Juniata sentinel and Republican. [volume] (Mifflintown, Juniata County, Pa.) 1873-1955, 1874-04-15
Scientific.

STRARIS CANpLEs.-The hard white |
stearin candle of to-day is quite q diff
ferent article from the tallow dip that
our grandmothers used to make, and
which was then a vast improvement over
the pine knot of the preceding genera
tion. Tallow dips were made directly
from the tallow, which was obtained by
melting beef suet and straining it to
remove animal fiber and impurities.
Stearin candles are also made from
tallow but in this case it is first sepa-
rated into its constituents, some OF
which are solids and others liquids, and
only those melting at temperature
above the ordinary summer heat are
employed.
Tallow is a mixture of stearin, pal
matin, and olein, compounds of glycerin
with stearic, palmitic and oleic acids
respectively. Oleic acid and glycerin
are both liquids at ordinary tempera-
lures, and hence it is desirable to re-
move them from the tallow before en-
ploying it in the manufactures of can
dies. To accomplish this, several
methods are in use. The simplest and
one of the best is that invented by
Wright and Fouche, and consists in
decomposing the fat with superheated
steam.
The apparatus employed is called
digester, and consists of two copper
boilers, placed one above the other and
connected by two pipes, one of which
reaches nearly to the bottom of the
lower vessel and ends at the bottom of
the upper one. The other is fixed to
the cover of the lower one and enters
the upper one near the top. The melted
fat mixed with an equal quantity OF
water is run into the digester, which is
not completely filled and is heated for
Is hours under a pressure of eleven
atmospheres. By the end of that time
the glycerin becomes separated from
the fatty acids, and is dissolved in the
water. The contents of the digester
are then blown into large watts where
they are allowed to settle, and the fatty
acids, being specifically lighter, rise to
the top, the glycerin water settling to
the bottom. As soon as this has taken
place, the glycerin water is drawn off
into a tank below and heated by a steam
coil to evapoIate the water, the evapora-
ton being kept up until the glycerin
acquires a specific gravity of 250. At
the proper moment, when all the gly-
cerin water has been drawn off, the
mixed fatty acids are run into large
lead-lined watts. Here they are mixed
with small quantity of oil of vitriol to
purify them, and heated by steam
coil. Then the liquid flows into much
larger vat beneath, from which it is run
,.-,la 1,x-1 Q
long and resembling huge cakes Of
chocolate. These pans are arranged on
racks and the acids to crystalize. The fat
now solidifies, but it still has distributed
through it the oleic acid. To remove
this, the cakes are wrapped in strong
cloth, usually hair cloth, and submitted
to the action of a powerful hydraulic
press, whereby a large proportion OF
the oil is squeezed out.
When no more oil can be pressed out,
the pressed cakes are taken directly
from this press and, without being un-
wrapped, are placed in a horizontal
press between plates of iron and heated
by steam pipes, where still more of the
oleic acid is removed. The pressed
cakes, although nearly pure, are again
melted, treated with dilute sulphuric
acid, and subjected a second time to
hot pressure This furnishes q very
solid, perfectly white substance, con-
sisting principally of stearic acid, i'm
properly called stearin, with some pal
mitic acid. From this, the candles are
nodded in the usual manner.
The oil which is pressed out consists
of oleic acid holding in solution more
or less of the solid acids, which it is
desirable to save. For this reason, it
is taken back to the tanks where the
acids are melted, and mixed with them
TO be worked over again. 1t is finally
sold for washing wool, softening leather,
or making soap.
Another method of separating stearic
acid from the glycerin and oleic acid,
formerly much used, consists in saponi-
fication by means of lime. When lime
is added to melted tallow and heated,
the fatty acids combine with it to form
an insoluble lime soap, the glycerin
remaining in solution. The lime soap
thus formed is decomposed with sui
phuric acid, sulphate of lime being
precipitated, and the melted fatty acids
IlSC W lllC 1uc ldlltI art
transferred to lead-lined tanks, treated
with oil of vitriol, drawn of, cooled,
and pressed cold and hot, as in the other
processes. If superheated steam is en-
ployed, much smaller quantity of lime
is required. At pressure of ten at
mospheres, with or per cent of lime,
saponifcation and decomposition are
complete in seven hours. This process
invented by De Milly. is a combination
of both the above, and effects saving
in time over the first, and a saving in
lime and acid over the second.
A fourth method, quite different from
any of the above, was introduced by
Dubrunfaut in 1S41. Unlike the other
processes, it can be employed to decom-
pose very impure fats from slaughter
houses, bone and marrow fats, kitchen
stuff, residues from refining fish oils,
and the like. Oil of vitriol is added to
the molten fat, moderate heat applied,
and the mass stirred for II or 20 hours.
The neutral fat is thus converted into a
mixture of sulpho- fatty acids and sulpho
glyceric acid. These are decomposed
by running them into large wooden
tanks lined with lead and one third
filled with water, and heating to 2120
Fab. After the fatty acids separate,
they are purified with water the water
evaporated, and the acids carefully
distilled by means of superheated
steam, at temperature of 500o Fab. to
6500 Fab, According to De Milly's
new process. the tallow is heated to 24S'
along with 6 per cent of oil of vitriol,
and the action limited to or hours.
1t is thereby possible to obtain so per
cent of the solid fatty acids in condi-
ton at once fit for making candles
without redistilation, only 90 per cent
having to be distilled.
ADAPTATION OF GUN-CoTToN TO FIRE
ARMs.-The use of explosives other than
gun-powder in firearms has hitherto
proved impracticable on account of their
sudden and violent action, ordinary
charges bursting the gun before the uis
iaertiG of the projectile is overcome.