament. We know
| that a strip of platinum red-hOt has a
| temperature in the neic2ioorhCod OF 1S00
| degrees Fahrenheit, and WHEN it Is white
hot a temperature of 3. 800 degrees Sup
| pose that We keep the plattnum strip red
| hot by a known current of electricity
and put delicate thermometer at a dis
| tance of three or four feet from the strip
| and read its indication. We will then
expose the same thermometer to an cleo
tr.c arc lamp which represents the cleo
:r5c furnace. and move II until It reads
| the same as IT did when it was exposed
10 the red hot platinum strip We shall
-tr5 'het we must move the thermometer
much further from the electric furnace,
and thus krowirs the tenPeTuture of the
red hot strip and the relative distances
we can ascertain approximately the tenn
| perature of the electric furnace