The evening times., 1898-09-02
Concentration of Heat in a
Small Compass.
THE FOURTH ELECTRIC ERA
A Temperature of Not Far From
Six Thousand Degrees Fahrenheit
Reached by EIcctricity-Hov the
Temperature Is Measured-1he
Amount of Heat Almost Unlimited
Trom the Boston Transcript. }

have been three distinct eras in the prac-
teal applications of electricity. The first
was characterized by its use in teleg-
raphy, the second by it's 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 a box or parallelopiped
of limestone, having a cavity of similar
shape cut into it. 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
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
minal to the other In this way aluminium
IS produced, and in a similar way car
| bide of lime. which being dropped into
the water gives forth the gas acetylene
in great quantity.
For scientific experimentation the cavity
holds small crucible. which is composed
! of mixture of carbon and magnesia- In
| this crucibe 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 Yoltaic arc
! and about the same distance from the
! bottom OF the limestone cavity In this
| carbon tube are placed the substances
| which are to be heated. Material can
! be introduced into one end of this tube
| by tipping The tube, without stopping
/ the current in ;he furnace
In order TO produce diamonds iron is
melted with large quantity OF carbon
! powder. and when tha mixture has at
! tanned high tempe!a ure-over 6.198 de-
| grees Fahrenheif--it IS suddenly plunged
! into cold water or a b1iE of molten lead.
| The lead being a better conductor of
| heat than cold water. more suddenly
deprives the mixture of lis heat. On ex-
| amining the Stag small coiorless 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 loCalize the heat in a narrow COM
. pass. and the amount OF heat we can
/ produce in such furnace is almost
! unlimited An amount of heat energy
| equivalent 10 100 horse power has been
! produced in an electric furnace cavity
which is not larger than an ordinary
| tumbler Of water. Sometimes a power
ful magnet is used 10 direct the electric
! arc upon a certain region in the furnace
| a magnet has the property Of attracting
! or repeiling an elec riC current and the
| voltaic arc in the furnace is such an
i electrical current. With such an ar
| rangement, namely, a voltaic arc and a
| magnet, We have practically a powerful
blowpipe. which melus glass and the
metals like wax and yaporizes even he
| lime walls of the furnace There are a
| number of electric furnaces al Niagara
| Falls. which are used 10 reduce the OK
ides of metals and 10 form such sub
| stances as carbide of lime. from which
acetylene is generated. and corundum.
! which is used as a grinding agent in the
| arts.
1 have said that the temperature OBJ
| tained by the electric furnace is not far
! from 5000 degrees Fahrenheit. Since all
substances which are available for max
| ing thermometers are melted by such
| heat the question naturally arises, how
| can we measure such a high tempera-
! 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. Suppose that
| "a measured quantity of electricity IL
/ sent through a thin strip of platinum or
! a hlament similar to that in an Edison
| lamp. The heat given out by the glowing
| platinum or carbon filament depends
| upon the quantity of electricity which
| we can force through 1t, We can meas
| ure this quality very accurately and
| from 1t determine the amount Of heat
| given out by the fiament. We know
| that a strip of platinum red-hot has a
| temperature in the nelshborhood of 1900
| degrees Fahrenheit, and when it is white
| hot a temperature of 3, 400 degrees. Sup
| pose that we keep the platinum strip red
| hot by a known current of electricity
and put a delicate thermometer at a d,s-
| tance of three or four feet from the strip
and read its indication. We will! then
| expose TIE same thermometer to an cleo
| tr!c arc lamp. which represents the cleo
| trio furnace. and move it until it reads
the same as it did when it was exposed
to the red hot platinum strip. w shall
find that we must move the thermometer
| much further from the electric furnace
| and thus knowing the ten perature of the
! red hot strip and the relative distances
| we can ascertain approximately the tenn
| perature of the electric furnace.