Milford chronicle., 1906-05-04
METALLIC TANTALuM.
Rt superaedes the Diamond as she
Hardest known Substance.

Ht SuDeraedes the diamond AS t~S
hardest Known Substance.
For centuries the diamond has been
recognized as the hardest Of all known
substances. The polish power of dia-
mond dust and the boring power Of the
diamond drill are familiar facts. So
is the fact that nothing can polish or
cut a diamond except another diamond.
But a new substance has made its ap-
pearance which, if it can be obtained
in sufficient quantity, will probably re-
place the diamond alike in the opera
tions of drill boring and in the lapi-
darv's workshop, for it is harder than
diamond-sO hard, in fact, that the only
effect produced by a diamond drlii
worked day and night for three days
on a sheet of the substance one twenty
fifth of an inch thick, with a speed OF
5000 revolutions per minute, was d
slight dent in the sheet and the wearing
out of the diamond. This substance Is
pure metallic tantalum.
Tantalum is not a common metal
vet it is also not one Of the rarest. Its
existence was discovered more than
century ago, but no attempt to separate
it from its compounds had SUCCEEDED
prior to 1903, when Meissan oDtallleu
a sample in the electric furnace. Inc
metal which he isolated was very nara
md brittle. and we now know that II
was so much contaminated with car
hon that most Of the characteristic
Dronerties of the pure metal had DIS
appeared. ...s -.
Pure tantalum was first prepared oy
DIR. Bolton. member Of the famous
electrical engineering firm Of Siemens
& HaIske. One of his methods is TO
Fuse the double fiuoride Of potassium
and tantalum with metallic potassium
in an electric furnace in vacuo, but he
seems to prefer a much simpler elec-
4rical method. Making up the oxide
into a filament exactly like that OF
a Nernst incandescent lamp, he places
at in a globe connected to an air pump
and turns on the current The oxide
IS decomposed, and, the oxygen being
gradually removed by the pump, the
ilament is reduced to the metallic
state.
Tantalum differs from all other known
substances in combining extreme hard
ness with extreme ductility. OF its
hardness we have already given an ex-
ample. so need only add that when red
hot it is easily rolled into bars and
sheets or drawn into wire. 1t is scarce
" affected by the oxygen Of the air
even at a red heat and not at all at
ordinary temperatures, and the strong
est acids fail to dissolve It. Nor does
It amalgamate with mercury. 1t melts
only at the highest attainable temper
atures and is therefore well fitted to
serve for flaments In incandesoent
lamps, being much stronger than car
bon. A pound Of it will make 2O,OOO
lamps, and these require exactly half
as much power to light them as do
carbon filaments giving the same bril-
liancy.
If only it can be procured in sufficient
quantity tantalum should prove most
useful metal. 1t will furnish better
boring tools than the diamond drill
and cheaper electric lights than car
bon, while the possible uses Of a plate
or a wire harder than diamond and yet
tough and strong are almost infinite,
for every other hard substance is brit
tle, and this fact has hampeTed the en-
gineer for centuries-New York Her
aid.